The first tropical storm of the Pacific storm season formed Tuesday far out to sea off the Mexican coast, the US-based National Hurricane Center said in a statement.

Tropical Storm Aletta was packing maximum winds of 40 miles (65 kilometers) per hour but posed no threat to land as it roiled the ocean of the tropical eastern north Pacific, said the NHC in Miami.

Aletta was moving on a west-northwestward course at nine mph (15 kmh) some 640 miles (1,025 km) south-southwest of Manzanillo, Mexico, US forecasters said, with winds expected to strengthen over the next 24 hours.