Dr. Jeff Masters' WunderBlog

Tropical Storm Arlene hits Mexico

By: JeffMasters, 02:44 PM GMT am 30. Juni 2011

Tropical Storm Arlene made landfall on the northeast coast of Mexico south of Tampico at 5am EDT this morning as an intensifying tropical storm with 65 mph winds. Wind gusts as high as 46 mph were recorded in Tampico last night, and intermittent heavy rain and winds gusting up to 34 mph have affected Brownsville, Texas today. The Brownsville Airport picked up 1.31" of rain as of 10am EDT, and Arlene has dropped rainfall amounts of 1 - 2 inches over extreme South Texas so far, according to radar-estimates of rainfall from the Brownsville radar. As Arlene pushes inland today, heavy rainfall amounts of 4 - 8 inches are likely over portions of Mexico, which will probably cause several million dollars in flooding damage. However, Arlene's rains are likely to provide a benefit to agriculture in the tens of millions of dollars, since the region of Mexico affected is experiencing their worst drought in over 50 years. It's fortunate that Arlene ran out of room in the Gulf of Mexico when it did; microwave satellite images of the storm at landfall show that Arlene was well on its way to establishing a complete eyewall, and would have likely become a hurricane if it had had another twelve hours over water.


Figure 1. Tropical Storm Arlene at landfall: 4:45am EDT June 20, 2011. Image credit: NASA/GSFC.


Figure 2. Rainfall amounts from Tropical Storm Arlene as estimated by the Brownsville, Texas radar. The radar is not able to see far enough to the south to capture the main rain areas from Arlene.

No additional action expected in the Atlantic over the coming week
There are no other areas of concern in the Atlantic today, and none of the computer models is predicting tropical cyclone formation in the Atlantic over the coming seven days. We've gotten our first storm of the season a bit on the early side; the typical first storm does not occur until July 9 in the Atlantic. High wind shear of 20 - 50 knots rules the Caribbean and the surrounding waters that tend to breed early season storms, which will make formation of an early July storm difficult.

Jeff Masters

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Tropical Storm Arlene slides toward Mexico coast

By: JeffMasters, 11:56 PM GMT am 29. Juni 2011

Tropical Storm Arlene hasn't intensified much on paper, but thunderstorm activity has increased, and it looks impressive on satellite considering it was just named 24 hours ago. In a 5:30pm EDT special update, the National Hurricane Center said the tropical storm had winds of 60 mph. Thunderstorm activity increased on the southern end of the storm this afternoon, and there is some suggestion that these stronger thunderstorms could begin to wrap around the storm, if it only had more time over the warm, conducive waters of the Bay of Campeche. Tampico, Mexico has sustained winds up to 20 mph out of the north-northeast this evening. Radar indicates the heaviest rainfall is occurring on the southern side of the storm in association with the coldest cloud tops on satellite. Although flooding is expected, this storm is bringing some much needed rain to central Mexico, assuming it can be absorbed into the very dry soil.


Figure 1. Visible satellite image of Tropical Storm Arlene at 5:32pm CDT on June 29, 2011. The strongest convection is to the south of the center of the storm.

An Air Force hurricane hunter reconnaissance mission was in Arlene this afternoon/evening, and found slightly stronger winds than expected. The circulation is broad and surface winds near the center of the storm are only around 35-40 mph. The highest wind speeds were found displaced from the center, associated with the strongest convection. The recon mission measured a minimum central pressure of 996 millibars, which is down from 1000 millibars in the 5pm advisory.

Arlene is having an impact on the U.S., as well. Brownsville, Texas saw a line of heavy showers earlier, and will continue to get rain throughout the evening from the outer rain bands of the storm. Coastal flood statements and rip current statements have been issued from South Padre Island to Port Lavaca, Texas. Strong rip currents and tidal overflow is expected during the next few days as lingering effects of Arlene.


Figure 2. Brownsville, Texas radar at 5:37pm CDT on June 29, 2011. The outer bands of Tropical Storm Arlene are reaching as far north as Brownsville, and coastal flood/rip currents are expected along the southern Texas coast for the next few days.

The forecast for Arlene remains almost the same as this morning. Slight strengthening (to 65 mph) is expected over the next few hours before landfall, though the National Hurricane Center admits there's a small chance winds could exceed hurricane strength. The tropical storm will come ashore south of Tampico, Mexico, just after 2am EDT, and likely will have just missed being 2011's first hurricane by few more hours over water.

Introducing wunderground's Angela Fritz
This evening's post was written by Angela Fritz, who joined wunderground this year after a stint doing weather for CNN. Angela has a Masters degree in meteorology from Georgia Tech, and specialized in hurricane research for her graduate work. She is doing hurricane forecasting for a private weather company this summer, and will be filling in for me on my blog this hurricane season when I am on vacation, mid-July through early August. Angela's excellent writing skills will be put to good use adding content to our Severe Weather Headlines and climate change sections of our web site.

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Tropical Storm Arlene--a heavy rainfall threat for Mexico

By: JeffMasters, 01:48 PM GMT am 29. Juni 2011

The 2011 Atlantic hurricane season has its first named storm, Tropical Storm Arlene, which rapidly spun up last night from a tropical wave that had emerged into Mexico's Bay of Campeche. An Air Force hurricane hunter aircraft is currently in the storm, and has found that Arlene is strengthening. At the plane's flight altitude of 1,000 feet, top winds reported as of 9:30am EDT were 54 mph, on Arlene's south side. The aircraft's SFMR instrument that remotely measures surface wind speeds found top surface winds of 67 mph on southeast side of the storm. This reading was probably a gust, since top winds of 45 - 50 mph have been more characteristic of the SFMR winds. The measured central pressure at 9am EDT was 1000 mb, which is a 2mb drop from the pressure estimate from 5am. Satellite loops show a marked increase in the intensity and organization of Arlene's heavy thunderstorms, with more prominent spiral bands. Mexican radar out of Alvarado also shows this trend. Wind shear has fallen to the moderate range, 10 - 15 knots, and is predicted to fall to the low range, 5 - 10 knots, by tonight. This should allow Arlene to continue to organize, and storm could be approaching hurricane strength by the time it makes landfall Thursday morning in Northeast Mexico. Arlene has moistened its environment enough so that the dry air over Mexico should no longer be a problem for it, and the topography surrounding the Bay of Campeche tends to boost counter-clockwise air flow, enabling systems there to spin up faster than in any other portion of the Atlantic. Arlene is bigger than most Bay of Campeche tropical storms, though, so it may not have time to spin up into a hurricane because of its large size. NHC's 5am EDT advisory was giving Arlene a 9% chance of reaching hurricane strength before landfall. These odds should probably be bumped up to 30%, in light of Arlene's recent intensification.


Figure 1. Microwave satellite image of Tropical Storm Arlene taken at 4:07am EDT June 29, 2011 showed that several spiral bands had formed. Image credit: N avy Research Lab, Monterey.

Rainfall forecast for Arlene
The major threat from Arlene is heavy rainfall, particularly since the portion of coast that will be affected is under extreme drought. Without much vegetation to absorb Arlene's rains and slow down run-off, the expected heavy rains are more likely to cause damaging flooding. NHC is currently estimating that 4 - 8 inches will fall, with isolated areas of up to 15 inches over the mountains. These predicted amounts will probably need to be revised upwards, given Arlene's recent increase in organization. At this time, it appears that Texas will not see any rain from Arlene.


Figure 2. Cumulative rainfall expected along the path of Arlene, as predicted by this morning's 2am EDT (06 UTC) run of the HWRF model. This model predicts a large region of 8+ inches of rain (yellow colors) will affect Mexico. These rainfall amounts are probably too high, as our other models are not showing such heavy rainfall amounts. Image credit: Morris Bender, NOAA/GFDL.

June hurricane climatology
Long-term hurricane records going back to 1851 show that on average, we see just one Atlantic named storm every two years in June. Only one major hurricane has made landfall in June--Category 4 Hurricane Audrey of 1957, which struck the Texas/Louisiana border area on June 27 of that year, killing 550. The highest number of named storms for the month is three, which occurred in 1936 and 1968. In the sixteen years since the current active hurricane period began in 1995, there have been twelve June named storms (if we include 2008's Tropical Storm Arthur, which really formed on May 31). Thus, recent history suggests the Atlantic hurricane season is becoming more active earlier in the season, in line with recent research that found that the Atlantic hurricane season is getting longer.

Arlene: the most common Atlantic storm name of all-time
This year marks the tenth appearance of a storm named Arlene in the Atlantic, making it the most recycled storm name of all-time. The other nine appearances: 1959, 1963, 1967, 1971, 1981, 1987, 1993, 1999, and 2005. It's pretty likely we'll see Arlene again in 2017--no storm that has formed in the Bay of Campeche and made landfall in Mexico has ever had its name retired. Hurricane Audrey of June 1957 formed in the Bay of Campeche and hit Texas as a Category 4 hurricane, killing 550 people, making Audrey one of only two June storms to get its name retired Hurricane Agnes of 1972 was the other. There have been seven storms beginning with the letter "A" that have had their names retired since 1950:

Allison (2001)
Andrew (1992)
Alicia (1983)
Allen (1980)
Anita (1977)
Agnes (1972)
Audrey (1957)

Of the 21 letters in the alphabet we use to name storms, names beginning with the letters "C" have been retired the most--nine times. Second place goes to "F" and "I" names, with eight retirees. The only letter used that doesn't have a retired storm is "V". There has been only one storm with a name beginning with "V"--Hurricane Vince of 2005. The list of retired hurricane names currently has 76 members.

An amazing low temperature of 107°F in Oman
At Khasab Airport in the desert nation of Oman, a remarkable record was set yesterday--the low temperature for the day was a scorching 41.7°C (107°F). The record was brought to my attention by weather records researcher Maximiliano Herrera. The previous highest minimum temperature for the world he was able to find was set just last year at Khasab Airport, 41.2°C (106°F). The U.S. record high minimum temperature may be a 39.4°C (103°F) taken in Death Valley, California in 1970. Higher record high minimums were set there in the early 1920s, but the quality of the data is suspect. Mr. Herrera notes that Khasab Airport in Oman lies at the base of a mountain range, behind which is desert. Winds blowing from the desert towards Khasab Airport flow downhill, undergoing compression and warming, like the Santa Ana winds in California. Incredibly hot conditions in Oman in late June are common, due to a seasonal shift in winds caused by the onset of the Southwest monsoon in India.

Record California rainstorm
Yesterday was the wettest day ever recorded in the San Francisco Bay Area between June 15 - September 15. All-time precipitation records for the month of June (total for the month) were set at SFO (San Francisco Airport), Oakland Downtown, Oakland Airport, Santa Rosa, Napa, Santa Cruz, and San Jose. Thanks go to Christopher C. Burt for this data.

Internet radio show on Arlene at 4pm EDT
I'll be discussing Tropical Storm Arlene on a special edition of our Internet radio show, the Daily Downpour, today (Wednesday) at 4:00pm EDT. Fellow wunderground meteorologists Shaun Tanner and Angela Fritz will be hosting the show. Listeners can email in or call in questions. The email address to ask questions is broadcast@wunderground.com.

Jeff Masters

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Large fire threatens Los Alamos nuclear lab; 95L headed for Mexico

By: JeffMasters, 02:04 PM GMT am 28. Juni 2011

The dangerous Los Conchas wildfire has burned to a spot one mile southwest of Los Alamos, New Mexico, forcing the nuclear laboratory there to close, and the evacuation of 8,000 people. The fire was fanned yesterday by winds that reached sustained speeds of 21 mph, gusting to 30 mph, along with temperatures in the low 80s and humidities as low as 14%. The fire was 0% contained as of Monday night, and had consumed 176 square miles. Today, winds will be out of the south at 10 - 20 mph, which will tend to force the fire towards the laboratory. According to the NOAA Storm Prediction Center, these will not be critical fire conditions, and critical fire conditions are not expected to return to the area until Wednesday or Thursday. Smoke from the fire has blown over 1,000 miles downwind, and is causing air pollution problems in downwind regions of New Mexico.



Figure 1. New Mexico's Los Conchas fire (marked by the cluster of red squares on the left) sends smoke across a large swath of southern Kansas in this image taken at 1:40pm EDT June 27, 2011. Image credit: NASA.

Tropical disturbance 95L headed towards Mexico
Heavy thunderstorm activity is increasing over the Gulf of Mexico's Bay of Campeche due to a tropical wave (Invest 95L), moving west-northwest at 5 - 10 mph towards the coast of Northeast Mexico. Satellite loops show that the thunderstorms are currently poorly organized, and there is no sign of a surface circulation. Mexican radar out of Alvarado also shows little organization and no spiral banding. Wind shear has fallen by 5 knots to 20 - 25 knots over the past day, and is predicted to continue to fall over the next two days. This should allow 95L to continue to organize, and the Hurricane Hunters are scheduled to visit the storm Wednesday afternoon to see if a tropical depression is forming. Several reliable computer models are predicting that 95L could become a tropical depression or weak tropical storm before making landfall. Landfall will probably occur on Mexico's Bay of Campeche coast several hundred miles south of the Texas border on Wednesday night. NHC is giving the system a 50% chance of developing into a tropical depression by Thursday. Development will be hindered by a large region of dry air to the west, associated with the great 2011 Texas-Mexico drought. However, the topography surrounding the Bay of Campeche tends to boost counter-clockwise air flow, enabling systems there to spin up faster than any other portion of the Atlantic.

There is a strong ridge of high pressure over the Gulf, which should act to keep 95L moving west-northwest or west, with impacts limited to Mexico and perhaps extreme South Texas. Rainfall amounts of 1 - 2 inches are possible over Brownsville, Texas on Wednesday. The main danger from the storm for Mexico is likely to be heavy rains of 4 - 8 inches, but the rain is likely to be more a blessing than a danger. Mexico is experiencing its worst drought in 70 years over 40% of the country, and wild fires have burned 500,000 acres in northern regions near the U.S. border.


Figure 2. Morning satellite image of Invest 95L.

All-time dry air record set at Las Vegas
On Monday, Las Vegas, Nevada reported its driest air in recorded history, when the temperature hit 107° and the dewpoint reached -22° at 4:32pm MDT. This gave the city a dewpoint depression of 129 degrees, and a relative humidity of just 0.6%. The dew point depression is defined as the difference between the air temperature and the dew point temperature. The previous all-time record dew point depression for Las Vegas was 120 degrees set on July 2nd 2007. Not surprisingly, this record dry air is creating dangerous fire conditions, and much of the Southwest U.S. including Las Vegas is under a Red Flag Warning for critical fire conditions today.

Jeff Masters

Updated: 03:54 PM GMT am 28. Juni 2011

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Hottest day on record in Texas Panhandle; fire threatens Los Alamos

By: JeffMasters, 04:54 PM GMT am 27. Juni 2011

The hottest temperatures in recorded history scorched large portions of the Texas Panhandle, Oklahoma Panhandle, and southwestern Kansas on Sunday. Amarillo hit 111°, breaking its hottest day-ever record of 109° (set just two days previously, on June 24). Borger, Texas hit 113°, smashing the previous hottest day-ever record set on June 24, 2011 of 108°. Dalhart, Texas had its hottest day on record, 110°, beating the 108° on June 24, 2011. Dodge City, Kansas tied its all-time record with 110° (last seen on June 29, 1998). Dodge City has temperature records back to 1874. Yesterday saw the hottest temperatures of the month for Texas with 116.2° at Childress, Northfield, and Memphis (all in the panhandle region.) These readings are not far from the state record of 120° set at Monahas on June 28, 1994 and at Seymore on August 12, 1936.

A cold front moved through the region overnight, bringing northerly winds and cooler temperatures to the region. However, a new ridge of high pressure will gradually build in this week and temperatures are expected to reach near-record levels again by Thursday, with 102°F expected in Amarillo, which is their all-time record for the date. The record-breaking temperatures in Texas are being caused, in part, by the record drought. Under normal conditions, the sun's heat expends part of its energy evaporating water from the soil and from vegetation. This energy is stored as "latent heat" in the water evaporated, and is not available to heat the air up. However, when a severe drought dries up the soil and kills the vegetation, there is much more heat available to go directly into heating up the air, since there is little moisture to evaporate. The increased temperatures help to strengthen the high pressure system dominating the drought region, making it even more difficult for rain-bearing low pressure systems to bring drought-busting rains. This positive feedback effect is a key reason why we expect more intense droughts and heat waves in a warmer climate.

Wunderground's weather historian Christopher C. Burt has many more details on the great Texas drought of 2011 in his latest post, updated Sunday night. He reports that Pecos, Texas has had no precipitation since September 23, 2010--one of the longest rain-free periods for a U.S. city in recorded history, outside of the desert regions of Arizona and California.


Figure 1. Latest weekly drought conditions for Texas, as compiled by the U.S. Drought Monitor. West Texas is experiencing its worst drought in recorded history.

Fire threatens Los Alamos, New Mexico
A major wildfire has burned to a spot one mile southwest of Los Alamos, New Mexico today, forcing the nuclear laboratory there to close and send home all 11,000 of its employees. The fire was fanned by winds that reached sustained speeds of 32 mph, gusting to 45 mph, along with temperatures in the upper 80s and humidities as low as 9%. Today, winds will be weaker, 10 - 20 mph, but are expected to to turn to the southwest, which would force the fire towards the laboratory. According to the NOAA Storm Prediction Center, these will not be critical fire conditions, and critical fire conditions are not expected to return to the area until Thursday.


Figure 2. Noon satellite image of the tropical disturbance crossing Mexico's Yucatan Peninsula.

Tropical disturbance approaching the Gulf of Mexico
Heavy thunderstorm activity is increasing over Mexico's Yucatan Peninsula and adjacent waters due to a tropical wave moving west-northwest towards the Gulf of Mexico. Wind shear is currently 20 - 30 knots, which is too high to permit significant development, but wind shear is forecast to fall to the moderate range, 10 - 20 knots, on Tuesday, as the wave emerges over the Gulf of Mexico. Several of our reliable computer models are predicting that a system that may approach tropical depression strength could form in the southern Gulf of Mexico in the Bay of Campeche Tuesday or Wednesday. NHC is giving the system a 20% chance of developing into a tropical depression by Wednesday. Development will be hindered by a large region of dry air to the west, associated with the great 2011 Texas-Mexico drought. However, the topography surrounding the Bay of Campeche tends to boost counter-clockwise air flow, enabling systems there to spin up faster than any other portion of the Atlantic.

