MIAMI — Tropical Storm Cosme is strengthening in Pacific waters southwest of the Mexican mainland and forecasters say it's expected to become a hurricane within a day.

The storm's maximum sustained winds have risen to 65 mph (105 kph) as of late Monday. The U.S. National Hurricane Center in Miami says more strengthening is expected in the coming 48 hours with Cosme expected to become a hurricane sometime Tuesday.

Cosme is centered about 320 miles (515 kilometers) southwest of Manzanillo, Mexico, and is moving northwest at 14 mph (22 kph).

No coastal watches or warnings are in effect.

The hurricane center says ocean swells generated by the storm will begin affecting a swath of the Pacific coast from Manzanillo to Cabo Corrientes overnight with life-threatening surf and rip currents possible.