The Motion of Simulated Convective Storms as a Function of Basic Environmental Parameters

Based on results from a three-dimensional cloud-resolving model, it is shown that simulated convective storm motions are affected by thermodynamic as well as kinematic properties of the environment. In addition to the mean wind and its vertical shear, the effect on isolated storm motion of parameters such as bulk convective available potential energy (CAPE), the vertical distribution of buoyancy in the profile, the heights of the lifting condensation level (LCL) and level of free convection (LFC), and cloud-base temperature is considered. Storm motions show at least some sensitivity to all input parameters. Consistent with previous studies, hodograph radius has the most pronounced effect, but the vertical distribution of shear (which also influences the mean wind) affects storm evolution and propagation, even when the effective hodograph radius is unchanged, Among the thermodynamic parameters, the most significant variations occur when the LCL-LFC configuration is modified or when cloud-base temperature is changed. The effects of increases in bulk CAPE act mainly to increase the temporal variability of storm motions. This temporal variability is found to consist both of oscillations about a mean state and trends (accelerations) and is related to increases in the complexity of storm evolution with increasing CAPE. The results point to the importance of environmental factors that enhance storm intensity and rotation, which play a key role in determining storm deviate motion.