Case Analysis of a Severe Pulse Thunderstorm Triggered in the Outflow of the Previous Thunderstorms
Using the conventional weather data, WSR88D Doppler weather radar dat a, SAFIR 3000 total lightning data, intensified sounding and automatic surface w eather observations, a severe pulse thunderstorm which caused four grandstands d estroyed and one blew away about 20 meters in the Shanghai F1 Circuit on August 3, 2007 is analyzed. The case analysis shows the interaction of boundary layer c onvergence lines, sea breezing front, and the cold outflow of previousthunderstorms triggered the initiation of some pulse storms in local area. The p ulse storm which caused the wind disaster in F1 Circuit was triggered by the col lision between the cold outflow of previous thunderstorms and the earlier bounda ry layer convergence lines. Due to the high atmospheric instability energy, suff icient ambient moisture, and convergence in the low and middle levels, the pulse storm intensified significantly in the cool pool of the previous thunderstorms and resulted in a damaging wind gust of 40.6 m/s and heavy rainfall in F1 Circui t. Furthermore, the sudden increase of total lightning flash rate of the storm i ndicated the eruption of the storm with a strong downdraft and the beginning of its declining phase.