While weather forecasters are predicting a strong El Niño that could signal the arrival of significant rain in the coming fall and winter season, the state climatologist is urging Californians to lower their expectations with respect to the weather phenomenon.
“California cannot count on potential El Niño conditions to halt or reverse drought conditions,” State Climatologist Michael Anderson said Thursday.
“Historical weather data shows us that at best, there is a 50/50 chance of having a wetter winter,” Anderson added. “Unfortunately, due to shifting climate patterns, we cannot even be that sure.”
The current drought has resulted in observations of new, record-high temperatures and record low snowpack for California.
Five of the lowest 10 snowpacks on record have occurred in the last decade, including the past four years, officials reported.
The seasonal snowpack is a key element to California’s water resources management, modulating winter precipitation into spring runoff for beneficial use through the dry summer.
As California heads into a new water year – which takes place from Oct. 1 to Sept. 30 – with a potential fifth year of drought and expectations of El Niño impacts in play during the winter, questions mount on what can be expected of winter temperatures, precipitation and snowpack for California.
The El Niño-Southern Oscillation, or ENSO, is “characterized by year-to-year fluctuations in sea surface temperatures along the equator in the Pacific Ocean between Peru and the International Date Line, and concomitant fluctuations in sea level air pressures between Tahiti and Darwin, Australia,” according to a July report from the Western Regional Climate Center.
The report, which can be seen below, gives more detail and information on the unpredictable nature of the El Niño phenomenon.
Officials like Anderson are pointing out that a historical look at past years with similar El Niño conditions as currently forecasted provide little guidance as to what California might expect this winter.
Of the seven years since 1950 with similar El Niño signals – 1958, 1966, 1973, 1983, 1988, 1992 and 1998 – three were wet years, one was average and three were dry, with water year 1992 perpetuating a drought, officials said.
Past years were cooler than the temperatures California is experiencing now, which officials said also will impact the rain/snow boundary for any storms that materialize this winter.
The Western Regional Climate Center report explains that the ENSO cycle is expressed as three states: neutral conditions, El Niño (warm ocean phase), and La Niña (cold ocean phase).
The National Oceanic and Atmospheric Administration’s Climate Prediction Center ENSO diagnostic discussion is predicting a 90-percent chance of El Niño conditions in the fall and early winter, based on the climate center's report.
However, that may not translate into much rain for Lake County and other Northern California areas, the center suggested.
“There is almost no correlation between precipitation and El Niño conditions in Northern and Central California. ENSO’s strongest signal in California is for Southern California to be drier than average in La Nina years,” the report stated.