The role of vertical buoyancy distributions in simulated low-topped supercells

Abstract

Tornadic potential in low-topped convection is difficult to forecast and to detect on radar. Observations of tornadic low-topped supercell environments allude to low-to-moderate CAPE and at least moderate low-level lapse rates in temperature. This study examines the role of low-level vertical buoyancy distributions in influencing supercell updraft intensity and persistence, and on mid-level and low-level mesocyclone development. The emphasis is to examine wind, temperature, and moisture profiles that are conducive to the development of low-topped supercells with tornadic potential. COMMAS, a non-hydrostatic 3-dimensional numerical cloud model, was used to simulate supercell development for nine idealized environments having a range of wind shears and total CAPE predictive of supercell type storms, and all having moderate vertical lapse rates in temperature. Supercell updraft forcing characteristics and low-level mesocyclone development in the models were similar for environments with adequate shear and buoyancy distributions in the low levels regardless of the environment's total CAPE. Model results suggest the vertical distribution of buoyancy over the sheared depth of the environment is a better indicator of an environment's potential to produce tornadic supercells than total CAPE.