Analysis of a non-tornadic storm and test of the supercell propagation theory using data from VORTEX 95

Analysis of the non-tornadic Hays supercell and its comparison to the tornadic Garden City supercell are presented as the first major part of this dissertation. The motivation for this study comes from the fact that although there are a number of studies of tornadic storms in the past, there has been few analyses of non-tornadic storms. The lack of studies of the non-tornadic storms prevents us from completely understanding why some supercells produce tornadoes while others do not. Through a detailed analysis of a non-tomadic storm and its comparison to a tornadic storm, we should be able to find out if there are fundamental differences between these two storm types. The data set used in this study was collected during VORTEX 95 by the NCAR ELDORA. It is found that a non-tornadic storm could be very similar to a tornadic one based on the resolvable scales of motion using airborne Doppler radar. The updraft/downdraft pattern, the peak vorticity and the mesocyclone core diameter are almost identical in the two storms analyzed. Our research has very important implications for tornado forecasting.; Another major part of this dissertation is the analysis of the observed propagation of the Garden City supercell. To the author's knowledge, there have been few attempts to observationally test supercell propagation theory advanced by numerical simulations, owing to lack of good data. Detailed Doppler radar data was collected over a 70-min period in the Garden City storm during VORTEX 95. A new technique was developed to retrieve the linear and nonlinear perturbation pressure fields. It is found that the rightward bias in the movement of the Garden City storm was primarily a result of the vertical gradient of nonlinear perturbation pressure. A decomposition of the nonlinear forcing into cyclostrophic and nonlinear shear effects was also presented. This partitioning revealed that both the forcing produced by the mesocyclone and the horizontal shear that was baroclinically-generated by the gradient of buoyancy along the flanks of the updraft were important effects to consider for the rightward movement of the Garden City supercell.