Friday is expected to see the first hurricane of the Eastern Pacific storm season, US meteorologists warned, heralding the start of a turbulent six-month period.

Tropical Storm Andres, which formed off the Mexican coast in the early morning hours Thursday, was located about 690 miles (1,110 kilometers) southwest of Manzanillo at 10:00 am (1500 GMT), according to the US National Hurricane Center.

It had top winds of 40 miles per hour but was not expected to threaten the coast.

"Additional strengthening is forecast during the next couple of days and Andres is forecast to become a hurricane late Friday or Friday night," the Miami-based NHC said in a bulletin.

The Pacific hurricane season began on May 15 and runs through November 30.

Last year's season was the most active since 1992, with 20 recorded storms, of which 14 went on to become hurricanes.

The most damaging was Hurricane Odile, which killed six people and caused millions of dollars' worth of damage in September in the Mexican tourist resort of Los Cabos.