There is a strong ridge of high pressure over the Gulf, which should act to keep any storm that might form far to the south, with impacts limited to Mexico and perhaps extreme South Texas. Mexico could use the rain. A report from The Latin American Herald Tribune states that 40% of the nation is experiencing its worst drought in 70 years. There are portions of the state of Coahulia where no rain has fallen since last September (just like Pecos in Texas). Wild fires have so far burned 500,000 acres in northern regions near the U.S. border.

Jeff Masters

Updated: 05:02 PM GMT am 27. Juni 2011

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2010 - 2011: Earth's most extreme weather since 1816?

By: JeffMasters, 01:32 PM GMT am 24. Juni 2011

Every year extraordinary weather events rock the Earth. Records that have stood centuries are broken. Great floods, droughts, and storms affect millions of people, and truly exceptional weather events unprecedented in human history may occur. But the wild roller-coaster ride of incredible weather events during 2010, in my mind, makes that year the planet's most extraordinary year for extreme weather since reliable global upper-air data began in the late 1940s. Never in my 30 years as a meteorologist have I witnessed a year like 2010--the astonishing number of weather disasters and unprecedented wild swings in Earth's atmospheric circulation were like nothing I've seen. The pace of incredible extreme weather events in the U.S. over the past few months have kept me so busy that I've been unable to write-up a retrospective look at the weather events of 2010. But I've finally managed to finish, so fasten your seat belts for a tour through the top twenty most remarkable weather events of 2010. At the end, I'll reflect on what the wild weather events of 2010 and 2011 imply for our future.

Earth's hottest year on record
Unprecedented heat scorched the Earth's surface in 2010, tying 2005 for the warmest year since accurate records began in the late 1800s. Temperatures in Earth's lower atmosphere also tied for warmest year on record, according to independent satellite measurements. Earth's 2010 record warmth was unusual because it occurred during the deepest solar energy minimum since satellite measurements of the sun began in the 1970s. Unofficially, nineteen nations (plus the the U.K.'s Ascension Island) set all-time extreme heat records in 2010. This includes Asia's hottest reliably measured temperature of all-time, the remarkable 128.3°F (53.5°C) in Pakistan in May 2010. This measurement is also the hottest undisputed temperature anywhere on the planet except for in Death Valley, California (two hotter official records, at Al Azizia, Libya in 1922, and Tirat, Zvi Israel in 1942, have ample reasons to be disputed.) The countries that experienced all-time extreme highs in 2010 constituted over 20% of Earth's land surface area.


Figure 1. Climate Central and Weather Underground put together this graphic showing the twenty nations (plus one UK territory, Ascension Island) that set new extreme heat records in 2010.

Most extreme winter Arctic atmospheric circulation on record; "Snowmageddon" results
The atmospheric circulation in the Arctic took on its most extreme configuration in 145 years of record keeping during the winter of 2009 - 2010. The Arctic is normally dominated by low pressure in winter, and a "Polar Vortex" of counter-clockwise circulating winds develops surrounding the North Pole. However, during the winter of 2009 - 2010, high pressure replaced low pressure over the Arctic, and the Polar Vortex weakened and even reversed at times, with a clockwise flow of air replacing the usual counter-clockwise flow of air. This unusual flow pattern allowed cold air to spill southwards and be replaced by warm air moving poleward. Like leaving the refrigerator door ajar, the Arctic "refrigerator" warmed, and cold Arctic air spilled out into "living room" where people live. A natural climate pattern called the North Atlantic Oscillation (NAO), and its close cousin, the Arctic Oscillation (AO) were responsible. Both of these patterns experienced their strongest-on-record negative phase, when measured as the pressure difference between the Icelandic Low and Azores High.

The extreme Arctic circulation caused a bizarre upside-down winter over North America--Canada had its warmest and driest winter on record, forcing snow to be trucked in for the Winter Olympics in Vancouver, but the U.S. had its coldest winter in 25 years. A series of remarkable snow storms pounded the Eastern U.S., with the "Snowmageddon" blizzard dumping more than two feet of snow on Baltimore and Philadelphia. Western Europe also experienced unusually cold and snowy conditions, with the UK recording its 8th coldest January. A highly extreme negative phase of the NAO and AO returned again during November 2010, and lasted into January 2011. Exceptionally cold and snowy conditions hit much of Western Europe and the Eastern U.S. again in the winter of 2010 - 2011. During these two extreme winters, New York City recorded three of its top-ten snowstorms since 1869, and Philadelphia recorded four of its top-ten snowstorms since 1884. During December 2010, the extreme Arctic circulation over Greenland created the strongest ridge of high pressure ever recorded at middle levels of the atmosphere, anywhere on the globe (since accurate records began in 1948.) New research suggests that major losses of Arctic sea ice could cause the Arctic circulation to behave so strangely, but this work is still speculative.


Figure 2. Digging out in Maryland after "Snowmageddon". Image credit: wunderphotographer chills.

Arctic sea ice: lowest volume on record, 3rd lowest extent
Sea ice in the Arctic reached its third lowest areal extent on record in September 2010. Compared to sea ice levels 30 years ago, 1/3 of the polar ice cap was missing--an area the size of the Mediterranean Sea. The Arctic has seen a steady loss of meters-thick, multi-year-old ice in recent years that has left thin, 1 - 2 year-old ice as the predominant ice type. As a result, sea ice volume in 2010 was the lowest on record. More than half of the polar icecap by volume--60%--was missing in September 2010, compared to the average from 1979 - 2010. All this melting allowed the Northwest Passage through the normally ice-choked waters of Canada to open up in 2010. The Northeast Passage along the coast of northern Russia also opened up, and this was the third consecutive year--and third time in recorded history--that both passages melted open. Two sailing expeditions--one Russian and one Norwegian--successfully navigated both the Northeast Passage and the Northwest Passage in 2010, the first time this feat has been accomplished. Mariners have been attempting to sail the Northwest Passage since 1497, and have failed to accomplish this feat without an icebreaker until the 2000s. In December 2010, Arctic sea ice fell to its lowest winter extent on record, the beginning of a 3-month streak of record lows. Canada's Hudson Bay did not freeze over until mid-January of 2011, the latest freeze-over date in recorded history.


Figure 3. The Arctic's minimum sea ice extent for 2010 was reached on September 21, and was the third lowest on record. Image credit: National Snow and Ice Data Center.

Record melting in Greenland, and a massive calving event
Greenland's climate in 2010 was marked by record-setting high air temperatures, the greatest ice loss by melting since accurate records began in 1958, the greatest mass loss of ocean-terminating glaciers on record, and the calving of a 100 square-mile ice island--the largest calving event in the Arctic since 1962. Many of these events were due to record warm water temperatures along the west coast of Greenland, which averaged 2.9°C (5.2°F) above average during October 2010, a remarkable 1.4°C above the previous record high water temperatures in 2003.


Figure 4. The 100 square-mile ice island that broke off the Petermann Glacier heads out of the Petermann Fjord in this 7-frame satellite animation. The animation begins on August 5, 2010, and ends on September 21, with images spaced about 8 days apart. The images were taken by NASA's Aqua and Terra satellites.

Second most extreme shift from El Niño to La Niña
The year 2010 opened with a strong El Niño event and exceptionally warm ocean waters in the Eastern Pacific. However, El Niño rapidly waned in the spring, and a moderate to strong La Niña developed by the end of the year, strongly cooling these ocean waters. Since accurate records began in 1950, only 1973 has seen a more extreme swing from El Niño to La Niña. The strong El Niño and La Niña events contributed to many of the record flood events seen globally in 2010, and during the first half of 2011.


Figure 5. The departure of sea surface temperatures from average at the beginning of 2010 (top) and the end of 2010 (bottom) shows the remarkable transition from strong El Niño to strong La Niña conditions that occurred during the year. Image credit: NOAA/NESDIS.

Second worst coral bleaching year
Coral reefs took their 2nd-worst beating on record in 2010, thanks to record or near-record warm summer water temperatures over much of Earth's tropical oceans. The warm waters caused the most coral bleaching since 1998, when 16 percent of the world's reefs were killed off. "Clearly, we are on track for this to be the second worst (bleaching) on record," NOAA coral expert Mark Eakin in a 2010 interview. "All we're waiting on now is the body count." The summer 2010 coral bleaching episodes were worst in the Philippines and Southeast Asia, where El Niño warming of the tropical ocean waters during the first half of the year was significant. In Indonesia's Aceh province, 80% of the bleached corals died, and Malaysia closed several popular dive sites after nearly all the coral were damaged by bleaching. In some portions of the Caribbean, such as Venezuela and Panama, coral bleaching was the worst on record.


Figure 6. An example of coral bleaching that occurred during the record-strength 1997-1998 El Niño event. Image credit: Craig Quirolo, Reef Relief/Marine Photobank, in Climate, Carbon and Coral Reefs

Wettest year over land
The year 2010 also set a new record for wettest year in Earth's recorded history over land areas. The difference in precipitation from average in 2010 was about 13% higher than that of the previous record wettest year, 1956. However, this record is not that significant, since it was due in large part to random variability of the jet stream weather patterns during 2010. The record wetness over land was counterbalanced by relatively dry conditions over the oceans.


Figure 7. Global departure of precipitation over land areas from average for 1900 - 2010. The year 2010 set a new record for wettest year over land areas in Earth's recorded history. The difference in precipitation from average in 2010 was about 13% higher than that of the previous record wettest year, 1956. Image credit: NOAA's National Climatic Data Center.

Amazon rainforest experiences its 2nd 100-year drought in 5 years
South America's Amazon rainforest experienced its second 100-year drought in five years during 2010, with the largest northern tributary of the Amazon River--the Rio Negro--dropping to thirteen feet (four meters) below its usual dry season level. This was its lowest level since record keeping began in 1902. The low water mark is all the more remarkable since the Rio Negro caused devastating flooding in 2009, when it hit an all-time record high, 53 ft (16 m) higher than the 2010 record low. The 2010 drought was similar in intensity and scope to the region's previous 100-year drought in 2005. Drought makes a regular appearance in the Amazon, with significant droughts occurring an average of once every twelve years. In the 20th century, these droughts typically occurred during El Niño years, when the unusually warm waters present along the Pacific coast of South America altered rainfall patterns. But the 2005 and 2010 droughts did not occur during El Niño conditions, and it is theorized that they were instead caused by record warm sea surface temperatures in the Atlantic.

We often hear about how important Arctic sea ice is for keeping Earth's climate cool, but a healthy Amazon is just as vital. Photosynthesis in the world's largest rainforest takes about 2 billion tons of carbon dioxide out of the air each year. However, in 2005, the drought reversed this process. The Amazon emitted 3 billion tons of CO2 to the atmosphere, causing a net 5 billion ton increase in CO2 to the atmosphere--roughly equivalent to 16 - 22% of the total CO2 emissions to the atmosphere from burning fossil fuels that year. The Amazon stores CO2 in its soils and biomass equivalent to about fifteen years of human-caused emissions, so a massive die-back of the forest could greatly accelerate global warming.


Figure 8. Hundreds of fires (red squares) generate thick smoke over a 1000 mile-wide region of the southern Amazon rain forest in this image taken by NASA's Aqua satellite on August 16, 2010. The Bolivian government declared a state of emergency in mid-August due to the out-of-control fires burning over much of the country. Image credit: NASA.

Global tropical cyclone activity lowest on record
The year 2010 was one of the strangest on record for tropical cyclones. Each year, the globe has about 92 tropical cyclones--called hurricanes in the Atlantic and Eastern Pacific, typhoons in the Western Pacific, and tropical cyclones in the Southern Hemisphere. But in 2010, we had just 68 of these storms--the fewest since the dawn of the satellite era in 1970. The previous record slowest year was 1977, when 69 tropical cyclones occurred world-wide. Both the Western Pacific and Eastern Pacific had their quietest seasons on record in 2010, but the Atlantic was hyperactive, recording its 3rd busiest season since record keeping began in 1851. The Southern Hemisphere had a slightly below average season. The Atlantic ordinarily accounts for just 13% of global cyclone activity, but accounted for 28% in 2010--the greatest proportion since accurate tropical cyclone records began in the 1970s.

A common theme of many recent publications on the future of tropical cyclones globally in a warming climate is that the total number of these storms will decrease, but the strongest storms will get stronger. For example, a 2010 review paper published in Nature Geosciences concluded that the strongest storms would increase in intensity by 2 - 11% by 2100, but the total number of storms would fall by 6 - 34%. It is interesting that 2010 saw the lowest number of global tropical cyclones on record, but an average number of very strong Category 4 and 5 storms (the 25-year average is 13 Category 4 and 5 storms, and 2010 had 14.) Fully 21% of 2010's tropical cyclones reached Category 4 or 5 strength, versus just 14% during the period 1983 - 2007. Most notably, in 2010 we had Super Typhoon Megi. Megi's sustained winds cranked up to a ferocious 190 mph and its central pressure bottomed out at 885 mb on October 16, making it the 8th most intense tropical cyclone in world history. Other notable storms in 2010 included the second strongest tropical cyclone on record in the Arabian Sea (Category 4 Cyclone Phet in June), and the strongest tropical cyclone ever to hit Myanmar/Burma (October's Tropical Cyclone Giri, an upper end Category 4 storm with 155 mph winds.)


Figure 9. Visible satellite image of Tropical Cyclone Phet on Thursday, June 3, 2010. Record heat over southern Asia in May helped heat up the Arabian Sea to 2°C above normal, and the exceptionally warm SSTs helped fuel Tropical Cyclone Phet into the second strongest tropical cyclone ever recorded in the Arabian Sea. Phet peaked at Category 4 strength with 145 mph winds, and killed 44 people and did $700 million in damage to Oman. Only Category 5 Cyclone Gonu of 2007 was a stronger Arabian Sea cyclone.

A hyperactive Atlantic hurricane season: 3rd busiest on record
Sea surface temperatures that were the hottest on record over the main development region for Atlantic hurricanes helped fuel an exceptionally active 2010 Atlantic hurricane season. The nineteen named storms were the third most since 1851; the twelve hurricanes of 2010 ranked second most. Three major hurricanes occurred in rare or unprecedented locations. Julia was the easternmost major hurricane on record, Karl was the southernmost major hurricane on record in the Gulf of Mexico, and Earl was the 4th strongest hurricane so far north. The formation of Tomas so far south and east so late in the season (October 29) was unprecedented in the historical record; no named storm had ever been present east of the Lesser Antilles (61.5°W) and south of 12°N latitude so late in the year. Tomas made the 2010 the 4th consecutive year with a November hurricane in the Atlantic--an occurrence unprecedented since records began in 1851.


Figure 10. Hurricane Earl as seen from the International Space Station on Thursday, September 2, 2010. Image credit: NASA astronaut Douglas Wheelock.

A rare tropical storm in the South Atlantic
A rare tropical storm formed in the South Atlantic off the coast of Brazil on March 10 - 11, and was named Tropical Storm Anita. Brazil has had only one landfalling tropical cyclone in its history, Cyclone Catarina of March 2004, one of only seven known tropical or subtropical cyclones to form in the South Atlantic, and the only one to reach hurricane strength. Anita of 2010 is probably the fourth strongest tropical/subtropical storm in the South Atlantic, behind Hurricane Catarina, an unnamed February 2006 storm that may have attained wind speeds of 65 mph, and a subtropical storm that brought heavy flooding to the coast of Uruguay in January 2009. Tropical cyclones rarely form in the South Atlantic Ocean, due to strong upper-level wind shear, cool water temperatures, and the lack of an initial disturbance to get things spinning (no African waves or Intertropical Convergence Zone.)


Figure 11. Visible satellite image of the Brazilian Tropical Storm Anita.

Strongest storm in Southwestern U.S. history
The most powerful low pressure system in 140 years of record keeping swept through the Southwest U.S. on January 20 - 21, 2010, bringing deadly flooding, tornadoes, hail, hurricane force winds, and blizzard conditions. The storm set all-time low pressure records over roughly 10 - 15% of the U.S.--southern Oregon, California, Nevada, Arizona, and Utah. Old records were broken by a wide margin in many locations, most notably in Los Angeles, where the old record of 29.25" set January 17, 1988, was shattered by .18" (6 mb). The record-setting low spawned an extremely intense cold front that swept through the Southwest. Winds ahead of the cold front hit sustained speeds of hurricane force--74 mph--at Apache Junction, 40 miles east of Phoenix, and wind gusts as high as 94 mph were recorded in Ajo, Arizona. High winds plunged visibility to zero in blowing dust on I-10 connecting Phoenix and Tucson, closing the Interstate.


Figure 12. Ominous clouds hover over Arizona's Superstition Mountains during Arizona's most powerful storm on record, on January 21, 2010. Image credit: wunderphotographer ChandlerMike.

Strongest non-coastal storm in U.S. history
A massive low pressure system intensified to record strength over northern Minnesota on October 26, 2010, resulting in the lowest barometric pressure readings ever recorded in the continental United States, except for from hurricanes and nor'easters affecting the Atlantic seaboard. The 955 mb sea level pressure reported from Bigfork, Minnesota beat the previous low pressure record of 958 mb set during the Great Ohio Blizzard of January 26, 1978. Both Minnesota and Wisconsin set all time low pressure readings during the October 26 storm, and International Falls beat their previous low pressure record by nearly one-half inch of mercury--a truly amazing anomaly. The massive storm spawned 67 tornadoes over a four-day period, and brought sustained winds of 68 mph to Lake Superior.


Figure 13. Visible satellite image of the October 26, 2010 superstorm taken at 5:32pm EDT. At the time, Bigfork, Minnesota was reporting the lowest pressure ever recorded in a U.S. non-coastal storm, 955 mb. Image credit: NASA/GSFC.

