Hurricane Hernan in the eastern Pacific off Mexico's northwest coast lost strength overnight and weakened into a tropical storm, US forecasters said early Monday.

The storm was swirling some 580 kilometers (360 miles) southwest from the southern tip of Baja California, packing maximum sustained winds of 110 kilometers per hour, the Miami-based National Hurricane Center said in its 0900 GMT bulletin.

Hernan was moving towards the northwest at 24 kilometers per hour and "this motion is forecast to continue through Monday night."

A turn towards the west and further away from land "with a decrease in forward speed is expected on Tuesday," the NHC said.

No coastal watches or warnings were in effect.