Three-dimensional evolution of simulated long-lived squall lines

Simulations that include Coriolis forcing lead to asymmetric systems with significant system growth and migration to the right (south) of the original system centerline. In both cases the evolution of the leading-line convection is primarily controlled by the surface cold pool expansion, with Coriolis forcing promoting rightward system propagation. In the Coriolis simulation, a midlevel mesoscale convective vortex (MCV) forms in the north, to the rear of the convection, while the outflow region aloft is strongly anticyclonic.

The northern location of the MCV is coincident with and influenced by a northward bias in the positive buoyancy anomaly aloft. Midlevel vertical vorticity generation by tilting of horizontal vorticity, both ambient and baroclinically generated, is observed in both the Coriolis and no-Coriolis simulations. On larger scales, the convergence of Coriolis rotation generates significant vorticity and is crucial to the formation of the MCV.