La Nina’s Back for Winter, NASA Says

The Pacific Ocean phenomenon La Nina has reappeared, prompting forecasts for a wet winter across the Northwest and a dry one in the Southwest, NASA scientists said.

The weather-altering pattern had appeared to all but vanish this summer. But a U.S.-French satellite monitoring sea surface height and temperature this month detected a pool of unusually cool water marked by lower-than-normal sea levels in the eastern North Pacific and warm water in the western and mid-latitude Pacific.

“Those conditions will have a powerful impact on the weather system delivering jet streams out of the North Pacific,” said oceanographer William Patzert of the Jet Propulsion Laboratory in Pasadena.

La Nina is characterized by unusually cold sea surface temperatures in the eastern and central equatorial Pacific, which trigger atmospheric patterns that influence weather around the world.

Last year’s La Nina contributed to a series of huge storms that blasted Washington, Oregon and Northern California with hurricane-force winds, heavy rains and mountain snows, and powerful storms elsewhere in the world.

Patzert said conditions are ripe for a stormy winter in the Pacific Northwest and a relatively dry winter in the Southwest.

“Clearly, these unusual conditions, which have persisted for 2 1/2 years, will not be returning to normal any time soon,” Patzert said. “This climate imbalance is big and we’re definitely going through a decade of wild, climatic behavior.”

Last winter’s La Nina followed the historic 1997-98 El Nino, which was blamed for heavy snow in the West, massive flooding in Africa and drought in Asia.