A “bomb cyclone” washed ashore in northern California Wednesday evening, in an atmospheric river event that left two dead by Thursday afternoon and caused havoc throughout the state.
Many Californians find themselves stuck in unresolvable scenarios. Intense rain can flood or wash out roads, especially around wildfire burn scars where debris flows are more likely. It can also knock down trees and power lines, making it unsafe to stay put. On the shorelines, the National Weather Service has issued gale and hazardous sea warnings for the entire western U.S. coast, as of this writing.
Los Angeles’ FOX 11 reported an infant died Wednesday inside a Sonoma County home when a redwood tree fell on it, according to firefighters. And in Fairfield, a 19-year-old woman died when her car hydroplaned on a partially flooded road and slammed into a utility pole, Fairfield Police confirmed.
Bracing For Impact
The National Weather Service (NWS) first warned of widespread flooding yesterday. Officials statewide issued evacuation notices. Meanwhile, Los Angeles’ KTLA news said anyone remaining behind was urged to stay off roads.
Governor Gavin Newsom declared a state of emergency to boost disaster response efforts and authorize the California National Guard to mobilize. The order also directed Caltrans to request immediate help from the Federal Highway Administration to expedite road repairs.
The state’s emergency operations center started coordinating efforts to set up sandbagging locations and shelters, and deploy ambulance teams, per FOX 11.
Sandbag update: We now have sandbags available for pickup at our Operations Yard. Come to gate at Marin & Kansas streets. Limit 5 per address for San Francisco residents & businesses. We will stay open till 8 pm unless we run out before then. We’ll post updates. pic.twitter.com/33bIKSRIpE
— San Francisco Public Works (@sfpublicworks) January 4, 2023
“California just hasn’t been used to this for probably the last 20 to 30 years,” Sacramento fire captain Keith Wade told FOX 11. “We’re moving through; the big thing we’re doing with our equipment that we’re asking to come in, we have a swift water team that’s pre-positioned here in the city of Sacramento.”
What Are Atmospheric Rivers and Bomb Cyclones?
The storm, which first approached the state from the northern city of Eureka, is one of three so-called atmospheric river events to reach California in the last week.
An atmospheric river is a narrow ribbon of moist air that carries vapor through the atmosphere. In a bomb cyclone, pressure in the river drops fast, resulting in rapidly-intensifying rain.
“Basically, an (atmospheric river) is a river in the sky of water vapor, and when it hits the mountains, (the moisture) is forced up over the mountains,” Marty Ralph, Director of the Center for Western Weather and Water Extremes, told FOX Weather. “That upward motion causes clouds and precipitation to form, and the faster the flow of air and water vapor is hitting the mountains, the faster the rain is falling, so you get more and more rain with the stronger ARs hitting the mountains.”
This particular bomb cyclone resulted from a “Pineapple Express” — a storm that carries moisture northward from Hawaii and often dumps it as precipitation on the U.S. west coast and Canada.
Conditions as of Thursday Afternoon
Rain keeps pounding some mountain and foothill areas, which have already seen heavy totals statewide. Some areas along the northern and central California coast could receive five to eight inches of rain. Further inland, rainfall totals in the mountains and their foothills could approach eight to 12 inches. In the ocean, forecasters were calling for 12-18-foot surf in the San Diego area and bigger all along the coast of California. (Note that Friday should see improved surfing conditions in the Southern California region with the swell’s westerly direction.)
Here are the rainfall totals so far. Definitely less than what we were expecting as the storm did not slow down, but still healthy totals. More showers or thunderstorms expected into the evening hours, with an additional 0.10 to 0.75 inches expected. #cawx #larain pic.twitter.com/vW2wGRDTJ8
— NWS Los Angeles (@NWSLosAngeles) January 5, 2023
Los Angeles’ KTLA reported widespread “minor flooding” and FOX Weather said 180,000 Californians were without power as of Thursday morning.
Road closures include an 18-mile stretch of Highway 101 in Humboldt County due to multiple downed trees and State Route 1 in Mendocino County due to downed trees “for a period” Wednesday.
Higher elevations will receive varyingly significant snowfall, the NWS said per KTLA.
“Mountain areas above 6,000 feet will see accumulating snow, just not as much as previously thought. Revised snow forecast calls for about a foot of snow across the highest peaks and so snow amounts of one to two feet are expected for those higher peaks with three- to six-inch amounts possible for elevations above 6,000 foot elevations,” according to the forecast.
California continues to brace for consequences during an extraordinarily wet winter season in many areas. Santa Cruz County reported over $10 million in damage from last weekend’s atmospheric river storm. And many areas in the state have already received as many as five to 12 inches of rain since before Christmas, according to FOX 11.
While meteorologists forecast the bomb cyclone should start to taper off throughout the evening, more Californians will face growing danger as ongoing rainfall continues to saturate the state.