Weakest and latest-ending East Asian monsoon on record
The summer monsoon over China's South China Sea was the weakest and latest ending monsoon on record since detailed records began in 1951, according to the Beijing Climate Center. The monsoon did not end until late October, nearly a month later than usual. The abnormal monsoon helped lead to precipitation 30% - 80% below normal in Northern China and Mongolia, and 30 - 100% above average across a wide swath of Central China. Western China saw summer precipitation more than 200% above average, and torrential monsoon rains triggered catastrophic landslides that killed 2137 people and did $759 million in damage. Monsoon floods in China killed an additional 1911 people, affected 134 million, and did $18 billion in damage in 2010, according to the WHO Collaborating Centre for Research on the Epidemiology of Disasters (CRED). This was the 2nd most expensive flooding disaster in Chinese history, behind the $30 billion price tag of the 1998 floods that killed 3656 people. China had floods in 1915, 1931, and 1959 that killed 3 million, 3.7 million, and 2 million people, respectively, but no damage estimates are available for these floods.


Figure 14. Paramilitary policemen help evacuate residents from Wanjia village of Fuzhou City, East China's Jiangxi province, June 22, 2010. Days of heavy rain burst the Changkai Dike of Fu River on June 21, threatening the lives of 145,000 local people. Image credit: Xinhua.

No monsoon depressions in India's Southwest Monsoon for 2nd time in 134 years
The Southwest Monsoon that affects India was fairly normal in 2010, bringing India rains within 2% of average. Much of the rain that falls in India from the monsoon typically comes from large regions of low pressure that form in the Bay of Bengal and move westwards over India. Typically, seven of these lows grow strong and well-organized enough to be labelled monsoon depressions, which are similar to but larger than tropical depressions. In 2010, no monsoon depressions formed--the only year besides 2002 (since 1877) that no monsoon depressions have been observed.

The Pakistani flood: most expensive natural disaster in Pakistan's history
A large monsoon low developed over the Bay of Bengal in late July and moved west towards Pakistan, creating a strong flow of moisture that helped trigger the deadly Pakistan floods of 2010. The floods were worsened by a persistent and unusually-far southwards dip in the jet stream, which brought cold air and rain-bearing low pressure systems over Pakistan. This unusual bend in the jet stream also helped bring Russia its record heat wave and drought. The Pakistani floods were the most expensive natural disaster in Pakistani history, killing 1985 people, affecting 20 million, and doing $9.5 billion in damage.


Figure 15. Local residents attempt to cross a washed-out road during the Pakistani flood catastrophe of 2010. Image credit: Pakistan Meteorology Department.

The Russian heat wave and drought: deadliest heat wave in human history
A scorching heat wave struck Moscow in late June 2010, and steadily increased in intensity through July as the jet stream remained "stuck" in an unusual loop that kept cool air and rain-bearing low pressure systems far north of the country. By July 14, the mercury hit 31°C (87°F) in Moscow, the first day of an incredible 33-day stretch with a maximum temperatures of 30°C (86°F) or higher. Moscow's old extreme heat record, 37°C (99°F) in 1920, was equaled or exceeded five times in a two-week period from July 26 - August 6 2010, including an incredible 38.2°C (101°F) on July 29. Over a thousand Russians seeking to escape the heat drowned in swimming accidents, and thousands more died from the heat and from inhaling smoke and toxic fumes from massive wild fires. The associated drought cut Russia's wheat crop by 40%, cost the nation $15 billion, and led to a ban on grain exports. The grain export ban, in combination with bad weather elsewhere in the globe during 2010 - 2011, caused a sharp spike in world food prices that helped trigger civil unrest across much of northern Africa and the Middle East in 2011. At least 55,000 people died due to the heat wave, making it the deadliest heat wave in human history. A 2011 NOAA study concluded that "while a contribution to the heat wave from climate change could not be entirely ruled out, if it was present, it played a much smaller role than naturally occurring meteorological processes in explaining this heat wave's intensity." However, they noted that the climate models used for the study showed a rapidly increasing risk of such heat waves in western Russia, from less than 1% per year in 2010, to 10% or more per year by 2100.


Figure 16. Smoke from wildfires burning to the southeast of Moscow on August 12, 2010. Northerly winds were keeping the smoke from blowing over the city. Image credit: NASA.

Record rains trigger Australia's most expensive natural disaster in history
Australia's most expensive natural disaster in history is now the Queensland flood of 2010 - 2011, with a price tag as high as $30 billion. At least 35 were killed. The Australian Bureau of Meteorology's annual summary reported, "Sea surface temperatures in the Australian region during 2010 were the warmest value on record for the Australian region. Individual high monthly sea surface temperature records were also set during 2010 in March, April, June, September, October, November and December. Along with favourable hemispheric circulation associated with the 2010 La Niña, very warm sea surface temperatures contributed to the record rainfall and very high humidity across eastern Australia during winter and spring." In 2010, Australia had its wettest spring (September - November) since records began 111 years ago, with some sections of coastal Queensland receiving over 4 feet (1200 mm) of rain. Rainfall in Queensland and all of eastern Australia in December was the greatest on record, and the year 2010 was the rainiest year on record for Queensland. Queensland has an area the size of Germany and France combined, and 3/4 of the region was declared a disaster zone.


Figure 17. The airport, the Bruce Highway, and large swaths of Rockhampton, Australia, went under water due to flooding from the Fitzroy River on January 9, 2011. The town of 75,000 was completely cut off by road and rail, and food, water and medicine had to be brought in by boat and helicopter. Image credit: NASA.

Heaviest rains on record trigger Colombia's worst flooding disaster in history
The 2010 rainy-season rains in Colombia were the heaviest in the 42 years since Colombia's weather service was created and began taking data. Floods and landslides killed 528, did $1 billion in damage, and left 2.2 million homeless, making it Colombia's most expensive, most widespread, and 2nd deadliest flooding disaster in history. Colombia's president Juan Manuel Santos said, "the tragedy the country is going through has no precedents in our history."


Figure 18. A daring rescue of two girls stranded in a taxi by flash flood waters Barranquilla, northern Colombia on August 14, 2010.

Tennessee's 1-in-1000 year flood kills 30, does $2.4 billion in damage
Tennessee's greatest disaster since the Civil War hit on May 1 - 2, 2010, when an epic deluge of rain brought by an "atmospheric river" of moisture dumped up to 17.73" of rain on the state. Nashville had its heaviest 1-day and 2-day rainfall amounts in its history, with a remarkable 7.25" on May 2, breaking the record for most rain in a single day. Only two days into the month, the May 1 - 2 rains made it the rainiest May in Nashville's history. The record rains sent the Cumberland River in downtown Nashville surging to 51.86', 12' over flood height, and the highest level the river has reached since a flood control project was completed in the early 1960s. At least four rivers in Tennessee reached their greatest flood heights on record. Most remarkable was the Duck River at Centreville, which crested at 47', a full 25 feet above flood stage, and ten feet higher than the previous record crest, achieved in 1948.


Figure 19. A portable classroom building from a nearby high school floats past submerged cars on I-24 near Nashville, TN on May 1, 2010. One person died in the flooding in this region of I-24. Roughly 200 - 250 vehicles got submerged on this section of I-24, according to wunderphotographer laughingjester, who was a tow truck operator called in to clear out the stranded vehicles.

When was the last time global weather was so extreme?
It is difficult to say whether the weather events of a particular year are more or less extreme globally than other years, since we have no objective global index that measures extremes. However, we do for the U.S.--NOAA's Climate Extremes Index (CEI), which looks at the percentage area of the contiguous U.S. experiencing top 10% or bottom 10% monthly maximum and minimum temperatures, monthly drought, and daily precipitation. The Climate Extremes Index rated 1998 as the most extreme year of the past century in the U.S. That year was also the warmest year since accurate records began in 1895, so it makes sense that the warmest year in Earth's recorded history--2010--was also probably one of the most extreme for both temperature and precipitation. Hot years tend to generate more wet and dry extremes than cold years. This occurs since there is more energy available to fuel the evaporation that drives heavy rains and snows, and to make droughts hotter and drier in places where storms are avoiding. Looking back through the 1800s, which was a very cool period, I can't find any years that had more exceptional global extremes in weather than 2010, until I reach 1816. That was the year of the devastating "Year Without a Summer"--caused by the massive climate-altering 1815 eruption of Indonesia's Mt. Tambora, the largest volcanic eruption since at least 536 A.D. It is quite possible that 2010 was the most extreme weather year globally since 1816.

Where will Earth's climate go from here?
The pace of extreme weather events has remained remarkably high during 2011, giving rise to the question--is the "Global Weirding" of 2010 and 2011 the new normal? Has human-caused climate change destabilized the climate, bringing these extreme, unprecedented weather events? Any one of the extreme weather events of 2010 or 2011 could have occurred naturally sometime during the past 1,000 years. But it is highly improbable that the remarkable extreme weather events of 2010 and 2011 could have all happened in such a short period of time without some powerful climate-altering force at work. The best science we have right now maintains that human-caused emissions of heat-trapping gases like CO2 are the most likely cause of such a climate-altering force.

Human-caused climate change has fundamentally altered the atmosphere by adding more heat and moisture. Observations confirm that global atmospheric water vapor has increased by about 4% since 1970, which is what theory says should have happened given the observed 0.5°C (0.9°F) warming of the planet's oceans during the same period. Shifts of this magnitude are capable of significantly affecting the path and strength of the jet stream, behavior of the planet's monsoons, and paths of rain and snow-bearing weather systems. For example, the average position of the jet stream retreated poleward 270 miles (435 km) during a 22-year period ending in 2001, in line with predictions from climate models. A naturally extreme year, when embedded in such a changed atmosphere, is capable of causing dramatic, unprecedented extremes like we observed during 2010 and 2011. That's the best theory I have to explain the extreme weather events of 2010 and 2011--natural extremes of El Niño, La Niña and other natural weather patterns combined with significant shifts in atmospheric circulation and the extra heat and atmospheric moisture due to human-caused climate change to create an extraordinary period of extreme weather. However, I don't believe that years like 2010 and 2011 will become the "new normal" in the coming decade. Many of the flood disasters in 2010 - 2011 were undoubtedly heavily influenced by the strong El Niño and La Niña events that occurred, and we're due for a few quiet years without a strong El Niño or La Niña. There's also the possibility that a major volcanic eruption in the tropics or a significant quiet period on the sun could help cool the climate for a few years, cutting down on heat and flooding extremes (though major eruptions tend to increase drought.) But the ever-increasing amounts of heat-trapping gases humans are emitting into the air puts tremendous pressure on the climate system to shift to a new, radically different, warmer state, and the extreme weather of 2010 - 2011 suggests that the transition is already well underway. A warmer planet has more energy to power stronger storms, hotter heat waves, more intense droughts, heavier flooding rains, and record glacier melt that will drive accelerating sea level rise. I expect that by 20 - 30 years from now, extreme weather years like we witnessed in 2010 will become the new normal.

Finally, I'll leave you with a quote from Dr. Ricky Rood's climate change blog, in his recent post,Changing the Conversation: Extreme Weather and Climate: "Given that greenhouse gases are well known to hold energy close to the Earth, those who deny a human-caused impact on weather need to pose a viable mechanism of how the Earth can hold in more energy and the weather not be changed. Think about it."

Related blog posts
U.S. had most extreme spring on record for precipitation in 2011
Is the U.S. climate getting more extreme?

Jeff Masters

Extreme Weather Climate Change

Updated: 01:35 PM GMT am 16. April 2013

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Floods overwhelm North Dakota levees; floods kill 175 in China

By: JeffMasters, 03:33 PM GMT am 23. Juni 2011

Flood waters from North Dakota's Souris River are pouring over the levees protecting Minot, North Dakota today, and flood heights are expected to rise to the highest levels in recorded history tonight. The Lake Darling flood control reservoir located about 15 miles upstream from Minot is full to overflowing, and record releases of water are occurring to prevent the lake's dam from over-topping. By this weekend, the Army Corps of Engineers will open the dam's flood gates to a maximum flow rate of 20,000 cubic feet per second, which is roughly double the flow rate that the levees in Minot can handle. Water began flowing over the levees yesterday, forcing the mandatory evacuation of 12,000 residents. By Sunday, water levels on the Souris River are expected to peak at four feet above the previous all-time flood height, set in 1881. Torrential rainfall in Canada on Sunday and Monday, combined with very heavy rainfall and snow melt over North Dakota over the past month, are responsible for the record flood. The Souris River Basin near the Rafferty Dam in Saskatchewan received four to seven inches of rain Sunday into Monday. Flood heights along the Souris River near the Canadian border upstream from Minot are already two feet above the previous all-time highest mark, and that pulse of water is now arriving in Minot. The unprecedented flood is expected to keep much of Minot underwater for at least two weeks. Fortunately, no new heavy rains are expected over the next five days, though up to 1/2" of rain could fall over portions of the Souris River watershed.


Figure 1. Still frame from a Youtube video of the Souris River in Minot, North Dakota flowing over the levees in that town. The video was shot on Wednesday June 22, 2011, from a North Dakota National Guard helicopter.


Figure 2. Observed (blue line) and forecast (green line) stage of the Souris River in Minot, North Dakota. The river is currently at its 3rd highest level on record, and is expected to rise above the record flood stage of 1558' tonight. The record was set back in 1881. Image credit: NOAA AHPS.

Record rains in China kill 175, do $5 billion in damage
Torrential rains triggered severe flooding in eastern China this week, with the death toll for June floods now standing at 175, with 86 people missing. Ironically, the same region experienced severe drought at the beginning of June. The estimated $5 billion in damage from the floods would make 2011 the third most expensive year for floods in China in the past decade. This year is the second consecutive year floods have caused exceptional damage in China. Last year, Western China saw summer precipitation more than 200% above average, and torrential monsoon rains triggered catastrophic landslides that killed 2137 people and did $759 million in damage. Monsoon floods in China killed an additional 1911 people, affected 134 million, and did $18 billion in damage in 2010, according to the WHO Collaborating Centre for Research on the Epidemiology of Disasters (CRED). This was the 2nd most expensive flooding disaster in Chinese history, behind the $30 billion price tag of the 1998 floods that killed 3656 people. China had floods in 1915, 1931, and 1959 that killed 3 million, 3.7 million, and 2 million people, respectively, but no damage estimates are available for these floods. During the period 2000 - 2009, China averaged $3.7 billion in damage and 674 deaths per year due to floods and landslides, according to the WHO Collaborating Centre for Research on the Epidemiology of Disasters. This does not include the toll from typhoons. Speaking of typhoons, Tropical Storm Meari, currently located a few hundred miles east of the Philippines' Luzon Island, is expected to track north-northwestwards towards China today and Friday. By Saturday, Meari is expected to be a Category 1 typhoon, and will spread heavy rains over eastern China, worsening the flooding situation there--though the heaviest rains will likely remain offshore.



Figure 3. Rainfall amounts in excess of 18 inches (450 mm) fell in Eastern China southeast of Shanghai in a 1-week period, June 13 -19, 2011. A China Daily report from June 18 described the rains in parts of Zhejiang Province as unprecedented. High waters broke 100-meter (300-foot) holes in levees, inundating nearby villages. Some homes were buried in 3 meters (10 feet) of water. This image is based on data from the Multisatellite Precipitation Analysis produced at Goddard Space Flight Center, which estimates rainfall by combining measurements from many satellites and calibrating them using rainfall measurements from the Tropical Rainfall Measuring Mission (TRMM) satellite. Image credit: NASA.



Figure 4. Visitors watch as water gushes out from the Xiaolangdi Reservoir on the Yellow River in Central China's Henan province, June 22, 2011. Image credit: Xinhua.

The Atlantic is quiet
The Atlantic is quiet, but several models, including the NOGAPS and GFS, are predicting that a tropical disturbance capable of becoming a tropical depression could form in the southern Gulf of Mexico in the Bay of Campeche Tuesday or Wednesday. There will be a strong ridge of high pressure over the Gulf next week, which would tend to keep any storm that might form far to the south, with impacts limited to Mexico and perhaps South Texas.

Jeff Masters

Flood

Updated: 03:53 PM GMT am 23. Juni 2011

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Record flooding in North Dakota forces evacuation of 11,000

By: JeffMasters, 02:10 PM GMT am 22. Juni 2011

A 1-in-100 to 1-in-200 year flood is in progress in North Dakota along the Souris River, where flood heights never seen in recorded history are putting unprecedented pressure on the river's levees. The Lake Darling flood control reservoir located about 15 miles upstream from Minot, North Dakota, the state's 4th largest city, is full to overflowing. Record releases of water are occurring to prevent the lake's dam from overtopping. A mandatory evacuation of 11,000 residents from Minot is underway, and must be completed before Thursday morning, when water levels on the Souris River are expected to rise several feet above the previous all-time flood height, set in 1881. Massive rainfall in Canada on Sunday and Monday, combined with very heavy rainfall and snow melt over North Dakota over the past month, are responsible for the record flood. The Souris River Basin near the Rafferty Dam in Saskatchewan received four to seven inches of rain Sunday into Monday. Flood heights along the Souris River near the Canadian border upstream from Minot are already almost a foot above the previous all-time highest mark, and all that water will arrive in Minot beginning on Thursday, likely overwhelming the city's levees and flooding large portions of the city for two or more weeks.


Figure 1. Observed (blue line) and forecast (green line) stage of the Souris River in Minot, North Dakota. The river is currently at its 4th highest level on record, and is expected to rise above the record flood stage of 1558' Thursday night. The record was set back in 1881. Image credit: NOAA AHPS.


Figure 2. The Souris River (in pink) is part of the Red River drainage basin. Image credit: Wikipedia.

