"Some additional weakening is likely while Oscar moves across the mountainous terrain of eastern Cuba, but Oscar is forecast to be a tropical storm when it moves north of Cuba late today and then moves near the southeastern and central Bahamas on Tuesday," the hurricane center said Monday morning.

Oscar, which the National Hurricane Center characterized as "very small," is the 15th named storm of the hurricane season.

Tropical Storm Oscar doused Cuba on Monday, three days after a massive power failure plunged more than 10 million people into the dark as the island worked to restore its decades-old power grid.

Hurricane Oscar made landfall in Cuba late Sunday, just hours after striking the Bahamas. The system has since weakened to a tropical storm, but it is still expected to bring heavy rainfall and "life-threatening flash flooding," according to the National Hurricane Center.

Up to 20 inches of rain is forecast in some regions of Cuba, which could trigger flash flooding and mudslides.

Tropical Storm Oscar is producing heavy rainfall and flash flooding over eastern Cuba, The National Hurricane Center said.

Tropical Storm Oscar dumped heavy rain across eastern Cuba on Monday after making landfall as a Category 1 hurricane on the island already beleaguered by a massive power outage. Its maximum sustained winds blew at 40 mph on Monday as Oscar moved northwest at 6 mph.