Tropical Storm Don is churning through the Gulf of Mexico, moving toward the coast of the southern U.S. state of Texas.

The U.S. National Hurricane Center in Miami says the storm is moving west-northwest at about 17 kilometers per hour with sustained winds of 65 kilometers per hour.

Forecasters also say Don could grow stronger before making landfall Friday. A tropical storm watch is in effect for parts of the southern Texas coast .

Tropical Storm Don is the fourth named storm of the Atlantic hurricane season.

Some energy companies with oil rigs and other facilities in the Gulf of Mexico have begun evacuating non-essential workers.

Gulf of Mexico oil refineries are responsible for almost one-third of U.S. oil output.