Coupled Weather-Fire Model Simulations of Extreme Winds and Fire Behavior during Recent Windstorm-Driven Wildfire Events

Several of the most destructive recent U.S. wildfire events were associated with strong downslope winds in the lee of mountain ridges, variously referred to as Diablo winds in northern California, Santa Anas in southern California, chinooks in the Front Range of the Rocky Mountains, and the more general term föehn winds in the eastern U.S. In several cases, ignitions and rapid early fire growth appear linked to strong winds in mountainous areas that anecdotal evidence suggests may have reached 30-40 m s^-1 in some locations. Surface stations are sparse in mountainous areas and thus do not map or, often, even detect the severe winds that are hypothesized to have occurred. Mesoscale model simulations of the weather leading up to and during these events capture broad spatial patterns of accelerated winds -- a good standard against which to evaluate a simulation in many applications -- but commonly produce peak winds that are lower by 30-50% than the anecdotal estimates. Understanding the magnitude, structure, and spatial distribution of these peaks has significant consequences for infrastructure design and operation in mitigating the damage from future events. I compare and contrast convective-scale (hundreds of meters horizontal grid spacing) simulations of the weather leading up to and during some of these events and early fire growth using coupled weather-wildland fire modeling capabilities of the CAWFE^â modeling system. I discuss the development and spatial distribution of extreme winds that appear in fine-scale modeling in the context of windstorm-driven fires.