Investigating the Future Evolution of Extreme Convective Wind Gusts Using Pseudo-Global Warming Experiments.

Extreme convective wind gusts (≥ 25 m/s) primarily occur when a thunderstorm downdraft sinks with high momentum to the ground level and diverges. Rising global temperatures and increased atmospheric moisture (as per the Clausius-Clapeyron relation) are expected to alter convective processes in a future climate. Atmospheric instability diagnostics (MUCAPE, DCP, K-Index, and Total-totals index) demonstrate some, but limited, skill in predicting extreme convective winds; Idealized model studies indicate that convection and severe weather will likely intensify due to higher CAPE, possibly intensifying extreme gusts. We employ a Pseudo-Global Warming (PGW) approach to investigate how an observed warm-season extreme wind gust event in New South Wales (NSW), Australia would have evolved if it occurred in a warmer climate. The event was simulated using the Weather Research and Forecasting (WRF) model run in a three-nested domain configuration ranging from 5 kilometers to 200 meters horizontal grid resolution, using initial and lateral boundary conditions from ERA-5 reanalysis. An ensemble of 13 Coupled Model Intercomparison Project Phase 6 (CMIP6) Global Climate Models (GCMs) was used to calculate the climate delta considering the SSP370 scenario, between the future (2070–2100) and historical (1984–2014) period, which is then added to the ERA-5 data to produce the PGW perturbed simulations. This presentation will explore whether the gust is indeed stronger in warmer climates, and what thermodynamic and dynamical mechanisms are at play.