African wave 99L may develop; Felicia threatens Hawaii; record rains from Morakot
A strong tropical wave with a high amount of spin moved off the coast of Africa yesterday, and has a good chance of becoming the first named storm of the 2009 Atlantic hurricane season. The wave was designated 99L by NHC Sunday morning. Wind shear is moderate, about 10 knots, and sea surface temperatures are moderately warm, about 27 - 28°C. There is a large area of dry air to 99L's north, but this is not currently interfering with the storm's organization. This morning's QuikSCAT pass showed a nearly closed surface circulation, stretched out along two axes. The storm can now be classified as tropical depression using the satellite-based Dvorak classification technique, but the surface circulation will have to show better definition before 99L can be classified as a tropical depression. Top winds were in the 20 - 30 mph range, as estimated by QuikSCAT and the Dvorak satellite estimates.
Figure 2. Visible satellite image of disturbance 99L.
Wind shear is expected to be low, 5 - 10 knots, tonight through Tuesday. SSTs will remain relatively constant at 27°C, so conditions favor development. NHC has given 99L a moderate (30 - 50% chance) of developing into a tropical depression by Tuesday morning, which is a reasonable forecast. The UKMET, GFS, and NOGAPS models all develop 99L into a tropical depression 1 - 4 days from now. The dry air of the Saharan Air Layer may become a problem for 99L 2 -4 days from now, as the storm moves slightly north of due west. It is too early to say if 99L will recurve north of the Lesser Antilles Islands or not, since it will be at least 6 days before the storm makes it that far.
The GFS model predicts development of a new tropical wave coming off the coast of Africa about 6 - 7 days from now.
Felicia weakens to a tropical storm, still a threat to Hawaii
Tropical Storm Felicia has weakened steadily over the past 24 hours, thanks to cool sea surface temperatures and increasing shear. Recent satellite imagery shows that wind shear is beginning to affect the storm, with strong upper-level winds from the west pushing the storm's heavy thunderstorm activity all to the east side of the center.
Figure 2. History of hurricane activity over Hawaii since 1950. Hawaii islands have been hit by only 9 tropical cyclones of tropical depression or greater strength, with 4 others passing withing 75 miles of an island. Image credit: NOAA Coastal Services Center.
Sea surface temperatures (SSTs) under Felicia are 25°C, well below the 26°C threshold typically needed to sustain a hurricane. SSTs will slowly increase to 26°C by the time the storm reaches Hawaii, though. Wind shear has increased to a moderate to high 20 knots, and is expected to increase further to 30 knots by Monday morning. The high shear combined with the cool SSTs should reduce Felicia to tropical depression strength by the time the center reaches the Hawaiian Islands Monday night. The wind speed probabilities forecast shows about a 40% chance Felicia will still be a weak tropical storm when it moves through the islands Monday night, and 40% chance it will be a tropical depression. If Felicia does hold together that long, it would be only the tenth tropical cyclone of tropical depression or higher strength to affect the islands since 1950 (Figure 1). Large swells from Felicia are already affecting the Big Island, and a high surf warning has been posted for the Big Island. Felicia or its remnants should bring heavy rain, flash flooding, and mud slides to the islands beginning Monday morning, and a Flash Flood Watch has been posted for most of the islands.
Typhoon Morakot hits China
Typhoon Morakot hit China this morning as a tropical storm, lashing the mainland with very heavy rain. Yesterday, Morakot hit Taiwan, dumping up to 80 inches of rain on the island over a 2-day period, according to news reports. The world 2-day rainfall record is 98.42", set at Reunion Island on March 15 - 17, 1952, so the Typhoon Morakot 2-day totals are some of the highest ever measured in the world. The highest 1-day rainfall total ever recorded on Taiwan occurred Saturday at Weiliao Mountain in Pingtung County, which recorded 1.403 meters (4.6 feet or 55 inches) or rain. Nine the ten highest one-day rainfall amounts in Taiwanese history were reached on Saturday, according to the Central Weather Bureau. Three are dead and 31 people missing on the island, and Morakot also killed 23 people in the Philippines.
I'll have an update on Monday.
Jeff Masters
Reader Comments
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Here you go
Darn,
We have the same Avatar.
MULTI-LAYER STEERING
So you are at the top of your class then?
Well I wouldn't say all that but i do have a 3.4 GPA and made the Dean's list twice my freshman year so i'm building a good resume but this is my dream its all i can ever see myself doing i'm going at it as hard and competive as i can
Well those patterns constantly change so it's anyones guess. I not even sure if the models know.
So basically what you're saying it means is that the wave is located where there's a 'shift' in the water falling (precipitating) against the surrounding area? Is it where there's more rainfall? What kind of shift?
Why is that flagged? Are you a conservative?
Look at the difference between the GFS, NOGAPS, and CMC on that mid latitude trough on the 144hr. The GFS is the deepest while the NOGAPS and CMC are the flattest in favor of the ridge.
aint it great :) lol...
convection seems to be a little less...but i take it we will see some fireworks in the upcoming 6-8 hours...
