"These swells are likely to cause life-threatening surf and rip current conditions," the National Hurricane Centre in Miami said.
In Miami, organisers called off the sea portion of the Miami Beach Air & Sea Show because of heavy rain and rough waters. And in the Tampa Bay area on the central Gulf Coast, cities offered sandbags for homeowners worried about floods.
Live video from webcams posted in Clearwater and Destin showed half-empty beaches, and whitecaps roiled the normally placid Gulf waters.
Jeffrey Medlin, meteorologist in charge at the National Weather Service's Mobile office, warned that even after the storm moves north there will still be swells coming up from the south that could cause dangerous rip currents.
Isolated tornadoes were possible across the region today and tomorrow.
- AP
