Discussion about 98L by Dr Jeff Masters.
Posted by: JeffMasters, 1:48 PM GMT on October 09, 2010
An area of disturbed weather (98L) is in the Western Caribbean, a few hundred miles east of the coast of Nicaragua. The disturbance has a modest and slowly increasing amount of intense thunderstorms, and is showing some spin. The disturbance is drifting northwest at less than 5 mph, and is under a moderate 15 knots of wind shear. Dry air in the Western Caribbean has been interfering with development, but 98L is now generating enough thunderstorms that the environment in the Western Caribbean is moistening, which will support further development. Pressures at Colombia's San Andres Island near the center of 98L are not falling, and satellite imagery show disturbed weather only over a very modest portion of the Caribbean, so any development today will be slow to occur.
Forecast for 98L
98L is likely to bring heavy rains to northeastern Honduras and Nicaragua on Sunday, and possibly the Cayman Islands and Jamaica as well. The latest SHIPS model forecast calls for wind shear to stay in the moderate range, 10 - 20 knots, through Tuesday. This should allow 98L to reach tropical depression status early next week, though NHC is only calling for a 20% chance of 98L becoming a tropical depression by Monday morning. The GFDL and HWRF models are the most aggressive developing 98L. These models predict 98L will intensify into Tropical Storm Paula by Monday, move northwest and then north, and pass through the Cayman Islands on Monday night and Tuesday morning as a tropical storm. Paula would then hit western or central Cuba as a hurricane on Tuesday or Wednesday, brush the Florida Keys, then accelerate northeastward through the western Bahamas on Wednesday or Thursday. This is probably too aggressive of a forecast, given 98L's current small size and lack of organization. The UKMET model also develops 98L, but keeps the storm in the Western Caribbean over the next seven days. The NOGAPS model keeps 98L weak and predicts a more west-northwesterly motion into Mexico's Yucatan Peninsula on Wednesday. The GFS and ECMWF models do not develop 98L. One argument against the development of 98L would be that the phase of the Madden-Julian Oscillation is currently promoting sinking, stable air over the Western Caribbean, which tends to make the atmosphere dryer and more stable. However, I think that 98L will spend enough time in the Western Caribbean to overcome the relatively stable, dry air, and become a tropical depression or tropical storm by Tuesday. The likelihood of the storm hitting Cuba versus moving more to the west-northwest and hitting Mexico's Yucatan Peninsula is difficult to call at this point.
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