MIssissippi tornado rated a violent EF-4

By: Dr. Jeff Masters , 02:30 PM GMT am 27. April 2010

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The devastating tornado that ripped through Mississippi on Saturday April 24, killing ten, was a violent EF-4 twister with 170 mph winds when it hit Yazoo City, according to a preliminary damage survey by the National Weather Service in Jackson, Mississippi. The tornado touched down near Tallulah, Louisiana, crossed the Mississippi River into Mississippi, and traversed nearly the entire state of Mississippi, carving a 149-mile long path of destruction. It is extremely rare for a tornado to stay on the ground this long. The world record longest path by a tornado is the 219-mile long path of the deadliest tornado in U.S. history, the violent F-5 Tri-State Tornado of 1925, which killed 695 people in Missouri, Illinois, and Indiana.


Figure 1. A church in Yazoo City works to restore its toppled steeple after Saturday's tornado. Image credit: J.A.

Saturday's tornado was strong almost from its initial stage of development in northeast Louisiana. EF-2 and EF-3 damage was common all along the tornado's path into central Mississippi with areas of EF-4 damage observed in both Yazoo and Holmes counties. After crossing Interstate 55, the tornado weakened with EF-1 and occasional EF-2 damage being common as the tornado moved across Attala County. The tornado re-intensified as it moved into Choctaw County, with at least high end EF-3 damage occurring northwest of the Weir community. The tornado remained strong before rapidly weakening and then dissipating just after moving into Oktibbeha County. It was the first violent EF-4 tornado of 2010. Over the past decade, the U.S. has averaged five violent EF-4 or EF-5 tornadoes per year. Our severe weather expert, Dr. Rob Carver, has a more detailed analysis of Saturday's tornado.


Figure 2. One mile wide wedge tornado from near Yazoo City, Mississippi on April 24, 2010. Tornadovideos.net intercepted the tornado near Holly Bluff just east of the Mississippi River, and tracked the huge wedge to the damage path in Yazoo City, after which they assisted with the rescue effort until emergency personnel gained control of the situation.

Portlight assesses needs after the Mississippi tornado
Portlight.org volunteer Riki Chomsky (AKA "kitchengypsy") paid a visit to tornado-ravaged Yazoo City, Mississippi on Sunday to assess whether or not Portlight should mount a response effort. Her report:

At this time, Portlight has decided not to deploy an emergency feeding unit to Yazoo City. We base this decision on 3 factors:

1) Scope. Although the scenes of devastation are terrible, by our estimate, more than half the city is relatively unharmed. With several restaurants, gas stations and other services open for business in such close proximity to the command center, we have faith that continuity of operations will soon be established for the whole city.

2) Current efforts: All current relief teams, with special emphasis on the Red Cross and Salvation Army, are doing an excellent job of handling the situation. They have taken pains to ensure food distribution across the affected areas, and we have confidence that they are truly the best organizations for this type of situation.

3) Anticipated Need / Speed of Recovery: although the extent of the damage will most likely require outside work crews, we saw very encouraging signs of progress. Work crews were active at almost every damaged site, which is highly impressive for less than 24 hours after the storm. Even when volunteer crews are brought in, we anticipate their needs being more than adequately met by the existing local churches, who have already started feeding work crews and rescue personnel. In addition to the Red Cross and Salvation Army, Portlight extends our appreciation to all members of this exemplary community response. While the damage is significant, the Salvation Army and local Red Cross seem to be doing a great job meeting the needs there, and Portlight recommends supporting one of these organizations.

Portlight continues aid efforts in Haiti
Portlight continues to focus its energy and funds on the situation in Haiti, where the rainy season is fast approaching the needs for shelter, medical supplies, food and water remain urgent. Their latest effort is a shipment of 10 pallets of Durable Medical Equipment, 30 pallets of water, 7,000 pounds of rice, a number of tents, tarps and various building supplies totaling some 14,000 pounds of goods. The supplies were loaded onto the schooner Halie and Mathew. The schooner was slowed by bad weather on its way to Haiti, and was forced to dock in Jamaica to make repairs. The ship is expected to land in Haiti later this week to deliver its supplies. Please visit the Portlight.org web site or the Portlight blog to learn more and to donate to this worthy cause.


