Severe convective storms initiated by intense wildfires: Numerical simulations of pyro‐convection and pyro‐tornadogenesis

Abstract

On the afternoon of 18 January 2003, wildfires swept through several outer suburbs of Canberra (Australia) producing, inter alia, a series of large pyro‐cumulonimbus cells and at least one tornado. The results of a large‐eddy simulation with a parameterized fire are reported here. The simulation, motivated by the Canberra wildfires and severe storms, captures the main characteristics of the observed pyro‐cumulonimbi, including the formation of a tornado close to where one was observed. In addition, the model develops prominent horizontally oriented vortices on the western side of the fire in the direction of the low‐level shear, and a series of horizontally oriented vortices on the upstream side of the convection column. The production of water by the fire is critical for the development of a pyro‐cumulonimbus cell intense enough to reach the tropopause as observed and plays a significant role in the associated tornadogenesis.