MEXICO CITY -- Hurricane Aletta strengthened to a powerful Category 4 storm in the open Pacific on Friday, but it was well off the Mexican coast and forecast to head farther out to sea. The National Hurricane Center noted the storm became a hurricane 19 days before June 26, the average date of the first eastern Pacific hurricane.

The U.S. National Hurricane Center says Aletta is centered about 530 miles west-southwest of Manzanillo, Mexico. The storm has maximum sustained winds of 140 mph and is moving toward the west-northwest at 6 mph.

The center said swells generated by Aletta would begin to hit portions of mainland Mexico and the west coast of Baja California Sur and continue through the weekend, likely causing "life-threatening surf and rip current conditions."