An analysis of spotting distances during the 2017 fire season in the Northern Rockies, USA

The wildfires that burned in the Northern Rockies region of the USA during the 2017 fire season provided an opportunity to evaluate the suitability of using broadscale and temporally limited infrared data on hot spot locations to determine the influence of several environmental variables on spotting distance. Specifically, correlations between the maximum observed spot fire distance for each unique combination of fire and day and geo-referenced environmental data on wind speed, vegetation, and terrain, along with specific fire characteristics (size, fire perimeter shape, and growth), were assessed. The data were also utilized to evaluate a popular theoretical model developed by Albini (1979) for predicting the maximum spotting distance for single and group tree torching. The results suggested a significant positive correlation between the maximum observed spot fire distance and an interaction between fire growth and wind speed. Significant negative correlations between maximum spotting distance and fire perimeter shape, canopy height, and terrain steepness were also discovered. The evaluation of Albini's (1979) model suggested that selecting a high estimate of potential wind speed was important to minimize the likelihood of underpredicting maximum spotting distance.