KENT PORTER Santa Rosa Press Democrat
A funnel cloud ripped off a section of roof from a Santa Rosa landscaping business on Friday, March 18, 2011. Picture courtesy of Kent Porter Santa Rosa Press Democrat.
Earlier there was an intense cell from the same weather system move over the North Bay. In Santa Rosa there was a report of a "fierce gust of wind" causing damage to buildings around 9:30 a.m.
There have also been many lightning strikes along the Peninsula as well as heavy downpours.
The weather pattern continued to have the potential to become dangerous throughout Friday afternoon. The warning was issued at 11:02 a.m. with winds moving northeast at 40 mph, according to the NWS.
As of 11:32 a.m. it was traveling east from Oakland and expected to cross the East Bay city of Alamo by 12:03 p.m. and a minute later in San Ramon. By 12:31 p.m. it is suppose to cross Antioch.
The warning expired by 11:40 a.m. but the strong weather pattern held over, according to Steve Anderson of the National Weather Service.
"The activity is slowly moving to the South," he said. "It is moving to the South Bay and San Jose within the next hour."
Anderson said the National Weather Service rarely issues tornado warnings for the Bay Area but when they are issued, residents should seek shelter and stay indoors.
If you are used to seeing a weather map, there is a long line of red and yellow that spans from Walnut Creek to San Mateo that is heading toward Livermore and San Jose.
At 10:58 a.m. the National Weather Service Doppler radar indicated a severe thunderstorm capable of producing a tornado near Half Moon Bay or 10 miles west of Belmont moving northeast at 30 mph.
If you are caught outside and see a tornado seek shelter in a nearby, reinforced building. As a last resort, seek shelter in a culvert, ditch or low spot and cover your head with your hands.