ABSTRACT
A three-dimensional numerical cloud model is used to simulate the structure and evolution of the flanking line of supercell thunderstorms. The flanking line forms as the rain water and associated cold pool reach the surface and storm begins to split. As the cold pool spreads from the main cell, the rear flank gust front forms, and convergence between the environment inflow and the cold pool produces upward motion. The "stair-stepped" appearance of the flanking line is well simulated and can be explained by two factors: 1)near the main cell, the cold pool is deeper, and the gust front has a stepper leading edge; and 2) the orientation of the gust front near the main cell is more favorable for upright updrafts given there is a better balance between the environmental shear and the cold pool as discussed by Rotunno et al.(1988). A cell forms along the flanking line near the main coincidentally with the formation of a low-level vortex which "sheds" off of the low-level mesocyclone. The cell then moves off to the northwest away from the gust front. A simulation with more sub-cloud curvature to the hodograph produces a more robust low-level mesocyclone and no "vortex shedding." Consequently, no cells forms along the flanking line. Future work will focus on the well-documented merging of flanking line cells with the main cell and the "vortex shedding" process simulated in this study.