Much of South Florida was placed under a tropical storm warnings Tuesday as a sprawling system got itself together enough for the National Hurricane Center to designate it depression No. 16.

It was expected to cross Cuba overnight, probably as Tropical Storm Nicole, and be somewhere off or on the Miami-Dade and Broward coastline by Wednesday afternoon.

At 11 a.m., the center said the depression, with maximum winds of 35 mph, was about 390 miles south-southwest of Miami. It was moving north-northeast at 10 mph.

With little time to develop, forecasters expected the system would remain at tropical storm strength but the depression was still a major flooding threat. It was expected to bring up to five to 10 inches of rain to Cuba, the Cayman Islands and Jamaica, with as much as 20 inches in isolated spots. The forecast for South Florida and the Florida Keys was four to eight inches.