Weather Watch

Rising seawater temperatures could signal arrival of El Niño

A seal perches on a rock Thursday at the Diablo Canyon intake cove. Heads up, little fellow! El Niño may be on its way back this year.
A seal perches on a rock Thursday at the Diablo Canyon intake cove. Heads up, little fellow! El Niño may be on its way back this year.

Whether it’s El Niño, La Niña or El Nothing, there sure has been a lot of interest in the seawater temperatures in the eastern Pacific these days. And for good reason — they can have a dramatic affect on our local weather.

As the temperatures and currents of the Pacific change, so does our Central Coast weather.

Since April 2010, we’ve either been in a La Niña or neutral condition when it comes to ocean temperatures. In other words, seawater temperatures have been near to below normal.

There is a rough correlation between seawater temperatures and seasonal rainfall. More times than not, below normal seawater temperatures produce below normal rainfall, and above normal seawater temperatures produce near or above normal rainfall.

The National Oceanic and Atmospheric Administration’s Climate Prediction Center (CPC) indicates that there’s a 70 percent chance of a weak to moderate El Niño onset in August, and an 80 percent chance that it will occur by November.

The CPC reduced the projected strength of the El Niño because subsurface ocean temperatures near the International Date Line have gradually cooled since earlier this year. Overall, El Niño events are notoriously difficult to predict.

In my humble opinion, astrophysicist Dr. Weymann of Atascadero said it best. “Many climate scientists think the most reliable strategy is ‘WAS’ (wait and see).”

However, seawater temperatures have already increased along our coastline during the first part of July.

Temperature recorders housed in steel canisters and placed at fixed locations near Diablo Canyon power plant have recorded millions of seawater temperatures since 1976.

So far, this July is one of the warmest on record at 57.9 degrees. By the way, the average for this month is 55.5.

At the Patton Cove monitoring station, which is just south of the power plant in approximately 10 feet of water indicate that the warmest July occurred in 1983 with an average temperature of 58.8. Another relatively warm July occurred in 1998 which averaged 57.6.

It’s interesting to note, that the last two most severe El Niño events occurred in 1983 and 1998.

In both cases well above normal rainfall occurred along the Central Coast. The 1983 rain season totaled 47.4 inches, while the 1998 rain season hit 44.0 inches at Cal Poly. Historically, the seasonal precipitation averages about 22.4 inches.

But, with that being said, not all El Niños are the same.

Jan Null, a former National Weather Service lead forecaster and PG&E meteorologist, is recognized as an expert on El Niños and La Niñas and their relationship to California’s weather.

According to Null’s studies (see his web page at, weak and moderate El Niños give near average rainfall along the Central Coast. However, strong El Niño events can produce about 140 percent of above-normal rainfall for our area and even greater amounts in other parts of the state.

The term El Niño was first documented centuries ago by Peruvian fishermen. Since the warming often occurred during the Christmas season, Peruvians called this event “Corriente del Niño,” meaning “current of the Christ child.”

Normally, equatorial Pacific winds blow east to west. These trade winds cause upwelling along Peru’s coast, and move cold and nutrient-rich subsurface water westerly toward the International Date Line. If the trade winds falter, the upwelling ceases and warm equatorial water shifts toward the coast.

Unfortunately, the lack of nutrient-rich water during an El Niño causes the fish and seabirds to migrate elsewhere, creating an adverse affect on the marine ecosystem.

In any case, San Luis Obispo County ranchers and farmers, water managers and fire fighters are all probably saying, “Welcome back, El Niño.”

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John Lindsey's column is special to The Tribune. He is a media relations representative for PG&E and a longtime local meteorologist. Email him at

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