Im very conservative and I voted for her .. but i found it funny =]
I wish you the best. Just remember, leave emotions out of the equation.
Hey watch long time no see. I see we could be seeing a TD anytime now. This blog is already crazy.
That's good!
I will be here early tomorrow morning.
Goodnight All
Back in the AM
Thanks! The reason i'm in the good position i am is because of this blog you can really learn alot i joined here as a 16 year old that barely knew anything but the senior people on here really helped and showed me the ropes
fantastic stuff
Great job. Try to get a 3.5 or higher
Albeit I changed majors, I am still trying to keep mines above a 3.5
Hey Storm!
Am I reading this as a southwesterly flow at all levels?
According to the QUIKSCAT at about 13.8 or so
INV/99L/XX
MARK
14.4N/23.2W
1008MB
25KTS
FXCA62 TJSJ 100139 AAA
AFDSJU
AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE SAN JUAN PR
939 PM AST SUN AUG 9 2009
.UPDATE...SHOWERS ARE STILL MOVING ACROSS PARTS OF ZONE 1 AND ZONE
3 AND PART OF ZONE 8 AS MOST SHOWERS HAVE NOW CLEARED FROM THE
REST OF PUERTO RICO. HAVE INCHED UP POPS TO REFLECT THE CONTINUED
POSSIBILITY OF SHOWERS IN NORTHEAST AND EAST PUERTO RICO. THE NAM
KEEPS GOOD MOISTURE OVER THE ATLANTIC THROUGH 10/12Z WHILE THE GFS
BRINGS SOME ADDITIONAL MOISTURE IN AFTER 06Z. SHOWERS CONTINUE IN
THE ATLANTIC AND MONA CHANNEL AT THIS TIME. 00Z SOUNDING SHOWED DRY
AIR ABOVE 13 THOUSAND FEET. MOISTURE CONTINUES TO LOOK PROMISING
FOR WEDNESDAY NIGHT THROUGH THURSDAY AS A STRONGER WAVE MOVES
THROUGH THE AREA.
A TROPICAL WAVE ALONG 48/49W IS EXPECTED TO APPROACH THE LOCAL AREA
TUESDAY NIGHT...WITH AN INCREASE IN SHOWERS AND THUNDERSTORMS
ACROSS THE LOCAL REGION. AFTER THE PASSAGE OF THIS WAVE...FOR
WEDNESDAY...COMPUTER MODELS SUGGEST THAT DRIER AIR WILL MOVE
BRIEFLY TO THE LOCAL AREA. HOWEVER...AN ACTIVE TROPICAL WAVE IS
EXPECTED TO AFFECT THE LOCAL AREA THURSDAY...BRINGING A
SIGNIFICANT INCREASE IN MOISTURE TO THE LOCAL AREA. THE COMBINATION
OF THE TWO WAVES...COULD PRODUCE A GOOD DEAL OF PRECIPITATION
ACROSS PUERTO RICO..WHICH WILL MAY LEAD TO URBAN AND SMALL STREAM
FLOODING. IN FACT...LATEST SJU-GFS 12Z TIME HEIGHT CROSS SECTIONS
INDICATED MOISTURE EXTENDING AT ALL LEVEL OF THE
ATMOSPHERE...BETWEEN THU 06Z AND FRIDAY AT 18Z. THIS PERIOD IS
WHEN WE EXPECT THE MOST ACTIVE WEATHER ACROSS THE LOCAL AREA.
THE TROPICAL ATLANTIC IS STARTING TO GET ACTIVE THIS AFTERNOON. A
VERY STRONG TROPICAL WAVE...WHICH WAS LOCATED BY THE NATIONAL
HURRICANE CENTER FEW HUNDRED MILES SOUTHEAST OF THE CAPE VERDE
ISLANDS...CONTINUES TO SHOW SOME SIGNS OF ORGANIZATION.
CONDITIONS APPEAR FAVORABLE FOR THIS SYSTEM TO BECOME A TROPICAL
DEPRESSION DURING THE NEXT COUPLE OF DAYS AS IT MOVES GENERALLY
WESTWARD AT 10 TO 15 MPH. STAY TUNED FOR FURTHER INFORMATION ABOUT
THIS SYSTEM.
the fact that im conservative and it was marginally amusing had no impact as to why it was flagged...from admin notice,"please refrain from posting material not relevant to the discussion of tropical weather"...ive been banned for less...
def. looking less impressive the last few hours...i imagine if it has a hard time refiring convection overnight the nhc would have a hard time upgrading...we will just have to wait and see...
Albeit I changed majors, I am still trying to keep mines above a 3.5
I have to hand it to you bro maintaining a 3.5 in college isn't easy thats impressive
hey man, hows it going...yea, we could...but ill wait and see how the system fares overnight/tomorrow ...unless it can sustain at least some decent convection over the coc/lcc for more than a few days, i doubt it gets upgraded...
Yup when you've got something that could develop within 24 hours the mob of trolls breaks in to the blog.
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