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News of the Arroyo


La Niña is on its way out. What does that mean for California?






Jacob Margolis




Typical impacts of La Niņa on U.S. winter temperature and precipitation. Such impacts have been associated with past episodes, but all impacts aren't seen with every episode. Drawing by Fiona Martin. FIONA MARTIN / NOAA

La Niņa, the climate system associated with drier and warmer than average winters in Southern California, will likely be over by spring, the National Oceanic and Atmospheric Administration reported Thursday.

Scientists regularly look for the formation or absence of the system when predicting weather in the American Southwest. La Niņas are driven by changes in ocean temperatures in the equatorial Pacific, as is the El Niņo climate system that typically brings wetter, cooler winters to Southern California.

This winter, La Niņa predictions of less rain and snow have been spot on as counties across SoCal have dipped back into to moderate-to-severe drought conditions.

Climate scientists began to flag this year's La Niņa as a possibility during the summer of 2017 when the waters in the eastern and central tropical Pacific began to cool, an early sign of the system. Through fall and early winter the waters continued to cool, and La Niņa strengthened into what is considered a moderate showing of the event.

Since then, the waters have begun to warm, indicating that La Niņa could be on its way out. NOAA gives it a 55 percent chance of dissipating some time between March and May.

But the predicted end of La Niņa coincides with the traditional end of California's wet season. While it's always possible the state could get hit by a large storm system, it gets the majority of its precipitation between December and February, and as of right now things aren't looking good. The Los Angeles basin has only received 17 percent of its average amount of rainfall while the eastern Sierra Nevada only has 27 percent of its expected snowpack.

While the dry weather was anticipated, predicting the impact of La Niņa conditions can be a perilous endeavor as scientists saw during the 2016-2017 rainy season. That was also a La Niņa winter, but to the surprise of many, it saw record rain and snowfall, particularly in Northern California.

As a result, most of the state was lifted out of a years-long drought.

This winter's La Niņa was a "double dip." Typically, the second La Niņa is weaker than the first, but this year's was much stronger than the first.

While a third year of La Niņa isn't likely, it's certainly a possibility. But there's also the possibility that we'll see neutral conditions or El Niņo. What that might mean for California is unclear, but given the rise in global temperatures, even if we get rain, next winter could still be warmer than normal.




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