US forecasters said Isaac will likely turn into a Category 1 hurricane by Friday as it nears the Dominican Republic and Haiti.
Tropical storm Isaac could be a hurricane by later Thursday, and arrive in Florida by Monday, the start of the GOP convention. Caribbean nations brace for the arrival of tropical storm Isaac.
Hurricane Irene is the first hurricane of 2011 season. Irene is heading for Haiti, the Dominican Republic, the Bahamas, and maybe Florida, say forecasters.