Figure 3. Relief supplies for Haiti earthquake victims being loaded onto the schooner Halie and Mathew.

Jeff Masters

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oil on water .. wouldnt that prevent alot of evaporative cooling?
Member Since: August 27, 2008 Posts: 0 Comments: 1497
Quoting Snowlover123:

R U Sarah Palin's son?

Quoting Snowlover123:

R U Sarah Palin's son?

Presslord McCain? :)
Member Since: Posts: Comments:
Quoting SouthALWX:
I actually thought about burning it off. Oil floats so I assume it would burn alot of it. the negative effects of that cant be any worse than letting it reach shore.


To be honest when I first read it I thought it would be a great idea minus all the smoke that it will cause. It will take awhile to burn as oil doesnt burn off really fast but it will help with clean up. I guess it is getting close to an area of whales and dolphins as well so if it helps conrol the spread and if it full burns off, you would think it would work and be better that the mess on the coast minus all the smoke.
Member Since: Mai 20, 2009 Posts: 0 Comments: 1640
Quoting BenBIogger:
SOI 1982-2010 chart

Wow... SOI generally has been very negative. It's all due to the warm PDO that we had from 1977-2008. There, it caused more frequent El Ninos, but now since the PDO has changed in 2008, the SOI should generally be positive, because with a Negative PDO, you usually get more frequent La Nina's. The PDO kind of "lets them hang over," the time that they're supposed to dissipate.
Member Since: April 1, 2010 Posts: 9 Comments: 2699
Heat continues to build in the eastern Pacific. A broad area of moderate convection is showing fairly good persistence and concentration today, especially compared to the past 3 days. Weak low-mid-level turning is evident on visible RGB satellite imagery near 9N, 92W. CIMSS analysis continues to show a 850-700mb vorticity maximum in the area, moving slowly WNW.

This disturbance, I believe, has persisted long enough to warrant issuance of an invest, but the Navy has not yet done so. If the area remains as consolidated as it is right now and sustains widespread moderate convection overnight, I see no reason why we shouldn't see an invest issued tomorrow.



Member Since: Posts: Comments:
Quoting Snowlover123:

R U Sarah Palin's son?

If you are going to begin with the politics I will be more than happy to report and ignore you, so please don't start.
Member Since: September 2, 2009 Posts: 130 Comments: 21032
Quoting HaboobsRsweet:


haha that is funny but you know what, if they did set it on fire it would take a long time to burn off and I bet you see some clouds forming with all the moisture, heat and CCN. I am sure the water in that area wont cool because of the fire haha.
lol
Member Since: September 2, 2009 Posts: 130 Comments: 21032
Sea ice has leveled slightly...

Member Since: April 1, 2010 Posts: 9 Comments: 2699
SOI 1982-2010 chart
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Quoting presslord:
Offshore drilling is perfectly safe...no environmental threat whatsoever...don't be such a baby...drill, baby, drill...

R U Sarah Palin's son?

Member Since: April 1, 2010 Posts: 9 Comments: 2699
Quoting Skyepony:
Cloudsat of the far west side of the EPAC blob.
I tried to post the WINDSAT or ASCAT but both failed to scan the EPAC low. Plus, the ASCAT that got a little bit of the area is from April 26th.
Member Since: September 2, 2009 Posts: 130 Comments: 21032
Offshore drilling is perfectly safe...no environmental threat whatsoever...don't be such a baby...drill, baby, drill...
Member Since: Posts: Comments:
I actually thought about burning it off. Oil floats so I assume it would burn alot of it. the negative effects of that cant be any worse than letting it reach shore.
Member Since: August 27, 2008 Posts: 0 Comments: 1497
Quoting Snowlover123:

The oil spill may cool SST's, because the sunlight relefcts off of the oil, and possibly lowering the Gulf's fever. Speaking of fever's Buzz Bernard's sarcastic fever, can be viewed Here


