2012年8月14日に宇治市周辺に大雨災害をもたらしたメソスケール対流システムの組織化について

Abstract

A heavy rainstorm occurred in the area from Uji City to Hirakata City on 13 and 14 August 2012. This paper studies organization manner of the mesosocale convective systems causing the rainstorm using radar and numerical model data of the Japan Meteorological Agency. At the first stage of the rainstorm event, warm moist airflow at the lowest level coming from Osaka Bay was decelerated in the border between Hyogo and Osaka prefectures and convergence of moisture flux occurred, generating back building-type convective systems. After the second stage of the event when convection was less active, wind speed over Osaka Bay increased and the moisture convergence was intensified in the area from the eastern Hyogo Prefecture to the southern Kyoto Prefecture, and convective systems of back and side building-type were developed. At the final stage, a squall line-type convective system was created under the change of mid-troposphere winds from westerly to northerly direction. The convective systems were almost stationary, because convective cells were successively generated at the western edge of the existing convective systems, although elderly convective cells were conveyed to the east by the low-level westerly jet.