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 , 2:36 PM GMT on October 19, 2006
An area of low pressure over the Virgin Islands, just east of Puerto Rico (90L), has gotten better organized this morning. Wind shear over the disturbance has dropped to 20 knots, and is forecast to stay in the 15-25 knot range over the next few days, which may allow some slow development. A QuikSCAT satellite pass at 6:04am EDT revealed a substantial wind shift associated with the low, but no well-defined closed circulation. Top winds from QuikSCAT were in the 25-30 mph range. Unfortunately, the Puerto Rico radar failed Wednesday, and the Martinique radar is too far away to see most of the thunderstorm activity.
Flood warnings have been posted this morning on St. Croix in the Virgin islands, where 4 inches of rain has fallen in four hours. Additional heavy rains are expected today, and 90L will also bring heavy rains and potential flash flooding to the rest of the Virgin Islands and eastern Puerto Rico over the next two days.
Visible satellite animations show that the disturbance is not moving much, but it is expected to push slowly northward over the next two days. After that, the NOGAPS and UKMET models predict a slow motion to the west-northwest towards the Bahama Islands. The GFS model prefers a due north track, and the other models (Figure 1) call for a more northeasterly track. By the middle of next week, a trough of low pressure should sweep 90L northeastwards out to sea. The disturbance is too small and under too much wind shear to develop into a tropical depression, in all likelihood.
Figure 1. Preliminary model tracks for disturbance "90L".
Elsewhere in the tropics
The NOGAPS model is showing a weak tropical storm forming in the southern Caribbean Tuesday. None of the other models are showing this, and given the lack of consistency of the NOGAPS's predictions of late, this forecast is not credible.
Most of the models show the possibility of a tropical storm forming along the Pacific coast of Mexico early next week and moving towards Baja. This is a believable forecast.
I'll be back with an update Friday morning.
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