A tropical disturbance, designated as Invest 91L, organized over the Northwest Caribbean Sea on Wednesday. At 8:00 a.m. EDT on Wednesday the center of Invest 91L was located at latitude 18.7°N and longitude 87.4°W which put it about 75 miles (120 km) east of Chetumal, Mexico. Invest 91L was moving toward the northeast at 3 m.p.h. (5 km/h). The maximum sustained wind speed was 30 m.p.h. (50 km/h) and and there were wind gusts to 40 m.p.h. (65 km/h). The minimum surface pressure was 1006 mb.

A center of circulation appeared to be spinning over the Northwest Caribbean Sea just to the east of the Yucatan Peninsula on visible satellite loops on Wednesday morning. The circulation center was designated as Invest 91L. The center was inside a larger tropical disturbance over the Northwest Caribbean Sea and Yucatan Peninsula. The strongest thunderstorms were occurring in bands in the eastern half of Invest 91L. Bands in the western half of the system were over the Yucatan Peninsula and those bands consisted primarily of showers and lower clouds. Storms in the eastern half of Invest 91L generated upper level divergence that pumped mass away to the east of the tropical disturbance.

Invest 91L will move through an environment that will be favorable for the formation of a tropical depression during the next 36 hours. Invest 91L will move over water where the Sea Surface Temperatures are near 28˚C. An upper level trough over the western Gulf of Mexico and an upper level ridge over the Northwest Caribbean Sea will interact to produce southwesterly winds that will blow toward the top of Invest 91L. Those winds will cause some vertical wind shear. The vertical shear will somewhat inhibit the formation of a tropical depression. However, the upper level ridge will also enhance the upper level divergence over Invest 91L. More upper level divergence would cause the surface pressure to decrease. The National Hurricane Center is indicating the probability is 80% that a tropical depression forms from Invest 91L. A reconnaissance plane is tentatively scheduled to investigate the system on Thursday, if necessary.

The upper level trough over the western Gulf of Mexico and the upper level ridge over the Northwest Caribbean Sea will steer Invest 91L slowly toward the northeast during the next several days. On its anticipated track, Invest 91L will move toward western Cuba and South Florida. Invest 91L could bring gusty winds and locally heavy rain to western Cuba and South Florida later this week.