NWS National Hurricane Center Miami FL
For the North Atlantic…Caribbean Sea and the Gulf of Mexico:
1. A concentrated area of thunderstorms associated with a westward-moving tropical wave is located about 850 miles east of the Windward Islands. Although this disturbance shows some signs of organization on satellite imagery, there is no evidence of a surface circulation at this time. Some additional development is possible today before upper-level winds become highly unfavourable for tropical cyclone formation starting tonight and continuing through the weekend.
* Formation chance through 48 hours…low…20 percent.
* Formation chance through 5 days…low…20 percent.
2. A non-tropical low-pressure system is forecast to develop by Friday night over the central subtropical Atlantic Ocean between Bermuda and the Azores. Conditions are expected to be conducive for the low to acquire some subtropical or tropical characteristics, and a subtropical or tropical cyclone could form over the weekend or early next week while the low meanders over the central Atlantic Ocean.
* Formation chance through 48 hours…low…near 0 percent.
* Formation chance through 5 days…medium…40 percent.
Source: The Daily Herald https://www.thedailyherald.sx/islands/80811-tropical-weather-outlook-800-am-edt-thu-sep-20-2018