All signs point to a strong El Niño bringing heavy winter rains
The Pacific Ocean and the atmosphere are indeed on course to produce a wet winter. About a month ago, I wrote about El Niño, and had some concerns that it may not bring abundant rainfall; a lot of these apprehensions have gone away, and here’s why.
Last week, the Australian Bureau of Meteorology reported, “The tropical Pacific Ocean and atmosphere are reinforcing each other, maintaining a strong El Niño that is likely to persist into early 2016.”
Last month, the National Oceanic and Atmospheric Administration’s Climate Prediction Center was forecasting a 90 percent chance that we would see El Niño this winter. This month, that prediction has increased to 95 percent.
In fact, many of the latest numerical model runs indicate this year’s El Niño could be stronger than the 1982-83 and 1997-98 events. The 1983 rain season (July 1, 1983, through June 30, 1984) totaled 47.28 inches. The 1998 rain season (July 1, 1997, through June 30, 1998) hit 44.06 inches at the Diablo Canyon nuclear power plant’s rain gauge. Historically, the rain-season average is about 23.5 inches.
Last year, I and many others predicted abundant rainfall. Obviously, my prediction didn’t come to pass — in large part because of decreasing seawater temperatures in the Niño 3.4 region (an area in the east-central equatorial Pacific) during the vital months of winter.
But this year, it’s different — with each month’s oceanographic observations and predictions, it is becoming more likely that seawater temperatures will peak during December, January and February, usually our wettest months.
Another worry was the “blob” of abnormally warm seawater off the Pacific Northwest and what has been dubbed the Ridiculously Resilient Ridge of high pressure there. But that area of high pressure has weakened considerably. Consequently, you can now put a fork into the blob. It’s done. In other words, it’s just about gone.
Many climatologists thought the southern branch of the polar jet stream that traditionally brings winter storms to our area would be driven north by the blob, keeping storms to the north of the Central Coast. According to PG&E meteorologist Scott Strenfel, “The preliminary precipitation outlook for the winter season resembles a classic El Niño signature of past events, which produced above normal precipitation in Southern and Central California.”
Unfortunately, it would take a record rain season along the Central Coast to erase the four-year deficit. Indeed, it would need about 60 inches of rain at Cal Poly. The all-time record for Cal Poly is 54.5 inches, which occurred in the 1968-69 rain season.
“It should be noted that making up the rainfall deficit is very different than the requirements to ‘end the drought,’ as the components of a drought are dependent upon a myriad of variables like the type of user, population, existing supplies, etc.,” said Jan Null of Golden Gate Weather Services.
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. With each passing month, I am feeling more confident about plentiful rain. Perhaps the rain showers expected Sunday will be a prognosticator of things to come.
If you would like to participate in a “Weather Watchers” tour of Diablo Canyon Power Plant and lands, which will include atmospheric and oceanographic instrumentation used for weather forecasting and other interesting weather information, please email me at pgeweather@pge.com to register.
The tour will be offered Tuesday, Oct. 27. The tour will start at 9 a.m. at the PG&E Energy Education Center, 6588 Ontario Rd, San Luis Obispo, CA 93405 and will finish by noon.
This story was originally published October 3, 2015 at 5:47 PM with the headline "All signs point to a strong El Niño bringing heavy winter rains."