Lesser Antilles need to watch two new disturbances

A tropical wave near 11N 43W, midway between Africa and the Lesser Antilles Islands (92L), has developed a modest amount of heavy thunderstorm activity overnight. A QuikSCAT pass at 6:21 am EDT this morning revealed a large, elongated circulation. Wind shear is a low 5-10 knots over the disturbance. Satellite loops show a limited amount of heavy thunderstorm activity that is slowly increasing. Water vapor satellite loops show that 92L is at the edge of a large area of dry air and Saharan dust to its west and north, which will slow development.


Figure 1. Latest satellite image of 92L.

The forecast for 92L
Water temperatures are a toasty 28° and forecast to increase to 29°C three days from now. Wind shear is forecast to remain below 10 knots for the next five days. The environment appears favorable for intensification, except for the dry air to the west. Circulations of the sloppy nature that 92L has usually take at least two days to get organized and form a tropical depression, particularly when there is dry air nearby to interfere. The SHIPS intensity model brings 92L to hurricane strength in just 3 days, which is way over-aggressive. The UKMET, GFS, and ECMWF models are more reasonable, bringing 92L to weak tropical storm strength by the time the disturbance crosses into the northern Lesser Antilles Islands on Wednesday or Thursday. The National Hurricane Center is giving 92L a medium (20-50% chance) that 92L will be a tropical depression by Tuesday morning. Residents and visitors to the Lesser Antilles should prepare for the possibility of tropical storm conditions arriving as early as Wednesday.

Elsewhere in the tropics
Most of the reliable computer models are also developing another tropical wave, just off the coast of Africa. This system is also expected to move westward, potentially threatening the Lesser Antilles Islands early next week.

Jeff Masters