Tropical Storm Isaac is south of the Cape Verde Islands moving west-north-west at 18 miles an hour. Its top winds are near 50 miles an-hour with higher gusts.
Hurricane specialist Jack Beven at the National Hurricane Center says Isaac is strengthening and "could turn into a hurricane in 24 to 48 hours." but forecasters don't know yet if it will threaten the U.S. mainland.
At 5 p.m. EDT, Isaac was about 1,915 miles east of the Caribbean islands, at latitude 13.8 north and longitude 31.0 west, the U.S. hurricane center said.
It was moving west-northwest at 18 mph, packing maximum sustained winds of 50 mph and was expected to strengthen over the coming day.
The storm strengthened from a tropical depression to a tropical storm on Thursday.
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