Potential Weakening of the June 2012 North American Derecho Under Future Warming Conditions

Abstract

AbstractDerechos are widespread and long‐lived straight‐line windstorms associated with fast‐moving mesoscale convective systems that cause severe life and property loss. This study investigates how the June 2012 North American derecho could unfold in the future with global warming. Convection‐permitting regional model ensemble simulations of the derecho as observed are compared with simulations under a pseudo‐global warming scenario of the future environments by the end of the 21st century following the Shared Socioeconomic Pathways (SSP5‐8.5). The control simulations can well reproduce the observed derecho features, including storm evolution, surface wind, and precipitation, except for a 2‐hr delay relative to observations. Compared to the control simulations, the derecho shrinks and decays earlier in the future environments, with much less destructive impacts on the Mid‐Atlantic coastal areas. The derecho shrinkage is attributed to lower relative humidity on both sides of the derecho propagation path under global warming, which suppresses updraft and strengthens downdraft, impeding the spatial extent of the derecho. The premature decay is due to the intensification of an isolated deep convection (IDC) event that develops ahead of the derecho. The meridional gradient of future warming strengthens the synoptic environments, enhancing convergence in a corridor of higher instability that facilitates intensification and continuous development of the IDC. By consuming energy and moisture on the derecho propagation path, the IDC hinders the derecho development in the Mid‐Atlantic coastal areas. Focusing on a single derecho, this study reveals how changes in the thermodynamic environment with warming could induce complex changes in the derecho.