In the National Oceanic and Atmospheric Administration’s recent winter outlook report, La Nina conditions have a 90 percent chance of continuing through the winter and a 50 percent chance of lasting through the spring season. The early winter’s exceptional precipitation has already proven to be helpful for California’s drought, but can we expect that continue? That’s a complicated question.
La Niña is an oceanic and atmospheric phenomenon that is the colder counterpart of El Niño, as part of the broader El Niño–Southern Oscillation climate pattern. During a La Nina year, trade winds are even stronger than usual, pushing more warm water toward Asia and bringing cold, nutrient-rich water to the surface on the west coast of the Americas. These cold waters in the Pacific push the jet stream northward, leading to drought in the southern U.S. and heavy rains and flooding in the Pacific Northwest and Canada.
Northern California sits right in the middle of this confluence between warm/dry and wet/cold, making it experience both wet and dry La Nina years. Last year saw a dry La Nina, but there have also been very wet ones in the past. With the start of the year being wet, that could be a positive indication for the region. Currently, the high pressure sits more west than last year, allowing storm systems to hit the sweet spot of NorCal, from Mount Shasta all the way down to Mammoth. But nothing is guaranteed for the duration of the winter.
NorCal is currently experiencing its second straight year of extreme drought, bringing catastrophic natural events like water shortage, low snowpack and devastating wildfires. However, the NOAA’s report forecasts drought improvement in the region. Precipitation should increase in all areas of NorCal, especially any region north of Chico. The same can’t be said for Southern California, which will likely experience a drier year and continue the overall drought throughout California.
There is still much to decipher in the upcoming months about whether we will be able to emerge from this drought and experience the fruitful NorCal conditions that wet years bring. But it will likely take multiple years of above average precipitation to return to full water levels in local reservoirs. When Lake Tahoe fell below its natural rim in October, researchers estimated that it would take a record winter of 800+ inches of snow in the Sierra to fill it up completely. You never know, it could happen…
As with any weather report, there are still many questions surrounding the upcoming winter and whether it can bring a positive impact to the region. So far, it’s looking pretty good.