ROSEAU, Dominica (AP) — Leaders across much of the Caribbean closed schools and government offices on Wednesday as Tropical Storm Isaac swept toward the region, and the U.S. military postponed hearings for Sept. 11 prisoners ahead of a storm that could sweep across Cuba and perhaps eventually menace Florida as a hurricane.

The storm was 75 miles (120 kilometers) east-northeast of Dominica early Wednesday afternoon, with maximum sustained winds of 45 mph (75 kph). Isaac was moving west at 21 mph (33 kph) and is expected to become a hurricane by Thursday, according to the U.S. National Hurricane Center.