Seminar: Understanding Evolving Climate Variability and Risk for Severe Convective Storms

Abstract

Severe convective storms — thunderstorms that produce damaging winds, large hail, and/or tornadoes — are increasingly becoming a dominant driver of insured losses. In particular, tornado outbreaks — when several tornadoes happen in a short time span — are rare yet impactful events. Observation-based estimates of tornado outbreak risk are limited. To address this gap, we developed a two-part stochastic tornado outbreak index for the contiguous United States. The first component produces a probability map for outbreak tornado occurrence based on spatially-resolved values of convective precipitation, storm relative helicity, and convective available potential energy. The second part of the index provides a probability distribution for the total number of U.S. tornadoes given the outbreak tornado probability map. Together, these two components allow stochastic simulation of location and number of tornadoes that is consistent with environmental conditions.

In this talk, I will present the development of the tornado outbreak index and show how we used it to generate a synthetic event set for U.S. tornado outbreaks. I will highlight applications for investigating climate-scale influences, e.g. El Niño-Southern Oscillation and long-term trends, on outbreak activity. Finally, I will discuss how the index supports event attribution of climate change influence on recent tornado outbreaks, providing an additional line of evidence to observational reports as well as physical context. Overall, these advances help build a clearer picture of evolving climate-related risk for severe convective storms.