Evolution and Maintenance of the 22–23 June 2003 Nocturnal Convection during BAMEX

Abstract

n 22?23 June 2003 a broad region of convection, comprising a squall line and discrete supercells, evolved throughout the evening and nighttime hours. These storms were studied by analyzing both observations and idealized numerical simulations. The squall line originated from a group of supercells that were initiated in a north?south line along a preexisting outflow boundary in eastern Nebraska. These supercells anchored to the boundary, facilitating cell mergers. The cell mergers and subsequent enhanced rainfall increased the depth and strength of the surface cold pool, which became the forcing mechanism for reorientation into an east?west, southward-propagating squall line. While this was occurring, isolated supercells developed along the dryline in north-central Kansas. These supercells moved northeastward throughout the night. These two modes of convection developed and evolved in a similar nocturnal environment, suggesting that there were two distinct forcing mechanisms responsible for their maintenance. The nocturnal boundary layer was stable; however, CAPE existed and convection would have been able to remain surface based so long as near-surface air was being lifted to its level of free convection (LFC). In this study, both cold pool dynamics and supercell dynamics appear to have played an important roll in lifting low-level air to its LFC throughout the night.