MIAMI, Aug 21 (Reuters) - A tropical depression formed in the Atlantic Ocean on Tuesday, prompting tropical storm warnings across several Caribbean islands, and forecasters predicted it will strengthen into a hurricane later this week.
The swirling mass of thunderstorms was located about 580 miles (930 km) east of Guadeloupe and moving at 20 miles per hour (32 kph) toward the Lesser Antilles, the U.S. National Hurricane Center said.
The depression had top winds of 35 mph (55 kph). It is forecast to become Tropical Storm Isaac later on Tuesday, the ninth named storm of the Atlantic-Caribbean hurricane season that runs from June 1 to Nov. 30.
Tropical storm warnings were issued for the eastern Caribbean islands of Martinique, Dominica, Guadeloupe, Antigua and parts of Curacao.
A tropical storm watch was in effect for the British Virgin Islands, Puerto Rico and the U.S. Virgin Islands.
Computer forecast models show the storm, called Tropical Depression Nine, reaching hurricane strength on Thursday as it approaches Puerto Rico, with the Dominican Republic, Haiti, Jamaica and a large swath of Cuba also in its projected path.
The depression is expected to move west across the Caribbean this week and then veer northwest, potentially putting South Florida in the storm's path.
Hurricane expert Jeff Masters of private forecaster Weather Underground said heavy rains were expected to begin in Jamaica and eastern Cuba on Friday night.
"But our vision of where the storm might be headed after Friday gets blurry," he wrote on his blog.
The storm will likely be followed closely by many in Florida, where the Republican National Convention will be held Aug. 27-30 in Tampa.
Masters said the chances of a hurricane disrupting the convention were in the "1 percent to 3 percent range."
"It would take 'perfect storm' sort of conditions to all fall in place to bring Tropical Depression Nine to the doorstep of Tampa as a hurricane during the convention, but that is one of the possibilities the models have been suggesting could happen." (Reporting by Kevin Gray; Editing by Stacey Joyce)