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By: Dr. Jeff Masters , 2:31 PM GMT on September 24, 2007
A disturbance in the Gulf of Mexico moved ashore into Louisiana early this morning and is no longer being tracked by NHC as "Invest 94". Long range radar out of New Orleans shows a steady stream of moisture associated with the disturbance continues to flow northwards into Louisiana today. 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 tonight or Tuesday. Wind shear has dropped to about 15 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.
Figure 1. Today's lineup of tropical systems to watch.
Lesser Antilles disturbance 97L
A tropical wave (97L) is very near Barbados in the Lesser Antilles Islands. This wave has not gotten any better organized during the past 24 hours, as seen in the latest Satellite imagery. The wave is under about 10 knots of wind shear. The shear is forecast to slowly rise to 20 knots by Thursday. There is some favorable anticyclonic outflow at high levels, and 97L has a good chance of developing into a tropical depression by Wednesday. At that point, 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, which would greatly disrupt the storm. The GFDL model predicts 97L will survive the disruption, and re-intensify as it continues to move northwest into the easternmost Bahama Islands on Saturday. However, there is a band of very high wind shear predicted to lie just north of the Bahamas all of this week, and 97L could well encounter this band of high wind shear Thursday, which should weaken the storm. In any case, this system represents a threat to the Dominican Republic, Haiti, and Puerto Rico on Wednesday and Thursday, and residents may experience tropical storm conditions as early as Wednesday morning. 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 1. Microwave image from 3:28 am EDT today showing low-level spiral bands starting to form on the west side of 96L. Image credit: Navy/NRL.
Atlantic disturbance 96L midway between Africa and the Lesser Antilles
A tropical wave (96L) near 9N 32W, midway between Africa and the Lesser Antilles Islands, is moving west-northwest at 10-15 mph. This wave has gotten much more organized late this morning, as seen in the latest satellite loops. The circulation associated with the wave is unusually large, and one can see a large area of inflowing low-level cumulus clouds spiraling into the center of 96L. The storm has been slow to organize, since it is 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. A few low-level spiral bands have already formed, as seen in recent microwave satellite images (Figure 1). Last night's QuikSCAT pass showed an elongated circulation, with winds generally in the 15-20 mph range. The wave is under about 10 knots of wind shear. The shear forecast has changed significantly since yesterday, and high levels of wind shear exceeding 20 knots are now expected to impact 96L beginning Tuesday, rising to 30 knots on Thursday. This is the type of wind shear Tropical Storm Ingrid encountered earlier this month, and the shear eventually destroyed the storm. Both the GFDL and HWRF models develop 96L into a tropical storm, but keep it a minimal tropical storm through the end of their 5-day forecast period. 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 Storm Jerry is only worth mentioning since it increases our storm totals for the year to ten. Jerry will be gone tomorrow, 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 at the latest.
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