Heavy rains this week over the neighboring Missouri River watershed forced the Army Corps of Engineers today to increase the flow rate at the key Gavins Point Dam to a record 160,000 cubic feet per second. The dam was already releasing water at more than double the previous record flow rate, and the increased flow is expected to raise flood heights by 0.3 - 0.7 feet along the Missouri River from Omaha to Kansas City. There have already been two levee failures and two places where levees have been overtopped along the Missouri River this month, resulting in large-scale flooding of low-lying farmlands. "This continues to be a very dynamic situation and dangerous at the same time," said Brig. Gen. John McMahon, commander of the Northwestern Division of the Army Corps of Engineers.

The Atlantic is quiet
The Atlantic is quiet, but several models, including the NOGAPS and GFS, are predicting that a tropical disturbance capable of becoming a tropical depression could form near Mexico's Yucatan Peninsula about seven days from now. In the Eastern Pacific, Hurricane Beatriz is gone, after being torn apart by Mexico's high mountains during landfall. Beatriz is responsible for at least three deaths in Mexico.

Jeff Masters

Flood

Updated: 02:12 PM GMT am 22. Juni 2011

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Hurricane Beatriz slams into Mexico; heavy rains, tornadoes hit the Midwest

By: JeffMasters, 02:34 PM GMT am 21. Juni 2011

Hurricane Beatriz plowed into the Pacific coast of Mexico near La Fortuna this morning as a Category 1 hurricane with 90 mph winds, bringing very heavy rains and mudslides to a 200-mile stretch of coast. Acapulco reported 5.20" of rain yesterday, and one injury due to a falling free. Hurricane-force winds extend outwards 25 miles from the center of Beatriz, and these winds are likely to cause moderate damage along a 200-mile stretch of the Mexican coast today as the storm moves northwestwards towards Cabo Corrientes. However, the primary threat from the storm will be heavy rain, and the expected rains of 6 - 12" are likely to cause very dangerous flooding and mudslides today and Wednesday morning. Satellite loops reveal that Beatriz weakened significantly over the past few hours, once the eye moved over land. The mountainous terrain of coastal Mexico will continue to tear up the storm today, and Beatriz will likely be a weak tropical storm by the time it moves back out to sea on Wednesday.


Figure 1. Morning satellite image of Hurricane Beatriz over the Pacific coast of Mexico taken at 9:30am EDT June 21, 2011. Image credit: NASA/GSFC.

Tornadoes, heavy rain slam the Midwest
Severe thunderstorms rumbled through a wide section of the Midwest yesterday, generating numerous tornadoes, baseball-sized hail, and heavy flooding rains. The storm also brought heavy snow to the mountains of Colorado above 9,500 feet, an unusual occurrence for so late in June. NOAA's Storm Prediction Center logged 43 preliminary tornado reports yesterday in Nebraska, Kansas, Iowa, Texas, and North Dakota. The tornadoes mostly avoided populated areas, and only sporadic damage was reported. Perhaps the most significant impact of the storm was the large area of 1 - 4 inches of rain it dropped on Nebraska and South Dakota. This rain will run off into the Missouri River, further aggravating the flooding that has breached two levees and overtopped two other levees in the past week. The large, slow-moving low pressure system responsible for the rains and severe weather will bring additional heavy rains of 1 - 3 inches over portions of the Missouri River watershed today, and will touch off a new round of severe weather today and Wednesday as the storm progresses slowly eastwards. However, the Storm Prediction Center is issuing only their "Slight Risk" forecast for severe weather for both days.


Figure 2. Radar reflectivity image of a supercell thunderstorm with a classic hook echo. The storm spawned a tornado that hit Elm Creek, Nebraska yesterday. The tornado ripped the roofs off of several houses and tore down power lines.

The Atlantic is quiet
The Atlantic is quiet, with no tropical cyclones predicted over the next seven days by the reliable computer models.

Jeff Masters

Tornado Hurricane

Updated: 02:37 PM GMT am 21. Juni 2011

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Hurricane warnings for Mexico; tornadoes and floods for the Midwest U.S.

By: JeffMasters, 02:26 PM GMT am 20. Juni 2011

The outer spiral bands of intensifying Tropical Storm Beatriz have reached the coast of Mexico between Acapulco and Puerto Vallarta, and a hurricane warning is now in effect for the coast of Mexico from Zihuatanejo northwestward to La Fortuna. Beatriz is headed to the northwest under the influence of the large trough of low pressure over the Midwest U.S. that is causing severe weather and flooding rains there. As Beatriz nears the coast Tuesday morning, the trough may have progressed far enough eastwards so that Beatriz wil miss making a direct hit on the coast, and instead turn west and move out to sea as a ridge of high pressure builds in. Regardless of whether the core of the storm makes landfall or not, the major threat from Beatriz will be heavy rains. Rainfall amounts of 4 - 8 inches will be common along the coast, and up to a foot of rain is likely in some mountainous regions, causing significant flooding and dangerous mudslides. NHC is giving Manzanillo a 5% chance of experiencing hurricane-force winds of 74 mph or greater; these odds drop to just 1% for Puerto Vallarta, and 8% for Barra Navidad. With ocean temperatures between 29 - 30°C and wind shear predicted to drop to 10 knots later today, there is no reason why Beatriz couldn't intensify into a Category 1 hurricane by Tuesday. NHC is giving a 15% chance the Beatriz could intensify into a Category 2 or stronger hurricane. A hurricane hunter aircraft is scheduled to visit Beatriz this afternoon to gauge its strength. Satellite loops reveal that Beatriz has become more organized this morning, and Microwave satellite imagery indicates that Beatriz has built about 50% of an eyewall. Once this process is complete, more rapid strengthening is likely.


Figure 1. Morning satellite image of Tropical Storm Beatriz taken at 8am EDT June 20, 2011. Image credit: NASA/GSFC.

Significant severe weather outbreak and flooding rains possible today in the Midwest
Severe thunderstorms developed along a warm front stretching from Eastern Colorado through Nebraska and into Iowa and Wisconsin last night. The result was an active evening with numerous severe thunderstorm, tornado, and flash flood warnings. Hail to the size of baseballs and winds to 77 miles per hour were reported at Champion and Imperial, Nebraska. Many other locations reported large hail and winds greater than 60 miles per hour, and NOAA's Storm Prediction Center logged thirteen preliminary tornado reports in Nebraska, Colorado, Iowa, and Wisconsin. The large, slow-moving low pressure system responsible for yesterday's severe weather will touch off a new round of severe weather this afternoon, and the Storm Prediction Center has placed Eastern Nebraska, Western Iowa, and portions of three other states in their "Moderate Risk" area for severe weather. Baseball and softball-sized hail is likely in some of the stronger supercell thunderstorms that form, and there is also the risk of a few strong EF-2 and EF-3 tornadoes.



Figure 2. Today's severe risk outlook from NOAA's Storm Prediction Center.

Also of concern is the large area of 2 - 4 inches of rain this storm is likely to bring to the Missouri River watershed this week. As I discussed in detail in Friday's post, the flood control system on the Missouri River is being strained beyond its designed limits, and this week's rains are likely to worsen existing flooding and potentially cause new levee breaches on the river.


Figure 3. Predicted rainfall for the coming five days (top image) shows that a large region of 2 - 4 inches is expected over the Missouri River watershed (bottom image.) Image credit: NOAA/HPC and Wikipedia.

Critical fire conditions to give Arizona a break this week
Powerful southwest winds gusting to 50 mph affected much of Arizona yesterday, producing some of the worst fire conditions the parched state has seen all year. Sierra Vista in Southeast Arizona experienced sustained winds of 31 mph, gusting to 50 mph yesterday, causing a major spread of the dangerous Monument Fire. With air temperatures of 94° and a humidity of just 13%, it was a tough day for firefighting. The 33-square mile fire jumped fire control lines and surged into the town, forcing the evacuation of thousands of people. However, after a difficult 4-day stretch of critical fire conditions, the winds will give Arizona a break today. Winds under 10 mph are expected in Sierra Vista, and strong winds and critical fire conditions are not expected in the state until at least Friday, according to NOAA's Storm Prediction Center. This respite should give firefighters a chance to gain the upper hand on the three significant fires burning in the eastern part of the state. Arizona's largest fire on record, the massive 800-square mile Wallow Fire, should be mostly contained by the end of the week if this forecast holds up. According to our weather historian, Christopher C. Burt, the Wallow Fire is a long way from being the largest fire in U.S. history. That distinction belongs to the great Peshtigo Fire of 1871, which burned 5,938 square miles of Wisconsin and Michigan.

The Atlantic is quiet
The Atlantic is quiet, with no tropical cyclones predicted over the next seven days by the reliable computer models.

Jeff Masters

Tornado Flood Hurricane

Updated: 02:39 PM GMT am 20. Juni 2011

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Missouri River flood hits unprecedented flow rates

By: JeffMasters, 03:18 PM GMT am 17. Juni 2011

The most expensive tornado/severe weather disaster in American history is the great May 21 - 26, 2011 storm that spawned the Joplin, Missouri EF-5 tornado. According to catastrophe modeling firm AIR Worldwide, insured damages from that storm will amount to $4 - $7 billion, the greatest damages ever for a spring severe weather outbreak. However, the damages from the huge, slow-moving low pressure system that spawned the Joplin tornado have not yet been fully realized. The powerful storm pumped huge quantities of warm, moisture-laden air from the Gulf of Mexico northwestwards into Montana, where the moisture condensed into record-breaking heavy rain and snow. In portions of eastern Montana, the storm brought a year's worth of precipitation in a week, swelling the tributaries of the Missouri River to unprecedented heights. Billings, Montana recorded 9.54" of precipitation in May, its single wettest month on record, and not far from its annual average precipitation of 14.5". A great 100-year flood has arrived along the Missouri River and its tributaries from Montana to Nebraska. Record spring rains, combined with snow melt from record or near-record winter and spring snows, brought the Missouri River at Williston, North Dakota to 30' today (June 17), two feet above the record crest set in 1912. Tributaries to the Missouri, such as the North Platte River in Nebraska, are also flooding at all-time record heights. With warm summer temperatures and 2 - 5" of rainfall expected over much of the area during the coming week, snow melt and rain runoff will swell area rivers even further, creating an even more dangerous flood.

Flooding along the Missouri River has already broken two levees and closed two portions of I-29, a key trucking route that extends from Kansas City through Iowa, South Dakota and North Dakota to the Canadian border. A 20-mile stretch between Council Bluffs and the Missouri Valley area is closed, as well as a 22-mile section in southwest Iowa and northwest Missouri, causing significant disruptions to the trucking industry.


Figure 1. Satellite image taken at 5:45pm CDT May 22, 2011, when the Joplin, Missouri tornado was occurring. The counter-clockwise flow of air around the spiraling low pressure system that caused the Joplin tornado drew large quantities of Gulf of Mexico air into Montana, creating record-breaking rains. Image credit: NASA/GSFC.



Figure 2. Levee breach along the Missouri River levee L-575 near Hamburg, Iowa, on June 14, 2011. The town of Hamburg is being protected by a new temporary levee. So far, only farmland has flooded. Image credit: U.S. Army Corps of Engineers.

Army Corps cranks up water releases on Missouri River dams to double the previous record
Six flood control dams lie on the Missouri River between eastern Montana and Sioux City, Iowa; these dams were built between 1940 and 1964. As water from this spring's record precipitation have flowed into the Missouri River basin, the reservoirs behind these dams have risen to record levels. On May 31, the Army Corps of Engineers was forced to open the the spillway gates on the massive Garrison Dam, 50 miles northwest of Bismark, North Dakota. It was the first time since the dam was built in 1955 that the spillway gates were opened. (Remarkably, during 2007 and early 2008, Lake Sakakawea water levels behind Garrison Dam were the lowest since the dam was built--46 feet below the current level--thanks to a decade-long drought.) On June 3, as the record flood progressed downstream, the spillway gates on the Big Bend Dam opened for the first time since that dam was completed in 1964. This week, the Army Corps of Engineers increased water flowing through all six dams to more than double the previous highs set during the floods of 1975 and 1997. The flow rates are now a massive 150,000 cubic feet per second, 1.5 times greater than the typical flow of Niagara Falls. These extreme flow rates will need to be maintained into at least mid-August, and are expected to severely strain levees on the Missouri River as it flows through North Dakota, South Dakota, Nebraska, Iowa, Missouri, and Kansas. According to a press conference put on by NWS and the Army Corps last week, the Missouri River flood control system is based on an 1881 estimate of the maximum amount of water an extreme flood season could generate--40 million acre-feet of water during the spring and summer flood season. However, this year's flood is expected to pump 42 - 43 million acre feet of water into the system, stressing it beyond its designed limits. In May alone, the Missouri River basin just upstream from Sioux City, Iowa, received 10.2 million acre feet of water, more than 25% above the previous May record of 7.2 million acre feet set in 1995. Additional levee failures along the Missouri are likely this summer, particularly if widespread heavy summer rains occur.


Figure 3. The Oahe Reservoir Stilling Basin north of Pierre, S.D., on June 5, 2011. The U.S. Army Corps of Engineers increased the water releases from the Oahe Dam into the stilling basin to a record 147,000 cubic feet per second (cfs) of water release on June 8. The previous record was 59,000 cfs in 1997. Image credit: U.S. Army Corps of Engineers/ Carlos J. Lazo

Four-day period of critical fire conditions expected in the Southwest
Powerful southwest winds of 20 - 30 mph, gusting to 40 mph will continue through Saturday in Eastern Arizona and western New Mexico, making progress containing the region's severe fires difficult. Even worse conditions are begin predicted for Sunday, when NOAA's Storm Prediction Center forecasts forecasts that wind gusts up to 50 mph will occur. With hot conditions and humidity values below 10%, these are likely to be among the worst fire conditions the region has seen this year.

While the exceptional drought gripping Arizona is largely to blame for terrible fire conditions this year, unusually windy and dry weather has also been a significant factor. These windy and dry conditions have been caused, in part, by a stronger-than-average jet stream over the region. According to the National Weather Service in Phoenix, the period April-May 2011 was the 11th windiest and had the 6th lowest average relative humidity value on record in Phoenix. Combined, it was the 3rd windiest-driest April-May on record.

Our weather historian, Christopher C. Burt, has an interesting post on The Worst Wild Fires in World History. Arizona's Wallow Fire, at 750 square miles, has a long way to go before matching the largest fire in U.S. history, the great Peshtigo Fire of 1871. That fire burned 5,938 square miles of Wisconsin and Michigan.

Tallahassee hits 105°, their hottest day on record
On Wednesday June 15 at 307 PM EDT, the Tallahassee Regional Airport in Florida recorded a high temperature of 105 degrees. This temperature breaks the previous all time high temperature record for Tallahassee of 104 degrees, set most recently on June 20th 1933. The period of record for Tallahassee dates back to 1892.

The Atlantic is quiet
The Atlantic is quiet, with no tropical cyclones predicted over the next seven days by the reliable computer models. However, the GFS model predicts that moisture will begin increasing early next week in the western Gulf of Mexico, and a tropical disturbance could form next week in the Gulf, bringing much-needed rains to the coast of Texas. Droughts of the magnitude of the current Texas drought are hard to break, though, so I'd like to see more support from the models before believing in this forecast.

Have a great weekend everyone! I'll be back Monday with a new post.

Jeff Masters

Flood

Updated: 12:19 AM GMT am 20. Juni 2011

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Globe has 10th warmest May on record; critical fire conditions for Arizona

By: JeffMasters, 02:27 PM GMT am 16. Juni 2011

May 2011 was the globe's 10th warmest May on record, according to the National Oceanic and Atmospheric Administration (NOAA) National Climatic Data Center (NCDC). May 2011 global ocean temperatures were the 11th warmest on record, and land temperatures were the 6th warmest on record. Sea surface temperatures (SSTs) in the Atlantic Main Development Region (MDR) for hurricanes from the Caribbean to the coast of Africa between 10°N and 20°N were 0.6°C above average, the 7th highest SSTs of the past 100 years. Global satellite-measured temperatures for the lowest 8 km of the atmosphere were above average, the 8th or 12th warmest in the 34-year record, according to Remote Sensing Systems and the University of Alabama Huntsville (UAH).


Figure 1. Departure of temperature from average for May 2011. Image credit: National Climatic Data Center (NCDC).

Unusual global extremes in May and spring 2011
As I discussed in yesterday's post, during the spring period of March, April, and May 2011, 46% of the U.S. had abnormally (top 10%) wet or dry conditions--the greatest such area during the 102-year period of record. On average, just 21% of the country has exceptionally wet conditions or exceptionally dry conditions during spring. In addition, heavy 1-day precipitation events--the kind that cause the worst flooding--were also at an all-time high in the spring of 2011.

A highly extreme precipitation pattern was also observed over the British Isles during spring 2011. England suffered its driest spring in over a century during May, with late May soils the driest on record over large parts of eastern and central England. In contrast, Scotland had its wettest spring on record.

New Zealand had its warmest May since records began there in 1909, whereas Australia saw its coolest March-May since their records began in 1950.

Our weather historian, Christopher C. Burt, has a detailed summary of May 2011 global weather extremes.

La Niña is gone; conditions are neutral
Although sea surface temperatures increased in the equatorial Pacific overall, El Niño/La Niña conditions remained neutral in the month of May, according to NOAA's Climate Prediction Center. Sea surface temperatures were near-average across the central Pacific Ocean, and were 0.5°C or more above average in the far western and eastern Pacific Ocean. Neutral conditions are expected to continue through the summer.

May Arctic sea ice 3rd lowest extent on record
Arctic sea ice in May 2011 was much-below average according to data from the National Snow and Ice Data Center, and ranked 3rd lowest on record for the Northern Hemisphere. Sea ice loss has accelerated during the first half of June, and as of June 16 was the lowest for the date since satellite measurements began in 1979. Snow cover extent in the Northern Hemisphere was also below average, making May 2011 the 7th consecutive May with below-average snow cover extent in the Northern Hemisphere.

Five-day period of critical fire conditions expected in the Southwest
The powerful winds that helped fan Arizona's massive Wallow fire into the state's largest fire on record will return in force today, after a two-day quiet period that allowed firefighter to achieve 29% containment of the fire by Wednesday evening. The forecast for Eastern Arizona calls for afternoon winds of 20 - 30 mph with gusts to 45 mph today and Friday. NOAA's Storm Prediction Center forecasts that even stronger winds will blow Saturday and Sunday. With hot conditions and humidity values below 10%, these are likely to be among the worst fire conditions the region has seen this year.


