Since 2011, a persistent ridge of high pressure over the eastern Pacific has dominated our weather.
At times, the high-pressure ridge has weakened or shifted east or southward for a week or two and allowed Pacific storms to bring their precious snow or rain to California. Despite these reprieves, our state has suffered through the worst four-year drought in modern history.
Last year, the ridge of high pressure was centered more offshore. This rain season, the ridge has shifted farther east and was more or less centered directly along the coastline. This small shift may have produced slightly more rain than last year.
However, it will come as no surprise that this rain season — which runs from July 1, 2014, through June 30, 2015 — has seen well below normal amounts of precipitation.
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In fact, only about 11.5 inches of rain was recorded at Cal Poly, home of climatology for San Luis Obispo. Historically, 22.4 inches is normal. In the North County, the Paso Robles Municipal Airport has seen only 8.8 inches, or near 70 percent of normal. Along the coastline, Diablo Canyon Power Plant logged 7.5 inches, while farther northward Rocky Butte near San Simeon received nearly 27 inches.
These sad rainfall totals only tell part of the story. Over the past four years, Cal Poly is 38.5 inches behind its normal four-year total. Consequently, to make up this deficit, the rainfall Cal Poly would need this coming season would be 60.9 inches (38.5 inches plus 22.4 inches), or 272 percent of normal. The all-time record for Cal Poly is 54.5 inches, which occurred in the 1968-69 rain season. Diablo Canyon would need 46.2 inches this rainfall season to erase its deficit.
In other words, it would take record rain seasons at both of these locations to erase the four-year deficit.
Paso Robles Municipal Airport has a 24-inch deficit over the past four years and would need 188 percent of normal rainfall this upcoming season, according to Jan Null of Golden Gate Weather Services (www.ggweather.com).
Santa Maria is short by 27.7 inches over the past four years. Normally, Santa Maria Public Airport gets about 14 inches a year. The wettest year on record for Santa Maria was 28.2 inches in the 1997-98 rain season.
Speaking of the 1997-98 rain season, that was a strong El Niño year; however, much of the rain fell gradually. In fact, there were over twice as many rainy days that season than average, unlike 1995, which saw fewer days of rain, but significantly heavier amounts. This condition caused flooding throughout the Central Coast in March 1995.
Paso Robles logged 25.6 inches of rain that year.
“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.,” Null said.
Which leads to the question, what will this next rain season bring?
The just-released International Research Institute for Climate and Society/CPC mid-June El Niño-Southern Oscillation Prediction Plume forecasts a strong El Niño event.
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 California.
But remember, I and many others predicted that we would see normal or even above-average rainfall amounts for San Luis Obispo County this rainfall season. Unfortunately, El Niño didn’t happen until February, when a weak condition developed. It was too little, too late.
Only time will tell what this next season will bring.
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PG&E is fortunate to include among its ranks veterans of the armed forces. These employees proudly serve our customers, and many work locally at Diablo Canyon Power Plant. PG&E has unveiled a long-term program aimed at hiring 1,000 veterans over the next eight years. To learn more about the project, visit: www.pgecurrents.com/2015/06/26/pge-initiative-aims-to-hire-1000-veterans-over-next-eight-years.