INVESTIGATION OF SINGLE CELL TO MULTICELL IN THE CLUSTER THUNDERSTORMS USING VORTICITY ANALYSIS

Abstract

 The investigation of single cell to multicell in the cluster thunderstorms using vertical vorticity analysis will be proposed. The techniques of vortex tube structure and identification of initial stage values of the first radar echo were applied to rainfall events with the unstable atmospheric conditions in Kinki region, Japan. Cluster thunderstorms cases during the two events were selected and the analysis of single cells to multicells were performed by investigating the initial stage of vorticity values and their structures. The vertical vortex tube of vorticity analysis was shown to examine the signature of merging of single cells to mutlicells. In the case of two events, the criteria index of persistence development for cells and dissipating cells were established and it was found that the positive vorticity greater than 0.015s^-1 possibly prolonged the duration of lifetime more than one hour. In the meantime, the positive vorticity less than 0.0025s^-1 might shorten the lifetime of single cells in the multicell clusters. The signature for merging of single cell to multicell was difficult to discover due to the change of core vorticity at upper level height before single cells merge into multicells.