Isaac churns in the Caribbean, threatens Republican Convention

Tropical Storm Isaac spun over the Caribbean Sea and could become a hurricane on Thursday as it moves on a track that would put it off the coast of Florida on Monday, the opening day of the Republican National Convention in Tampa. As the center of Isaac moved away from the Leeward Islands, the storm prompted hurricane warnings in Haiti and the Dominican Republic. Isaac may also threaten U.S. energy interests in the Gulf of Mexico, weather experts said. It was centered about 265 miles southeast of San Juan, Puerto Rico, early on Thursday, the U.S. National Hurricane Center said.