NSF NCAR RAL - Modeling Firebrand Spotting in WRF-Fire for Coupled Fire-Weather Prediction

Fire spotting can be a dominant fire spread mechanism in wind-driven events, particularly those that occur in the wildland-urban interface (WUI), such as the Marshall Fire. To simulate these fires, the model’s ability to spot is critical, in that it accelerates the rate of spread and enables the fire to spread over streams and urban features such as highways. The firebrand spotting parameterization was implemented in WRF-Fire V4.4 to improve simulations of wind-driven fires in a fire-atmosphere coupled system. In the parameterization, particles are generated from locations aligned with the fire front, firebrands are then transported using a Lagrangian framework, and fire spots may occur when firebrands land on unburned grid points.
Our model can simulate thousands of individual embers and predict the locations where spotting is more likely
During windy and dry weather, particularly when the surrounding vegetation is also dry, embers can travel farther and over fire barriers, such as water streams and roads, and result in rapid fire growth. Intense spotting increases danger to firefighters, affects our ability to predict fire spread, and challenges efforts to suppress it. In an urban setting, embers are the leading cause of home ignitions.
The WRF Model with extended functionality predicts spotting likelihood by simulating embers lofted into the atmosphere from locations where the fire is intense, carried with the wind, and landing on the surface near or far ahead downwind. The model takes into account the number of embers landing at each location, and that location's soil and vegetation conditions.
ral.ucar.edu/w...