SACRAMENTO, Calif —
California, fresh off its record setting winter, now faces the prospect of another wet winter amid the development of El Niño.
NOAA’s latest update on El Niño declares a greater than 90% chance that it lasts through the upcoming winter. The agency first declared the presence of El Niño last month once temperatures hit 0.5 degrees Celsius above average in the Niño 3.4 region, which encompasses much of the central equatorial Pacific.
The El Niño Southern Oscillation (ENSO) shifts back and forth irregularly every two to seven years, bringing predictable shifts in ocean surface temperature and disrupting the wind and rainfall patterns across the tropics, according to NOAA.
The update also predicts a 1-in-5 chance of a “historically strong” El Niño, but places the highest probability of peaking at moderate to strong in strength this winter.
“An event that becomes 'historically strong' (seasonally averaged Niño-3.4 ≥ 2.0°C), rivaling the winters of 1997-98 or 2015-16, has an approximately 1 in 5 chance. In summary, there is a greater than 90% chance that El Niño will continue through the Northern Hemisphere winter,” said NOAA.
The threshold for a historically strong El Niño is 2 degrees Celsius above average in the Niño 3.4 region. Currently, sea surface temperatures are reading almost 1 C above normal in the equatorial Pacific.
El Niño doesn't typically play a role in the summer weather pattern here in California, but winter is another story.
During strong El Niño years, there is a strong signal California is wetter than average. During a weak to moderate El Niño, California is typically wetter than average, although the signal is much weaker, especially north of Sacramento. During strong years, most areas of the state are much above-average in terms of precipitation.
Interestingly enough, the last two cases of a historically strong El Niño featured both a significantly wet winter (1997) and a very dry winter that plunged California further into drought in 2015-16.
While ENSO is typically a good predictor of winter weather in California, the presence of El Niño is by no means a guarantee of wet weather. Still, it is worth keeping an eye on as the rainy season nears.
