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 systemcould produce deadly storms and flash-floodson 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 couldbe nearhurricane strength as it approaches Jamaica on Wednesday.