The Garden City, Kansas, Storm during VORTEX 95. Part I: Overview of the Storm’s Life Cycle and Mesocyclogenesis

Abstract

Analysis of a supercell storm that produced an F1 tornado near Garden City, Kansas, is presented. This event provided one of the first opportunities to synthesize data collected by a new airborne radar platform called ELDORA (Electra Doppler radar) developed by the National Center for Atmospheric Research. The early stages of development of the midlevel mesocyclone and the entire evolution of the low-level mesocyclone are captured over a 70-min period. The low-level mesocyclone began as an incipient shallow circulation along a synoptic-scale trough. The circulation intensified and grew in depth via vortex stretching under the influence of a strong updraft. As this rotation built up from the boundary layer, it initially remained separate and distinct from the midlevel mesocyclone. Subsequently, the two mesocyclones merge to produce a single column of rotation 4?5 km in diameter. An occlusion downdraft develops within the mesocyclone circulation during the last passes by the storm signaling the beginning of the tornadic phase. Perturbation pressure retrievals provide conclusive evidence that this downdraft is driven by a downward-directed pressure gradient force.