The Future of Supercells in the United States

Abstract

A supercell is a distinct type of intense, long-lived thunderstorm that is defined by its quasi-steady, rotating updraft. Supercells are responsible for most damaging hail and deadly tornadoes, causing billions of dollars in losses and hundreds of casualties annually. This research uses high-resolution, convection-permitting climate simulations across 15-yr epochs that span the 21st century to assess how supercells may change across the United States. Specifically, the study explores how late 20th century supercell populations compare with their late 21st century counterparts for two—intermediate and pessimistic—anthropogenic climate change trajectories. An algorithm identifies, segments, and tracks supercells in the simulation output using updraft helicity, which measures the magnitude of corkscrew flow through a storm’s updraft and is a common proxy for supercells. Results reveal that supercells will be more frequent and intense in future climates, with robust spatiotemporal shifts in their populations. Supercells are projected to become more numerous in regions of the eastern United States, while decreasing in frequency in portions of the Great Plains. Supercell risk is expected to escalate outside of the traditional severe storm season, with supercells and their perils likely to increase in late winter and early spring months under both emissions scenarios. Conversely, the latter part of the severe storm season may be curtailed, with supercells expected to decrease midsummer through early fall. These results suggest the potential for more significant tornadoes, hail, and extreme rainfall that, when combined with an increasingly vulnerable society, may produce disastrous consequences.

Supercell precipitation contribution to the United States hydroclimate

“…During winter, supercell precipitation contribution is confined to the South, particularly along the Gulf Coast and in the Mid-South (Figure S2a). Seasonal volumetric precipitation follows a similar pattern as seasonal supercell counts (Ashley et al, 2023) and is highest during spring and summer with seasonal means of 12 and 14 km 3 , respectively, for UH75 supercells (21 and 25 km 3 UH60). Unsurprisingly, due to the seasonality of supercells, notably lower volumes are found during fall and winter (Figure 3b,d).…”

“…Spatially, the central CONUS receives the highest mean annual precipitation contribution from supercells, with percentage maxima over southeast South Dakota and south-central Texas. Each of these regions receive greater than 3% of their annual precipitation from UH75 supercells (>4% UH60; Figure 4c,d); these maxima correspond to regions with the greatest mean annual supercell populations (Figure 2a,b; Ashley et al, 2023). Outside of the central CONUS, supercells generally contribute <0.5% of the total mean annual precipitation due to the relatively uncommon occurrence of particularly longlived, robust supercells in these parts of the country (Figure 2a,b).…”

“…Results suggest an overall increase in days supportive for SCSs in the future; however, the distribution of SCS populations may vary due to changes in forcing, moisture, convective inhibition (CIN), overlapping of ingredients (e.g., CIN with convective available potential energy [CAPE]), convection initiation and overall sustenance of SCSs (Ashley et al, 2023;Hoogewind et al, 2017;Pilguj et al, 2022;Taszarek et al, 2021). Research suggests SCSs and their associated severe perils will be more frequent and intense with an expansion in their seasonality by the end-of-the-21st-century (Trapp et al, 2011(Trapp et al, , 2019Gensini & Mote, 2014, 2015Trapp & Hoogewind, 2016;Hoogewind et al, 2017;Rasmussen et al, 2020;Gensini, 2021;Ashley et al, 2023). Should these projections come to fruition, a plethora of environmental and societal factors such as habitation loss, economic cost and casualties, will be at risk.…”

Assessing the Impact of Stratospheric Aerosol Injection on US Convective Weather Environments

“…It would also be insightful to examine Earth‐system model simulations with different SAI deployment goals and timelines (e.g., MacMartin et al., 2022), as well as simulations under different climate change scenarios, such as the Stratospheric Aerosol Geoengineering Large Ensemble Project that utilized the high‐end RCP8.5 emissions scenario (Tilmes et al., 2018). Use of the output from Earth‐system models to force high‐resolution, regional climate models to explicitly examine how projected changes in the large‐scale environment impact the distribution of convective modes could provide additional understanding as to how SAI deployment impacts convective weather (Ashley et al., 2023; Gensini & Mote, 2015; Gensini et al., 2023; K. L. Rasmussen et al., 2017; Trapp et al., 2019).…”

Major Role of Marine Heatwave and Anthropogenic Climate Change on a Giant Hail Event in Spain

“…Supercells and hailstorms pose a recurrent threat over Europe (Dahl, 2006) resulting in substantial economic losses, societal impacts, and hazards to aviation safety (Antonescu et al, 2017;Kunz et al, 2020;Nisi et al, 2016;Púčik et al, 2019). There is growing evidence that the ongoing climate change is having a relevant impact on the frequency and intensity of severe convective events involving hail (Ashley et al, 2023;Battaglioli et al, 2023;Brimelow et al, 2017;Raupach et al, 2021).…”