1988年7月島根・広島豪雨の気象特性について

Abstract

A case study of heavy rainfalls is made, which occurred in Shimane andHiroshima Prefecture from midnight to the early morning on 15 and 20-21 July1988. The former maximum total precipitation recorded 395 mm and amount of 342 mmconcentrated within 6 hrs. at Hamada, the latter, 344 mm and amount of 308 mm, within4 hrs. at Misumi.These heavy rainfalls occurred in the warm sector of a weak cyclone passingthrough the Sea of Japan. Before the occurrence of heavy rainfall, the atmospherewas very moist and its stability was conditionally unstable. The heavy rainfallsdeveloped as a result of strong convective activity. These synoptic meteorologicalcoditions were maintained by inflow of warm, moist air due to the southwesterlyflow at low level and the cold, dry air due to the northwesterly flow at high level.Some meteorological characteristics of these rainfalls are compared with those ofheavy rainfall on 22-23 July 1983.Relations among 10 min. rainfall rate, wind and meso-scale pressure variationsare analysed. The results suggest that 4-5 meso-scale disturbances associated withrain came from the Sea of Japan to the San-in coast and propagated eastwards witha speed of 36km/hr.