TS Ernesto's projected track as of late Friday morning.
(CNN) -- Tropical Storm Ernesto hit parts of the Windward Islands on Friday morning, bringing rain and occasionally robust gusts as forecasters predicted it could become a hurricane in the central Caribbean Sea by the end of the weekend.
The storm's center passed over or nearly over St. Lucia in the eastern Caribbean and was about 90 miles west of the island shortly before 11 a.m. ET, the U.S. National Hurricane Center said.
Ernesto - with maximum sustained winds of 50 mph and faster gusts - was moving west at about 21 mph.
The storm is expected to bring 2 to 3 inches of rain - with isolated maximum amounts of 5 inches - to St. Lucia and the rest of the Windward Islands through Friday, according to the center.
The Windward Islands are the southern portion of the Lesser Antilles in the eastern Caribbean, north of Venezuela and southeast of Puerto Rico.
Ernesto is forecast to move west through the eastern Caribbean before turning on a more west-northwest track Saturday night. It is expected to strengthen and possibly become a category 1 hurricane - with maximum sustained winds of at least 74 mph - late this weekend.
The storm's center could be near Jamaica late Sunday or early Monday, according to the National Hurricane Center's three-day track forecast cone. But it's too soon to predict whether it will hit the island, with the cone showing it could travel as many as 225 miles to the south.