A tropical storm swirling in the eastern Caribbean has raised the remote possibility that this year's Republican National Convention could be more blustery than usual.

Tropical Storm Isaac was east of Guadeloupe on Tuesday, and forecasters say it could become a hurricane on track to hit Florida next week, when Republicans gather in Tampa.

The US National Hurricane Center's five-day forecast shows the storm blowing over the Dominican Republic, Haiti and Cuba but does not extend to Monday, when the four-day convention kicks off.

"It is too early to determine what, if any, impacts might be experienced in the Tampa area next week during the RNC," said Dennis Feltgen of the US National Weather Service.

"The US is not yet in the forecast track cone, and there is a great deal of uncertainty beyond that five-day time frame."

Thousands of party luminaries, top officials and supporters will convene in the Gulf coast city to formally nominate Mitt Romney to challenge President Barack Obama in the November 6 election.

The convention is largely a formality -- Romney has been the presumptive nominee for months -- but will feature prime-time speeches by the party's leading lights aimed at rallying supporters to deny Obama a second term.

Obama's Democratic Party will hold its own convention in Charlotte, North Carolina between September 4-6.

Meteorologist Jeffrey Masters, writing on wunderground.com last week, pointed out that there have been two mass evacuations of Tampa in the past 25 years during the peak three-month hurricane season of August to October.

He puts the chances of such an evacuation during next week's convention at "somewhere in the one to three percent range."

"It would take a 'perfect storm' sort of conditions to all fall in place to bring (the tropical storm) 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," he told AFP by email.

The convention center would have to be evacuated in the event of a category one hurricane, and in the worst-case scenario of a category four hurricane, it would be submerged under 20 feet of water, according to Masters.

For now, tropical storm warnings have been called for Caribbean islands from Martinique north-west to the US Virgin Islands, which means residents should expect heavy winds and rains, strong currents and surging tides within 36 hours.

At 0001 GMT, the storm was about 435 miles (700 kilometers) east of Guadeloupe, moving west at 17 miles (28 kilometers) an hour, with maximum sustained winds of about 40 miles (65 kilometers) an hour.