NEW YORK, Aug 20 (Reuters) - Hurricane Dean, the Atlantic season's first major storm, was heading toward Mexico's Yucatan Peninsula as a powerful Category 4 storm early Monday as it continued to track west across the Caribbean, the U.S. National Hurricane Center said in its latest advisory.

Dean passed just south of Jamaica on Sunday with winds near 150 miles per hour, dumping heavy rain on the island.

At 11 a.m. EDT (1500 GMT), Dean was located about 125 miles (200 km) southwest of Grand Cayman and about 385 miles east of Belize City in Belize which borders Mexico.

Dean was moving west at 21 mph, with maximum sustained winds still at about 150 mph, and was expected to hit the east coast of the Yucatan Peninsula early Tuesday morning.

The NHC said Dean was approaching Category 5 status, the highest on the Saffir-Simpson scale with winds of 156 mph or greater, and was expected to reach that threshold later today as it continued across the warm waters of the western Caribbean.

A westward or west-northwestward motion was expected to continue for the next two to three days.

Most computer models show Dean sweeping across the Yucatan on Tuesday, then moving into the Bay of Campeche in the southwest Gulf of Mexico before making landfall near Tampico, Mexico, late Wednesday.

While Dean was not expected to land anywhere near the refineries or key oil and gas producing platforms located along the Texas coast, it was expected to disrupt operations in Mexico's Cantarell oil field in the Bay of Campeche.

Cantarell, one of the world's largest oil fields, produced an average of 1.57 million barrels per day in June, about half of Mexico's total crude oil production.

The NHC said it expected Dean to weaken as it crossed the Yucatan but still retain hurricane status before it restrengthens in the Bay of Campeche.

The NHC will issue an intermediate advisory at 2 p.m.

((Reporting by Joe Silha, editing by John Picinich; New York Energy Desk; joe.silha@reuters.com; +1 646 223 6071))

AlertNet news is provided by