Sirico, R. (2020). INVESTIGATION OF THE ENVIRONMENTAL INFLUENCES RELATED TO THE PRECIPITATION STRUCTURE OF SUPERCELL THUNDERSTORMS AND THEIR EVOLUTION. Unc Charlotte Electronic Theses And Dissertations.
The precipitation structure of supercell thunderstorms (e.g., low-precipitation(LP), classic (CL), high-precipitation (HP)) has been associated with differing severeweather threats (wind, hail, or tornadoes) to the public, thus motivating work examiningthe causes for these supercell categories. Previous research has demonstrated that theprecipitation structure of these storms is impacted by both the kinematic andthermodynamic profiles within their inflow environments; in particular, it has beenhypothesized via analysis of a set of observed supercells across the precipitation spectrumthat the upper-level wind profile is of paramount importance, due to the ability of thesewinds to transport hydrometeors close to (i.e., weak winds leading to HP) or farther away(i.e., strong winds leading to LP) from the updraft (Rasmussen and Straka 1998). However,a recent idealized modeling study conducted by Warren et al. (2017) has found theopposite association, which suggests additional investigation is necessary.The present study uses an automated tracking algorithm to identify and classify104 supercell thunderstorms into either LP/CL or HP categories; 66 were identified asLP/CL and 38 as HP. Model-derived soundings were then used to describe the inflowenvironments of these storms throughout their lifetimes. Distributions of numerousthermodynamic and kinematic parameters were created to compare the two dominantsupercell categories using statistical significance tests. Following these statistical comparisons, it was clear that a number of differences were present between LP/CL andHP environments. In particular, the kinematic profiles of LP/CL supercells tended tocontain stronger bulk shear, storm-relative helicity, and stronger upper-level windscompared to HP supercells, consistent with the prior observational study of Rasmussenand Straka (1998). However, the LP/CL wind profiles also contained veering winds aloft,which did provide consistency with Warren et al. (2017). Along with these kinematicdifferences, variations in the thermodynamic profile also proved to be important; HPstorms exhibited significantly higher lifted condensation level (LCL) and level of freeconvection (LFC) heights, in addition to lower convective available potential energy(CAPE).Many of the key inflow environmental differences could be tied to the synopticset-up for each of the given precipitation modes. Notably, LP/CL storms often findthemselves in much stronger synoptically forced environments, evident at multiple levelsin the atmosphere (e.g., jet-level [300 hPa], 500 hPa, surface). Overall, the broaderconsistency of the present study with other prior observational studies, as opposed to therecent modeling studies, suggests that additional work is still needed to betterunderstand the interplay of variations in kinematic and thermodynamic profiles inproducing varying precipitation structures within supercells.