KEY WEST, Fla. — Tropical Storm Isaac this morning rolled over the open Gulf of Mexico, where it was expected to grow into a hurricane before hitting land between Louisiana and Florida and close to the seventh anniversary of Hurricane Katrina.

The storm that left eight dead in Haiti blew past the Florida Keys with little damage and promised a drenching but little more for Tampa, where the start of the Republican National Convention today was pushed back to Tuesday in case Isaac passed closer to the bayside city.

The National Hurricane Center predicted Isaac would grow to a Category 1 hurricane over the warm Gulf and possibly hit late Tuesday somewhere along a roughly 300-mile stretch from the bayous southwest of New Orleans to the Florida Panhandle.

That would be one day shy of seven years after Hurricane Katrina struck catastrophically in 2005.

Earlier predictions said Isaac would be a Category 2 hurricane but National Hurricane Center director Rick Knabb told ABC’s “Good Morning America” today that Isaac wouldn’t be as strong as they initially thought.