A tropical system swirling across the western Caribbean became dramatically more organized Friday and is now expected to become a depression or Tropical Storm Philippe late Friday or Saturday.
As of the 11 p.m. Friday advisory by the National Hurricane Center, forecasters said tropical storm warnings are in effect for parts of Cuba and the Bahamas after a hurricane hunter plane found winds topping 40 mph. The system, which was located about 370 miles south-southwest of Havana, still lacked a defined center. But forecasters said the disturbance was gradually becoming better organized and some slow strengthening as the system crosses warm ocean waters and encounters weak wind shear was expected.
Over the next two days, forecasters don’t expect sustained winds to climb over 50 mph.
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The storm, which was moving north at 7 mph, has not been named. A tropical storm warning was in effect for Isla de la Juventud, La Habana, Ciudad de la Habana, Matanzas, Cienfuegos and Villa Clara in Cuba, and the northwestern Bahamas. A tropical storm watch was in effect for the central Bahamas.
South Florida and the Keys can expect heavy rain, with forecasters calling for 3 to 5 inches, and up to 8 inches possible in some locations.
“We’re going to get really, really wet tomorrow. That’s the bad news,” hurricane center spokesman Dennis Feltgen said. “The good news is whatever this is should stay well to our east.”
For much of the week, the system has been brewing off the coast of Central America, generating showers and thunderstorms. Forecasters gave the system a 60 percent chance of forming, then backed off when it looked like high winds associated with a cold front crossing South Florida would hinder intensification.
Still, they warned that as the system moved north over warm Caribbean waters and encountered low wind shear, there was a chance the system could become better organized.
Late-season storms forming in the western tropics are not unusual and have historically behaved dramatically, sometimes intensifying rapidly. Both hurricanes Mitch and Wilma were late Caribbean storms with lethal power.
“It’s just been a very moist monsoonal flow through Central America. It’s very typical for October and it’s not at all unusual for tropical storms to form in the western Caribbean,” Feltgen said.
Forecast models generally agree on a track that takes the storm south of Florida, forecasters said, but warned the messy storm is increasing uncertainty in the models.
Over the next day or two, heavy rain is also expected over the Cayman Islands, Jamaica, parts of Cuba and the northwestern and central Bahamas. As the system moves up the U.S. coast, it’s expected to merge with a cold front and likely hit the coast with a fierce Nor’easter.
During that transformation, it’s possible the system undergoes a ‘bombogenesis,’ Feltgen said, when air pressure drops 24 millibars in 24 hours, Feltgen said.
Follow Jenny Staletovich on Twitter @jenstaletovich