Jeff co-founded the Weather Underground in 1995 while working on his Ph.D. He flew with the NOAA Hurricane Hunters from 1986-1990.
By: Dr. Jeff Masters , 1:41 PM GMT on September 21, 2007
A large low pressure system (93L) over the Gulf of Mexico has gradually been acquiring tropical characteristics, but is in no hurry to intensify. Top surface winds measured at buoys in the Gulf of Mexico this morning have been 30 knots (35 mph), so this storm could technically qualify as a tropical depression if the current hurricane hunter mission finds a well-defined center of circulation. There are two Hurricane Hunters aircraft in the storm right now, and they have found several swaths of surface winds of 35 mph. Long range radar loops from the Florida Panhandle clearly show the storm's circulation, but the low level spiral bands are not well organized and are only slowly getting more organized. Satellite loops show a large, sloppy-looking storm. Storms that start off as large, non-tropical systems like 93L typically take several days to organize and become fully tropical, and 93L will not have time to become anything worse than a minimal tropical storm. The storm is capable of dumping some heavy rains along its path--radar estimated precipitation from the Tallahassee radar (Figure 1) were as high as three inches. As 93L becomes more tropical in nature, it will be able to generate higher rain amounts. But, with the storm expected to move inland by Saturday afternoon, it does not appear 93L has time to generate the kind of tropical rains that would make it a serious flood threat.
Figure 1. Estimated rainfall from the Tallahassee, Florida radar.
Elsewhere in the tropics
An area of disturbed weather has developed in the western Caribbean between the Yucatan Peninsula and Jamaica, in association with a surface trough of low pressure. This disturbance will bring heavy rains to Cozumel and Cancun on Saturday as it crosses the Yucatan Peninsula. The region will need to be watched for development on Sunday as it crosses the Gulf of Mexico. The NOGAPS and GFS models predict an upper air pattern favorable for formation of a tropical depression over the Gulf of Mexico on Sunday and Monday. Heavy rains from this system may hit Louisiana and/or Texas on Monday.
A non-tropical low pressure system about 1000 miles east of Bermuda is being watched by NHC for tropical development. This low is expected to move northeastwards out to sea 2-4 days from now.
Figure 2. Current visible satellite image showing 93L near the Florida Panhandle (top of image) and the western Caribbean disturbance (bottom right of image).
I'll have an update late this afternoon when the next set of computer models runs are available.
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