A hurricane watch is in effect from Florida to Louisiana after Tropical Storm Karen formed in the Gulf of Mexico.

The National Hurricane Center in Miami says the late-season storm formed Thursday morning. It was about 485 miles south of the mouth of the Mississippi River and already had maximum sustained winds of 65 mph.

The hurricane watch was in effect from Grand Isle, La., to Indian Pass in the Florida Panhandle. A tropical storm watch also was in effect for parts of the Louisiana coast west of Grand Isle, including the metro New Orleans area and Lake Pontchartrain.

Karen was moving north-northwest at 12 mph. It could be at or near hurricane strength by Friday.