In the latest sign that El Niño conditions are likely to bring wet weather to drought-parched California, federal scientists on Thursday announced for the first time that the entire state — including the northern part of California from the Bay Area to the Oregon border — is now expected to receive average or above-average rainfall this winter.
Until Thursday, scientists at the National Oceanic and Atmospheric Administration had been predicting that Southern California was most likely to get drenching storms this winter, with Northern California — home of the state’s largest reservoirs — less likely to receive a soaking.
Water temperatures and wind patterns in the Pacific Ocean have created the strongest El Niño in a generation. And although heavy rains are not guaranteed, the last two times when conditions were this strong, in the winters of 1982-83 and 1997-98, rainfall totals in the Bay Area and much of the state were double the historic average, triggering massive flooding and mudslides.
The new report still establishes Southern California as the odds-on favorite for major downpours, but it expands the rainy outlook more broadly across the state for the months of January, February and March, which are expected to be the wettest.
“We’re very confident that this will persist though the winter and should result in some of the typical El Niño impacts that we’ve seen in the past,” said Mike Halpert, deputy director of the NOAA’s climate prediction center in College Park, Maryland.
Scientists at the NOAA — the parent agency of the National Weather Service — released maps showing that from Santa Barbara to the Mexican border, there is a 93 percent chance of average or above-average rainfall during those three months. From San Jose to Santa Barbara, there is an 83 percent chance of average or above-average rainfall, and from Humboldt County to San Jose there is a 73 percent chance of average or above-average precipitation.
Could that “Ridiculously Resilient Ridge” return again this year to block El Niño storms?
Not likely, said the man who coined the term.
In past years, warm ocean conditions in the western Pacific Ocean built up the ridge, said Daniel Swain, a climate researcher at Stanford University. But now, he said, the western Pacific is not as warm — and even if the ridge reappears this El Niño is likely to affect the subtropical jet stream in ways that storms could barrel around the southern edges of the ridge and deliver rain to California.
Computer models are showing that by January the ridge will become a trough, which is favorable to bringing big storms into the state, Swain said.
http://www.mercurynews.com/drought/ci_28974825/el-nino-wet-winter-conditions-now-likely-across