A powerful storm swept through parts of Northern California early Saturday, knocking down trees, causing widespread power outages and prompting weather officials to issue what they said was the first-ever tornado warning for San Francisco.
The warning blared from cellphones around 5:45 a.m., jolting residents across the city from their sleep and into the sudden realization that many had long prepared themselves for what to do in the case of a sudden earthquake, but not a tornado.
And it came less than two weeks after a similar alert echoed across the Bay Area warning of a different kind of disaster scenario: an impending tsunami that forecasters worried could strike along a vast stretch of the Northern California coast.
That warning had been spurred by an earthquake in the Pacific Ocean and briefly caused a panic as people sought to get to higher ground. The warning was canceled a little more than an hour after it was issued.
The tornado warning on Saturday, which was in effect for about 30 minutes, was urgent: “Take shelter now in a basement or an interior room,” it read in part.
“That is the first time that we’ve issued a tornado warning for San Francisco,” said Crystal Oudit, a meteorologist with the National Weather Service in the Bay Area. She said the service had done so after seeing conditions that tend to favor tornadoes as the storm approached the city.
“Well, that was quite a way to wake up,” Mary Ellen Carroll, who leads the San Francisco Department of Emergency Management, said on X. She said the city was assessing many reports of downed trees and minor building damage. Some wondered if the warning had been necessary.
A Weather Service team was conducting a damage assessment on Saturday to determine whether a tornado had in fact touched down, Ms. Oudit said. But it was clear that the storm had been strong enough to knock out power for more than 200,000 people up and down the coast from Monterey to Sonoma Counties, as well as inland areas.
The severe weather in Northern California was caused by an atmospheric river — a long stream of moisture in the sky — that brought gusty winds, rains and, in the Sierra Nevada, some heavy snow.
Ms. Oudit said the rest of the weekend would likely be dry before more wet weather arrived on Monday.
Such atmospheric rivers are a regular feature of weather in California. But tornado warnings? Not so much.
Rebecca Wersan, 41, said she was rattled awake by the loud alarms coming from both her phone and her husband’s phone early on Saturday. “He said, ‘A tornado warning in the Bay Area?’” she recalled.
She remembered lying awake thinking about finding a safe place to go and about the movie “Twisters,” which she had recently seen on a plane. She kept checking the time, waiting for the warning to expire so she could stop worrying.
“I was laying there thinking, I don’t have a good plan,” she said. But the episode did not make a strong impression on her husband, who had fallen back asleep. Later on Saturday, he told her, he did not remember the tornado warning at all.
Not everyone in San Francisco received the warning. Karishma Kumar-Wessel, 33, said she heard about it only later in the day as she went to a dentist appointment. She said her first thought was disbelief. And then she thought about how she was not really prepared for a tornado.
“I’m born and bred Californian, so I really did think tornadoes were only in Oz,” said Ms. Kumar-Wessel, who lives near Golden Gate Park. “I have an earthquake kit. If a tornado truly hit, what are you supposed to do? I would probably Google it, and then it would be too late.”
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