Forecasters say Tropical Depression 18 has formed over the southwestern Caribbean Sea, south of Jamaica.
The National Hurricane Center has issued a Tropical Storm Watch for Jamaica, saying the system could produce deadly storms and flash-floods on the island, as well as on Cuba and Hispaniola.
As of 11 a.m. Monday, TD 18 has maximum sustained winds of 30 mph. It's located about 320 miles south-southwest of Kingston, Jamaica and is moving southwest at 5 mph.
The NHC expects the storm to strengthen and possibly become Tropical Storm Sandy later in the day and could be near hurricane strength as it approaches Jamaica on Wednesday.