Initiation and Development of Rear Inflow within the 28-29 June 1989 North Dakota Mesoconvective System

Abstract

Five dual-Doppler analyses spanning a period of 1.5 h are used to document the initiation and development of rear inflow within a High Plains squall line. The squall line developed as part of the 28-29 June 1989 mesoconvective system that passed through the North Dakota Thunderstorm Project observational network. This storm was explosively initiated along a preexisting, isolated gust front in an environment of much instability and weak upper-air flow, and moved within dual-Doppler coverage soon after its initiation. The kinematic analyses were performed over a 90-min period as the squall line continued to develop and move to the east-northeast. The Doppler analyses reveal that the rear inflow was initiated near the high-reflectivity cores of the squall line, within 20 min of the formation of the system. With time, the, rear inflow expanded rearward, increased in intensity, and descended to near the surface behind the northern section of the squall line. In regions where the squall line dissipated, the rear inflow also dissipated near the leading edge of the system but remained near the, base of the trailing anvil. Line-parallel analyses indicate that the rear inflow exhibited significant variance in both elevation and magnitude along the length of the squall line. The observations herein suggest that the primary forcing for the rear inflow in this case was the result of processes associated with the strong convention at the leading edge of the squall line and that secondary processes within the trailing anvil-stratiform region may also have contributed to the forcing of rear inflow.