MIAMI — Tropical Storm Isaias formed early Wednesday in the warm waters off eastern Mexico and forecasters said it was expected to strengthen into a hurricane and hit the U.S. Gulf Coast later in the week.

Isaias was located about 285 miles (460 kilometers) west of Progreso, Mexico, and about 580 miles (935 kilometers) southwest of the Mississippi River’s mouth with maximum sustained winds of 40 mph (65 kph) and moving east-northeast at 8 mph (13 kph), according to the Miami-based National Hurricane Center.

It was not immediately known where the storm may make landfall on the Gulf Coast. The hurricane center’s initial projections said the center of Isaias could come onshore somewhere between eastern Louisiana and the western Florida Panhandle.