San Francisco residents woke up early Saturday morning to a tornado warning during a powerful storm system that lashed the region with heavy rain and wind.
It was the first-ever tornado warning for San Francisco, but not the first tornado, according to CBS News Bay Area meteorologist Paul Heggen.
The National Weather Service issued the warning for northern San Mateo County and parts of downtown San Francisco just before 6 a.m. to 6:15 a.m.
According to the NWS, there was a cyclonic signature on the radar that had produced enough of a rotational signature to trigger the warning.
“The radar scan at 5.52am clearly shows a ‘hook echo’ offshore – that is the signature we look for to identify a developing tornado. This feature was embedded in a broad area of very heavy rainfall, but it is still falling always on,” says Heggen. explained.
The NWS Bay Area said the warning for San Francisco was over at 6:07 a.m. and the tornado warning expired at 6:15 a.m.
The warning prompted a flood of messages on social media from residents who woke up to the alert on their cell phones. It was reported as the first-ever tornado warning for San Francisco.
A special warning was also issued for a possible water spout in San Francisco Bay in the Bay Bridge area, which expired ten minutes after the tornado warning.
Although the strongest part of the system has passed, isolated severe thunderstorms remain possible throughout the morning in parts of the Bay Area, the National Weather Service said.
According to PG&E, the storm conditions caused power outages for thousands of people in the Bay Area.
The tornado warning in San Francisco was just the first of several extreme wind events associated with the powerful storm that ripped through Northern California overnight and continued to cause problems Saturday.
The high winds caused impacts across the region, including a citywide power outage in the North Bay town of Novato And a complete closure of Interstate 580 in both directions near the San Joaquin and Alameda county line after a multi-vehicle crash involving a big rig due to high winds.
On Saturday afternoon, a tornado touched down in the Santa Cruz County city of Scotts Valley. Police initially warned of a multi-vehicle crash, but later reported that witnesses said a tornado had touched down on Mount Hermon Drive, causing “several cars to go off the road.”
The Bay Area office of the National Weather Service later confirmed that a tornado had occurred based on “video, photographs, first-hand accounts and radar signatures”
