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
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wow i'm surprised!!!
But it needs 500mb vorticity
~WEST @ ~9kt?
Regarding the wave...the radar loop shows the circulation nicely.
ECMWF may be on to something with the wave behind.
The main feature this morning in the Tropical Atlantic remains 99L. Current satellite loop imagery indicates convection has diminished with this system. However, satellite loop imagery also would indicate that vorticity is well established and a little more symmetric. Close up satellite loop imagery from CIRA RAMMB may also show that the COC (Center Of Circulation) may be trying to reform slightly further south of the center depicted in the latest Quikscat pass.
that will change once 99L gets further west
As StormW said in his blog a TCFA has been issued here it is:
WTNT 21 KNGU 100600
SUBJ/TROPICAL CYCLONE FORMATION ALERT 100600Z AUG 09//
RMKS/
1. FORMATION OF A SIGNIFICANT TROPICAL CYCLONE IS POSSIBLE WITHIN
100 NM EITHER SIDE OF A LINE FROM 14.7N 24.2W TO 15.6N 28.8W
WITHIN THE NEXT 12 TO 24 HOURS. AVAILABLE DATA DOES NOT JUSTIFY
ISSUANCE OF NUMBERED TROPICAL CYCLONE WARNINGS AT THIS TIME.
WINDS IN THE AREA ARE ESTIMATED TO BE 15 TO 20 KNOTS. METSAT IM-
AGERY AT 100600Z INDICATES THAT A CIRCULATION CENTER IS LOCATED
NEAR 14.4N 24.0W. THE SYSTEM IS MOVING WEST-NORTHWESTWARD AT 10-15
KNOTS.
2. REMARKS:
3. THIS ALERT WILL BE REISSUED, ALLOWED TO EXPIRE OR CANCELLED BY 110600Z.
//
It is very possible that it is relocating
Look at the burst of convection on the south side:
(AP) Two typhoons in Asia have killed dozens of people, left hundreds missing and forced nearly 1 million people to flee to safety, officials and reports said Monday.
In Taiwan, an estimated 400 people are unaccounted for after a mudslide spawned by Typhoon Morakot struck their isolated mountain village, a police official said, and a newspaper quoted a resident as saying as many as 600 were buried.
In Japan, meanwhile, Typhoon Etau slammed into the west coast Monday. Twelve people were killed in raging floodwaters and landslides, and 10 others were missing, police said.
More...
Link
Same here I live in Semmes. I was here in 79 during Fred.
These systems dont develop rapidly very often, they take time.
I have that feeling...We have dodged the bullet so many times in the past 10 years as far as a direct hit...
I started some precautionary notifications this morning to our department directors (esp. Public Works) that we may be looking at an elevated threat to our area (Central Florida) in the next few weeks.
I don't. All I have is a g-mail account.
Hi stormdude! Can you post the link to the GFS long range? Thanks!
i wouldn't mind one. i live in dominica and have never been in any seriouis storms. dean wasn't bad, just the rain
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It is hurricane season and it is Florida, not that alarming.
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