Numerical Study of a Tornado-Like Vortex in a Supercell Storm

The Canadian Mesoscale Compressible Community model (MC2) .is used to simulate tornadogenesis. The simulation is initialized with profiles of a horizontally homogeneous thermodynamic sounding with a CAPE of 2100 J/Kg and horizontal winds similar to those in Wicker and Wilhelmson (1995).

The simulation reproduced the main features of conceptual models of tornadic supercell storms, including the forward flank downdraft (FFD), the rear flank downdraft (RFD), and a hook echo shaped reflectivity region surrounding a cyclonic rotating updraft. A tornado like vortex developed in the hook echo region, within the vertical velocity gradient between the updraft and RFD and a zone of strong horizontal shear. Aanalysis of the vorticity budget suggests that the tilting of horizontal vorticity (generated by the baroclinic environment within the RFD) into the vertical and the stretching of the vertical vorticity generated by shear are the main mechanisms in the production of a tornado like vortex.