Tropical Storm Isaac was leaving the coast of Haiti on a path toward Cuba and the Florida Keys, where it is forecast to arrive tomorrow at hurricane strength, the U.S. National Hurricane Center said. Some energy output in the Gulf of Mexico is shut.

The Keys and parts of southern Florida’s west coast were put under a hurricane warning today, while areas of the state’s southeastern coast are on a hurricane watch, the center in Miami said in an advisory on its website just before 5 a.m. local time.

Isaac, which may threaten the Republican National Convention in Tampa next week, had maximum sustained winds of 60 miles per hour (95 kilometers per hour) and was moving northwest at 14 mph. The system was centered about 145 miles south of Great Inagua Island in the Bahamas.

A hurricane watch, meaning hurricane conditions are possible within 24 hours to 36 hours, was posted for all of the Florida Keys, Florida Bay, the state'swest coast from Bonita Beach southward and the east coast from Golden Beach southward. The government of the Bahamas has also issued a hurricane watch for Andros Island.

Energy companies including BP Plc (BP/) began suspending crude and gas operations in the Gulf region, home to 23 percent of U.S. oil production, 7 percent of natural-gas output and 44 percent of refining capacity, according to the U.S. Energy Department. As much as 20 inches (51 centimeters) of rain and life-threatening mudslides a.