Future Climate Projections of Hazardous Convective Weather Using an Ensemble of Environment-Informed, Convection-Permitting Dynamical Downscaling Simulations

Convection-permitting dynamical downscaling (CPDD) allows for an explicit representation of the convective storms that generate tornadoes, hail, severe thunderstorm winds, and locally heavy precipitation. Possible changes in such hazardous convective weather (HCW) due to human-induced climate change are therefore projected with higher confidence using CPDD than with analyses of relatively coarse global climate models (GCM). However, due to the computational expense, CPDD-based future projections of HCW have tended to be based on a single experiment rather than an ensemble of experiments which allow for assessments of uncertainty. Herein, we present “environment-informed” CPDD as a means to efficiently generate a CPDD ensemble driven by different GCMs. This variant of CPDD is applied only to a subset of days and geographical domains over which the meteorological conditions potentially favor supercell thunderstorms, which are the most frequent generators of significant HCW in the United States. The temporal and geospatial occurrence of supercells over the United States is demonstrated from the perspective of environment-informed CPDD as applied to eight different GCMs and the ERA5 reanalysis. Such occurrences vary considerably from downscaled GCM to GCM, thus demonstrating the value of an ensemble. Based on the ensemble mean, future supercell occurrence is projected to be most frequent over an area centered on the Missouri Bootheel. An earlier-start to the annual cycle of HCW risk is also projected.