Isaac, went from a Tropical Storm to a tropical depression on Thursday, has become a tropical storm again but its future is unclear, the U.S. National Hurricane Center (NHC) said on Friday.
The storm is about 600 miles (965 km) east-southeast of Kingston, Jamaica with maximum sustained winds of 40 miles per hour (65 km/h), the Miami-based weather forecaster said.
"Isaac is forecast to become a tropical depression on Sunday and degenerate into a wave on Monday.
However this is an uncertain prediction," the NHC added.
On the forecast track, Isaac will move over the eastern and central Caribbean Sea during the next few days, and be near or south of Jamaica early next week.
Little change in strength is forecast during the next 36 hours.
Tropical-storm-force winds extend outward up to 45 miles (75 km) from the center.
Isaac is expected to produce additional rainfall of 2 to 3 inches with isolated maximum totals of up to 5 inches across southeast Puerto Rico.
Rainfall totals of 1 to 2 inches with maximum amounts of 3 inches are possible across the remainder of Puerto Rico, the Virgin Islands, the Leeward Islands and the northern Windward Islands.
Rainfall totals of 2 to 3 inches with isolated maximum amounts of 4 inches are possible across the south-central portion of the Dominican Republic, southwest Haiti and most of Jamaica except for the eastern portion of Jamaica where rainfall totals of 2 to 4 inches and maximum amounts of 6 inches are possible.
The NHC says this rainfall may cause life-threatening flash floods.