Weather Watch

La Niña set to bring some wild weather to the Central Coast

Terrain surrounding the Port San Luis Lighthouse turned green from recent rainstorms on the Central Coast.
Terrain surrounding the Port San Luis Lighthouse turned green from recent rainstorms on the Central Coast.

A few years ago, my family and I drove old Highway 101 along the Avenue of the Giants in Humboldt County and passed through seemingly endless groves of redwood trees.

Along the way, we saw numerous “High Water” marks that staggered the imagination. They were from when the Eel River flooded in December 1964. Like this rain season, 1964-65 was a La Niña condition.

The name La Niña, meaning “the girl,” originates from Spanish; it’s analogous to El Niño, meaning “the boy” or “the Christ child,” which produces above-normal sea water temperatures. The latest model runs from NOAA’s Climate Prediction Center are indicating the current La Niña cycle will continue through early 2017.

Back in 1964, an Arctic air mass moved into Northern California in early December and created large quantities of snow in the mountains. Then, around Christmas of 1964, a strong blocking high in the Gulf of Alaska split the jet stream into the polar to the north and the Pacific jet stream to the south like a sand bar in the middle of a river. The jet stream is typically a tubular ribbon of high-speed winds about 18,000 to 40,000 feet up, flowing in a wavelike pattern that circles the globe and flows west to east.

This split of the jet stream often occurs during La Niña conditions when a blocking high develops in the Gulf of Alaska. In 1964, the Pacific jet stream shifted farther southward and steered a significant surge of subtropical moisture from the Pacific Ocean toward Northern California and Oregon, resulting in unprecedented rainfall from Dec. 19 to 27. This condition is referred to as an atmospheric river, Pineapple Express or, in the meteorological community, turning on the hose.

Needless to say, the warm rain melted much of the snow from the previous storms and caused widespread, record-breaking floods along the Northern California coast. Unfortunately, many lumber mills kept logs stockpiled near the Eel River. These fallen trees, which weighed tons, came down the river during the deluge and crashed into bridges, taking out many of them, and washed away many small towns along the Eel River. The floods of December 1964 resulted from meteorological conditions somewhat similar to those predicted this week along the Central Coast. This event reminds me of December 2010, when another plume of subtropical moisture produced tremendous amounts of rainfall. In fact, 2010 was last year the Central Coast received above-average precipitation.

This week, an unyielding 1,045-millibar area of high pressure in the Gulf of Alaska will block the polar jet stream and force it north over Alaska, then southward through the Yukon toward California. This condition will move a cold air mass from western Canada, the so-called Yukon Express, down the West Coast this Monday into Wednesday with cold overnight lows and cool daytime highs.

A weak low-pressure system is expected to produce rain Tuesday night into Wednesday. Snow levels will drop to about 2,000 feet by Wednesday morning; however, the model guidance continues to increase snow levels and will only likely produce decent snow accumulation above 3,000 feet. But there’s still a chance of a dusting of snow on the higher mountain peaks.

On Thursday, the Pacific jet stream will start to produce a dramatic shift in the weather pattern for the upcoming weekend. The medium-range models are advertising a stormy pattern as a series of low-pressure systems tap into copious amounts of subtropical moisture, which could translate into several days of gale-force southerly winds, relatively warm temperatures and between 3 and 7 inches of rain next Saturday, Sunday and Monday. In the Santa Lucia Mountains, more than 10 inches of rain could accumulate.

Please remember that details are still unclear regarding next weekend’s forecast and will probably change, but this is certainly good news as far as the drought is concerned.

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Note: The CHP and PG&E urge drivers to use extra caution on the roads, avoid distracted driving and designate a sober driver this holiday season and throughout the year. Taking these steps can reduce the likelihood of motor vehicle accidents involving utility poles that cause injuries or fatalities.

“Distracted driving is 100 percent preventable. Unfortunately, an estimated 80 percent of traffic accidents involve some form of driver distraction. Everyone plays a part in keeping the roads safe — including PG&E — and as a part of our commitment to the communities we serve, we join with the CHP urging motorists to avoid distractions that can lead to serious, even fatal, accidents,” said Pat Hogan, senior vice president of electric transmission and distribution for PG&E.

John Lindsey’s column is special to The Tribune. He is PG&E’s Diablo Canyon marine meteorologist and a media relations representative. Email him at pgeweather@pge.com or follow him on Twitter: @PGE_John.

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