By Paul Rogers, Bay Area News Group
After the driest January in recorded history, the Bay Area is back in the rain business.
Meteorologists are reporting that conditions in the Pacific are generating what appears to be a strong “Pineapple Express” storm that is expected to hit Northern California starting Thursday evening, bringing steady rain through the weekend to the drought-stressed Golden State.
Although conditions could still change, the storm is expected to bring between 1 and 3 inches of rain to the Bay Area, with the heaviest amounts in the Santa Cruz Mountains and other high elevations, and up to 5 inches in North Bay communities like Sonoma County by Monday morning.
“This is the first big storm since December,” said Austin Cross, a meteorologist with the National Weather Service in Monterey. “One storm is not enough to solve the drought, of course, but every bit counts.”
Computer models and satellite images for this storm, a type of warm, powerful system known as an “atmospheric river,” project that it could bring 10 inches or more — similar to the big storms in mid-December — to far Northern California towns near the Oregon border such as Redding.
That’s important for the drought because that’s where many of the state’s large reservoirs, such as Shasta Lake, are located, and a soaking storm will bring runoff that will add billions of gallons to their below-normal levels.
The storm, now barreling out of Hawaii, may be too warm to generate much snow to the parched Sierra Nevada, however.
“It looks like the snow levels are going to be fairly high with this one, like 8,000 feet,” said Jan Null, a meteorologist with Golden Gate Weather Services in Saratoga. “It’s going to be more rain than snow, and it won’t help the ski resorts much. But it will help the reservoirs. In general warm storms have more precipitation than cold storms.”
The past three years — 2012, 2013 and 2014 — have made up the driest three-year period in recorded California history back to 1850. A persistent ridge of high-pressure air off the West Coast has acted like a battering ram for Pacific storms, sending them north into Canada, then down along the East Coast with large amounts of snow. And it has left California with record hot temperatures — Monterey Bay beaches were full of people in shorts and swimwear through January — and very little rain. The ridge broke down in December, bringing several soaking storms. But it came right back in January.
San Francisco received not a single drop of rain for the entire month of January, the first time in its history. San Jose and Sacramento also recorded their driest January ever, dashing hopes after the wet December that the drought may finally be ending.
This week’s healthy storm is expected to reduce fire danger across Northern California for at least another month in many places, and wash away the sooty air that has built up over six weeks in the Bay Area.
Landscaping experts say residents can shut off their irrigation devices for about two weeks after a good rain, saving money and water.
“People turned their sprinklers off in December, and they have been turning them on again now,” said Jim Borneman, with Ewing Irrigation in Fremont. “This has been such an unusual circumstance, a lot of people don’t know how long to run them.”
Borneman said homeowners can save money not only by replacing part or all of their lawn with water-efficient native plants, but also by replacing cool season grasses like fescue and bluegrass with warm season grasses like Bermuda grass and St. Augustine, which use 20 percent less water. They can also buy a rain shut-off device for about $50 in any garden store that will automatically detect rain and shut down sprinklers.
Unfortunately, say forecasters, after this week’s storm, next week appears to be shaping up for more hot and dry weather.
Nevertheless, atmospheric river storms like the one on the way are vitally important. Like weather fire hoses, eight or fewer such storms every year bring 35 to 50 percent of the total annual precipitation that California receives, said Michael Dettinger, an atmospheric scientist with the Scripps Institution of Oceanography in La Jolla.
“Big atmospheric rivers have been the straws that have historically broken the backs of sustained droughts about 40 to 60 percent of the time historically,” he said.
That was the hope after rain clouds parked over much of the state in December. Despite the bone-dry January, however, December was so much wetter than normal that San Jose on Monday had 10.33 inches of rain since July 1, still 128 percent of the historic average for this date. Similarly, Oakland was at 100 percent of normal, and San Francisco was at 110 percent.
One key question in this week’s storms is how far south they go. Forecasters say the South Bay will receive about 1 inch, but places south of Salinas, like perilously dry Fresno, may not see much rain at all.
Link to original article: http://www.santacruzsentinel.com/general-news/20150202/big-storm-on-the-way-for-northern-california.html