Weather Watch

Umbrellas, yes, sandbags, no, on the Central Coast this winter?

Rain pelts a man walking with an umbrella in downtown San Luis Obispo in December 2015.
Rain pelts a man walking with an umbrella in downtown San Luis Obispo in December 2015. jjohnston@thetribunenews.com

Last year’s El Niño was one of the strongest on record.

Unfortunately, it didn’t produce the amount of rainfall hoped for along the Central Coast.

Northern California to Monterey County saw near-to-above normal rainfall and snow, which lessened the intensity of the drought for them. Many of those counties transitioned from the most severe D4 (exceptional drought) category to D1 (moderate drought) or even the lesser D0 (abnormally dry).

San Luis Obispo is among California’s central and southern counties, however, that all remain at the epicenter of a six-year drought, all mired in the D3 (extreme drought) and D4 categories. The other counties are Santa Barbara, Kern, Kings, Tulare, Fresno, Ventura and Los Angeles.

So will this winter bring any improvement?

Don’t count on it, judging from the pattern we may see developing.

Since 1950, the National Oceanic and Atmospheric Administration 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 fortune-telling SST cycles in Niño 3.4 are categorized by the amount they deviate from the average SST.

A weak El Niño is classified as an SST deviation of 0.5 to 0.9 degrees Celsius, while a strong El Niño ranges from 1.5 to 1.9 degrees Celsius. A very strong El Niño anomaly is anything above 2 degrees Celsius (or 3.6 degrees Fahrenheit), a very rare event indeed.

On the other side of the coin, the cooler La Niña is categorized in the same manner but with minus degrees from normal. The important thing to know is that La Niña often shifts the storm track further north into the Pacific Northwest, producing below-average rainfall along the Central Coast.

This year, seawater temperatures in this region are forecast to range between -0.5 and 0.5 degrees Celsius, not warm enough to be classified El Niño or cold enough to be La Niña. In other words, El Nothing — or, officially, a neutral condition.

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, neutral conditions historically produce about 95 percent of normal rainfall along the coast from San Francisco to San Luis Obispo County.

Further southward, it produces approximately 83 percent of normal rainfall along the coastline from northern Santa Barbara County toward San Diego. Null told me that if a weak La Niña condition develops, historical rainfall amounts drop to 82 percent of normal in San Luis Obispo County and 75 percent of normal in Santa Barbara County.

William Patzert, a respected climatologist with Caltech’s NASA Jet Propulsion Laboratory in Pasadena, told me, “One of our largest, most intense and longest-lasting El Nino’s is in the rearview mirror. The hope for us could be the very warm sea surface temperatures present in the Northern Pacific. That strong feature is the wild card. Will a series of Northern Pacific storms give Central and Southern Californians some relief?

“I dream about this, but I wouldn’t bet on it. Unless conditions change, I would plan for worsening drought conditions, with less snowpack and rain than last winter. The headline for the next six months will most likely be ‘Punishing California Drought Continues.’ It would be sweet if I was wrong.”

The other wild card in this equation is atmospheric rivers.

Since December 2010, the Central Coast has seen an absence of these rivers in the sky that can stretch for thousands of miles across the world’s oceans, but are only a few hundred miles wide. At any given time, there are typically several of these narrow plumes of moisture in the Northern and Southern hemispheres.

In the northern Pacific Ocean they are often formed by storms drawing huge amounts of water vapor into narrow bands ahead of cold fronts. They can transport fantastic amounts of water across vast expanses. In fact, they can carry more freshwater than the Amazon River.

Along the West Coast, they are informally called the “Pineapple Express” because they originate in the tropical waters near Hawaii. In the past, meteorologists simply referred to these as “the hose.”

But here’s the paradox: As the atmosphere continues to warm, it can hold greater amounts of water vapor, which increases both the chances for more intense periods of rain and a greater occurrence of prolonged droughts.

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Employees from PG&E’s Diablo Canyon Power Plant raised more than $17,000 for the Make-A-Wish Foundation at the 19th annual Nuclear Challenge Golf Tournament.

“Our employees are committed to supporting the communities in which we live and serve,” said Ed Halpin, PG&E senior vice president of generation and chief nuclear officer. “The Nuclear Golf Challenge is a shining example of that commitment.”

John Lindsey is PG&E’s Diablo Canyon Power Plant marine meteorologist and a media relations representative. Email him at pgeweather@pge.com or follow him on Twitter @PGE_John

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