MIAMI (AP) – Subtropical Storm Gabrielle formed Friday off the Southeast U.S. coast, and a tropical storm watch was issued for portions of the South Carolina and North Carolina coast.

At 11 p.m, Gabrielle had top sustained winds near 45 mph and was centered about 385 miles southeast of Cape Lookout, N.C., the National Hurricane Center said. It was moving west northwest near 10 mph and was expected to continue along the same path during the next 24 hours.

A tropical storm watch was issued for portions of the South Carolina and North Carolina coast from Edisto Beach northward to Oregon Inlet, including Pamlico Sound. A tropical storm watch means that tropical storm conditions are possible within the watch area within the next 36 hours.

Subtropical systems are hybrid weather formations that are typically weaker than hurricanes. They share characteristics of tropical storms, which get their power from warm ocean waters, and more normal storms that form when warm and cold fronts collide.

Gabrielle is the second subtropical storm to form this year. Subtropical Storm Andrea formed in May about 150 miles northeast of Daytona Beach, before the June 1 official start to hurricane season. Andrea skirted the southern Atlantic coast but caused minimal damage.