Image caption Storm warnings have already been declared for Puerto Rico and parts of the US Virgin Islands

A tropical storm forming in the Caribbean could pose a potential threat to Florida next week during the Republican National Convention.

Computer models from the US National Hurricane Center predict Tropical Storm Isaac would grow into a hurricane.

Some models had the storm striking Florida as early as Sunday.

Thousands of Republicans will gather in Tampa, Florida beginning on Monday to officially nominate Mitt Romney as the party's candidate for president.

Republican and Tampa officials say they have contingency plans for a such a storm. In May, a four-day mock hurricane drill was held. That drill ended with planners cancelling the convention.

Forecasters caution that long-range storm predictions can be off by hundreds of miles.

A major hurricane, with winds higher than 111mph (178 km/h), has not directly hit the city in 90 years. Florida's west coast was last hit by a major hurricane in 2004, by Hurricane Charley, with 150mph winds.

On Tuesday afternoon, Isaac was located 500 miles (800 km) east of Guadeloupe, and had winds up to 40mph. It is expected to strengthen.