A tropical depression swirling in the Atlantic weakened slightly overnight but still appears likely to become Tropical Storm Ernesto by the week's end, experts said.
The system was poorly organized with about 35 mph winds as it neared the Lesser Antilles early Thursday, prompting the National Hurricane Center to issue tropical storm watches in countries throughout the Caribbean.
If the system strengthens to 39 mph, it would be named Ernesto, the fifth tropical storm of the 2012 hurricane season.
Hurricane experts say there is a 27 percent chance that the system will become a hurricane by Friday afternoon, when it is expected to pass over those islands.
It was still too early to predict whether the system, moving west-northwest at about 20 mph, could impact Florida or the East Coast of the United States.
This is the first system to draw the attention of the National Hurricane Center since late June, when Tropical Storm Debby ravaged Florida.