Mesoscale Convection along the Dryline

Abstract

A linearized two-dimensional model was used to study the formation of convective rolls in the prestorm stage and organized squall lines near the dryline in the Great Plains. With a strong virtual potential temperature gradient across the dryline zone, the results show the without condensation symmetric instability can produce convective rolls with a horizontal wavelength of a few tens of kilometers. With condensation, a large cloud develops near the center of the dryline zone. This cloud subsequently splits into two clouds; one moves to the west and disappears, and the other moves to the east, where the PBL is relatively moist, and grows. The numerical results are qualitatively comparable with observations. This study provides a possible explanation that symmetric instability with condensation can generate storms near the center or on the east side of the dryline zone, whereas low-level convergence develops at the western edge according to the inland sea-breeze circulation.