Figure 2. Smoke from Arizona's Wallow fire (top area with red squares denoting active fires) drifts northeastward over New Mexico in this image taken by NASA's Terra satellite at 20:30 UTC on June 15, 2011. Arizona's Horseshoe Two fire is also visible, as well as fires burning in New Mexico and Mexico.

The Atlantic is quiet, with no tropical cyclones predicted over the next seven days by the reliable computer models.

Jeff Masters

Fire Drought Climate Change Climate Summaries

Updated: 05:39 PM GMT am 16. Juni 2011

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U.S. had most extreme spring on record for precipitation

By: JeffMasters, 02:20 PM GMT am 14. Juni 2011

Nature's fury reached new extremes in the U.S. during the spring of 2011, as a punishing series of billion-dollar disasters brought the greatest flood in recorded history to the Lower Mississippi River, an astonishingly deadly tornado season, the worst drought in Texas history, and the worst fire season in recorded history. There's never been a spring this extreme for combined wet and dry extremes in the U.S. since record keeping began over a century ago, statistics released last week by the National Climatic Data Center (NCDC) reveal. Their Climate Extremes Index (CEI) looks at the percentage area of the contiguous U.S. experiencing top 10% or bottom 10% monthly maximum and minimum temperatures, monthly drought, and daily precipitation. During the spring period of March, April, and May 2011, 46% of the nation had abnormally (top 10%) wet or dry conditions--the greatest such area during the 102-year period of record. On average, just 21% of the country has exceptionally wet conditions or exceptionally dry conditions during spring. In addition, heavy 1-day precipitation events--the kind that cause the worst flooding--were also at an all-time high in the spring of 2011. However, temperatures during spring 2011 were not as extreme as in several previous springs over the past 102 years, so spring 2011 ranked as the 5th most extreme spring in the past 102 years when factoring in both temperature and precipitation.


Figure 1. Nine states in the U.S. saw their heaviest precipitation in the 117-year record during spring 2011, with record-breaking precipitation concentrated in the Pacific Northwest and along the Ohio River. Seven other states had top-ten wettest springs. Texas had its driest spring on record, and New Mexico and Louisiana had top-ten driest springs. When compared with Figure 2, we see that this is a classic winter La Niña pattern, but at extreme amplitude. Image credit: NOAA/NCDC.


Figure 2. La Niña events since 1950 have brought wetter than average conditions to the Pacific Northwest and Ohio River Valley in winter, and drier than average conditions to the South in both winter and spring. Spring 2011 (Figure 1) had a pattern very similar to the classic winter La Niña pattern (left image in Figure 2.) Image credit: NOAA Climate Prediction Center.


Figure 3. The percent area of the Contiguous U.S. experiencing much above average heavy 1-day precipitation events in spring 2011 hit a record high, nearly 16%. The 102-year average is 9%. The previous record of 15.5% was set in 1964. Heavy springtime 1-day precipitation events in the U.S. have been increasing since 1960, in line with measured increases in water vapor over the U.S. due to a warming climate. See also Figure 4 below. Image credit: NOAA/NCDC.


Figure 4. Percent increase in the amount falling in heavy precipitation events (defined as the heaviest 1% of all daily events) from 1958 to 2007, for each region of the U.S. There are clear trends toward more very heavy precipitation events for the nation as a whole, and particularly in the Northeast and Midwest. Climate models predict that precipitation will increasingly fall in very heavy events, similar to the trend that has been observed over the past 50 years in the U.S. Image credit: United States Global Change Research Program. Figure updated from Groisman, P.Ya., R.W. Knight, T.R. Karl, D.R. Easterling, B. Sun, and J.H. Lawrimore, 2004: Contemporary changes of the hydro-logical cycle over the contiguous United States, trends derived from in situ observations. Journal of Hydrometeorology, 5(1), 64-85.

What caused this spring's extremes?
During a La Niña episode in the Eastern Pacific, when the equatorial waters cool to several degrees below average, abnormally dry winter weather usually occurs in the southern U.S., and abnormally wet weather in the Midwest. This occurs because La Niña alters the path of the jet stream, making the predominant storm track in winter traverse the Midwest and avoid the South. Cold, Canadian air stays north of the jet stream, and warm subtropical air lies to the south of the jet, bringing drought to the southern tier of states. La Niña's influence on the jet stream and U.S. weather typically fades in springtime, with precipitation patterns returning closer to normal. However, in 2011, the La Niña influence on U.S. weather stayed strong throughout spring. The jet stream remained farther south than usual over the Pacific Northwest and Midwest, and blew more strongly, with wind speeds more typical of winter than spring. The positioning of the jet stream brought a much colder than average spring to the Pacific Northwest, with Washington and Oregon recording top-five coldest springs. Spring was not as cold in the Midwest, because a series of strong storms moved along the jet stream and pulled up warm, moist Gulf of Mexico air, which mixed with the cold air spilling south from Canada. The air flowing north from the Gulf of Mexico was much warmer than usual, because weaker winds than average blew over the Gulf of Mexico during February and March. This reduced the amount of mixing of cold ocean waters from the depths, and allowed the surface waters to heat up. Sea surface temperatures (SSTs) in the Gulf of Mexico warmed to 1°C (1.8°F) above average during April--the third warmest temperatures in over a century of record keeping (SST anomalies were a bit cooler in May, about 0.4°C above average, due to stronger winds over the Gulf.) These unusually warm surface waters allowed much more moisture than usual to evaporate into the air, resulting in unprecedented rains over the Midwest when the warm, moist air swirled into the unusually cold air spilling southwards from Canada. With the jet stream at exceptional winter-like strengths, the stage was also set for massive tornado outbreaks.


Figure 5. A La Niña-like positioning of the jet stream, more typical of winter than spring, brought much colder air than normal to the Pacific Northwest and Upper Midwest during the spring of 2011. Washington and Oregon had top-five coldest springs, and near-record snowfalls and snow packs were recorded in portions of the Northern Rockies and Northern Plains. South of the mean position of the jet stream, top-ten warmest springs were recorded in Texas, New Mexico, and Louisiana. Image credit: NOAA/NCDC.

Was climate change involved?
Whenever an unprecedented series of extreme weather events hit, it is natural to ask how climate change may be affecting the odds of these events, since our climate is undergoing unprecedented changes. This spring's unusual precipitation pattern--wet in the Northern U.S., and dry in the South--does fit what we'd expect from a natural but unusually long-lived winter La Niña pattern (Figure 2). However, it also fits the type of precipitation pattern climate models expect to occur over the U.S. by the end of the century due to human-caused warming of the climate (though shifted a few hundred miles to the south, Figure 6.) This drying of the Southern U.S. and increased precipitation in the Northern U.S. is expected to occur because of a fundamental shift in the large scale circulation of the atmosphere. The jet stream will retreat poleward, and rain-bearing storms that travel along the jet will have more moisture to precipitate out, since more water vapor can evaporate into a warmer atmosphere. The desert regions will expand towards the poles, and the Southern U.S. will experience a climate more like the desert regions of Mexico have now, with sinking air that discourages precipitation. A hotter climate will dry out the soil more, making record intensity droughts like this year's in Texas more probable. So, is it possible that the record extremes of drought and wetness this spring in the U.S. were due to a combination of La Niña and climate change. It is difficult to disentangle the two effects without doing detailed modelling studies, which typically take years complete and publish. One weakness in the climate change influence argument is that climate models predict the jet stream should retreat northwards and weaken due to climate change. Indeed, globally the jet stream retreated 270 miles poleward and weakened during the period 1970 - 2001, in line with climate model expectations. Thus, a stronger and more southerly jet stream over the U.S. during the spring is something we should expect to see less and less of during coming decades.


Figure 6. The future: simulated change in precipitation during winter and spring for the years 2089 - 2099 as predicted by fifteen climate models, assuming we continue high emissions of heat-trapping carbon dioxide. Confidence is highest in the hatched areas. Compare with Figure 7, the observed change in precipitation over the past 50 years. Image credit: United States Global Change Research Program.


Figure 7. U.S. annual average precipitation has increased by about 5% over the past 50 years, but there has been pronounced drying over the Southeast and Southwest U.S. Even in these dryer regions, though, heavy precipitation events have increased (see Figure 4.) Thus, rainfall tends to fall in a few very heavy events, and the light and moderate events decrease in number. Image credit: United States Global Change Research Program. Data plotted from http://www.ncdc.noaa.gov/oa/climate/research/ushc n/.

Keep in mind, though, that climate models are best at describing the future global average conditions, and not at predicting how climate change might affect individual continents--or at predicting how rare extreme events might change. Major continent-scale changes in atmospheric circulation are likely to result over the coming few decades due to climate change, and I expect the jet stream will shift farther to the south in certain preferred regions during some combination of seasons and of the natural atmospheric patterns like La Niña, El Niño, and the Arctic Oscillation. For example, there has been research published linking recent record Arctic sea ice loss to atmospheric circulation changes in the Arctic Oscillation that encourage a southwards dip of the jet stream over Eastern North America and Western Europe during late fall and winter. Until we have many more years of data and more research results, we won't be able to say if climate change is likely to bring more springs with a circulation pattern like this year's.

One thing we can say is that since global ocean temperatures have warmed about 0.6°C (1°F) over the past 40 years, there is more moisture in the air to generate record flooding rains. The near-record warm Gulf of Mexico SSTs this April that led to record Ohio Valley rainfalls and the 100-year $5 billion+ flood on the Mississippi River would have been much harder to realize without global warming.

I'll have a new post by Thursday.

Jeff Masters

Climate Change Climate Summaries

Updated: 10:11 PM GMT am 21. Oktober 2011

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Volcanic eruptions in Chile and Africa disrupt aviation; Arizona fire nears record

By: JeffMasters, 03:23 PM GMT am 13. Juni 2011

Eastern Arizona's massive Wallow Fire grew to 700 square miles over the weekend, bringing it very close to being Arizona's largest fire on record. The 2002 Rodeo-Chediski fire (732 square miles) currently holds that distinction. However, NOAA's Storm Prediction Center forecasts that critical fire conditions will spread over Eastern Arizona and Western New Mexico this afternoon. Strong southwesterly winds of 15 - 20 mph are expected, with very low relative humidities of 5 - 15%. With the Wallow Fire just 10% contained, this means that the fire will likely expand significantly today and become Arizona's largest fire on record. Firefighting conditions are expected to improve on Tuesday and Wednesday, with much weaker winds, but stronger winds may return again on Thursday. A separate fire burning in Southeast Arizona, the Horseshoe Two fire, has grown to 200 square miles, and is 40% contained. This is Arizona's 5th largest fire on record.


Figure 1. Smoke from the Horseshoe Two fire in Southeast Arizona, taken on Friday, June 10, 2011. Image credit: wunderphotographeer rixx.

The Earth is active
We now have two volcanic eruptions that are emitting large ash clouds causing significant disruptions to aircraft flights. Last week, the Puyehue-Cordón Caulle volcano in Chile erupted, sending aloft an ash cloud that circled the Southern Hemisphere, canceling flights thousands of miles away in Australia and New Zealand. At approximately 5pm EDT on Sunday, a new major eruption occurred in Africa at Eritrea's Nabro volcano. This volcano has no eruptions in historical records, but sent an ash plume over 21,000 feet (13 km) high over Eritrea after an earthquake of magnitude 5.7 rocked the area. The ash has now spread to the northwest over Sudan, and is expected to spread to the north over Egypt later today. On Tuesday, the ash is expected to get caught in a west-to-east jet stream flow, and spread over much of the Middle East. The latest forecasts from Meteo France (Figure 3) show impacts to Israel, Saudi Arabia, Jordan, and Iraq on Tuesday morning. The latest MODIS image from NASA shows the plume nicely.


Figure 2. Eruption of Puyehue-Cordón Caulle volcano, Chile as seen by NASA's Aqua satellite at 18:05 UTC on June 12, 2011. Image credit: NASA.


Figure 3. Forecast issued at 8am EDT by Meteo France showing the expected spread of the ash plume from Eritrea's Nabro volcano. Ash between 35,000 and 45,000 feet altitude (light dashed lines) is predicted to move over the Middle East, including southern Israel, by 2am EDT (0600 Z) on Tuesday, June 14. The volcano is mis-identified as the Dubbi volcano on this image.

The Atlantic is quiet
In the Atlantic, none of the reliable computer models is predicting tropical cyclone development over the next seven days.

Jeff Masters

Volcano

Updated: 03:36 PM GMT am 13. Juni 2011

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Arizona's fire danger to increase Saturday; Adrian hits Category 4

By: JeffMasters, 03:06 PM GMT am 10. Juni 2011

The powerful winds that have fanned Arizona's massive Wallow fire into the state's second largest fire on record will remain relatively modest on Friday, and the forecast for Eastern Arizona calls for afternoon winds of just 10 - 15 mph. On Thursday, Luna, New Mexico, located about 50 miles northeast of the fire, had sustained winds that peaked at just 12 mph, with gusts to 22. These are the lightest afternoon winds the fire region has seen all week, though firefighting efforts were hindered by very low relative humidities that reached 5% on Thursday. Firefighters were able to make progress Thursday, and the Wallow fire is now 5% contained. Unfortunately, NOAA's Storm Prediction Center forecasts that critical fire conditions will return on Saturday and Sunday, with strong southwest winds of 15 - 20 mph, gusting to 35 mph. The return of critical fire conditions this weekend means that the Wallow fire will likely become Arizona's largest wildfire in history, a distinction currently held by the 2002 Rodeo-Chediski fire (732 square miles.) The Wallow fire has grown steadily from 300 square miles on Sunday to 603 square miles on Thursday--about 50% of the size of Rhode Island.


Figure 1. Smoke from Arizona fires, including the Wallow Fire, continued traveling toward the northeast on June 8, 2011. As the Moderate Resolution Imaging Spectroradiometer (MODIS) on the Terra satellite acquired this natural-color image at 12:10 Central Daylight Time, thick smoke stretched from New Mexico and Texas northeastward to Illinois. Image credit: NASA Earth Observatory.

94L bringing heavy rains to the Bahamas
The large, disorganized tropical disturbance (94L) that brought heavy rains to Jamaica, Cuba, and Haiti early this week reorganized slightly overnight, and is now bringing heavy rains to the Bahama Islands. The storm killed at least 23 people in Haiti earlier this week, due to torrential flooding rains. Satellite-estimated rainfall amounts indicate 8 -10 inches of rain fell over Haiti's southwestern peninsula this week. None of the reliable computer models is showing development of 94L into a tropical depression, and NHC is giving the disturbance a 10% chance of developing by Sunday. Wind shear is a high 20 - 30 knots in the region between Cuba and South Carolina, making development unlikely. Elsewhere in the Atlantic, none of the reliable computer models is predicting tropical cyclone development over the next seven days.


Figure 2. Morning satellite image of Hurricane Adrian taken at 10:15am EDT June 10, 2011.

Annular Adrian becomes the first major hurricane of the Eastern Pacific hurricane season
Hurricane Adrian put on an impressive bout of rapid intensification Thursday, intensifying into the season's first major hurricane in the Eastern Pacific. Adrian is the globe's 6th Category 4 or stronger tropical cyclone of the year. Adrian is expected to remain far enough offshore the coast of Mexico to not pose a threat to that country. Gradual weakening is likely through the weekend, since Adrian will be tracking over cooler ocean waters. Adrian's decay will be slower than usual for a hurricane, since it has become what is called an annular hurricane. Annular hurricanes feature a large eye surrounded by a very thick eyewall, with no spiral rain bands. The very thick eyewall makes annular hurricanes resistant to weakening due to wind shear, dry air, or cool waters. Annular hurricanes are rare; only 3% of all Eastern Pacific tropical cyclones become annular, and 1% of all Atlantic ones.

A record 100-year flood on the Missouri River
The greatest flood in recorded history is occurring along sections of the Missouri River, which runs from Montana to St. Louis, Missouri. On Thursday, the river hit 28.0' feet at Williston, North Dakota, surpassing the record flood height set in 1912. The river is expected to continue to rise to 1.4' above the 1912 mark by Tuesday. This week, the Missouri River at Omaha, Nebraska surpassed the level set during the great 1993 flood, and the river's height is currently the 2nd greatest on record, 9' below the mark set in 1952. Water releases at the six flood control dams on the Missouri River are now at more than double their previous all-time highs; these dams were built between 1940 and 1964. This great 100-year flood on the Missouri River is just beginning, and is likely to cause major damage over the next few weeks.

Have a great weekend everyone, and I'll be back Monday with a new post.

Jeff Masters

Fire

Updated: 09:28 PM GMT am 16. August 2011

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Winds diminish for Arizona's fire; flooding from 94L kills 23 in Haiti

By: JeffMasters, 02:27 PM GMT am 09. Juni 2011

The powerful winds that have fanned Arizona's massive Wallow fire into the state's second largest fire on record will diminish today, and the forecast for Eastern Arizona calls for more modest afternoon winds of 15 - 20 mph through Saturday. For the first time this week, NOAA's Storm Prediction Center has not issued red flag warnings for critical fire conditions in Eastern Arizona, and firefighters should be able to make progress battling the Wallow fire, which is 0% contained. Yesterday, Luna, New Mexico, located about 50 miles northeast of the fire, had wind gusts in excess of 30 mph for almost 7 hours, temperatures near 80°F, and humidities as low as 5%. The fire has grown steadily this week--300 square miles on Sunday, 365 square miles on Monday, 484 square miles Tuesday, and 608 square miles on Wednesday. Its current size is about 50% of the size of Rhode Island. The fire is close to beating the 2002 Rodeo-Chediski fire (732 square miles) as Arizona's largest fire in recorded history. Smoke from the Wallow fire has now blown downwind over 2,000 miles over the Atlantic Ocean, as seen using our wundermap for the U.S. with the Fire layer turned on. Smoke caused "Unhealthy" levels of air pollution (code red on the Air Quality Index) over much of new Mexico Wednesday. A separate fire burning in Southeast Arizona, the 167-square-mile Horseshoe Two fire, is the state's 5th largest fire on record, and is 50% contained. According to the Interagency Fire Center, 3.6 million acres have burned in the U.S. so far this year, the most on record for this early in the year--and more than double the 10-year average from 2001 - 2010 of 1.4 million acres. During May, 1.8 million acres burned, the greatest May fire acreage burned in the 12-year record. Extreme to exceptional drought conditions over most of Texas, New Mexico, and Eastern Arizona are largely responsible for the record fire season.


