Projected Mid‐ and Late‐Century Changes in Severe Convective Storms Across the United States From Dynamically Downscaled Climate Simulations

ABSTRACT

Output from dynamically downscaled, convection‐permitting regional climate simulations is used to examine projected changes in the frequency, timing and spatial distribution of synthetic severe convective storm (SCS) detections based on peril proxies across three 15‐year epochs—1990–2005, 2040–2055 and 2085–2100—under intermediate and pessimistic emissions scenarios, including the first mid‐century projections of SCS activity, providing a rare assessment of how SCS climatology may evolve throughout the 21st century. An explicit multi‐hazard approach is employed to define severe convective perils using permutations of simulated upward vertical velocity and lowest model level reflectivity thresholds, allowing SCS activity to be assessed collectively for tornado, wind and hail perils. In response to enhanced greenhouse forcing and related changes in fundamental severe storm ingredients, projected synthetic SCS activity exhibits spatiotemporal changes relative to the historical baseline, including lengthening of the severe season, increases in the overall frequency of SCS days and an eastward shift of event frequency maxima. In addition to changes in mean frequency, results illustrate enhanced variability and increases in relatively high‐activity days across all future epochs, driven by more frequent spring and early summer occurrences. Regionally, increases in SCS days are projected for south‐central and Gulf Coast states, the southern Great Plains and the Midwest in the spring and the Midwest, Northeast and Southeast during the summer, while decreases are projected for the Great Plains during the summer. These changes are accompanied by a broadening geographic footprint of SCS activity, indicating a redistribution of severe storm risk under warming. Results provide physically grounded insight into the potential evolving severe storm landscape, which stakeholders, policymakers and the public may use to mitigate and build resilience against future events.