Puerto Rico disturbance fizzles; Hawaii disturbance slowly organizing

An area of disturbed weather (90L) over the northern Lesser Antilles Islands has lost most of its heavy thunderstorm activity this morning and is no longer a threat to develop into a tropical depression in the next two days. Wind shear is a low 10 knots over the disturbance, and is expected to remain below 10 knots for the next two or three days, so the disturbance does still have a chance to develop by Sunday. However, there is quite a bit of dry air to the west, which may distrupt any heavy thunderstorm activity that tries to form. Wind shear is expected to rise significantly beginning on Sunday, and the long term prospects for 90L to become a tropical storm in the Caribbean are low.

Puerto Rico radar shows only disorganized thunderstorm activity at present. Winds in the northern Lesser Antilles Islands have been unspectacular so far today--no more than 15 mph at St. Kitts, St. Maartin, and Antigua. The morning pass of the QuikSCAT satellite missed 90L; we'll have to wait until about 9pm EDT tonight for the next pass. Satellite imagery and surface reports show that no surface circulation exists.

Most of the computer models forecast a track over the northern Lesser Antilles Islands the next two days, with the disturbance moving over Puerto Rico Saturday morning and the Dominican Republic on Saturday night. The system is being drawn northwest by a strong trough of low pressure passing to the north of the islands. However, it appears that this trough is not strong enough to pull 90L out to sea, and high pressure should build in and force the storm westward by Sunday.


Figure 1. Preliminary model tracks for disturbance "90L".

Hawaii
Residents of Hawaii should continue to watch an area of disturbed weather (97C) near 9N, 166W, about 1000 miles southwest of the Hawaiian Islands. A QuikSCAT satellite pass from 12:56am EDT this morning showed a closed surface circulation, and some wind barbs of 40-45 mph to the south of the center. The thunderstorm activity has gotten a little better organized today. Wind shear has remained about 15 knots today, which is low enough to allow some continued slow development. Sea Surface Temperatures (SSTs) are about 29C, and there is a very deep pool of warm water underneath to fuel intensification. The last two runs of the GFDL model have predicted that 97C will become a tropical storm that could threaten Hawaii by Tuesday.


Figure 2. Preliminary model tracks for disturbance "97C".

Elsewhere in the tropics
The models continue to show the possibility of a low pressure system forming in the Gulf of Mexico near the Texas coast early next week. This low will probably be non-tropical, though. Several models are calling for a tropical storm to develop along the Pacific coast of Mexico by Monday and move northwest towards Baja. Baja does not need to worry about Tropical Depression Olivia, which is expected to dissipate Friday before reaching Baja.

I'll have an update Friday morning.

Jeff Masters