Investigating the role of atmospheric flow dynamics on the behavior of the Lahaina Fire

The wildland urban interface (WUI) fire in Lahaina, HI is America's deadliest wildland fire in the past 100 years. Here we describe the driving meteorological factors and fire spread dynamics that contributed to this tragedy. To be specific, we use a Weather Research and Forecasting (WRF) model nested large-eddy simulation (LES) to examine the development, intensification, and spatial evolution of a severe downslope windstorm over the western slopes of west Maui, which produces winds exceeding 40 m/s in Lahaina during the fire's ignition. Using the simulated wind field to drive an urban fire spread model called Streamlined wildland-urban interface fire tracing, or SWUIFT, we find that the fire initially progresses rapidly in the along-wind direction, burning from the point of origin to the shoreline in downtown Lahaina. Subsequently, the structure of the downslope wind storm changed rapidly during the event, with WRF-LES simulating the location of a hydraulic jump over and east of Lahaina, resulting in a reversal of the mean wind direction and extreme turbulence and variability in the flow. As shown by SWUIFT, this second phase of the wind storm produced fire spread to the north, south, and east, resulting in the expansive destruction of structures, and likely contributing to the loss of life.