Note: This article originally published in High Country News
For the past two years, La Niña, the cooling of ocean temperatures in the equatorial Pacific, has wreaked havoc on weather around the globe. Now the World Meteorological Organization expects the phenomenon to return for a third consecutive year, a rare occurrence that forecasters predict could bring wackier-than-usual winter weather to the West, once again.
La Niña is the yin to El Niño’s yang. Normally, trade winds — the tropical winds near the Earth’s surface — blow west along the equator, moving warm Pacific Ocean water from the Americas toward Asia. This cycle is disrupted every two to seven years by El Niño-Southern Oscillation, or ENSO, events, which typically last about a year. During El Niño, the winds weaken, and warm water is pushed back toward the Americas. La Niña, meanwhile, strengthens trade winds, bringing cool water to the surface of the Americas’ West Coast.
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A study published this summer by University of Washington researchers suggests