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. The National Hurricane Center has issued hurricane warnings for northwestern Florida's coastline and part of Mexico's Yucatan Peninsula. Helene is forecast to be “near hurricane strength” when it passes near the Yucatan Peninsula early Wednesday. Forecasters say the entire west coast of Florida faces a possibly life-threatening storm surge.