Author(s): Masato Kita; Yoshihisa Kawahara; Ryota Tsubaki; Cho Thanda Nyun
Keywords: Back-building thunderstorm; WRF; Spatial resolution; Hiroshim
Abstract: Urban areas have been becoming more prone to flooding due to the increase in frequency or magnitude of heavy rains. The advancement in numerical prediction methods for heavy rainfalls is one of the key issues for early warning. This study applies the WRF (Weather and Research Forecasting model) to the back-building thunderstorm that attacked Hiroshima city in 2015 in order to clarify the evolution mechanism of rainfall system. Comparison between the calculated rainfall intensity and that measured by X-band dual polarimetric radars shows that the WRF with numerical grid system of 1 km resolution can reproduce the training thunderstorm. The calculated results explain that the multi-cell storm had evolved in such a way that the southerly high moisture was supplied in the lower layer over the Bungo channel to Hiroshima city and the unstable air mass uplifted in the presence of the eastward wind and the moist tongue in the middle layer over Hiroshima.