Tropical Storm Isaac heads for Haiti, Dominican Republic

Tropical Storm Isaac headed towards the Dominican Republic and Haiti on Friday, rumbling slowly west across the Caribbean after unleashing heavy rain on parts of Puerto Rico. In Haiti, Isaac was threatening thousands of people still living in tents after a devastating earthquake more than two years ago. The storm also posed a threat to Florida, where it could pass near the state’s Gulf Coast on Monday as the U.S. Republican National Convention starts in Tampa.