Four dead across U.S. West Coast as atmospheric river brings record rains and 20 landslides in California
The strongest atmospheric river of the season, driven by a bomb cyclone with a central pressure of 945 hPa, ravaged the U.S. West Coast on Wednesday, November 20, 2024, bringing unprecedented rainfall, flooding, and wind damage. Northern California bore the brunt of the storm, with 543.4 mm (21.39 inches) of rain recorded in Sonoma County and widespread flooding that stranded hundreds. Meanwhile, fierce winds of up to 206 km/h (128 mph) toppled trees and left communities without power.
Vehicle stranded on the street after floods triggered by atmospheric river. Image credit: Roberta Gonzales
- Four people lost their lives due to the storm: two in Northwest Washington caused by falling trees, and two in California due to flooding and rough seas.
- Over 1 million customers were left without power at the storm’s peak. As of early Sunday, November 24, 51 700 remained without power in Washington, over 6 000 in California, and approximately 133 in Oregon.
- Santa Rosa set a new three-day rainfall record with 322 mm (12.68 inches).
- Nearly 20 landslides occurred between Wednesday and Thursday, including a boulder falling on Highway 281 in Clearlake Riviera and rocks blocking lanes of Highway 20 in Saratoga Springs.
An atmospheric river event, accompanied by a bomb cyclone that struck the U.S. West Coast on Wednesday, has claimed at least four lives so far.
The storm, which struck the Pacific Coast with hurricane-force winds, left over 1 million people without power as it downed numerous trees and powerlines.
The cyclone was extremely powerful, with its minimum central pressure dropping to nearly 945 hPa as it approached the coast of Washington. This triggered tornado warnings northwest of Portland, Oregon.
Two fatalities were reported in Northwest Washington due to falling trees, while two others died in California due to rough seas and flooding. An Amtrak train struck a tree in Stanwood, Washington, but no one sustained any serious injuries.
This was the strongest atmospheric river of the autumn season so far, drenching parts of California with up to 508 mm (20 inches) of rain.
Up to 254 mm (10 inches) of rainfall fell in the Northern Bay Area, with over 508 mm (20 inches) recorded in Sonoma County. The Cazadero area in Sonoma County recorded 543.4 mm (21.39 inches) of total rain between Wednesday and Friday. Meanwhile, Healdsburg recorded 450.9 mm (17.75 inches) of rain during the three-day stretch.
Santa Rosa recorded 322 mm (12.68 inches), setting a new three-day rain record, surpassing the previous record of approximately 254 mm (10 inches) set in October 2021.
The heavy rains caused intense flooding across California, with floodwaters stranding around 300 people at a hotel and clinic in Santa Rosa on Thursday, November 21.
Several water rescues were conducted as vehicles became trapped in up to 0.91 m (3 feet) of floodwaters in some areas. Several roads were closed between Santa Rosa and Windsor due to flooding, and Sonoma County Sheriff’s deputies reported between 7 and 10 water rescues along Mark West Springs Road.
The flooding also triggered several landslides, with nearly 20 occurring between Wednesday and Thursday. A boulder fell onto Highway 281 in Clearlake Riviera, causing an accident. Rocks also blocked lanes of Highway 20 in Saratoga Springs.
Flood warnings were issued for the San Francisco area, with rain gauges measuring 102 mm (4 inches) in some spots. Floodwaters stranded cars on Interstate 180 in San Francisco and Interstate 580 in Oakland, along with US 101 and California Route 17 in the South Bay.
Strong winds accompanied the atmospheric river. A coastal wind gauge at Mattole Road in Humboldt County, south of Eureka, recorded a gust of 158 km/h (98 mph) on Friday morning. At elevation, Palisades Tahoe recorded a gust of 206 km/h (128 mph) at its summit, which is 2 621 m (8 600 feet) above sea level.
An 18.3 m (60-foot)-tall tree toppled at Sansome and Pacific Streets in San Francisco due to strong winds, damaging a car underneath it.
The Siskiyou and Sierra Nevada regions recorded heavy snow during the event. Castle Peak received 508 mm (20 inches) of snow through 04:00 local time (LT) on Thursday, while Soda Springs received 432 mm (17 inches), and Kingvale recorded 279 mm (11 inches).
The Russian River in Guerneville overflowed flooding the surrounding areas on Friday, November 22.
Efforts to restore power are expected to last a few days. As of early Sunday, November 24, 51 700 customers remained without power in Washington, over 6 000 in California, and approximately 133 in Oregon.
By 16:49 UTC on November 24, 36 800 customers were still without power in Washington.
“This system was so strong that it was comparable to a hurricane and did unprecedented damage to our high-voltage transmission system—the poles and wires that carry electricity from where it is produced to the communities we serve. Without fixing those lines first, we cannot get power back into many neighborhoods. Much of this work takes place in hard-to-reach, remote parts of western Washington,” said Puget Sound Energy, the largest energy provider in Washington State.
More precipitation is forecast for the coming week across the West Coast.
References:
1 Atmospheric river dumps snow and record rain on California – BBC -November 23, 2024
2 Atmospheric river brings 10-20 inches of rain to Northern California, triggering flooded roads, landslides – Fox Weather – November 23, 2024
3 At least 4 dead after powerful atmospheric river event clobbers West Coast – Fox Weather – November 23, 2024
I am an Assistant Editor and Severe Weather & Science Journalist at The Watchers, specializing in real-time severe weather coverage, geophysical event reporting, and research-driven scientific analysis. You can reach me at rishav(at)watchers(.)news.
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