Forecasters say Tropical Storm Olaf has formed off Mexico's Pacific coast, becoming the 15th named storm of the 2009 season.

The National Hurricane Center in Miami says Olaf is not likely to get much stronger, and will probably begin weakening sometime Friday.

Olaf's center was about 565 miles west-southwest of the southern tip of Mexico's Baja California peninsula on Thursday afternoon. The storm was moving to the west-northwest near 6 mph, with winds near 40 mph.