Up to late yesterday, a better organised Tropical Storm Isaac was closing in on the Lesser Antilles with maximum sustained winds of 45 miles per hour (mph).
A number of Caribbean countries have issued warnings for their residents and, according to the Miami-based National Hurricane Centre (NHC), the storm, located near latitude 15.5 north, longitude 57.3 west, is moving towards the west near 18 mph.
The storm is situated 280 miles east of Guadeloupe.
"This general motion is expected to continue for the next couple of days," NHC said, adding "the centre of Isaac is expected to move over the northeastern Caribbean Sea today".
NHC warned that the storm will strengthen and could become a hurricane.
Dominica's Prime Minister Roosevelt Skerrit said he was appealing to employers to allow their workers to remain home to ride the storm out.
Skerrit said he expects "landslides and swollen rivers" as a result of the heavy rains associated with Tropical Storm Isaac, adding, "so instead of bringing people out to work, it is better for them to stay home".
However, he warned that they should not be home watching television, but must be making adequate preparations to ride out the storm.
The NHC said that tropical storm warnings are in effect for Martinique, Dominica, Guadeloupe and the surrounding islands of St Martin, St Kitts-Nevis, Antigua and Barbuda, Montserrat, Anguilla, Saba, St Eustace, St Maarten, British Virgin Islands.
A hurricane watch is in effect for Puerto Rico, the United States Virgin Islands, the south coast of the Dominican Republic including the southern border of the Haitian-Dominican Republic border.
NHC said that tropical storm conditions are expected to reach the Leeward Islands later on Wednesday and rainfall accumulations of four to eight inches are possible over the Northern Windward Islands and the Leeward Islands.