The Paso Robles Municipal Airport broke two temperature records in less than nine hours Dec. 13 when a bone-dry air mass combined with clear skies, allowing for a record low of 22 degrees followed by a record high of 73 degrees — a 51-degree swing.
I reviewed the temperature records for our Central Coast airports — Paso Robles, San Luis Obispo and Santa Maria — and couldn’t find another such occurrence.
What I did discover was that December 1958 was much like this month with numerous record-breaking high temperatures. In fact, only 0.18 of an inch of rain was recorded that month at Cal Poly, home of climatology for San Luis Obispo. So far this month, the three weather stations at our airports have reported less than a tenth of an inch of rain.
Historically in San Luis Obispo, December is our third wettest month of the year, with January and February recording more precipitation on average. Of course, March can also produce massive amounts of rain, as evident by our Miracle March in 1991 and the floods of 1995.
After a short reprieve earlier this week, another colossal high-pressure ridge has redeveloped over the West Coast. Consequently, not even the long-range models are advertising any significant storms on the horizon.
Judging by the number of emails and phone calls that I’ve received, Central Coast farmers and ranchers are increasingly worried about another drought. Farther south, in Santa Barbara and Ventura counties, it never really ended.
According to the United States Drought Monitor, San Luis Obispo County is at D0 (abnormally dry) level, and Santa Barbara and Ventura counties are at D1 (moderate drought) levels. South of Point Conception, no significant rainfall has fallen since Sept. 4, when a microburst of rain exploded from the sky in Santa Barbara.
This lack of moisture and record-breaking temperatures combined with relentless Santa Ana winds in Ventura County and a morning sundowner in Santa Barbara to spark the Thomas Fire, the largest wildfire in California’s history. Who could ever have predicted that the state’s most massive wildfire would occur during December?
Which leads to the question, what will happen during the crucial months of January, February and March of 2018? Here’s the prediction from some well-respected sources.
Climatologist extraordinaire Bill Patzert at NASA’s Jet Propulsion Laboratory wrote the following to me: “If you live in Central or Southern California and can’t remember the last good soaking downpour, it may be because it has been one of the driest times ever in the region. In the last 10 months in downtown Los Angeles, we’ve had less than an inch of rain. It has been one of the driest 10 months in Southern California history.”
With the start of winter, the outlook isn’t promising. Patzert said it appears that La Niña is wrapping itself around the equator.
“Normally, our wettest months are January, February, and March, so there is still a little hope,” he said. “But the presence of a mild La Niña, the notorious ‘Diva of Drought’ present at the equator doesn’t bode well for winter rainfall.”
To make matters worse, the Pacific Decadal Oscillation (PDO) has turned neutral.
“If the PDO goes negative, it will probably produce more drought; positive, perhaps wetter,” he said.
John Neil, a civil engineer and the manager of the Atascadero Mutual Water Company, loves the science of hydrology and meteorology and their potential impact on people’s lives. After he reviewed the historical data from this rain gauge, Neil discovered that when the area receives more than 2 inches of precipitation during October, the rest of the rain season — which runs through June 30 of the following year — was higher than normal. Neil calls this the “2-inches- of-rain- in-October rule.” Unfortunately, the Atascadero Mutual Water Company did not record more than 2 inches of rain this past October.
The Climate Prediction Center in their latest El Niño Southern Oscillation (ENSO) report states that Equatorial Sea Surface Temperatures (SST) are below average across the central and eastern Pacific Ocean. Consequently, a La Niña condition will continue through winter 2017-18, with a transition to ENSO-neutral (El-Nothing) during mid-to-late spring, which indicates between a 40 to 50 percent probability of below-average rainfall and above-normal temperatures for Central and Southern California through March.
It’s interesting to note that the 1958-59 rain season was well below average with only 11.76 inches of rain recorded at Cal Poly. That rain season followed a strong El Niño that produced 34.37 inches the previous year. Last year, Cal Poly recorded 38.93 inches.
We all hope for a series of Atmospheric Rivers (AR), Pineapple Express or, in the meteorological community, turning on the hose. Last year, ARs came through in a big way. These systems can transport ridiculous amounts of water across the Pacific. In fact, they can carry more freshwater than the Amazon River.
However, as the atmosphere continues to warm (due to anthropogenic drivers like emissions from internal combustion engines in our cars) the more water vapor it can hold. I lose sleep at night, worried that we could receive way too much of a good thing: rain that could create flooding, especially in the burn areas of the state.
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