Expect El Niño this winter, and probably plenty of rain

Posted by on Sun, August 9, 2009

This winter is likely to be a moderate-to-severe El Niño season, according to the National Weather Service.

The Mercury News says that an El Niño makes it likelier we’ll have a wet winter:

The El Niño now under way doesn’t guarantee that California will receive drenching winter rains. But the stronger the conditions and the warmer the water, the greater likelihood.

Since 1951, there have been six winters with strong El Niño conditions. In four of them, rainfall between the Bay Area and Bakersfield was at least 140 percent of normal. Some of California’s wettest winters, including 1982-83, when Coyote Creek burst its banks, flooding Alviso under eight feet of water, occurred during those strong El Niño winters.

In 1983, severe rainfall led to the collapse of Highway 1 over Martini Creek in Montara, and the closing of the Devil’s Slide for 84 days.

The Mercury News story is accompanied by a nice chart showing the the rainfall in moderate and severe El Niño years.

Comment 1
Sun, August 9, 2009 10:28am
All my comments

The chart seems to suggest that the likelihood of below-average rainfall in an El Niño year is just about equal to the likelihood of above-average rainfall.

My understanding is that El Niño tends to increase rainfall to the south of us, and decrease it to the north, with the boundary between above- and below-average rainfall being hard to predict.

Good point.  That’s certainly true if you don’t know whether this will be a moderate or severe year.  And the truth is that you don’t have enough data to draw strong conclusions about the correlation between El Niño and rainfall.

KQED’s Forum had an interesting half hour a month ago on the subject, discussing the prospect for a strong El Niño and its implications for the Bay Area in particular. Worth a listen.


The Return of El Nino
US government forecasters announced yesterday that El Nino—which warms the waters in the tropical Pacific Ocean and alters global weather patterns—is back. We’ll discuss the climate phenomenon and what it means for California.

Host: Dave Iverson

Craig Miller, senior editor of KQED’s Climate Watch
Mike Halpert, deputy director of the Climate Prediction Center