The National Hurricane Center issued Tropical Storm Watches for South Florida and all of the Florida Keys on Thursday afternoon. The government of Cuba also issued Tropical Storm Watches for western Cuba. The National Hurricane Center designated former Invest 91L as Potential Tropical Cyclone One on Thursday afternoon. At 5:00 p.m. EDT on Thursday the center of Potential Tropical Cyclone One was located at latitude 21.4°N and longitude 87.5°W which put it about 75 miles (120 km) north-northwest of Cozumel, Mexico. Potential Tropical Cyclone One was moving toward the north at 5 m.p.h. (8 km/h). The maximum sustained wind speed was 35 m.p.h. (55 km/h) and and there were wind gusts to 45 m.p.h. (75 km/h). The minimum surface pressure was 1003 mb.

A Tropical Storm Watch was issued for the coast of Florida from Longboat Key on the west coast to the Volusia/Brevard County Line on the east coast. A Tropical Storm Watch was also issued for all of the Florida Keys. The government of Cuba issued Tropical Storm Watches for the provinces of Matanzas, Mayabeque, La Habana, Artemisa, Pinar del Rio and the Isle of Youth.

The National Hurricane Center designated former Invest 91L as Potential Tropical Cyclone One in keeping with its policy on the issuance of watches and warnings. The circulation around Potential Tropical Cyclone One consisted of a broad area of low pressure. One or more smaller centers of circulation were revolving around inside the broad area of low pressure. The National Hurricane Center identified a center near the northeast tip of the Yucatan Peninsula as the center of Potential Tropical Cyclone One. Images from satellites and radar indicated that a middle level center of circulation might be located near the western end of Cuba. The strongest thunderstorms were occurring in bands in the eastern side of Potential Tropical Cyclone One. Those thunderstorms were generating upper level divergence that pumped mass away to the east of the low pressure system. Bands in the western half of the circulation were over the Yucatan Peninsula and those bands consisted primarily of showers and lower clouds.

Potential Tropical Cyclone One will move through an environment that will be somewhat favorable for intensification during the next 36 hours. Potential Tropical Cyclone One 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 Potential Tropical Cyclone One. Those winds will cause moderate vertical wind shear. The vertical shear will somewhat inhibit intensification. However, the upper level ridge will also enhance the upper level divergence over Potential Tropical Cyclone One. More upper level divergence would cause the surface pressure to decrease. Potential Tropical Cyclone One is forecast to strengthen to a tropical storm during the next 36 hours.

The upper level trough over the western Gulf of Mexico and the upper level ridge over the Northwest Caribbean Sea will steer Potential Tropical Cyclone One toward the northeast during the next several days. On its anticipated track, Potential Tropical Cyclone One will approach Southwest Florida on Saturday morning. Potential Tropical Cyclone One will bring gusty winds and heavy rain to western Cuba and South Florida later this week. Heavy rain is likely to cause flash floods in some locations.