San Francisco, CA — Oct. 13, 2026 — Ladris today enabled urban conflagration in its fire behavior models, allowing simulations to continue past the community boundary and into the developed areas where the majority of structure loss in recent American wildfires has occurred.
The problem this enhancement addresses is well known. The Rothermel-based fire models that underpin nearly all operational U.S. fire modeling treat houses, streets, and businesses as non-burnable. Consequently, these models simulate fires that run to the edge of the wildland and then stop. Real fires do not. In recent years, devastating fires have moved through built areas after the wildland fuels behind them were spent. Modeling this structure-to-structure spread, where a majority of losses occur, has never been possible.
Researchers at the University of Montana’s National Center for Landscape Fire Analysis and the USDA Forest Service took on this problem by asking what fuel parameters would make an existing spread model behave like an observed urban fire. Drawing on rate-of-spread data from seven conflagrations dating back to the 1991 Tunnel Fire, they identified fuel models that reproduce urban fire behavior within the constraints of currently fielded modeling systems. Ladris engineers customized this approach for its own fire models.
The urban fire spread research performed by the University of Montana and the Forest Service is a breakthrough for fire science. Their approach gave us a rigorous method for representing fire behavior in developed areas, and building on it has improved how we can model a fire as it moves through a community.
Bowen Kyle — Chief Technology Officer, LadrisFor Ladris customers, this modeling extension leads to improvements across products. In Ladris Core, the fire spread simulations planners use for evacuation timing and pre-season risk work now keep running once the fire crosses into developed land, rather than stopping at the wildland edge. This carries through to Prime, which automatically turns fire-spread and traffic projections into sequenced evacuation plans. With urban fire spread built in, these plans can now account for a fire that keeps advancing through structures after the vegetation runs out, with Prime’s continuous re-forecasting keeping the plan current as the fire advances. The same underlying model reaches the public through the free Sentinel app, enabling residents to see fire spread forecasts that don’t stop at neighborhood boundaries.
While enhancements from urban fire spread modeling are apparent across Core, Prime, and Sentinel, Ladris understands that runs with burnable urban fuels are best read as a scenario alongside conventional runs, not as a replacement for them. Spotting over non-burnable barriers is not captured, and the underlying wind response inherits the assumptions of a model built for vegetation. As clearly indicated by the urban fire spread researchers, this method is a stopgap until urban-specific spread models reach operational use.
Access to improved fire spread modeling is available through Core, Prime, and Sentinel, all available today, with Sentinel free to the public through Ladris Ready PBC. More than 90 agencies across the United States currently use Ladris products.