Figure 1. Smoke from Arizona's Wallow fire passed over the Washington DC area at a height of 5 - 9 km during the day on Wednesday, June 8, 2011. NASA Goddard's micropulse lidar in Greenbelt, Maryland took a vertical profile of particles in the atmosphere during the day. A lidar (short for LIght Detection And Ranging) is a laser detection system that bounces light waves off of particles in the atmosphere to determine where clouds and elevated pollution layers exist. During the afternoon hours, the lidar also detected large amounts of air pollution particles near the surface (orange colors) after 18 UTC (2pm EDT.) Air quality in the Washington D.C. area during the day on June 8 for particles was Moderate (84 on the Air Quality Index, code yellow), and was Unhealthy for Sensitive Groups (Air Quality Index of 150) for ozone pollution. The University of Maryland Smog Blog is where I got this image from, and is a good place to get daily discussions of air pollution.


Figure 2. Smoke billows from the rapidly growing Wallow fire in Eastern Arizona in this image taken by NASA's Aqua satellite at 1:25pm MDT June 8, 2011. The actively burning fire front (outlined in red) surrounds a vast area of charred land. High winds propelled the fire, igniting spot fires as much as three miles ahead of the fire front. Image credit: NASA.

Flooding from 94L kills 23 people in Haiti
The large, disorganized tropical disturbance (94L) that brought heavy rains to Jamaica, Cuba, and Haiti early this week is no more, but at least 23 people are dead and six missing in Haiti due to torrential flooding rains from the disturbance. Satellite-estimated rainfall amounts indicate 8 -10 inches of rain fell over Haiti's southwestern peninsula this week. The heaviest rains from the remains of 94L lie just north and west of Haiti, and may be capable of bringing 1 - 3 inches of rain to Haiti, the Bahamas, and eastern Cuba today. The NOGAPS model is suggesting the remains of 94L could reorganize into a strong tropical disturbance this weekend off the coast of South Carolina, but none of the other models are showing this. The NOGAPS model has had a poor track record handling the evolution of the wind shear pattern this week, and I'm not expecting any major regeneration of 94L. Wind shear is very high 30 - 50 knots in the region between Cuba and South Carolina, making development very unlikely. Elsewhere in the Atlantic, none of the reliable computer models is predicting tropical cyclone development over the next seven days.


Figure 3. Morning satellite image of Hurricane Adrian.

First hurricane of the Eastern Pacific hurricane season forms
Hurricane Adrian is putting on an impressive bout of rapid intensification, and has emerged as the season's first hurricane in the Eastern Pacific Ocean. Adrian is in an ideal environment for intensification, with light wind shear and ocean temperatures of 30°C (86°), and will likely become a major hurricane later today. Adrian is expected to remain far enough offshore the coast of Mexico to not pose a threat to that country, at least for the next three days. June hurricanes in the Eastern Pacific are much more common than in the Atlantic.

NOAA's pre-season prediction of the Eastern Pacific hurricane season, issued on May 16, calls for below average activity, with 12 named storms, 6.5 hurricanes, and 2 major hurricanes, with an ACE index 75% of the median. The 1981-2010 averages for the Eastern Pacific hurricane season are 15 - 16 named storms, 8 - 9 hurricanes, and 4 major hurricanes.

Jeff Masters

Fire

Updated: 09:28 PM GMT am 16. August 2011

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Smoke, heat, and air pollution across much of the U.S.

By: JeffMasters, 01:41 PM GMT am 08. Juni 2011

Smoke from Arizona's second largest fire on record, the massive Wallow fire near the New Mexico border, has now blown downwind over 1,500 miles to the Northeast U.S. The fire, which is 0% contained, is expected to rage full-force for at least another day due to unfavorable weather. Hot, dry, and windy weather is predicted again today over Eastern Arizona, where NOAA has issued red flag warnings for critical fire conditions. A large trough of low pressure is anchored over the Southwest, and a disturbance rippling along this trough will bring strong southwesterly surface winds of 20 - 25 mph, with gusts near 35 mph today to eastern Arizona. Extremely low humidities of 5 - 15% and hot summer temperatures are also expected, creating a dangerous fire weather situation. Yesterday, Luna, New Mexico, located about 50 miles northeast of the fire, had wind gusts in excess of 20 mph for 9 hours, temperatures near 80°F, and humidities as low as 7%. The fire grew from 300 square miles on Sunday to 365 square miles on Monday and 487 square miles Tuesday--about 40% of the size of Rhode Island. A separate fire burning in Southeast Arizona, the 166-square-mile Horseshoe Two fire, is the state's 5th largest fire on record. Winds are expected to diminish for Thursday and Friday, which should allow firefighters to make headway controlling the blazes. According to the Interagency Fire Center, 3.5 million acres have burned in the U.S. so far this year, the most on record for this early in the year--and more than double the 10-year average from 2001 - 2010 of 1.4 million acres. Extreme to exceptional drought conditions over most of Texas, New Mexico, and Eastern Arizona are largely responsible for the record fire season.


Figure 1. Active wildfires and smoke as visualized at 9am EDT June 8, 2011 using our wundermap for the U.S. with the Fire layer turned on. Smoke from the Wallow fire and Horseshoe Two fire in Arizona extended more than 1,500 miles, and was pushing into the Northeast U.S.


Figure 2. Smoke billows from the rapidly growing Wallow fire in Eastern Arizona in this image taken by NASA's Aqua satellite on June 7, 2011. Heavy smoke from the fire covers large portions of New Mexico, Texas, Colorado, Kansas, Oklahoma, South Dakota, and Nebraska in this image. Image credit: NASA.

Unusual June heat wave
An intense blast of heat set new daily high temperature marks in 14 states from Texas to Minnesota Tuesday, including a remarkable 103°F in Minneapolis. It was the hottest day in the city in nearly 23 years, since 105°F was recorded on July 31, 1988, and the second earliest date the city had ever hit 100°. Minneapolis' earliest 100° day came on May 31, 1934, when the mercury also hit 103°. Yesterday was the 5th consecutive day that the Austin, Texas Bergstrom Airport tied or set a new daily temperature record. On Monday, June 6, the airport hit 103°F, the earliest in the year that location had ever hit 103°. Record keeping began there in 1942, and the last time Austin was so warm so early in the year was on June 14, 1998, when the mercury hit 109°.


Figure 3. Air pollution forecast for Wednesday, June 8, 2011, calls for a large-spread region of pollution that is Unhealthy for Sensitive Groups (USG), over the eastern third of the nation. Image credit: EPA Airnow.

Significant air pollution episode today
The heat will continue today for much of the eastern half of the country, and heat advisories are posted in fourteen states. The high heat, combined with abundant sunshine and very stagnant air, is expected to bring the most severe large-scale air pollution event of the year to the nation. Adding to the hazard is the presence of fine smoke particles from the fires in Arizona, which have blown downwind to cover most of the eastern 2/3 of the country. Air quality on Wednesday is expected to be Unhealthy for Sensitive Groups (Code Orange, or over 100 on the Air Quality Index), in more than 80 cities, including Baton Rouge, La., Indianapolis, Detroit, Nashville, Tenn., Columbus, Ohio, Philadelphia, Pittsburgh, Newark, N.J., Richmond, Va., and Atlanta. If you live in these areas, cut back on strenuous outdoor exercise today if you have asthma or other respiratory problems.

Caribbean disturbance 94L no threat to develop
The large, disorganized tropical disturbance (Invest 94L) in the Northwestern to North Central Caribbean Sea near Jamaica is very disorganized this morning, but is still capable of bringing heavy rains as it pushes slowly northwards at less than 5 mph. I heard from wunderground user Anthony Zed in the Kingston, Jamaica suburb of Norbrook, and he reported that his rain gauge received 11.27" of rain from 94L from June 1 - 7, which is more rain than had fallen all year. The big rain day was yesterday, with 3.47". Satellite loops show a few disorganized clumps of thunderstorms in the region, and NHC has downgraded 94L's chances of development by Friday to 0%. Wind shear is very high, 30 - 50 knots, making development very unlikely.

First tropical cyclone of the Eastern Pacific hurricane season forms
Tropical Storm Adrian, the first named storm of the Eastern Pacific hurricane season, formed last night off the coast of Mexico. Adrian is in an ideal environment for intensification, with light wind shear and ocean temperatures of 30°C (86°), and will likely become a hurricane on Thursday. Adrian is expected to remain far enough offshore the coast of Mexico to not pose a threat to that country, at least for the next three days. June hurricanes in the Eastern Pacific are much more common than in the Atlantic.

NOAA's pre-season prediction of the Eastern Pacific hurricane season, issued on May 16, calls for below average activity, with 12 named storms, 6.5 hurricanes, and 2 major hurricanes, with an ACE index 75% of the median. The 1981-2010 averages for the Eastern Pacific hurricane season are 15 - 16 named storms, 8 - 9 hurricanes, and 4 major hurricanes.

Amazing solar flare erupts
In recent months, the sun has awakened from its longest and quietest period since the satellite era bgan in the late 1970s. An increasing number of sunspots, solar flares, and Coronal Mass Ejections have occurred, as solar activity builds towards a peak expected in 2013. Yesterday, the sun unleased the most spectacular solar flare ever captured on video, highlighted in the Youtube link below.


Video 1. A spectacular solar flare erupted at 06:41 UTC on June 6, 2011, when magnetic fields above sunspot complex 1226-1227 became unstable. The blast produced a massive Coronal Mass Ejection (CME) that was not aimed directly at Earth, but fringes of the blast may cause aurora activity on June 8 and 9. This is probably the most dramatic and beautiful solar flare captured by the cameras on NASA's Solar Dynamics Observatory (SDO.) Additional movies and information are available at spaceweather.com, and additional information on the latest solar activity is available from NOAA's Space Weather Prediction Center.

Jeff Masters

Air and Water Pollution Fire Heat

Updated: 11:17 PM GMT am 15. August 2011

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Arizona wildfires spread smoke 1,000 miles; 94L little threat to develop

By: JeffMasters, 01:50 PM GMT am 07. Juni 2011

Smoke from Arizona's third largest fire on record, the massive Wallow fire, has now blown downwind over 1,000 miles to Iowa. The fire, which is 0% contained, is expected to rage full-force for at least three more days due to unfavorable weather. Hot, dry, and windy weather is predicted again today over Eastern Arizona, where NOAA has issued red flag warnings for critical fire conditions. A large trough of low pressure is anchored over the Southwest, and several disturbances rippling along this trough will bring strong southwesterly surface winds of 20 - 30 mph, with gusts near 35 mph, through Thursday. Extremely low humidities of 5 - 15% and hot summer temperatures are also expected, creating a dangerous fire weather situation. Yesterday, Luna, New Mexico, located about 50 miles northeast of the fire, had wind gusts in excess of 30 mph for 8 hours, temperatures near 80°F, and humidities as low as 12%. During the day yesterday, the fire grew from 300 square miles to 365 square miles, 30% of the size of Rhode Island. A separate fire burning in Southeast Arizona, the 163-square-mile Horseshoe Two fire, is the state's 5th largest fire on record. According to the Interagency Fire Center, 3.5 million acres have burned in the U.S. so far this year, the most on record for this early in the year--and more than double the 10-year average from 2001 - 2010 of 1.4 million acres. Extreme to exceptional drought conditions over most of Texas, New Mexico, and Eastern Arizona are largely responsible for the record fire season.


Figure 1. Active wildfires and smoke as visualized at 9am EDT June 7, 2011 using our wundermap for the U.S. with the Fire layer turned on. Smoke from the Wallow fire and Horseshoe Two fire in Arizona extended more than 1,000 miles, covering most of the Midwest.


Figure 2. Smoke billows from the rapidly growing Wallow fire in Eastern Arizona in this image taken by NASA's Aqua satellite on June 6, 2011. The fire beneath the smoke is outlined in red. A large pyrocumulus cloud spawned by the fire is visible along the Arizona-New Mexico border. Pyrocumulus clouds are produced by the intense heating associated with fires or volcanic eruptions. Image credit: NASA Natural Hazards website.

Caribbean disturbance 94L little threat to develop
The large, disorganized tropical disturbance (Invest 94L) in the Western Caribbean near Jamaica is looking much less organized this morning, but is still capable of bringing heavy rains as it pushes slowly northwards at less than 5 mph. Satellite estimates of rainfall for the 24-hour period ending at 8pm EDT Monday night run as high as 5 inches for northeastern Nicaragua and Honduras, with 2 - 4 inches falling over portions of Jamaica and southeast Cuba. Satellite loops show a decrease in the heavy thunderstorm activity and organization of 94L in recent hours, and the storm's low-level spiral bands and upper-level outflow are very poorly defined. The storm's center of low pressure is located about 100 miles south-southeast of Grand Cayman Island. Water vapor satellite loops show the Caribbean is quite moist, and water temperatures in the Central Caribbean are about 1°C above average, 28 - 28.5°C, which is 2°C above the threshold needed to support development of a tropical storm. Wind shear has edged into the high range, 20 - 25 knots, which has probably contributed to 94L's deterioration.


Figure 3. Morning satellite image of 94L.

Since 94L is so large and poorly organized, today's mission by the Hurricane Hunters has been cancelled. The storm is moving slowly to the north, into a band of very high wind shear of 30 - 50 knots that lies over Cuba and the southern Bahama Islands. The SHIPS model predicts shear will rise above 30 knots by late tonight, which will make development into a tropical depression difficult. This morning's 00Z and 06Z model runs were unimpressed with 94L, with most of them showing little or no development. The 00Z run of the NOGAPS model predicts that a gap may open up in the shear sufficient for the storm to organize into a tropical depression late this week, but this is looking increasingly unlikely. At 8am EDT today, NHC gave 94L a 20% chance of developing into a tropical depression by Thursday. Regardless of development, 94L is capable of bringing heavy rains of 2 - 4 inches to Jamaica, eastern Cuba, the Cayman Islands, and Haiti through Thursday. These rains will probably spread northwards into the Bahama Islands, and possibly South Florida, by Thursday or Friday.

Jeff Masters

Fire

Updated: 09:29 PM GMT am 16. August 2011

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Little change to 94L; exceptional heat in Texas, record rains in California

By: JeffMasters, 02:43 PM GMT am 06. Juni 2011

There is not much change to report on the large, wet, and disorganized tropical disturbance (Invest 94L) in the Western Caribbean, between Jamaica and Mexico's Yucatan Peninsula. The disturbance has brought intermittent heavy rains to Jamaica over the past two days, but nearby islands have thus far escaped the deluge. Satellite-estimated rainfall amounts of 1" per hour occurred in ocean regions just east of Jamaica this morning, but the heaviest rains have missed the island so far this morning. Visible satellite loops show no increase in organization of 94L in recent hours, and the storm's low-level spiral bands and upper-level outflow are poorly defined. The storm's center of low pressure is located about 130 miles south of Grand Cayman Island, in a region with no heavy thunderstorm activity. An intense clump of thunderstorms exists on either side of this low, near Jamaica, and just east of Mexico's Yucatan Peninsula. Water vapor satellite loops show the Caribbean has moistened over the past two days, and upper air balloon soundings from the Cayman Islands continue to show much moister air at mid levels of the atmosphere (2% humidity at 500 mb on Saturday, compared to 69% last night.) Wind shear remains in the moderate range, 15 - 20 knots, and is predicted by the SHIPS model to remain below 20 knots through tonight. Water temperatures in the Central Caribbean are about 1°C above average, 28 - 28.5°C, which is 2°C above the threshold needed to support development of a tropical storm.


Figure 1. Rainfall rates of up to 1" per hour (orange colors) were estimated by the F-17 satellite for 94L at 7:03am EDT Jun 6, 2011. Image credit: Navy Research Lab, Monterey.

Since 94L is so large and poorly organized, today's mission by the Hurricane Hunters has been cancelled. A new mission is scheduled for Tuesday afternoon at 2pm EDT. This morning's 00Z and 06Z model runs were unimpressed with 94L, with most of them showing little or no development. A band of very high wind shear of 30 - 50 knots lies over Cuba and the southern Bahama Islands. The GFS and ECMWF models show 94L pushing slowly northwest at about 5 mph, hitting this shear on Tuesday and Wednesday, preventing any further development. The NOGAPS model predicts that a gap may open up in the shear sufficient for the storm to organize into a tropical depression late this week. Given 94L's current disorganization, I doubt the storm will ever develop. NHC gave 94L a 40% chance of developing into a tropical depression by Wednesday, and I believe these odds should be lower, near 20%. Regardless of development, 94L is capable of bringing very heavy rains to Jamaica, Cuba, the Cayman Islands, and Haiti through Wednesday. These rains will probably spread northwards into South Florida and the Bahama Islands by Thursday or Friday.


Figure 2. Morning satellite image of 94L.

Exceptional heat in the South
A sizzling June heat wave set record high temperatures across much of Texas, Louisiana, Alabama, Mississippi, and the Florida Panhandle on Sunday. The high temperature at the Houston, Texas airport hit 105 degrees, the warmest temperature ever recorded in the month of June (old record: 104 degrees on June 24th and June 26th, 2009.) The earliest Houston ever recorded a temperature of 105 degrees prior to Sunday was July 26th, 1954. Records for Houston date back to 1891. There have been only 15 days in which the temperature has reached or exceeded 105 degrees in Houston:

4 - 1909
1 - 1954
2 - 1962
3 - 1980
5 - 2000

So far this month, new maximum temperature records in Houston have been established on four out of the first five days. Galveston and Houston both crushed their previous record high temperature for the day (June 5th) by a remarkable seven degrees. Residents can expect another day of triple-digit heat today, thanks to the upper level ridge of high pressure parked over the state. Houston will likely break the old record of 98°F for the date.


