The Central Coast landscape turned green late this year as an atmospheric river created a “Mini March Miracle,” but far too soon our hills are already transforming to shades of brown to golden hue as the relentless afternoon northwesterly winds and longer days combine to dry our countryside.
From July through December of last year, the Diablo Canyon tipping bucket rain gauge recorded less than one inch of rain, one of driest second halves of the year for rainfall totals on record. January saw improvements in rainfall with more than 3 inches recorded at Diablo Canyon, but February was a bust, with less than a quarter of an inch of rain. March gave us much-needed relief with 9.1 inches of rain at Cal Poly, home for climatology for San Luis Obispo, which usually receives 3.2 inches for the month. Santa Maria Public Airport recorded 3.4 inches or 131 percent above average for March.
Which leads to the question, what will the upcoming summer, fall and winter have in store for us?
The Climate Prediction Center is advertising neutral condition — the infamous “El Nothing” developing this spring and continuing through summer. It’s interesting to note that several of the numerical model runs are indicating a moderate El Niño developing this winter, which could mean a chance of above average rainfall for this upcoming rain season. A few of these models are even venturing into strong El Niño territory.
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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, which can be viewed at ggweather.com, a moderate El Niño condition historically produces about 113 percent of average rainfall along the coast from San Francisco to San Luis Obispo County.
Farther south, it generates approximately 124 percent of average precipitation along the coastline from northern Santa Barbara County toward San Diego.
Since 1950, NOAA has used sea surface temperatures (SST) 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).
Neutral conditions — El Nothing or El Nada — range between plus 0.5 and minus 0.5 degrees Celsius anomaly levels — or the sector between El Niño and La Niña. Neutral conditions typically don’t produce any reliable seasonal rainfall predictions along the Central Coast.
However, at this time of the year, these predictions often change. Here’s why:
We’re in the so-called “Spring Predictability Barrier.” In spring, the El Niño Southern Oscillation (ENSO) is often in transition from one phase to another. For example, a La Niña phase could be decaying and passing through neutral condition to a El Niño condition, or vice versa. Of course, as you get closer to winter, the models become more accurate because there’s less time for inaccurate oceanographic and atmospheric data to be amplified at model initialization. At this time of the year, many climate scientists think the most reliable strategy is “WAS” (wait and see).
As far as air temperatures, the Climate Prediction Center is calling for between a 40 and 50 percent probability of above average temperatures for all of California through July — if not longer. This prediction was nearly identical to last year’s, which saw well-above-average summer temperatures.