Comparing Tornado Production from Merging and Isolated Supercells across Several Convective Events

This project aims to analyze tornado production across merging supercells using an extensive database of ‘right-moving’ supercell tracks in the contiguous United States. The two main objectives are: (1) contributing to a robust database consisting of thousands of supercell tracks, and (2) analyzing this database to address key questions about the behavior and characteristics of merging supercells and their associated tornadoes. The database is developed by tracking all observed supercells using archived radar imagery (GR2Analyst) and pairing these tracks with tornado paths, severe thunderstorm warnings, and environmental parameters such as storm-relative helicity (SRH), convective available potential energy (CAPE), and the supercell composite parameter (SCP).

The focus of this project is on supercells that have other supercell(s) merge into them during their lifespan. Some research questions to be addressed include: the frequency of tornadic and non-tornadic merging supercells, the tendency of azimuthal shear before and after a supercell merger, and the timing of tornado production compared to the supercell merger. The results of this project will be updated as additional contributions are made to the comprehensive supercell database. Current findings are based on more than thirty convective days from early 2022 through mid-2023. Based on this analysis, more than half of the dominant merging supercells produced at least one tornado. Additional preliminary findings show that both the mid-level and low-level maximum azimuthal shear tends to slightly increase, on average, after a dominant supercell experiences a merger with another supercell.

Keywords: Supercell, Merge, Tornado, Azimuthal Shear, Database Development