Caribbean disturbance 93L slowly organizing

Tropical disturbance 93L is slowly getting more organized. Visible satellite loops show that heavy thunderstorm activity has moved closer to the center and has increased in recent hours. However, there is no evidence of a closed surface circulation on satellite images or from last night's QuikSCAT pass. Wind shear has fallen to the moderate level, about 15 knots, and some additional slow organization of 93L appears likely today.

Wind shear is forecast to remain 10-20 knots over the next five days, and four of the six reliable forecast models now predict that 93L will develop into a tropical depression by Tuesday. This development is forecast to happen near the southeastern Bahamas. The NHC is giving 93L a medium (20%-50% chance) of developing into a tropical depression by Monday. I give a 60% chance that 93L will eventually develop into a tropical depression.

Expect heavy rains of 3-6" to affect Puerto Rico tonight through Sunday. On Sunday, heavy rain will spread to the Dominican Republic and Haiti, potentially causing life-threatening flash floods and mudslides. The southeastern Bahamas can expect rains from 93L beginning on Monday night.

Links to follow
Puerto Rico radar
San Juan, Puerto Rico weather


Figure 1. Current satellite image of 93L.

Possible development off the coast of Africa
A strong tropical wave with some solid heavy thunderstorm activity emerged from the coast yesterday. The GFS and NOGAPS models are predicting this system will develop into a tropical depression by the middle of next week. Wind shear is predicted to be in the moderate range, 10-20 knots. However, the system is too close to the Equator to develop very quickly.

Many of the models are also predicting development of a strong storm off the coast of North Carolina about six days from now, but this will probably be extratropical--the season's first Nor'easter.

I'll have an update Sunday morning at the latest.
Jeff Masters