The Northern Hemisphere looks ready to transition into a La Niña winter in the next month, according to the latest outlook from the National Oceanic and Atmospheric Administration’s Climate Prediction Center, KTLA sister station WUTR reported.
Most forecasting models indicate La Niña conditions are set “to emerge shortly and continue through winter 2021-22,” the analysis released Monday said.
NOAA said the latest outlook indicates a 70-80% chance of a La Niña winter this year.
La Niña is a climate pattern where winds that blow from east to west become stronger than normal, pushing warmer water towards Asia but upwelling colder water on the coast of the western United States. The colder waters in the Pacific end up affecting the atmosphere, pushing the jet stream further north.
What does this mean in laymen’s terms for winter weather?
“It really depends where you are in the United States. It will vary by location,” NOAA climate scientist Michelle L’Heureux told Nexstar in August. “The southern tier during a La Nina is often drier than average during the winter, and that often extends into spring.”
That southern tier includes Southern California, the southwestern states, Texas, and the Gulf Coast states through to Florida. Many of those states, especially in the southwest, are plagued by drought, and a La Niña year could make that worse.
The opposite is actually true for Northern California and the Pacific Northwest, where La Nina winters tend to bring more precipitation, not less. Later in winter, that extra precipitation tends to hit Ohio and the Tennessee Valley.
How La Niña affects the northeast is the biggest mystery, L’Heureux said. It’s pretty much equal chances of a wet winter and a dry winter.
The forecast data is hinting toward a moderate La Niña during the fall and winter 2021-22. The previous forecast hinted towards a borderline or weak La Niña. The weaker the La Niña conditions are, the more it will feel like a normal winter where you live.
The Climate Prediction Center’s seasonal temperature outlook indicates most of the country could see a slightly warmer winter. All but the most northern states are leaning above average.
La Niña is the opposite of El Niño. El Niño occurs when trade winds weaken and warmer water is pushed back east, toward the west coast of the United States. This pushes the polar jet stream south, leading to warmer and more mild winters in the north, and wetter winters in the south.