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..On January 3, 2015, a historic event occurred: the San Francisco Tornado. With winds of 267 mph, the National Weather Service in San Francisco reported an EF-5 rating.
The event begins in San Francisco where NWS Doppler Radar indicated Severe Thunderstorms with a history of producing Supercells that were moving south heading for the city. A rotating wall cloud hung over downtown San Francisco at about 2:30. Six minutes or so later, the tornado made landfall. The city was under a tornado warning. The tornado that destroyed the Golden Gate Bridge was reported by storm spotters at approximately 2:50. With winds exceeding 187 mph, the tornado became an EF-4 seven minutes later. The tornado was moving toward Los Angeles between 3:00 and 3:10.
When the National Weather Service issued a tornado warning for portions of the San Francisco Bay Area early Saturday morning, hundreds of thousands of Bay Area residents were startled awake by an emergency alert on their smartphones.
The tornado warning was lifted shortly after 6:07 a.m. by the National Weather Service.
A severe thunderstorm with the potential to produce a tornado was spotted close to Daly City, prompting the warning. The weather service posted on social media, "The tornado warning is 'radar indicated' we do not yet have any confirmation of a tornado at the moment."
Radar showed rotation within the storm as of 5:51 a.m., with the storm traveling 45 mph northeast. San Francisco, Daly City, South San Francisco, Pacifica, and other nearby cities were among the impacted areas.
Go to the lowest floor of a sturdy building and find an interior room. Steer clear of windows and shield yourself from flying objects. Move to the nearest substantial shelter if you are outside or in a car, and shield yourself from flying debris," the advisory stated. People in the areas under warning were advised to seek shelter right away in interior rooms away from windows on the lowest floor of sturdy buildings.
Driving is dangerous, especially on flooded roads, as a result of the storm's heavy rainfall, which may cause flash flooding. The most intense downpour and the The warning occurred after radar detected rotation in the clouds, which is a strong indication of a water spout. Water spouts form when that rotation hits the ground. If that happened, and the water spout hit the ground and made landfall, it officially would have become a tornado.
In Twin Peaks, power flashed several times at 6 a.m. Sounds of wind gusts resembled a car engine starting for nearly a minute, before winds suddenly died.
Streetlights and power went out over the major artery of San Jose Avenue in the Excelsior neighborhood of San Francisco.
Check the Chronicle's live storm map here; Check the PG&E outage map here.
This story is developing. Check back for updates.
