Investigating Lightning Flash Rates in Tornadic Environments

Lightning jumps, or a rapid increase in total flash rate, often precede severe weather and mesocyclogenesis. While there is plentiful research comparing lightning flash rates and general severe weather, there is less research on temporal relationships between flash rates and tornadogenesis in mixed storm modes. This study analyzes the total lightning flash rates associated with 49 tornadoes and 19 non-tornadic cells from 12 tornadic environments from the Propagation, Evolution, and Rotation in Linear Storms (PERiLS) NSSL Lightning Mapping Array (LMA) deployments and the Oklahoma LMA. Cells were defined and tracked by their flash extent density. Comparative analyses were made between tornadic and non-tornadic cells, isolated supercells and cells embedded in quasi-linear convective systems (QLCSs), weak (EFU, EF0-1) and strong (EF2+) tornadoes, and time periods before and surrounding tornadogenesis. In a sample of non-EF0, non-cyclic tornadoes, 80% were preceded by a 2-sigma lightning jump; however, more lightning jumps occurred in non-tornadic cells. When comparing flash rates before tornadoes to peaks in low-level rotation in non-tornadic storms, the tornadic storms experienced more total lightning. Flash rates in cells before tornadogenesis were nearly identical with QLCS and supercellular tornadoes. There were differences in the flash rates of cells associated with weak and strong tornadoes, though no statistically significant results were found. Lightning flash rates were found to have steadily increased before tornadogenesis, peaking around 17 minutes prior to tornado formation. After that, flash rates remained fairly steady across the sample. The difference in the flash rate trends before and after 17 minutes prior to tornadogenesis was statistically significant, providing confidence that an increase in flash rates regularly precedes tornadogenesis.