A Three-Dimensional Numerical Model of an Isolated Deep Convective Cloud: Preliminary Results

Abstract The development of an isolated convective storm in a sheared environment is studied with an anelastic three-dimensional numerical model. Each grid cell has horizontal dimensions of Δx=Δy=3.2 km and a vertical dimension of Δs=0.7 km. Although it is ultimately planned to use at least a 31×31×20 grid with turbulence and liquid precipitation included, the present study uses an 11×11×8 trial grid with both of these processes suppressed, simulating only early cloud growth. Comparative experiments are run for three vertical profiles of ambient wind: no ambient wind, positive speed shear but no directional shear, and positive speed shear with veering. The cases are compared in regard to airflow, pressure and thermal patterns. It is found that: A vortex doublet develops at middle levels when ambient shear is present. A contributing factor may be tilting of horizontal vorticity into the vertical by differential vortex-tube lifting. Shear introduces asymmetry, with upshear dominance of perturbation outflow ...