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January 15, 2010 / Dave Gorham

California: In the Crosshairs Again

 

Remember this past summer when we saw a 747 jumbo jet dropping fire retardant over the forests of southern California? The evening news was dominated by such images, along with the widespread devastation brought about by the nearly uncontrollable forest fires.



A Boeing 747 bomber from Evergreen International. Image: Goleta Air & Space

It now looks like California is going to be in the news again and it won’t be the fires, the budget, the prisons, the cost of living, the governor or any of the other things which so often make California the subject of the evening news. This time it will be rain. And snow. And floods.

All kinds of things are happening in the Pacific these days. If you’re not a pilot, a marine biologist, a ship captain or a meteorologist you’re likely unaware. It’s called El Niño and it’s responsible for all sorts of things, not the least of which is increased rainfall and cooler temperatures across the southern states. El Niño today is close to its peak intensity and it’s about to take the blame for a lot of rainfall in California. But there’s more. The subtropical jet for the past few weeks has been quite strong. These winds, in the 35,000-40,000ft range, have been screaming across the southern portions of the North Pacific at between 150 and 200 knots (173-230mph). These upper winds are the steering currents for storm systems. Up until now a “blocking” weather pattern has kept these storms off the California coastline, but with the block gone these storms now have an unobstructed superhighway from the Pacific to the coast.



The storm systems are beginning to line up. Image: ImpactWeather Gmaps Interactive Mapping System

At first, the jet stream will be from central latitudes of the North Pacific. The resulting storm systems over the next 10-12 days will be relatively cold in nature. Not only will there be lots of rain, but lots (and lots and lots) of snow. It’s quite likely many areas of California will receive their entire annual rainfall in the coming two weeks. In the higher elevations the snow will be measured in the 10s of feet. One storm system after the next will pound the coast. In addition to the rain and snow, high winds will whip everything into a frenzy. Sustained winds of 35mph will be common, while gusts to 50mph will not be infrequent.

There’s more.

With time, a developing low pressure center well to the west of California will drive the jet stream south, directing storm systems not from the cooler central North Pacific waters but from the warmer waters of the North Pacific north of the Equator. Now the jet stream is oriented, more or less, Honolulu-to-Los Angeles and the so-called Pineapple Express (“Do I smell pineapples in LA?”) continues to deliver these storm systems to the coast. The warmer systems however, now begin to quickly melt the copious snowfall of the previous storm systems. The saturated ground and the swollen streams, rivers, canals, lakes, retention systems won’t be able to take any more. Widespread flooding will result.

It looks like it will be a long three weeks for California, perhaps Oregon as well.

 

 

 

 

 


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