[A-AS03] Extreme Events and Mesoscale Weather: Observations and Modeling

[AAS03-P09] Analysis of dynamical structure of a downburst-producing cumulonimbus cloud system using multi-parameter phased array weather radar

*Yuki Ono¹, Atsushi Hamada¹ (1.University of Toyama)

Keywords:Phased Array Weather Radar, Downburst

This reports that analyzed the dynamical structure and verified the mechanism of the outbreak of cumulonimbus clouds caused downburst that occurred from Nerima to Suginami in Tokyo, on August 27, 2018. This paper use observations from a state-of-the-art multi parameter phased-array weather radar. Before the outbreak the downburst, three changes were observed that is considered to be precursors of the downburst in the cumulonimbus cloud ; (1) the precipitation core, which was above 5 km at 1935 Japan standard time(JST), descended to the ground toward 1940 JST (2) the echo depression deepened at 4 to 5 km altitude (3) a strong horizontal convergence area appeared at 4 to 3 km altitude. Corresponding to these depression and convergence regions, there are vortex pairs with positive and negative vertical vorticity, respectively, and the downdraft was distributed across the vortex pairs. These results suggest that the horizontal vortices of the background wind may have been raised by the downdrafts in the cumulonimbus cloud to form vortex pairs and contribute to the generation of the downbursts.