After a year of hype and hope, El Niño’s punch is finally arriving in California, bringing a series of storms to soak Northern California and most of the rest of the drought-stricken state through this week and probably into next.
The National Weather Service is forecasting the wettest week of this winter so far — rain in six of the next seven days in some areas, with the heaviest downpours expected Tuesday and Wednesday in the Bay Area, bringing potential rain totals of up to 5 inches in higher elevations. By the time the system passes, forecasters expect 1 to 3 inches across much of the region.
Steady Tuesday rains waned in the afternoon. The system was expected to produce scattered showers last night, with an additional inch of precipitation possible.
The new and more powerful wave arriving today could produce heavy downpours, according to the NWS. More than an inch of rain is expected by the end of the evening.
On Thursday the odds of rain drop to 60 percent for Lake County, but the NWS believes any thread of El Niño bringing showers will also produce late thunderstorms.
Although forecasts call for another wave over the weekend, the NWS believes this may deliver only a glancing blow to much of the county.
All told, the soggy week could bring 3 to 5 inches of rain to the county.
A flash flood watch for Lake County expired Tuesday night.
A winter storm warning is underway through Tuesday night for the southern Sierra Nevada, from Yosemite National Park to Kern County, where 2 feet or more of snow is expected in the next few days.
“These are the first storms this winter with definite El Niño DNA,” said Bob Benjamin, a forecaster with the NWS in Monterey. “A lot of the attributes you expect from El Niño are present this week and will be next week.”
California — now entering the fifth year of the worst drought in its recorded history — received moderate rain in December. But those cold storms, which even brought some snow to the Bay Area around Christmas, came off the Gulf of Alaska and were typical of a normal winter rainy season.
The latest series of three storms hitting the state, however, is different. In strong El Niño years like this one, warmer storms line up across the mid-latitudes of the Pacific, flowing one after another along the sub-tropical jet stream from Japan across the north of Hawaii to California.
That’s exactly what’s happening this week.
“If someone said you could have one satellite image to illustrate El Niño storms for a textbook, what we have right now is that. It’s a conga line of storms,” said Jan Null, a meteorologist with Golden Gate Weather Services in Saratoga.
El Niño conditions occur when water warms at the equator off Peru due to shifts in trade winds. The warmer the water, the stronger the El Niño event and the higher historic likelihood of above-normal rainfall for California. El Niño conditions have been present since last March, with water temperatures peaking about a month ago near the all-time high, recorded in 1997. That year, California received double its historic average rainfall.
Clear Lake flooded in February of 1998, four feet on the Rumsey Gauge above full.
The National Weather Service has issued a “wetter than normal” outlook for the next two weeks across California.
“Instead of glancing blows of storms, we are more directly in the storm track now,” said Daniel Swain, a climate researcher at Stanford University. “It will be wetter in San Francisco and Los Angeles this week than in Seattle and Vancouver.”
Both Swain and Null noted that El Niño already has been impacting storms and weather around the globe for months now, including contributing to huge fires in Indonesia, dry conditions in Australia and freakishly hot temperatures on the East Coast in December.
What does it all mean for the drought? The state is off to a good start, but the final answer is months away.
On Monday afternoon, the statewide Sierra Nevada snowpack was at 97 percent of the historic average for this date and likely to go well above that in the next few weeks.
Rainfall totals in many areas were about the historic average or below. And critically important, reservoir levels remain very low after four brutally dry years.
Rains in December added 900,000 acre feet of water — that’s 293 billion gallons — to the 154 major state and federal reservoirs in California tracked by the state Department of Water Resources, according to Maury Roos, California’s state hydrologist.
But impressive as that sounds, it only brought them to 31 percent of capacity by Dec. 31, and the prior Dec. 31, they were at 41 percent. The historic average for Dec. 31 is 58 percent full.
Many of the watersheds are reasonably wet, and water is beginning to run off into the big reservoirs like Shasta, Oroville and Folsom, he said. But much more rain is needed.
“Things are looking fine for a normal year,” he said, “but we have a big hole to fill, a large deficit in storage, and it’s going to take some time.”
Staff writer Mark Gomez contributed to this report.
