MIAMI -- Tropical Storm Chantal has formed off the southeast U.S. coast. The National Hurricane Center in Miamia says tropical storm warnings have been issued for portions of the Carolinas. Tropical storm conditions are expected in the affected areas later Saturday.

At 9 a.m. EDT, the storm's center was located about 150 miles (240 kilometers) south-southeast of Charleston, South Carolina, and about 240 miles (385 kilometers) south-southwest of Wilmington, North Carolina.

Chantal's maximum sustained winds were measured at 40 mph (65 kph). It was moving north at 2 mph (4 kph.

The center of Chantal is expected to move across the coast of South Carolina on Sunday morning, the hurricane center said. Some additional strengthening is expected before Chantal reaches the coast.