That funnel cloud that knocked down power lines and damaged rooftops in South San Francisco yesterday was no funnel cloud after all — it was a tornado. Mark Strobin of the National Weather Service confirms his agency has classified the event as an F1 tornado. The twister struck about 3:40 p-m yesterday in the middle of a heavy thunderstorm. It shattered windows and damaged several rooftops in the downtown area. No injuries were reported.