Weather Watch

This winter’s El Niño is poised to be the strongest on record

Elephant seals on the beach near San Simeon about two weeks ago.
Elephant seals on the beach near San Simeon about two weeks ago.

This season’s El Niño event could be the strongest on record, according to the National Oceanographic and Atmospheric Administration.

Since 1950, NOAA has used sea surface temperatures in a central equatorial region of the Pacific Ocean called Niño 3.4 as the standard for classifying El Niño (warmer-than-normal SST) and La Niña (cooler-than-normal SST) events. The fortunetelling SST cycles in Niño 3.4 are categorized by the amount they deviate from the average SST. In other words, an anomaly.

A weak El Niño is classified as an SST anomaly between 0.5 and 0.9 degrees Celsius, a moderate El Niño is an anomaly of 1.0 to 1.4 degrees Celsius and a strong El Niño ranges from 1.5 to 1.9 degrees Celsius. A very strong El Niño anomaly is anything above 2.0 degrees Celsius (or 3.6 degrees Fahrenheit), a very rare event indeed.

The past two very strong El Niño episodes occurred during the 1982-83 and 1997-98 rain seasons. Both of these generated huge amounts of precipitation, with a deep snowpack in the Sierra Nevada and copious rain along the Central Coast. The 1982-83 rain season (July 1, 1982, to June 30, 1983) totaled 47 inches, while the 1997 rain season (July 1, 1997, to June 30, 1998) hit 44 inches at the Diablo Canyon nuclear power plant’s rain gauge. Historically, the seasonal precipitation averages about 23 inches.

This season’s El Niño could be the strongest on record, according to NOAA, because the weekly average mid-November SST in the Niño 3.4 region reached an all-time record of 3 degrees Celsius (or 5.4 degrees Fahrenheit) above average. Not to be outdone, SST data released last week indicates the average temperature for the entire month of November was the warmest in history at 2.35 degrees Celsius — even warmer than the previous record month set in November 1997.

So is this the strongest El Niño on record, besting the monster events of 1982-83 and 1997-98? I asked Jan Null, a former National Weather Service lead forecaster and PG&E meteorologist, an expert on El Niños and La Niñas and their relationship to California’s weather.

“It depends on what statistics you look at,” Null said. “To use a sports analogy: How do you rate a quarterback? By the number of wins, pass completions or the number of interceptions. No matter what statistic you look at, this El Niño is one of the strongest on record.”

NOAA tends to utilize a three-month running mean SST. So far, at 2 degrees Celsius, the September, October and November 2015 time frame was one of the warmest on record. However, this season’s El Niño could certainly peak later in the year and make it the strongest on record. The potential later peak could also lend itself to producing heavier amounts of rainfall.

So far this rain season, the Central Coast hasn’t exactly been awash with rain. But this can certainly change. The long-range numerical models and charts are indicating a good chance of a wet weather pattern developing by mid-December. More importantly, El Niño-driven storms are not expected to start until January 2016. In fact, January, February and March are predicted to produce well-above-normal rainfall for most of California.

As I’ve written before, El Niño does not guarantee above-normal rainfall. But, historically, the stronger the El Niño event, the higher the probability of greater amounts of average precipitation in Central and Southern California. It should also be noted, even if we do receive record rain this season, it probably won’t end the drought. Water conservation and management will be critical in the years ahead.

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The last major El Niño storm season in 1997-98 created widespread flooding and caused power outages impacting more than a million PG&E customers. PG&E has been preparing for storms like those by practicing for extreme-weather events and natural disasters using advanced meteorology tools to forecast where storm impacts will be most significant and adding innovative technology to its electrical grid.

PG&E also urges its customers to be ready for natural disasters. That includes creating a family emergency plan and creating emergency kits for your home, your office and your vehicle. PG&E offers emergency-preparation tips on its website at www.pge.com/en/safety/preparedness/index.page.

John Lindsey’s column is special to The Tribune. He is PG&E Diablo Canyon’s marine meteorologist and a media relations representative. Email him at pgeweather@pge.com or follow him on Twitter @PGE_John.

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