'Hurricane Norbert is already a category-four storm (just short of maximum category five) in the Saffir-Simpson scale, so we're under a green or precaution alert in southern Baja California,' said local State Civil Protection Unit spokesman Jose Gajon.

The NHC's five-day forecast showed Norbert, currently located in the Pacific Ocean about 715 kilometres south of Baja's southern tip, striking the peninsula at hurricane strength late on Friday or early Saturday.

'Some fluctuations in intensity are possible during the next day or so ... followed by gradual weakening on Friday,' the Miami-based NHC said.

'Interests in the southern Baja California peninsula should monitor the progress of Norbert,' the centre said.

Southern Baja California includes the state capital of La Paz and the resort centers of Cabo San Lucas and San Jose del Cabo.

The 1,100-kilometre-long peninsula in northwestern Mexico abuts the US state of California and is mostly separated from mainland Mexico by the Gulf of California, also known as the Sea of Cortez.

Norbert is forecast to cross the peninsula, then head across mainland Mexico as it weakens and strike the US states of Texas, New Mexico and Arizona as a tropical depression. -- AFP