Weak La Niña means likelier cold, snowy winter in Pacific Northwest
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The annual NOAA winter outlook calls for weak La Niña conditions in the tropical Pacific Ocean to be a key factor in influencing the path that storms take.
Zoom in: A warmer and drier than average winter is favored along the southern tier, with the likely emergence of drought conditions in the Southwest in particular.
- The Great Lakes and the Pacific Northwest are expected to see above- average precipitation during the December-February period, and this may be combined with colder-than-average conditions in the Pacific Northwest.
- La Niña winters tend to be snowier in the Northwest, whereas the Mid-Atlantic and coastal Northeast tends to see below average snowfall.
- Other factors, like the stratospheric polar vortex and patterns of air pressure in the North Atlantic are likely to assert themselves this winter, leading to large week-to-week variability, NOAA experts said Thursday.
Zoom out: NOAA's climate outlooks are probabilistic, which means they communicate the odds of a particular outcome, rather than predicting definitive conditions.
- Therefore, the projections show above-average odds for a colder, snowier winter than normal in the Pacific Northwest; higher odds of drought expansion into the Southwest; and strong odds of a milder-than-average winter from the southern tier of the U.S. to parts of the East Coast.
Yes, but: The world's oceans are near record warm, which could damper some of the predicted weak La Niña's typical effects.
- Such events feature cooler-than-average waters in parts of the tropical Pacific Ocean.
- Also, human-caused climate change plays a role during the season.
Between the lines: Human-caused climate change could overcome the typical effects of a weak La Niña to be a top factor influencing winter weather for regions.
- "Winter for many regions across the US is the fastest warming season of all the seasons," said NOAA climate expert Tom Di Liberto on a press call Thursday.
The bottom line: El-Niño, La Niña and the absence of these conditions (known as ENSO neutral) tend to be the biggest predictors of winter weather patterns across the U.S.
- However, the expected weakness of the La Niña could allow other players in influencing winter weather, which are difficult to predict beyond a few weeks in advance, may play a significant role this year, too.
