Decoding the August Complex Fire: Investigating the Atmospheric and Surface Characteristics Driving One of California’s Largest Wildfires

Wildfires have detrimental impacts on transportation, power and gas services, agriculture, infrastructure, water systems, and human health. More specifically, NOAA reported approximately $81.6 billion in United States wildfire damages from 2017 through 2021. Wildfire frequency, duration, and intensity of wildfires are projected to increase across the western United States. The August Complex Fire is one of the largest wildfires in California history. From August 16th through the 18th, several cloud-to-ground lightning strikes ignited multiple fires that persisted for over four months. Previous studies have linked temperature and precipitation extremes to the promotion and driving of wildfires. This study focuses on the August Complex wildfire to investigate atmospheric and surface characteristics that influenced the temporal and spatial extent of the fire. Using ECMWF Reanalysis v5 data, we examined patterns and changes in the atmospheric and surface characteristics before and during the August Complex wildfire. We observed hot-windy-dry extreme events prior and during the fires, along with specific weather regimes driving heat fluxes influencing the wildfire event. Extreme heat and dry conditions were noted leading up to the fires, while above normal precipitation in March 2020 fueling vegetation growth prior to the wildfires. We conclude that the weather regimes occurring before and during the August Complex wildfire may serve as predictors of atmospheric patterns associated with meteorological events that prompt wildfire initiation across California.