Weak La Nina Shaping Up; Dry Winter Already Well Under Way In West, Southwest
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In two new studies, Okumura and her colleagues figured out how to predict this multiyear pattern more than 12 months in advance. Using computer models, they forecast the current second-year La Niña in the fall of 2015.
The researchers also found that the second La Niña year is often drier than the first – even though the second La Niña may be weaker – and the drought-affected area may grow larger. That’s what the West is facing now: a second consecutive La Niña year, and the prospect of reduced precipitation across California – even though Gov. Jerry Brown declared the drought over only eight months ago.
This precipitation forecast, made December 5 by the National Center for Atmospheric Research, shows the entire West is likely to see below-average precipitation through December 26. (Image Courtesy National Center for Atmospheric Research)
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Unfortunately, December looks like it will be completely dry across most of the West. A dome of high pressure has parked itself off the West Coast, diverting storms far to the North, into Canada. It is very similar to the “ridiculously resilient ridge” that contributed to California’s severe drought. The latest pattern, dubbed a “Godzilla Ridge” by University of Washington atmospheric scientist Cliff Mass, appears likely to keep the West dry until at least mid-December. One new long-range forecasting tool, developed by the National Center for Atmospheric Research in Boulder, Colorado, indicates dry conditions are likely for the entire month.
Looking further out, a three-month forecast from the Climate Prediction Center at the National Weather Service shows dry conditions are likely across the southern half of the U.S. through February. This fits the “typical” La Niña pattern, but is much more uncertain given the long forecast time frame.
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https://www.newsdeeply.com/water/articles/2017/12/11/second-la-nina-winter-could-extend-drought-across-the-west