Figure 3. An intense low pressure system moves inland over California as seen in this satellite photo taken June 4, 2011, at 2pm PDT. Image credit: NASA/GSFC.

Record rains in California
A large and unusually intense low pressure system moved inland over California over the weekend, bringing large areas of the state rains unheard of in June. According to our weather historian, Christopher C. Burt, rainfall at Mining Ridge on the Big Sur coast totaled 8.31" Sunday, which, if verified, would be California's heaviest 1-day June rainstorm on record. According to the document "Historic Rainstorms in California" Dept. of Water Resources, Aug. 1997, the previous maximum June daily rainfall was 5.83" at Forni Ridge on June 18, 1982. San Francisco had its 2nd greatest June 1-day rainfall, going back to 1850, and both the San Francisco and Oakland airport have now had their rainiest Junes on record. Rainfall at Santa Barbara Airport yesterday totaled 1.24 inches, the wettest June day there on record (previous record: 0.51" on June 5, 2009.) The 1.38"of rain so far this June has made it the wettest June in recorded history at Santa Barbara Airport, going back to 1941.

Jeff Masters

Heat Hurricane

Updated: 06:15 PM GMT am 17. August 2011

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Caribbean disturbance 94L dumping heavy rains on Jamaica

By: JeffMasters, 04:44 PM GMT am 05. Juni 2011

A large, wet, and disorganized tropical disturbance (Invest 94L) continues to spread heavy rain to the Central Caribbean near Jamaica. Rain has fallen continuously at Jamaica's Kingston Norman Manley Airport since midnight, with 1.89" having fallen from midnight to noon local time. Sustained winds of 24 mph also affected Kingston between 7am and 8am this morning. Satellite-estimated rainfall amounts of 1.4" per hour occurred in ocean regions 100 miles to the southeast of Kingston this morning, and heavy rains of up to 1/2" per hour are probably affecting portions of Jamaica early this afternoon, judging by the recent increase in heavy thunderstorm activity seen on visible satellite loops. This imagery also shows a slow increase in organization of 94L in recent hours, with spiral bands beginning to develop to the southeast of the center. There is a broad, poorly-defined circulation apparent that is not well enough defined to make 94L a tropical depression. Water vapor satellite loops show a region of dry air on the west side of 94L, and this dry air is interfering with the storm's organization. However, upper air balloon soundings from Kingston and the Cayman Islands taken at 8am EDT this morning show much moister air at mid levels of the atmosphere compared to Saturday (2% humidity at 500 mb on Saturday, compared to 49% this morning at Grand Cayman), and 94L appears to be gradually overcoming its dry air issues. Wind shear remains in the moderate range, 15 - 20 knots, and is predicted by the SHIPS model to remain below 20 knots through Tuesday morning. Water temperatures in the Central Caribbean are about 1°C above average, 28 - 28.5°C, which is 2°C above the threshold needed to support development of a tropical storm.


Figure 1. Rainfall rates of up to 1.4" per hour (pink colors) were estimated by the F-15 satellite for 94L at 6:02am EDT Jun 5, 2011.

Since 94L is so large and is battling dry air, it is taking its sweet time to develop, and today's mission by the Hurricane Hunters has been cancelled. A new mission is scheduled for Monday afternoon at 2pm EDT. This morning's 06Z model runs are pretty unimpressed with 94L, with most of them showing little or no development. At 2pm EDT on Sunday, NHC gave the disturbance a 40% of developing into a tropical depression by Tuesday. If 94L stays to the south, its chances of development are greater, since a band of very high wind shear of 30 - 50 knots lies over Cuba and the southern Bahama Islands. The disturbance is expected to meander slowly westward or northward over the next two days, with Jamaica and southeastern Cuba being the primary targets for very heavy rains of 4 - 8 inches through Tuesday. Haiti and Central Cuba can expect somewhat lesser rains of 3 - 6 inches. If 94L does develop into a tropical depression and moves northwards over Cuba by Wednesday, I don't see the storm attaining hurricane strength, due to the high wind shear. The primary threat from 94L will be very heavy rains, capable of causing life-threatening flash flooding.


Figure 2. Afternoon satellite image of the Central Caribbean disturbance 94L.

Jeff Masters

Hurricane

Updated: 06:16 PM GMT am 17. August 2011

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Caribbean disturbance slow to develop; 5 EF-5 tornadoes this year confirmed

By: JeffMasters, 03:33 PM GMT am 03. Juni 2011

The tropical disturbance (Invest 93L) that crossed over Florida on Wednesday, bringing welcome rains of 1 - 3 inches, is now a naked swirl of low clouds over the central Gulf of Mexico. The disturbance is embedded in a large area of dry air associated with an upper level low pressure system, and this dry air is discouraging development. 93L is also moving into a region of moderate wind shear of 10 - 20 knots, and NHC is giving 93L a 0% chance of developing into a tropical depression before the storm makes landfall in Mexico south of Brownsville on Saturday. There are a few heavy thunderstorms trying to fire up near the center of 93L's fairly well-formed circulation, but I don't think this storm is going to bring more than 1 - 2 inches of rain to the coast on Saturday.


Figure 1. Morning satellite image of the Central Caribbean disturbance.

Central Caribbean disturbance 94L
Disorganized heavy thunderstorm activity continues in the region between Central America and Jamaica. Wind shear has fallen to the moderate range, 10 - 20 knots, and is predicted to continue to fall over the next two days. This should allow the disturbance, dubbed Invest 94L by NHC on Friday afternoon, to increase in organization, though it will take many days for it to approach tropical depression status, since it is so large and poorly organized. The last two runs of the NOGAPS model have developed the disturbance into a tropical depression or storm by early next week, with the system moving northwards into Jamaica, the Cayman Islands, and eastern Cuba. The other major models do not show the disturbance developing during the coming week. NHC is giving the disturbance a 10% of developing into a tropical depression by Sunday. A surge of moisture accompanying a tropical wave may aid development when the wave arrives in the Western Caribbean on Sunday. Water temperatures in the Central Caribbean are about 1°C above average, 29°C, which is plenty warm enough to support development of a tropical storm. Residents of Jamaica, eastern Cuba, the Cayman Islands, Haiti, and the Dominican Republic should anticipate the possibility that heavy rains of 2 - 4 inches may affect them today through Sunday.

Five EF-5 tornadoes confirmed in 2011
The National Weather Service in Oklahoma City announced Wednesday that the violent tornado that hit Binger, El Reno, Peidmont, and Guthrie, Oklahoma on May 24, killing nine people, was an EF-5 with winds greater than 210 mph. The rating was given based on measurements made by a University of Oklahoma portable "Doppler on wheels" radar. The long track, large wedge tornado caused extensive damage, with well built houses cleanly swept from their foundation and trees debarked. This tornado brings the total number of EF-5 tornadoes this year to five, tying 2011 with 1953 for 2nd place for greatest number of these top-end tornadoes in one year. Only 1974 (six) had more. The EF-5 tornadoes of 2011:

1) The April 27, 2011 Neshoba/Kemper/Winston/Noxubee Counties, Mississippi tornado (3 killed, 29 mile path length.)

2) The April 27, 2011 Smithville, Mississippi tornado (22 killed, 15 mile path length.)

3) The April 27, 2011 Hackleburg, Alabama tornado (71 killed, 25 mile path length.)

4) The May 22, 2011 Joplin Missouri tornado (138 killed, 14 mile path length.)

5) The May 24, 2011 Binger-El Reno-Peidmont-Guthrie, Oklahoma tornado. (9 killed, 75 mile path length.)


Figure 2. Aerial view of damage from the May 22, 2011 Joplin, Missouri tornado. Image credit: Wikipedia.

A few other remarkable statistics on the tornado season of 2011, compiled from NOAA's official press release and Wikipedia's excellent tornado pages:

- The April 25 - 28 tornado outbreak, with 330 tornadoes, was the largest tornado outbreak of three days or less duration on record. The previous record was 148 tornadoes, set during the April 3 - 4, 1974 Super Outbreak.

- For April 27, 186 tornadoes have been confirmed. This is the largest 1-day tornado total on record, beating the 148 recorded in 24 hours on April 3 - 4, 1974.

- The April 14 - 16 tornado outbreak, with 162 confirmed tornadoes, ranks as the fourth largest tornado outbreak of three days or less duration on record.

- The May 21 - 26 tornado outbreak, with 158 confirmed tornadoes, ranks as the 5th largest 6-day or shorter tornado outbreak on record. A May 2003 6-day outbreak had 289 tornadoes, and a May 2004 6-day outbreak had 229 tornadoes. The year 2011 now has three of the top five tornado outbreaks on record.

- April confirmed tornado total was 683, making it the busiest tornado month on record. The previous record was 542 tornadoes, set in May 2003. The previous April record was 267 tornadoes, which occurred in April 1974. The 30-year average for April tornadoes is 135.

- If the three deaths in Massachusetts from Wednesday's tornadoes are confirmed, this year's tornado death toll will be 522, beating 1953 as the deadliest tornado year since modern tornado records began. That year, 519 people died, and three heavily populated cities received direct hits by violent tornadoes. Waco, Texas (114 killed), Flint, Michigan (115 killed), and Worcester, Massachusetts (90 killed) all were hit by violent F-4 or F-5 tornadoes. A similar bad tornado year occurred in 1936, when violent tornadoes hit Tupelo Mississippi (216 killed), and Gainesville, Georgia (203 killed.) During that time period, the tornado death rate per million people was 60 - 70 times as great as in the year 2000 (Figure 4), implying that this year's tornadoes would have killed many thousands of people had we not had our modern tornado modern warning system.

- The May 22, 2011 Joplin, Missouri tornado killed 138 people and injured 1150, making it the deadliest U.S. tornado since 1947, and 8th deadliest in history. The $1 - $3 billion estimate of insured damage makes it the most expensive tornado in history.

- Damage from the April 25 - 28 super tornado outbreak was estimated at $3.5 - $6 billion, making it the most expensive tornado outbreak of all-time.

- The tornado that hit Springfield, Massachusetts on June 1 was at least an EF-3 with 136 - 165 mph winds. It was only the 9th EF-3 or stronger tornado to hit Massachusetts since 1950, and the third deadliest, with three deaths.

- The year 2011 now ranks in 3rd place behind 1974 and 1965 for highest number of strong to violent EF-3, EF-4, and EF-5 tornadoes (Figure 3.)


Figure 3. Number of strong to violent EF-3, EF-4 and EF-5 tornadoes from 1950 to 2011. The year 2011 now ranks in 3rd place behind 1974 and 1965. There is not a decades-long increasing trend in the numbers of these most dangerous of tornadoes. Image credit: NOAA/National Climatic Data Center (updated using stats for 2008 - 2011 from Wikipedia.)


Figure 4. Death rate per million people per year in U.S., 1875-2000. Thin line with dots is raw rate, curved thick line is death rate, filtered by 3-point median and 5-point running mean filter, and straight solid lines are least squares fit to filtered death rate for 1875-1925 and 1925-2000. Dashed lines are estimates of 10th and 90th percentile death rates from 1925-2000. The death rate fell from 8 per million to .12 per million between 1940 and 2000. Image credit: A Brief History of Deaths from Tornadoes in the United States, Harold Brooks and Charles Doswell III.

Joplin tornado the 7th U.S. billion-dollar weather disaster of 2011
The Joplin tornado is the 7th U.S. weather disaster of 2011 costing more than a billion dollars. With a major flooding disaster coming on the Missouri River, and hurricane season still to come, 2011 has an excellent chance of beating 2008's record of nine billion-dollar weather disasters. The billion dollar weather disasters of 2011 so far:

1) 2011 Groundhog Day's blizzard ($1- $4 billion)
2) April 3 -5 Southeast U.S. severe weather outbreak ($2 billion)
3) April 8 - 11 severe weather outbreak ($2.25 billion)
4) April 25 - 28 super tornado outbreak ($3.5 - $6 billion)
5) Mississippi River flood of 2011 ($9 billion)
6) Texas drought ($1.2 billion)
7) Joplin tornado ($1 - $3 billion)


Figure 5. River flood outlook for the U.S. Image credit: NOAA.

The next U.S. billion-dollar weather disaster: a Missouri River flood?
A great 100-year flood has arrived along the Missouri River and its tributaries from Montana to Nebraska. Record spring rains, combined with snow melt from record or near-record winter and spring snows, brought the Missouri River at Williston, North Dakota to 27.9' yesterday, just an inch short of the highest crest on record (28.0' on 4/01/1912.) Tributaries to the Missouri, such as the Souris River in North Dakota and the North Platte River in Nebraska, are already flooding at all-time record heights. With warm summer temperatures and additional rainfall expected over much of the area during the coming week, snow melt and rain runoff will swell area rivers even further, creating a damaging 100-year flood. Wunderground weather historian Christopher C. Burt has the details in his latest post, and I will be writing more on this latest epic flood next week.

I'll have a new post on Monday, or earlier if the Caribbean disturbance shows significant development.

Jeff Masters

Tornado Hurricane

Updated: 06:16 PM GMT am 17. August 2011

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Tornadoes rip Massachusetts, killing 4

By: JeffMasters, 01:30 PM GMT am 02. Juni 2011

The governor declared a state of emergency in Massachusetts last night after two rare and powerful tornadoes ripped through the state's third largest city, Springfield (population 150,000.) Separate tornadoes hit the city near 4:30 pm and 6:20pm EDT, killing four people, injuring 40, and causing extensive damage. The four deaths ties 2011 with 1973 as Massachusetts' deadliest tornado year since 1953, when 90 people died in an F-4 tornado that hit Worcester. NOAA's Storm Prediction Center logged seven preliminary reports of tornadoes in Massachusetts yesterday. The region was in their "Slight Risk" area for severe weather. The tornadoes were spawned by a large low pressure system centered over Canada that trailed a cold front southwards over New England. Record heat pushed northwards ahead of the cold front, with Newark, Washington D.C., Burlington, and Montpelier all recording record highs for the date. The contrast between the cold, dry air flowing south from Canada and the record warm, moist air ahead of the cold front created an extremely unstable atmosphere, helping fire off unusually intense thunderstorms over New England. And as we've seen so often this year, the jet stream over the thunderstorm region was unusually strong and had plenty of wind shear--a sharp change in wind speed and direction with height. This wind shear created shearing forces on the air over New England that helped get it spinning, creating rotating supercell thunderstorms capable of producing strong tornadoes.


Figure 1. Yesterday's tornadoes caused damage characteristic of at least an EF-2 tornado with 110 - 137 mph winds in Springfield, Massachusetts. Image credit: Springfield Falcons hockey team, via the cbslocal.com Boston website.


Video 1. Incredible tower cam view from wfsb.com of the June 1, 2011 Springfield, Massachusetts tornado crossing the Connecticut River. Another amateur video posted here on Youtube shows the tornado crossing I-91 in Springfield during rush hour (many swear words on this one!)

Springfield damage characteristic of an EF-2 tornado
Damage photos I've seen of the Springfield tornadoes show destruction characteristic of at least an EF-2 tornado with 111 - 135 mph winds. The damage photo above (Figure 1) shows the collapse of the top story walls of a brick building. According to the Storm Prediction Center's Description of Damage for this type of structure, the winds needed to do this type of damage typically range between 103 and 143 mph, or EF-2 speeds. I wouldn't be surprised if some of the damage gets rated EF-3, since there is a report of a 3-story building that collapsed (EF-3 winds are 136 - 165 mph.)


Figure 2. Satellite image taken at 6:01pm EDT June 1, 2011, showing the line of tornadic thunderstorms over Massachusetts, and Invest 93L near Tampa, Florida. Image credit: NASA/GSFC.

Massachusetts tornado history
One of yesterday's Springfield tornadoes pulled debris from Springfield and deposited it 45 miles to the east-northeast in Millbury, according to an NWS storm report. Powerful, long-track tornadoes like this are rare in New England. Most tornadoes in the region are small, weak, EF-0 and EF-1 twisters that touch down briefly and do minor damage. Only once every eight years, on average, does a strong or violent EF-3 or EF-4 tornado hit Massachusetts. According to the tornadohistoryproject.com, since 1951, there have been only eight strong to violent EF-3 or stronger tornadoes in Massachusetts:

May 29, 1995: An F4 tornado killed 3 and injured 24 in Great Barrington. The tornado tracked for 11 miles, and damage was estimated at more than $5 million.
Jun 22, 1981: An F3 tornado injured 3 people in Worcester County.
Sep 29, 1974: An F3 tornado injured one person as it hit Middlesex and Essex Counties.
Aug 28, 1973: An F4 tornado killed 4 and injured 36 in West Stockbridge as it tracked 9 miles from New York into Berkshire County.
Sep 13, 1971: An F3 tornado killed one person in Worcester County.
Oct 3, 1970: An F3 tornado killed one person in Worcester County. This tornado was on the ground for 35 miles.
Jun 9, 1953: The great 1953 Worcester tornado killed 90 and injured 1228 when it hit Worcester. The tornado had a path 40 miles long and up to 900 yards wide.
Jun 9, 1953: A separate F3 tornado hit Franklin in southern Massachusetts on the same day as the great Worcester tornado, injuring 17 people. The Franklin tornado had a path length of 28 miles.

