Mar 22, 2023 - Science

California bomb cyclone leaves at least 5 dead

A person walks past an uprooted tree after a tornado touched down on March 22 in Montebello, California. Photo: Mario Tama/Getty Images

At least five people have died after a "bomb cyclone" associated with an atmospheric river swept through California on Tuesday and Wednesday — unleashing heavy rain, powerful winds and at least one tornado.

Threat level: Tens of thousands of customers were still without power on Wednesday evening, mostly in the Bay Area — where meteorologists on Tuesday recorded data indicating the strongest-ever March storm, judging by atmospheric pressure. The threat of flooding and mudslides remained for several places.

A screenshot of a tweet from the NWS LA office saying "#MontereyBay buoy today really took a dip. Sea level pressure dropped 24 millabar in just under 17 hours! Yikes! That's a meteorological💣(24 mb or more drop in 24 hours or less). And we had the winds to prove it. That round up will be coming shortly."
Photo: National Weather Service Los Angeles/Twitter

The big picture: The National Weather Service's Los Angeles office confirmed a tornado had touched down in Montebello during the storm on Wednesday morning. Another tornado was reported in Carpinteria on Tuesday, with winds estimated up to 75 mph, per the agency.

  • Tornadoes and bomb cyclones in both areas are rare and the NWS is assessing damages.

Zoom in: One person was killed and another was injured after a large tree fell onto a car in Walnut Creek, according to the Contra Costa County Fire Protection District.

  • Two people also died after being hospitalized in San Francisco on Tuesday in separate storm-related incidents, city officials said.
  • Another person was killed when a tree fell onto his vehicle in San Mateo County, the Contra Costa County coroner’s office confirmed per the Los Angeles Times.
  • A man was pronounced dead in Oakland Tuesday after a tree fell on the tent he was in near Lake Merritt, per the Times.

By the numbers: More than 61,000 customers were without power in the state on Wednesday evening, per utility tracker

Where it stands: Rain showers were expected to taper off Wednesday night, with some showers lingering into Thursday morning along the Central Coast and in the mountains, per an NWS forecast discussion.

  • Another storm is possible next Tuesday and Wednesday, the weather service noted.

Context: Climate change is adding even more moisture to atmospheric rivers as ocean and air temperatures increase.

  • This enables them to dump higher rain and snow totals.
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