Ledbetter, C. (2018). Analyzing supercell intensity changes in a heterogeneous environment in the VORTEX2 supercell pair in southeastern Colorado on 11 June 2009. Unc Charlotte Electronic Theses And Dissertations.
Predicting supercell thunderstorm evolution in strongly-forced environments is relatively well-understood. However, this is not always the type of environment that spawns supercells. In fact, some supercell environments can be quite complex in nature. A variety of environmental complexities are possible, including interactions with frontal boundaries, merging with other storms, the presence of high shear-low CAPE (HSLC) environments, and the nocturnal transition; each of these scenarios can produce temporal and spatial variations in key quantities of instability, shear, and helicity. The goal of this study is to do an in-depth mesoscale analysis of a pair of supercells examined during the VORTEX2 project in southeastern Colorado on the evening of 11 June 2009, with the goal of determining what environmental factors lead to intensity changes within the supercell pair. This will be done by combining environmental data, primarily upper air sounding launches performed by both VORTEX2 researchers and the National Weather Service (NWS) office in Dodge City, KS, as well as radar data in the form of both NEXRAD level II radar data from NWS Pueblo, CO and mobile radar data from Doppler-on-wheels (DOW) and Shared Mobile Atmospheric Research and Teaching Radar (SMART) radars. Mobile radar data will be used to perform a dual-Doppler analysis in order to calculate 3-dimensional wind and vorticity fields for the cells. These datasets will be compared with one another, as well as previous research, in order to try to determine if any, or all, aspects of this storm’s environment, attribute to any of the intensity fluctuations in either supercell. Overall, the fluctuations during and after the merger begins between to occur between the two supercells were more intense compared to those before the merger occurred. This could be linked to the merger itself, or to the favorable amounts of shear in the inflow environment throughout the analysis period. Additionally, there seemed to be a direct relationship between increasing mesocyclone strength at the mid-levels and LSR occurrences. This would make some sense, given that the rotation is somewhat indicative of increased updraft strength. Lastly, as consistent with previous research, the period just following the beginning of the merger seemed to be an inflection point that marked a significant increase in mesocyclone strength at all levels. During the merger period, there are several instances of low-level rotation as well, which also would tend to indicate some strengthening, since rotation was able to extend down towards the surface. Dual-Doppler data seemed to only affirm these trends, as most trends in updraft and vertical vorticity strength and size seemed to be consistent with that of mesocyclone intensity and depth.