Will El Niño Ease California's Drought?

Will El Niño Ease California’s Drought?

The warmer months of 2015 are behind us, and the development of a strong “El Niño” in the Pacific Ocean has many Californians wondering if this means the end of the devastating four-year drought. Certainly the rain over the past few weekends has been encouraging. But, when will the drought be over?

Jeff and Betsy Reid are atmospheric scientists and they, with their daughter Ellie, have been farmers market regulars since 2002 (well, since 2009 for Ellie). The Reids keep a close eye on global weather patterns as part of their day jobs and frequently talk shop with the market farmers. So I posed the question, do the Reids believe we’re in for a drought busting winter?

“Right now for the central coast, forecasters are suggesting a 33-40% chance for enhanced rainfall for the next 3 months due to patterns associated with El Niño,” Jeff explained. “It is good news given the California drought. But it is still only a probability, not a promise. Certainly the odds are in our favor for normal to above normal precipitation this winter, but we will not know if it is a drought buster for months. After so many years of drought, even an ‘above average’ year may be insufficient to restock aquifers and reservoirs.”

“El Niño” is part of a larger coupled ocean and atmosphere phenomenon termed the El Niño-Southern Oscillation (ENSO) which is often linked to dramatic changes in weather patterns over the globe. El Niño is a pattern associated with warmer ocean surface temperatures in the eastern tropical Pacific Ocean that recur every 3 to 7 years. Many years before this weather cycle was officially recognized and researched, fishermen of northern Peru had noticed that this warming of the ocean surface water occurred near Christmas, and thus named the weather pattern after the Christ child, “El Niño.”  

Because it involves such a large area and interacts with already complicated weather and climate systems, El Niño’s effect on global weather patterns varies from cycle to cycle, making it difficult to accurately predict the ultimate outcome in terms of winter rain.  “Often when we think of El Niño we think back to local flooding in the winter of 1997 to 1998,” Jeff says, “But in reality the relationship between El Niño and central coast precipitation is quite variable.” El Niño’s influence on southern California’s climate is much stronger than its impact on northern California. And for the central coast, this year the outcome is even more uncertain, because not only are the tropical ocean surface waters warm (typical El Niño), but the water temperatures off the central coast are also at a record high, further complicating existing weather patterns.

Jeff  chuckles at the difficulty of forecasting winter rainfall. “Last December we got 7″ of rain in 5 days at our house in Prunedale. We felt so good about that we made reservations for a spring snow vacation. When we got to Tahoe at the end of March the snow pack was at 5% of normal.”

While recent rain and cooler temperatures signal the onset of the central coast’s version of winter, the continuing concern about the drought makes this winter’s hope for rain more fervent than ever, even among weather forecasters. Given the uncertainty in weather patterns, Jeff offers this advice: “If there is a lesson here, it is that agriculture and residential water users alike should be thinking about long-term water efficiency.” In other words, hope for the best, prepare for the worst.

That’s good advice, rain or shine.