Tropical Storm Helene formed over the northwestern Caribbean on Tuesday and triggered a tropical storm warning for the Lower Florida Keys. The storm is forecast to be a major hurricane for the Florida panhandle Thursday.

Thousands of Florida residents have been forced to evacuate as the state prepares for rapidly strengthening Tropical Storm Helene, which could bring powerful winds, flooding and life-threatening storm surge to areas already hard-hit by recent hurricanes.

Forecasters say they expect Tropical Storm Helene in the Caribbean Sea to strengthen rapidly and become a hurricane as it moves north across the Gulf of Mexico on Wednesday toward the U.S.