Fearing potentially deadly flooding, Mexican disaster officials are closely monitoring the weather after Tropical Storm Hernan formed off the country's Pacific coast of Mexico late Saturday.

Hernan was located 585 kilometers (more than 360 miles) southwest of the tourist port of Manzanillo and was moving in a northwesterly direction, parallel to the coastline, at a speed of 22 kilometers per hour, Mexico's National Meterological Service (SMN) reported at 0300 GMT.

The storm was packing maximum winds of 65 kilometers per hour, with gusts up to 85 kilometers per hours, the SMN said.

The Miami-based National Hurricane Center, which had slightly different figures, warned that Hernan was picking up strength.

"Additional strengthening is expected" overnight Saturday to Sunday, "and Hernan could be near hurricane strength by Sunday afternoon," the NHC said.

It added however that the storm is expected to weaken on Monday.

Heavy rain from tropical storms Douglas and Elida earlier this month killed three people in the northen state of Chihuahua, while three other people were killed by Hurricane Amanda in May in the states of Michoacan and Guerrero.

Neither Mexican nor US weather monitors expect Hernan to make landfall.