Tropical Storm Helene was rapidly strengthening in the Caribbean Sea and expected to become a hurricane Wednesday while moving north along Mexico's coast toward the U.S., prompting residents to evacuate,

By Rich McKay, Brendan O'Brien (Reuters) -Powerful storm Helene officially became a hurricane on Wednesday morning, the National Hurricane Center said, packing maximum sustained winds of 80 mph (130 kph) as it churned in the eastern Gulf of Mexico just off the coast of the Yucatan Peninsula.