Photo Shot By Greg Yannazzo and Published in the Chronicle 5/5/98 Estimate that the view is towards the northeast. Video shows that this feature was rotating clockwise (anticyclonic). There is now mounting evidence that this indeed was the Sunnyvale F2 tornado. Analyses of radar and other videos taken by citizens suggest that the Sunnyvale tornado was anticyclonic and, possibly, multiple vortex. This image suggests a double funnel, with an additional nearly horizontal small funnel off to the left about half-way up the main lowering. The image suggests that another funnel cloud was present on a more distant lowered cloud base. N E W !! New sections on radar, synoptic and surface controls



New high quality graphics in all sections New evidence and damage reports show that the second tornado (which hit Los Altos about 10 minutes after the Sunnyvale tornado) caused substantially more damage than previously thought. In addition, the Los Altos tornado caused one serious and several minor injuries. Post-analysis of damage suggests that the Los Altos tornado was a high-end F1 or an F2. Forming Funnel. Contraction and spinup. Between 0425 PDT and 0432 PDT, 5/4/98, an outflow boundary encountered a developing thunderstorm in the Sunnyvale area. Both analyses of radar and hodograph information suggest that this storm had a clockwise rotating updraft through a relatively deep portion of the storm. As the outflow boundary (with a spin around the horizontal axis) encountered the storm, it probably was tilted upwards. Lateral contraction and vertical stretching would "spin up" the rotation into strong motion, visible as a funnel cloud if cloud material was present. The picture above left (taken by Karl Anderson) shows both the forming funnel and another anticyclonic vortex visible on its left (north) side. Picture is taken towards the south. It probably was taken at the same time as the larger picture above. (Click on image to see larger version) The picture above right (also taken by Mr. Anderson) shows the intensification of the funnel, and propogation downwards. (Click on image to see larger version)