It may also warm SSTs as the dark colour absorbs more heat.
Member Since: August 30, 2008 Posts: 8 Comments: 2834
Quoting MiamiHurricanes09:
Oh, ok that makes some sense. But if they do that SST's will warm rapidly!!! Lol, Jk.


haha that is funny but you know what, if they did set it on fire it would take a long time to burn off and I bet you see some clouds forming with all the moisture, heat and CCN. I am sure the water in that area wont cool because of the fire haha.
Member Since: Mai 20, 2009 Posts: 0 Comments: 1640
Quoting MiamiHurricanes09:


SSTs have warmed up rapidly in the EPac and Caribbean. I expect most of the Caribbean to be 29C+ by early May. This doesn't usually occur until early September.
Member Since: August 30, 2008 Posts: 8 Comments: 2834
Quoting BenBIogger:
Current SST along the South Florida coast.

The oil spill may cool SST's, because the sunlight relefcts off of the oil, and possibly lowering the Gulf's fever. Speaking of fever's Buzz Bernard's sarcastic fever, can be viewed Here
Member Since: April 1, 2010 Posts: 9 Comments: 2699
Quoting Snowlover123:

Why is it bad?
Well as I posted before, an increase in SOI means dying El niño. El niño is usually the deciding factor between and active and a slow season, if the El niño dies we will make a transition from El niño to La niña (a weak one most likely), but either way that is not good.
Member Since: September 2, 2009 Posts: 130 Comments: 21032
Quoting Snowlover123:

Why is it bad?


It means we are approaching a more neutral or La Nina season.
Member Since: August 30, 2008 Posts: 8 Comments: 2834
Quoting HaboobsRsweet:


Just saying what the article said...Coast Guard is considering it. I assume they are talking about the oil that is getting closer to the coastline and starting on that end. Oil can burn on top of water and there is a lot of it sitting on top of the water right now. It might help control it from spreading it reaching the coast buying more time for them to stop the leak.


Fried shrimp, anyone?
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216. Skyepony (Mod)
Cloudsat of the far west side of the EPAC blob.
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Member Since: September 2, 2009 Posts: 130 Comments: 21032
Quoting MiamiHurricanes09:
Expect SOI to go above 17 if it continues to follow the current trend.

*By the way for the newbies, High SOI=Bad thing.

Why is it bad?
Member Since: April 1, 2010 Posts: 9 Comments: 2699
Quoting HaboobsRsweet:


Just saying what the article said...Coast Guard is considering it. I assume they are talking about the oil that is getting closer to the coastline and starting on that end. Oil can burn on top of water and there is a lot of it sitting on top of the water right now. It might help control it from spreading it reaching the coast buying more time for them to stop the leak.
Oh, ok that makes some sense. But if they do that SST's will warm rapidly!!! Lol, Jk.
Member Since: September 2, 2009 Posts: 130 Comments: 21032
Quoting MiamiHurricanes09:
If the oil is under water, how the hell are they going to burn it off? That's almost as smart as trying to put out a fire with gas.


Just saying what the article said...Coast Guard is considering it. I assume they are talking about the oil that is getting closer to the coastline and starting on that end. Oil can burn on top of water and there is a lot of it sitting on top of the water right now. It might help control it from spreading it reaching the coast buying more time for them to stop the leak.
Member Since: Mai 20, 2009 Posts: 0 Comments: 1640
Quoting HaboobsRsweet:
Just read they are considering to set the oil on fire to try and burn it off. Wonder if that is the smart thing to do.
If the oil is under water, how the hell are they going to burn it off? That's almost as smart as trying to put out a fire with gas.
Member Since: September 2, 2009 Posts: 130 Comments: 21032
Just read they are considering to set the oil on fire to try and burn it off. Wonder if that is the smart thing to do.
Member Since: Mai 20, 2009 Posts: 0 Comments: 1640
Quoting tornadodude:

Hey T-Dude! Thanks for the frosty 47F morning here in Arlington, TX. We're gonna send you some severe thunderstorms from TX :o)!!

