Evolution of a Multicell Thunderstorm in Association with Mid-level Rear Inflow Enhanced by a Mid-level Vortex in an Adjacent Thunderstorm

Abstract

A meso-β-scale convective system (MCS) passed over the Tokai District of Japan on 8 Sep., 1994. Only one multicell thunderstorm (Storm C) exceeded the tropopause level in the MCS. This paper presents the evolution of the kinematic and radar echo structures of Storm C observed by the dual-Doppler radar system of Nagoya University. Storm C lasted more than 2 hours and its elongated axis was normal to the direction of mean cell motion. The early developing stage of Storm C was characterized by a downdraft on the left flank (left flank downdraft or LFD) and the development of cells on the right flank above the outflow of the LFD. A mid-level rear inflow descending within the storm and a new downdraft on the rear flank (rear flank downdraft or RFD) were observed in the explosively developing stage. The mid-level rear inflow was accelerated and localized in the vicinity of an anticyclonic vortex developed in a nearby decaying storm. Cells developed strongly above the merged outflows of the LFD, the RFD and the descending mid-level rear inflow. In the decaying stage, the intensified RFD and mid-level rear flow divided the main updraft region on the right flank into two and their outflows prevented the outflow of the LFD from spreading to the right flank. On the basis of the observational results, the effect of the vortex on the behavior of the rear inflow as well as the influence of the rear inflow on the evolution of Storm C were discussed.