Deadly combination of bomb cyclone, atmospheric river drenches West Coast

At least two people died in the bomb cyclone that struck the West Coast Wednesday into Thursday -- the second massive storm to hit the coast in less than a week.

Fueled by an atmospheric river from the Pacific Ocean, the potent storm unleashed a fury of strong wind and rain across the West Coast that quickly turned deadly. A 19-year-old woman from Fairfield, California, was killed Wednesday morning when her car hydroplaned on a partially flooded road and crashed into a utility pole, according to the Fairfield Police Department. Fairfield is located in Solano County, nearly 40 miles northeast of San Francisco.

The second fatality was reported Wednesday evening, also in the San Francisco region, in Occidental, Sonoma County, after a redwood tree fell on a mobile home and killed 1-year-old Aeon Tocchini, The Associated Press reported.

California Gov. Gavin Newsom declared a state of emergency on Wednesday ahead of the storm, authorizing the mobilization of the California National Guard to support disaster response.

Evacuation orders and advisories were issued in parts of Northern California, including around San Francisco and Sacramento.

Seaside homes were evacuated in the Bay Area county of Santa Cruz under the threat of landslides as the storm ushered in a combination of towering waves, drenching downpours and fierce winds. Photos showed ocean waves surging past the shorelines, the water flooding into nearby roads and moving dangerously close to beachside homes.

"We had the first big wave come over the wall and come into our garage and bring debris underneath the cars and dump about 60 inches of sand in the driveway here," Capitola resident Mary McKittrick told KGO ABC7 News reporter Zach Fuentes.


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The rough surf heavily damaged piers in Capitola and Seacliff, including one that was split in half as one section collapsed into the ocean. One video showed a pier in Aptos, also located in Santa Cruz County, as a wave crashed into it, crumpling the structure into the sea.

In a video captured by Storm Chaser Brandon Clement in the coastal city of Carmel-By-The-Sea, located south of San Francisco, large, powerful waves could be seen crashing down on the rocky shoreline. According to authorities, massive storm swells, estimated to be 35-50 feet tall, came crashing into parts of the town, Monterey County Weekly reported.

"We've lived here 11 years and this is the worst flooding we've seen," Carmel Point resident Simon Bull told the Monterey County Weekly.

As the storm approached the coast Wednesday, the pressure in the center of the storm rapidly dropped, allowing the storm to undergo a process called "bombogenesis." In this process, the barometric pressure must fall to at least 0.71 of an inch in mercury (24 millibars) within 24 hours, after which meteorologists may informally refer to it as a "bomb cyclone."

The pressure dropped by 0.86 of an inch in mercury (29 mb) between 4 a.m. PST Tuesday and 4 a.m. PST Wednesday, according to an Ocean Prediction Center surface analysis, officially qualifying the storm as a bomb cyclone.

This process strengthens the winds associated with the storm, and it was certainly reflected in the recorded wind gusts. According to reports from Wednesday and Thursday, a 132-mph gust was recorded at Alpine Meadows, California, in Placer County, northeast of Sacramento. Farther east, a gust of 119 mph was recorded in Kirkwood, California, as well as in Palisades Tahoe, California. Of the recorded wind gusts from the storm, the strongest were recorded in Northern and Interior California.

Crews had their work cut out for them on Thursday as the morning light revealed the extent of the storm damage. Trees had come crashing down amid the strong winds, bringing down power lines and sections of roofs along with them.

A spokesperson for San Francisco's emergency operation center said Thursday that of the 445 incidents of fallen trees and branches reported in the city over the last week, 286 of them had been reported in a 24-hour period during the storm.

In San Mateo County, located south of San Francisco, CAL FIRE officials tweeted that "firefighters were responding to non-stop calls early into the morning hours."

Over 26,000 power outages were reported in San Mateo County by Thursday morning, accounting for 16% of all power outages across California at the time, according to PowerOutage.US. While that number had fallen slightly as of early Friday morning as crews ventured out to restore power, over 63,000 customers across California -- primarily along the coastal counties of Northern California -- remained without electricity. That number dipped down to just below 33,000 customers as of Saturday evening, before a new storm boosted that number to above 500,000 outages as of Sunday morning. Outages were still above 300,000 statewide as of Sunday evening.

Butte County officials in Northern California issued a local emergency proclamation on Thursday in response to the ongoing storm, according to Action News Now. The proclamation provides access to financial assistance opportunities for reimbursement associated with response and recovery following damaging elements from the storm, according to Butte County Chief Administrative Officer Andy Pickett. The county offered several locations for residents to pick up sand and sandbags to protect their homes from floodwaters, and several roads remain closed following the heavy rainfall.

A satellite image showing a powerful bomb cyclone over the Pacific Ocean on Jan. 4, 2023. (NOAA/GOES-WEST)

The atmospheric river that fueled the system was unlike the one that soaked California on New Year's Eve and killed at least three. This week's storm was classified as a "pineapple express" as the moisture originated from the tropical Pacific Ocean near Hawaii, which is the nation's leading producer of pineapples.

The concentrated band of moisture produced heavy rainfall across the U.S. West Coast, with rainfall totals reaching as high as 8 inches in some locations. In Shasta County, a site at Sims recorded 7.75 inches of rainfall over the course of 72 hours, and Ragged Point on California's Central Coast recorded 8.37 inches within the same span of time.

The rainfall contributed to travel hazards across the state as floodwaters turned roads into rivers. One video taken in Sebastopol, California, located in Sonoma County, showed a car driving along a road that was fully submerged in murky water, the road only briefly visible in the car's path.

By Wednesday, Downtown San Francisco measured its wettest stretch of 10 days since 1871, according to the National Weather Service. The site received 10.33 inches from Dec. 26, through Jan. 4. The all-time 10-day record was 14.37 inches in January 1862.

The train of storms is forecast to continue to line up across the Pacific Ocean, taking aim for the Golden State. While more moisture could continue to help ease drought conditions, AccuWeather forecasters warn the threat of flooding and mudslides will increase with each storm.

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