Russ Schumacher (@rschumacher.cloud)

Convective Mode Classification and Distribution of Contiguous United States Tornado Events from 2003–2023 Abstract Tornadoes and severe thunderstorms represent a significant threat to life and property in the United States annually. Approximately one thousand tornadoes, two-hundred being significant (F/EF-2+), are documented on average every year. Using archived radar and Storm Data storm report information, 21 912 tornado grid hours were manually analyzed for convective mode from the years 2003–2023. This dataset builds upon prior work by Smith et al. (2012) (hereafter S12) by more than doubling the sample size to produce a robust, multidecadal climatology of tornadoes by convective mode. Comparisons were made between tornado samples spanning 2003–2011 and 2012–2023 to assess changes in the frequency and spatial occurrence of tornadoes. Convective mode characterization consisted of a subjective analysis of WSR-88D imagery into three categories: 1) supercell, 2) quasi–linear convective system (QLCS), and 3) disorganized. Spatial climatologies of the different modes were performed and Kernel Density Estimate plots of events per decade were generated as in S12. The highest climatological frequency for tornadic supercells is reaffirmed to extend from KS and OK east-southeastward to MS and AL, while QLCS tornadoes are more frequent from the northern Gulf Coast states into the lower Ohio River Valley. Comparing the new sample to the original, QLCS tornado relative frequency increased by over 100%. Substantial variation in QLCS tornado occurrence may be due to non-meteorological factors such as dual polarization radar and different observing/reporting practices. https://share.google/M3ty4pVs5TldZuryx