Portion of Area Forecast Discussion, NWS DFW, TX from 3:46PM CDT:

MODELS ARE IN GOOD AGREEMENT NOW THAT THE UPPER LEVEL TROUGH WILL
REMAIN OVER THE DESERT SOUTHWEST ON THURSDAY AND THE DRYLINE WILL
REMAIN IN WEST TEXAS. THE TROUGH WILL ADVANCE EAST THURSDAY NIGHT
AND SO WILL THE DRYLINE. A LINE OR COMPLEX OF THUNDERSTORMS IS
EXPECTED TO DEVELOP EARLY FRIDAY MORNING AND MOVE ACROSS NORTH
TEXAS. THIS STORMS WILL LIKELY INITIATE IN OKLAHOMA AND CONTINUE
BUILDING SOUTH INTO TEXAS. HAVE KEPT THE HIGHEST POPS FRIDAY
MORNING OVER THE NORTHEASTERN QUADRANT OF NORTH TEXAS. SEVERE
WEATHER WILL BE POSSIBLE.

THE DRYLINE WILL STALL OVER NORTH TEXAS FRIDAY NIGHT AND IT LOOKS
LIKE WE WILL SEE A BRIEF BREAK IN THE PRECIPITATION LATE FRIDAY BEFORE
ANOTHER ROUND OF STORMS DEVELOPS FRIDAY NIGHT INTO SATURDAY. THE
UPPER LEVEL TROUGH WILL STILL BE LOCATED WEST OF THE
REGION...HAVING NOT MADE ANY MORE SIGNIFICANT PROGRESSION EAST.
THE BEST CHANCE FOR RAIN WILL BE OVER THE EASTERN HALF OF NORTH
TEXAS...AHEAD OF THE DRYLINE/COLD FRONT.
Member Since: August 25, 2009 Posts: 20 Comments: 6785
Quoting KEEPEROFTHEGATE:

No NOT again!!!
Member Since: August 25, 2009 Posts: 20 Comments: 6785
Expect SOI to go above 17 if it continues to follow the current trend.

*By the way for the newbies, High SOI=Bad thing.
Member Since: September 2, 2009 Posts: 130 Comments: 21032
Current SST along the South Florida coast.
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Good evening from the Turks & Caicos
It was hot Hot HOT here today and still...
and it's only April.
CRS
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Pdiddy does the Tropical formula gig thing too?

Go figure..
Member Since: Juli 3, 2005 Posts: 414 Comments: 125552
Quoting StormW:


SOI

Thanks a lot Storm.
Member Since: September 2, 2009 Posts: 130 Comments: 21032
Hey storm!
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Quoting Tropicsweatherpr:
30 day SOI continues to spike up,now at +15.7.

Do you have a link to that graph?
Member Since: September 2, 2009 Posts: 130 Comments: 21032
Quoting AstroHurricane001:


If this thing makes it through the Isthmus of Tehuantepec, I'm worried about it exploding in the BoC and GOM.
You don't need to worry about that. First of all the rough terrain will not allow a weak area of low pressure go through it. Number 2, If it does go through then you expect it to die quickly due to below average SST's. And number 3, shear in the northern/central Gulf is above 100 knots, I wouldn't expect anything to develop.
Member Since: September 2, 2009 Posts: 130 Comments: 21032
Quoting jrweatherman:
Okay, what is SOI?


High SOI: El Niño that is dying because of colder SST's in the Pacific.

Low SOI: El Niño that is gaining strength because of warmer Pacific SST's.

* El Niño 3.4 I believe is at 0.7, expect a big plummet soon. I expect most of the 2010 hurricane season, especially August, September, and October to have a weak to moderate La Niña, which should help to have more named storms. And that is never a good thing, unless you're a doomcaster.
Member Since: September 2, 2009 Posts: 130 Comments: 21032
Quoting MiamiHurricanes09:
GFS 18z showing bad time-line progression. In the 12z run they had the 1001 MB EPAC low making land fall at 114 hours, now it is at its highest intensity but no where close to land fall.

