The National Weather Service is warning of the chance of bombogenesis conditions forming in the Pacific Ocean just off the Bay Area.
“Bombogenesis is an ominous sounding term frequently used in the winter to describe powerful low pressure systems that intensify rapidly,” according to the Weather Channel. “The process of bombogenesis begins as cyclogenesis, meaning the development or strengthening of an area of low pressure or trough.”
In order to for the weather to bombogenesis (aka "bombing-out"), central pressure of a low pressure system would have to fall “at least 24 millibars within 24 hours.” If bombogenesis conditions were to strike, the Bay Area could see increased winds and a bombardment of rain in short but heavy spurts. The Sierras and other mountainous regions would also see increased snowfall.
Southern California is already getting hit with a series of storms, making this the wettest February on record for Los Angeles. The area is expected to receive the brunt of the storm.
Very strong winds w/ cyclogenesis aloft. LLJ bringing strongest winds over Big Sur/Monterey Bay this morn. Winds heading north l8r #cawx pic.twitter.com/XbxDmnMeGW— NWS Bay Area (@NWSBayArea) February 17, 2017
1. When are heavy rains expected?
They’ve already started, but the aforementioned bombogenesis conditions are forecasted for Friday evening. Storms have already caused flooding and ponding on local roads.
The NWS says, “Saturated soils from previous rains could lead to additional floods, flash floods, and mudslides along the west coast.” And according to CBS SF, “flooding continued at Lakeport in Clear Lake as the lower Sacramento River ran over its banks and in the Central Valley community of Lathrop.”
2. What about wind?
Expect major gusts of wind. San Francisco should see 34 MPH winds today. Other areas are getting hit much harder. Monterey, for example, is experiencing hurricane force winds. Trees have toppled along major roadways
Highest winds spreading north&east,Hollister Airport SE 37 to 55 mph. Downsloping&drying strongest where rain's absent in current radar loop pic.twitter.com/HhBpfJy451— NWS Bay Area (@NWSBayArea) February 17, 2017
Strong southeast winds proved too much for this big rig traveling north bound Hwy 1 in Marina #CAwx @NWSBayArea pic.twitter.com/rW9Z6BFISc— Vern Fisher (@VFisher45) February 17, 2017
4. What about snow?
Lots of powder in Tahoe and other snowy areas.
“In a winter season where it seems every other day or so is a powder day at Lake Tahoe, we are on our way to having a ski season that will go down in history,” reports Sierra Sun. “North Tahoe-Truckee resorts have been reporting record amounts of snowfall, as staff has been continuously digging out chairlifts, working with local agencies to keep the roads open, and doing whatever it takes to keep functioning throughout torrential winter storms.”
5 How will this affect the Oroville dam and spillway?
The residents of Oroville have experienced the worst of the storms after part of their dam failed last week. An estimated 200,000 Californians from nearby Oroville, Yuba City, Marysville, Gridley, Live Oak, and other communities were evacuated from their towns. They have since returned, but this new storm could pose an even greater threat.
AP Exclusive: If Oroville Dam Failed, People Likely Stuck https://t.co/x4a3L9c03J #sanfrancisco pic.twitter.com/117DUDUNH0— San Francisco News (@SFnewsnow) February 17, 2017
According to Associated Press, if they dam failed, the residents could be in danger. “Communities just downstream of California's Lake Oroville dam would not receive adequate warning or time for evacuations if the 770-foot-tall dam itself — rather than its spillways — were to abruptly fail, the state water agency that operates the nation's tallest dam repeatedly advised federal regulators a half-decade ago,” reports AP.
In 2011, the state Department of Water Resources “informed federal dam regulators that local emergency officials ‘do not believe there is enough time to perform evacuations in the communities immediately downstream of the dam during a sudden failure.’ “