The Role of Preexisting Airmass Boundaries in the Maintenance and Rotation of Deep Convection in a High -Cape, Low -Shear Environment

Abstract

In the second phase of this research, numerical experiments were used to examine the open issues that emerged from the observational analysis. Simulations were conducted using an idealized cloud model with a horizontally heterogeneous initialization that included the dominant preexisting airmass boundaries of the 27 May 1997 event. With a localized initialization and no preexisting boundaries, the simulated storm was short-lived and therefore consistent with the high-CAPE, low-shear archetype. When both the dryline and cold front were included in the initialization, the overall behavior of the simulated storm complex and boundaries closely resembled the early stages of the 27 May 1997 event. The quasi-continuous maintenance/propagation of the simulated storm was found to be controlled by the cold front. Moreover, strong, temporally coherent near-surface vertical vorticity required the horizontal shear associated with either preexisting boundary.