GFS 18z 114 hours:



Makes landfall at 132/138 hours, looks elongated on the GFS, looks interesting...



If this thing makes it through the Isthmus of Tehuantepec, I'm worried about it exploding in the BoC and GOM.
Member Since: August 30, 2008 Posts: 8 Comments: 2834
[ Pdiff - Pdiffav ]
SOI = 10 -------------------
SD(Pdiff)

where

Pdiff = (average Tahiti MSLP for the month) - (average Darwin MSLP for the month),
Pdiffav = long term average of Pdiff for the month in question, and
SD(Pdiff) = long term standard deviation of Pdiff for the month in question.


...yea...this is the formula I always use...
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Quoting Patrap:
Oil Spill: NASA Images From Space (PHOTOS)


The oil slick is seen from space in its entirety, showing the scope of the spill.


I don't like this, the oil is spreading toward the ecologically vulnerable Delta and Chandeleur region.
Member Since: August 30, 2008 Posts: 8 Comments: 2834
; )
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Quoting HaboobsRsweet:


Not really but wonder if all that oil in the Gulf will have an effect on SSTs. Anyone know the impact?


Probably won't impact SSTs that much, but it could take a few months to cap all the oil. If a hurricane hits the Gulf during that time...you could probably say goodbye to quite a few species in those Wildlife Refuges.
Member Since: August 30, 2008 Posts: 8 Comments: 2834
Quoting skepticall2:


Southern Oscillation Index

Don't ask me what it means I just know that is what SOI stands for.


The Southern Oscillation Index (SOI) is calculated from the monthly or seasonal fluctuations in the air pressure difference between Tahiti and Darwin.

Sustained negative values of the SOI often indicate El Nio episodes. These negative values are usually accompanied by sustained warming of the central and eastern tropical Pacific Ocean, a decrease in the strength of the Pacific Trade Winds, and a reduction in rainfall over eastern and northern Australia. The most recent strong El Nio was in 1997/98, although its effect on Australia was rather limited. Severe droughts resulted from the weak to moderate El Nio events of 2002/03 and 2006/07.

Positive values of the SOI are associated with stronger Pacific trade winds and warmer sea temperatures to the north of Australia, popularly known as a La Nia episode. Waters in the central and eastern tropical Pacific Ocean become cooler during this time. Together these give an increased probability that eastern and northern Australia will be wetter than normal. The most recent strong La Nia was in 1988/89. A moderate La Nia developed slowly during 2007.

For further information, have a look at the Climate Variability and El Nio brochure.
Click here to find out more about El Nio and associated topics.

For the mathematically minded:

There are a few different methods of how to calculate the SOI. The method used by the Australian Bureau of Meteorology is the Troup SOI which is the standardised anomaly of the Mean Sea Level Pressure difference between Tahiti and Darwin. It is calculated as follows:


[ Pdiff - Pdiffav ]
SOI = 10 -------------------
SD(Pdiff)

where

Pdiff = (average Tahiti MSLP for the month) - (average Darwin MSLP for the month),
Pdiffav = long term average of Pdiff for the month in question, and
SD(Pdiff) = long term standard deviation of Pdiff for the month in question.

The multiplication by 10 is a convention. Using this convention, the SOI ranges from about %u201335 to about 35, and the value of the SOI can be quoted as a whole number. The SOI is usually computed on a monthly basis, with values over longer periods such a year being sometimes used. Daily or weekly values of the SOI do not convey much in the way of useful information about the current state of the climate, and accordingly the Bureau of Meteorology does not issue them. Daily values in particular can fluctuate markedly because of daily weather patterns, and should not be used for climate purposes. A table of monthly SOI values is available here. Approximate 30-day values are often included in the weekly El Nio Wrap-Up.
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Quoting jrweatherman:
Okay, what is SOI?


Here is the whole explanation about it.

Link
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Southern Oscillation Index
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A beautiful day in Sydney.

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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.