Dr. Masters co-founded wunderground in 1995. He flew with the NOAA Hurricane Hunters from 1986-1990. Co-blogging with him: Bob Henson, @bhensonweather
By: Dr. Jeff Masters , 7:03 PM GMT on September 24, 2007
Satellite imagery this morning shows that a new surface circulation has developed in the Gulf of Mexico near 23N 93W, about 350 miles southeast of Brownsville, Texas. This new circulation has been labeled 94L by NHC this morning. Heavy thunderstorm activity has begun forming near the center of circulation, and this system has the potential to become a tropical depression by Tuesday. Wind shear is about 15-20 knots over the disturbance, and is expected to remain 15 knots or below for the next three days. The disturbance is headed west-northwest at less than 10 mph, and should bring heavy rains to northern Mexico--and possibly southern Texas--by Wednesday. However, most of the computer models show that 94L may stall before it reaches the coast, then loop erratically in the Gulf for several days. A Hurricane Hunter flight is scheduled to investigate 94L Tuesday afternoon.
Figure 1. Today's lineup of tropical systems to watch.
Lesser Antilles disturbance 97L getting more organized
A tropical wave (97L) is just north of Barbados in the Lesser Antilles Islands. This wave has developed a closed circulation centered over the southern Lesser Antilles Islands, as seen on the 9:10 am EDT pass from the ASCAT satellite. This is confirmed by wind observations from Barbados this afternoon, where the winds have turned to westerly and increased to 20 mph. The latest Satellite imagery shows a marked increase in heavy thunderstorm activity in the past few hours, and a tropical depression could form by Tuesday. The wave is under about 10 knots of wind shear. The shear is forecast to slowly rise to 20 knots by Thursday, which may slow intensification. The future evolution of the storm depends on how close it comes to the mountainous island of Hispaniola. Most of the models predict 97L will pass over the island on Wednesday or Thursday, which would greatly disrupt the storm. None of the models predict 97L will grow stronger than a 55 mph tropical storm for the next four days. There is a band of very high wind shear predicted to lie just north of Hispaniola all of this week, and 97L could well encounter this band of high wind shear Thursday, which would weaken the storm. In any case, this system represents a threat to the Dominican Republic, Haiti, Puerto Rico, and the northern Lesser Antilles Islands, and residents may experience tropical storm conditions as early as Wednesday afternoon. The Hurricane Hunters are on call to investigate 97L Tuesday afternoon, if necessary. This afternoon's flight was canceled.
Links to follow for 97L
St. Lucia weather
Figure 2. Microwave image from 11:28 am EDT today showing low-level spiral bands starting to form around 96L. Image credit: Navy/NRL.
Atlantic disturbance 96L midway between Africa and the Lesser Antilles nearing tropical depression strength
A tropical wave (96L) near 9N 33W, midway between Africa and the Lesser Antilles Islands, is moving west-northwest at 10-15 mph. This wave has gotten much more organized this afternoon, as seen in the latest satellite loops. The circulation associated with the wave is unusually large. The storm has been slow to organize, since it is so large and so far south. At the storm's current latitude--9 degrees north of the Equator--it cannot leverage the earth's spin very much to help spin up the huge circulation it has. However, the storm will probably be a tropical depression by Tuesday morning. Low-level spiral bands have already formed, as seen in recent microwave satellite images (Figure 2). This morning's 7:29 am EDT ASCAT pass showed a better defined circular wind pattern with top winds of 25-30 mph. The wave is under about 10 knots of wind shear. The shear forecast is problematic, with some of the models expecting high wind shear later this week, and others keeping the wind shear low. I expect 96L will become at least a weak tropical storm by Wednesday, then we'll have to see how the upper level winds evolve. The storm is expected to gradually work its way north as it crosses the Atlantic, and appears likely to pass north of the Lesser Antilles Islands next week. The last few runs of the GFS model show 96L eventually recurving out to sea next week.
Tropical Storm Jerry
Tropical Depression Jerry is only worth mentioning since it increases our storm totals for the year to ten. Jerry will be gone tonight, absorbed by an extratropical low pressure system.
Hurricane Rita anniversary
Today marks the second anniversary of Hurricane Rita's landfall in Southwest Louisiana. Wunderblogger Mike Theiss has written a blog and posted his usual amazing photos documenting his experience with Hurricane Rita. One of the more remarkable features of the account is his encounter with hundreds of exhausted birds in the eye of Rita. The unfortunate birds got trapped in the eye for days, unable to escape.
I'll have an update Tuesday morning.
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