El Niño Induced Storms finally hit California

El Niño, a warming of the waters in the central and eastern equatorial Pacific, is associated with a variety of weather patterns. One such pattern, a strong southern jet stream, brought a series of storms to drought-stricken California in early January. The jet stream took a dip to the south and a series of storms brought high winds, heavy rain, flooding, mountain snow and even a couple of tornado warnings. The effects from this El Niño have been anticipated in California for at least six months, with the hope being that it could be a “drought buster.’ Whether it will be or not won’t be known until spring, but if this week’s storms are any indication California’s water problems may ease a bit this year.

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This El Niño got its official start in the late spring, when the rainy season is usually over in California, but a couple of late season storms in the southern part of the state were followed by the rainiest summer on record in San Diego and Los Angeles. This didn’t do much to lessen the drought conditions, but it did give hope that there might be more to come. “Traditional” El Niño storms ride in on a strong southern branch of the jet stream, rapidly bringing storm after storm into the state on the jet streams 100+ mile per hour winds.

The fall and early winter did not have this synoptic setup, so the storms that hit California were not what people typically think of as El Niño storms, but nevertheless they were good rainfall producers with decent snowfall totals in the mountains. On December 30, when the winter’s first manual snowpack survey was taken, the results were that for the state as a whole the water content of the snowpack was 105% of normal. While not terribly impressive, this was more than twice what the previous year’s survey found at the same time of year. More recent data from the automated SNOTEL sites shows the snowpack in all of the reporting basins (Northern Great Basin, Truckee River, Lake Tahoe, Carson River, Walker River and Klamath) reporting above average snowpack for the date.

Another set of drought indicators are the Northern Sierra “8 Station Index” (8SI) and the San Joaquin “5 Station Index” (5SI) that are calculated from the cumulative rainfall at chosen sites in the Sierra Nevada. These indexes are use determine the water allocations for central valley farmers. The 8SI is about 96% of normal to date, but is actually well behind the value from last year at this time; while the 5SI is about 125% of normal. The difference is not too surprising since the 5SI sites are farther south and El Niño precipitation favors the southern portion of the state.

While it is far too early to tell whether or not this year’s strong El Niño will be a “drought buster”, it does appear that it’s off to a good start in terms of water supply, Californians are just keeping their fingers crossed that along with the much needed water, El Niño does also bring with it too much destruction.