Florida's surprise tropical disturbance 93L weakens
Invest 93L sped over Florida yesterday afternoon, bringing welcome rains of 1 - 3 inches over the center part of the state. Winds gusted as high as 29 mph at Daytona Beach as the storm came ashore. The storm has a rather unusual origin for a tropical disturbance--it began as a cluster of thunderstorms called a Mesoscale Convective System (MCS) that pushed across southern New England on May 30. On May 31, the MCS emerged over the ocean, and rotated clockwise towards Florida, steered by a large high pressure system centered over Kentucky. The center of the disturbance stayed over the warm waters of the Gulf Stream, a region of low pressure developed, and intense thunderstorms began to build on Tuesday. By Wednesday morning, 93L had grown organized enough to earn the designation 93L from NHC. However, passage over Florida disrupted 93L, and the storm is moving with such a fast forward speed--about 25 mph--that it has struggled to regroup. Wind shear is a low 5 - 10 knots, and SSTs in the Gulf are about 27°C (81°F), 0.5 - 1.0°C above average, so it is possible that 93L could make a comeback. NHC is currently giving 93L a 0% chance of developing into a tropical depression by Saturday. I think these odds should be higher, at least 10%, given the recent increase in heavy thunderstorm activity near the center of 93L, as seen on satellite imagery. Steering currents will keep 93L moving quickly to the west-southwest today and Friday, and 93L should make landfall in Mexico just south of Brownsville, Texas, on Saturday afternoon.


Figure 3. Radar-estimated precipitation from 93L's passage over Florida yesterday.

Central Caribbean disturbance
Disorganized heavy thunderstorm activity continues in the region between Central America and Jamaica. Wind shear has fallen to the moderate range, 10 - 20 knots, and is predicted to continue to fall over the next two days. This should allow the disturbance to increase in organization, though it will take many days for it to approach tropical depression status, since it is so large and poorly organized. The computer models are generally showing only very slow development of the disturbance over the coming week. NHC is giving the disturbance a 20% of developing into a tropical depression by Saturday. A surge of moisture accompanying a tropical wave may aid development when the wave arrives in the Western Caribbean on Sunday. Water temperatures in the Central Caribbean are about 1°C above average, 29°C, which is plenty warm enough to support development of a tropical storm. Residents of Jamaica, Cuba, the Cayman Islands, Haiti, Honduras, and Nicaragua should anticipate the possibility that heavy rains of 2 - 4 inches may affect them today through Sunday. Heavy rains have already hit Jamaica, where a flash flood watch is posted.


Figure 4. Morning satellite image of the Central Caribbean disturbance.

Catch my intro to the 2011 hurricane season on Internet radio
I'll be discussing the coming hurricane season on our Internet radio show, the Daily Downpour, today (Thursday) at 4:30pm EDT. Fellow wunderground meteorologists Shaun Tanner and Tim Roche will be hosting the show. We'll talk about the latest model runs, hurricane research, modeling accuracy, and hurricane climatology, and answer any questions listeners email in or call in. The email address to ask questions is broadcast@wunderground.com. We'll also discuss the Massachusetts tornadoes.

Jeff Masters

Tornado

Updated: 01:33 PM GMT am 02. Juni 2011

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CSU predicts a very active hurricane season: 16 storms, 9 hurricanes

By: JeffMasters, 04:30 PM GMT am 01. Juni 2011

A very active Atlantic hurricane season is on tap for 2011, according to the seasonal hurricane forecast issued June 1 by Dr. Phil Klotzbach and Dr. Bill Gray of Colorado State University (CSU). The CSU team is calling for 16 named storms, 9 hurricanes, and 5 intense hurricanes, and an Accumulated Cyclone Energy (ACE) 166% of average. Between 1950 - 2000, the average season had 10 named storms, 6 hurricanes, and 2 intense hurricanes. But since 1995, the beginning of an active hurricane period in the Atlantic, we've averaged 14 named storms, 8 hurricanes, and 4 intense hurricanes per year. The new forecast is identical to their April forecast. The forecast calls for a much above-average chance of a major hurricane hitting the U.S., both along the East Coast (48% chance, 31% chance is average) and the Gulf Coast (47% chance, 30% chance is average). The risk of a major hurricane in the Caribbean is also high, at 61% (42% is average.)

The forecasters cited four main reasons for an active season:

1) Neutral to weak La Niña conditions are expected during the most active portion of this year's hurricane season (August-October). This should lead to average to below average levels of vertical wind shear.

2) Above average May sea surface temperatures in the tropical Atlantic.

3) Below average surface pressures during May in the tropical Atlantic.

4) We are in the midst of a multi-decadal era of major hurricane activity, which began in 1995. Major hurricanes cause 80-85 percent of normalized hurricane damage.

Analogue years
The CSU team picked five previous years when atmospheric and oceanic conditions were similar to what we are seeing this year: neutral to weak La Niña conditions in the equatorial Eastern Pacific, and above-average tropical Atlantic and far north Atlantic SSTs during April - May. Those five years were 2008, which featured Hurricane Ike and Hurricane Gustav; 1996, which had two hurricanes that hit North Carolina, Fran and Bertha; 1989, which featured Category 5 Hurricane Hugo; 1981, a very average year with 12 named storms, 7 hurricanes, and 3 intense hurricanes; and 1951, a year that featured 6 major hurricanes. The mean activity for these five years was 12 named storms, 8 hurricanes, and 4 intense hurricanes.

How accurate are the June forecasts?
The June forecasts by the CSU team between 1998 and 2009 had a skill 19% - 30% higher than a "no-skill" climatology forecast for number of named storms, number of hurricanes, and the ACE index (Figure 1). This is a decent amount of skill for a seasonal forecast, and these June forecasts can be useful to businesses such as the insurance industry and oil and gas industry that need to make bets on how active the coming hurricane season will be. Unfortunately, the CSU June 1 forecasts do poorly at forecasting the number of major hurricanes (only 3% skill), and major hurricanes cause 80% - 85% of all hurricane damage (normalized to current population and wealth levels.) This year's June forecast uses a brand new formula never tried before, so there is no way to evaluate its performance. An Excel spreadsheet of their forecast skill (expressed as a mathematical correlation coefficient) show values from 0.41 to 0.62 for their June forecasts made between 1984 and 2010, which is respectable.


Figure 1. Comparison of the percent improvement over climatology for May and August seasonal hurricane forecasts for the Atlantic from NOAA, CSU and TSR from 1999-2009 (May) and 1998-2009 (August), using the Mean Squared Error. Image credit: Verification of 12 years of NOAA seasonal hurricane forecasts, National Hurricane Center.


Figure 2. Comparison of the percent improvement in mean square error over climatology for seasonal hurricane forecasts for the Atlantic from NOAA, CSU and TSR from 2001-2010, using the Mean Square Skill Score (MSSS). The figure shows the results using two different climatologies: a fixed 50-year (1950 - 1999) climatology, and a 2001 - 2010 climatology. Skill is poor for forecasts issued in December and April, moderate for June forecasts, and good for August forecasts. Image credit: Tropical Storm Risk, Inc.

TSR predicts 25% more activity than normal
Expect the Atlantic hurricane season to be about 25% more active than usual, the British private forecasting firm Tropical Storm Risk, Inc. (TSR) said in their pre-season forecast issued on May 24. TSR calls for 14.2 named storms, 7.6 hurricanes, 3.6 intense hurricanes, and an Accumulated Cyclone Energy (ACE) of 124, which is 22% above average. Their May 24 forecast numbers are very close to their previous forecast issued in April. TSR predicts a moderate 55% chance that activity will rank in the top 1/3 of years historically, and a 59% chance that U.S. landfalling activity will be above average. TSR rates their skill level as 16-25% higher than a "no-skill" forecast made using climatology, though an independent assessment by the National Hurricane Center (Figure 1) gives them somewhat lower skill numbers.

TSR projects that 4.4 named storms will hit the U.S., with 1.9 of these being hurricanes. The averages from the 1950-2010 climatology are 3.1 named storms and 1.5 hurricanes. They rate their skill at making these June forecasts for U.S. landfalls at 7 - 11% higher than a "no-skill" forecast made using climatology. In the Lesser Antilles Islands of the Caribbean, TSR projects 1.3 named storms, 0.6 of these being hurricanes. Climatology is 1.1 named storms and 0.5 hurricanes.

TSR cites two main factors for their forecast of an active season:

1) Their model predicts that sea surface temperatures will be 0.11°C warmer than average in August and September over the Main Development Region (MDR) for Atlantic hurricanes. They define this as the area between 10°N and 20°N, between the coast of Africa and Lesser Antilles Islands (20°W and 60°W). It is called the Main Development Region because virtually all African waves originate in this region. These African waves account for 85% of all Atlantic major hurricanes and 60% of all named storms. When SSTs in the MDR are much above average during hurricane season, a very active season typically results (if there is no El Niño event present.)

2) Their model predicts slower than normal trade winds in August and September over the Main Development Region (MDR). Trade winds are forecast to be 0.19 meters per second (about 0.4 mph) slower than average. This would create more spin for developing storms, and allow the oceans to warm up, due to reduced mixing of cold water from the depths and lower evaporational cooling.

FSU predicts a very active hurricane season: 17 named storms
The Florida State University (FSU) Center for Ocean-Atmospheric Prediction Studies (COAPS) issued their third annual Atlantic hurricane season forecast today. This year's forecast calls for a 70% probability of 14-20 named storms and 8-10 hurricanes. The mean forecast is for 17 named storms, 9 hurricanes, and an accumulated cyclone energy (ACE) of 163. They cite warm tropical North Atlantic sea surface temperatures, a weakening of La Niña conditions, and the ongoing positive phase of the Atlantic Multi-decadal Oscillation as the major factors influencing their forecast.

Other seasonal forecasts
The UK Met Office's Glosea4 model is predicting a moderately more active season than normal, with 13 named storms and a ACE index of 151. The Cuba Institute of Meteorology is calling for 13 named storms and 7 hurricanes. NOAA predicts 15 named storms, 8 hurricanes, and 4.5 intense hurricanes. Pennsylvania State University predicts 16 named storms.

A surprise tropical disturbance for Florida
The Atlantic hurricane season is officially underway, and Mother Nature appears to be taking her cue from the calendar, as we have a surprise storm off the coast of Florida that is a threat to develop into a tropical depression later this week, after it crosses Florida into the Gulf of Mexico. An cluster of thunderstorms called a Mesoscale Convective System (MCS) pushed across southern New England early yesterday, emerged over the ocean, and rotated clockwise towards Florida, steered by a large high pressure system centered over Kentucky. The center of the disturbance stayed over the warm waters of the Gulf Stream, a region of low pressure developed, and intense thunderstorms began to build yesterday afternoon. Early this morning, the National Hurricane Center (NHC) designated the disturbance Invest 93L, and gave it a 10% chance of developing into a tropical depression. At 8am EDT, they upped those chances to 30%. Invest 93L is becoming increasingly organized, with Melbourne, Florida radar showing the beginnings of some rotation, with a solid band of heavy rain on the southwest side of the disturbance. The pressure and winds have leveled out at Buoy 41012, 40 nm ENE of St. Augustine, Florida. Winds peaked at 19 mph, gusting to 22 mph, at 10:50am EDT. Satellite imagery shows a small but intensifying region of thunderstorms. Sea surface temperatures (SSTs) are about 26°C (79°F) off the east coast of Florida, which is just warm enough to support formation of a tropical depression, and about 0.5°C above average. Wind shear is a low 5 - 10 knots, and it is likely that 93L will continue intensifying until it makes landfall over Central Florida this afternoon. A 50-mile wide swath of Florida from Daytona Beach to just north of Tampa can expect 1 - 3 inches of rain from 93L as it tracks over the state this afternoon and tonight. A Windsat pass this morning did not show a closed circulation, and I doubt 93L has enough time to develop into a tropical depression before landfall in Florida. The coast between Daytona Beach and Cocoa Beach could see wind gusts of 25 - 35 mph this afternoon, though.


Figure 3. Afternoon radar image of 93L from the Melbourne, Florida radar.

Fate of 93L once in the Gulf of Mexico
Since 93L is expected to continue its rapid west-southwest motion at 15 - 20 mph through Thursday, it will cross the Florida Peninsula in about 12 hours and emerge over the Gulf of Mexico early Thursday morning. It is possible that the passage over Florida will greatly disrupt 93L, since it is such a small system. I give a 40% chance that the storm will see its peak strength this afternoon, and not significantly regenerate over the Gulf of Mexico. However, the latest SHIPS model forecast predicts that wind shear will remain low to moderate, 5 - 15 knots, as 93L moves westwards over the Gulf of Mexico Thursday and Friday. SSTs in the Gulf are about 27°C (81°F), 0.5 - 1.0°C above average, and it is possible that 93L could gain enough strength to become Tropical Depression One as it crosses the Gulf. Since 93L will be moving parallel to the coast a short distance offshore, it is difficult to predict where the storm might make a second landfall, since a slight change in heading will make a large difference in landfall location. I don't expect widespread heavy rains from 93L along the Gulf Coast, since the storm is so small, but some locations close to the coast could receive 2 - 4 inches as 93L brushes by. Heavier rains are possible at the eventual landfall location. Since 93L is so small, the computer models are having trouble seeing the system, and are not very helpful forecasting the behavior of the storm over the Gulf of Mexico. The Hurricane Hunters are on call to fly into 93L Thursday afternoon at 2pm EDT, if necessary.

Central Caribbean disturbance
Moisture and heavy thunderstorm activity continues to slowly increase in the region between Central America and Jamaica, and wind shear is falling. With wind shear now 20 - 30 knots, we can expect this disturbance to show increased organization today, and recent satellite images show the beginnings of a surface circulation trying to get going about 100 miles off the coast of Northeast Nicaragua. All of the computer models predict that an area of low pressure will form in this region by Thursday, and this low will have the potential to develop into a tropical depression late this week or early next week. A surge of moisture accompanying a tropical wave currently south of Hispaniola may aid development when the wave arrives in the Western Caribbean on Thursday. Water temperatures in the Central Caribbean are about 1°C above average, 29°C, which is plenty warm enough to support development of a tropical storm. Residents of Jamaica, Cuba, the Cayman Islands, Haiti, Honduras, and Nicaragua should anticipate the possibility that heavy rains of 2 - 4 inches may affect them Thursday through Saturday this week.


Figure 4. Satellite image of the Central Caribbean disturbance.

Catch my intro to the 2011 hurricane season on Internet radio
I'll be discussing the coming hurricane season on our Internet radio show, the Daily Downpour, tomorrow (Thursday) at 4:30pm EDT. Fellow wunderground meteorologists Shaun Tanner and Tim Roche will be hosting the show. We'll talk about the latest model runs, hurricane research, modeling accuracy, and hurricane climatology, and answer any questions listeners email in or call in. The email address to ask questions is broadcast@wunderground.com. Welcome to the hurricane season of 2011!

Jeff Masters

Hurricane

Updated: 06:18 PM GMT am 17. August 2011

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Hurricane season blows in 93L for Central Florida

By: JeffMasters, 01:32 PM GMT am 01. Juni 2011

The Atlantic hurricane season is officially underway, and Mother Nature appears to be taking her cue from the calendar, as we have a surprise storm off the coast of Florida that is a threat to develop into a tropical depression later this week, after it crosses Florida into the Gulf of Mexico. An cluster of thunderstorms called a Mesoscale Convective System (MCS) pushed across southern New England early yesterday, emerged over the ocean, and rotated clockwise towards Florida, steered by a large high pressure system centered over Kentucky. The center of the disturbance stayed over the warm waters of the Gulf Stream, a region of low pressure developed, and intense thunderstorms began to build yesterday afternoon. Early this morning, the National Hurricane Center (NHC) designated the disturbance Invest 93L, and gave it a 10% chance of developing into a tropical depression. At 8am EDT, they upped those chances to 30%. Invest 93L is becoming increasingly organized, with Melbourne, Florida radar showing the beginnings of some rotation, with a solid band of heavy rain on the southwest side of the disturbance. The pressure is falling and winds are rising at Buoy 41012, 40 nm ENE of St. Augustine, Florida. Winds were 16 mph, gusting to 20 mph, at 8:50am EDT. Satellite imagery shows a small but intensifying region of thunderstorms, with the high level cirrus clouds of 93L already moving over Florida. Sea surface temperatures (SSTs) are about 26°C (79°F) off the east coast of Florida, which is just warm enough to support formation of a tropical depression, and about 0.5°C above average. Wind shear is a low 5 - 10 knots, and it is likely that 93L will continue intensifying until it makes landfall over Central Florida this afternoon. A 50-mile wide swath of Florida from Daytona Beach to just north of Tampa can expect 1 - 3 inches of rain from 93L as it tracks over the state this afternoon and tonight. I don't believe 93L has enough time to develop into a tropical depression before landfall in Florida, but the coast between Daytona Beach and Cocoa Beach could see wind gusts of 25 - 35 mph.


Figure 1. Morning radar image of 93L from the Melbourne, Florida radar.

Fate of 93L once in the Gulf of Mexico
Since 93L is expected to continue its rapid west-southwest motion at 15 - 20 mph through Thursday, it will cross the Florida Peninsula in about 12 hours and emerge over the Gulf of Mexico early Thursday morning. It is possible that the passage over Florida will greatly disrupt 93L, since it is such a small system. I give a 40% chance that the storm will see its peak strength this afternoon, and not significantly regenerate over the Gulf of Mexico. However, the latest SHIPS model forecast predicts that wind shear will remain low to moderate, 5 - 15 knots, as 93L moves westwards over the Gulf of Mexico Thursday and Friday. SSTs in the Gulf are about 26°C (79°F), 0.5 - 1.0°C above average, and it is possible that 93L could gain enough strength to become Tropical Storm Arlene as it crosses the Gulf. Since 93L will be moving parallel to the coast a short distance offshore, it is difficult to predict where the storm might make a second landfall, since a slight change in heading will make a large difference in landfall location. I don't expect widespread heavy rains from 93L along the Gulf Coast, since the storm is so small, but some locations close to the coast could receive 2 - 4 inches as 93L brushes by. Heavier rains are possible at the eventual landfall location. Since 93L is so small, the computer models are having trouble seeing the system, and are not very helpful forecasting the behavior of the storm over the Gulf of Mexico.

I'll have an update by noon today, when the latest CSU seasonal Atlantic hurricane forecast will be available.

Jeff Masters

Updated: 01:33 PM GMT am 01. Juni 2011

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About JeffMasters

Jeff co-founded the Weather Underground in 1995 while working on his Ph.D. He flew with the NOAA Hurricane Hunters from 1986-1990.