A case study on persistent appearance of the ensemble of precipitation bands in the warm sector of the Baiu front in the western Japan around 19 June 2001

Abstract

A case study on persistent appearance of the ensemble of precipitation bands in the warm sector of the Baiu front in Kyushu District, the western part of Japan around 19 June 2001 was performed based on the operational observational data. Around 00UTC (09JST) 19 June when the Baiu front on the surface weather map was still located about a few 100kms to the north of Kyushu, the number and the total area of the meso-β or γ-scale line-shaped precipitation bands increased around Kyushu rapidly. These precipitation bands had been sustained there and gradually gathered each other to change into the Baiu frontal precipitation zone extending from the northern Kyushu to Seto-Naikai (Seto Inland Sea) around 09UTC (18JST) 19 June (the intense rainfall zone was still located in the warm sector of the Baiu front). Until ~09UTC (18JST) 19 June, the moist air flow with the latently unstable stratification had been sustained around Kyushu corresponding to the low-level southerly wind toward the surface Baiu front to the north of Kyushu. This large-scale situation would contribute greatly to the maintenance of the ensemble of the line-shaped precipitation bands in the warm sector of the Baiu front