Helene is expected to rapidly intensify into a major and massive hurricane with 115-mph winds by the time it makes landfall Thursday.

A hurricane watch and warnings of storm surges up to 15 feet high were issued Tuesday for almost all of Florida's western coastline as Tropical Storm Helene formed over the Caribbean Sea and headed toward the Gulf Coast.

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.