Tropical Storm Ernesto kept on a westerly course in the Caribbean Sea on Saturday, and was expected to strengthen slowly over the next 48 hours, soaking Jamaica as it passes by the island on its way to the Yucatan, U.S. forecasters said.
Officials in Jamaica issued a tropical storm warning as Ernesto moved in open waters at 22 miles per hour on a predicted track that should keep it at sea until a forecast landfall, possibly at hurricane strength, over Mexico's Yucatan peninsula on Wednesday.
With maximum sustained winds of 60 mph, Ernesto on Saturday night was 285 miles southwest of Santo Domingo in the Dominican Republic and was expected to stay clear of Jamaica and Hispaniola, the mountainous island Haiti shares with the Dominican Republic. It was expected to strengthen slowly on Monday as it moves south of the Cayman Islands.
Tropical storm conditions would strike Jamaica on Sunday afternoon, and heavy rains were expected through Sunday in Puerto Rico and Hispaniola, U.S. forecasters said.
Three to 6 inches were expected in Jamaica. Showers and thunderstorms - sometimes severe - were possible on the islands of Aruba, Curacao and Bonaire off Venezuela's northern coast.
"The center of Ernesto should pass south of Hispaniola tonight and south of Jamaica on Sunday evening," the U.S. forecasters in Miami said. "Ernesto is forecast to become a hurricane in the northwestern Caribbean in a day or two."
The storm is not expected to strengthen significantly on Sunday, and slow strengthening is forecast for Monday. Ernesto expected to move over the Yucatan peninsula in the next three to five days.
Ernesto, which did no reported damage on Friday as it passed over the tiny island of Saint Lucia, would be deemed a hurricane if its winds reach 74 mph.
Forecasters expect Ernesto to move into the southern Gulf of Mexico by Thursday but it was too early to know whether it could disrupt oil and gas operations in the gulf.
U.S. National Hurricane Center forecasters said another tropical storm, called Florence, formed on Saturday in the eastern Atlantic and was moving west in open waters. As of early evening, forecasters said, Florence was about 600 miles west of the southernmost Cape Verde Islands.
With maximum sustained winds of 60 mph, Florence was the sixth named storm of the Atlantic-Caribbean hurricane season, moving west at 15 mph, and was expected to near hurricane strength on Sunday.
August and September are usually the most active months of the Atlantic-Caribbean hurricane season, which runs from June 1 to November 30.
(Reporting by Michael Connor in Miami; Editing by Bill Trott and Jackie Frank)