Storm warnings have been issued Tuesday across a swath of islands in the Caribbean including Martinique, Guadeloupe and St. Martin.
It is too soon to say what exact path the storm will take. But some computer models show it headed toward Cuba and then Florida. Others have it making a sharp northern turn in the next couple days near Puerto Rico and then into the open Atlantic.
The National Hurricane Center says Isaac has maximum sustained winds near 40 (64 kph) but is expected to strengthen.
The storm is about 500 miles (804 kilometers) east of Guadeloupe and is moving west near 17 mph (28 kph).