NBIC-ACS Stage 2 Forest Fire Danger Index - baseline scenario, 20% and 10% annual exceedance probabilities

The McArthur Forest Fire Danger Index (FFDI) is a fire weather potential index that describes how current weather conditions and recent precipitation patterns could support a fire in forested areas. FFDI calculations are based on McArthur, A.G. (1967) and dependent on air temperature, relative humidity, wind speed. The metric was developed with the worst bushfire event at the time – Victoria 1939 – corresponding to a value of 100. Here we provide predicted upper-bound FFDI values across the Australian landscape, defined for a set of Annual Exceedance Probabilities. We calculate FFDI based on the latest Bureau of Meteorology historical weather reanalysis BARRA-R2, reporting modelled hourly weather conditions from 1979 to current at a spatial resolution of approximately 11 kilometres. More than 400,000 data points at every location are then processed using the National Bushfire Intelligence Capability (NBIC) Extreme Values Analysis to predict extreme daily maximums and their likelihood. FFDI was historically used to define bushfire hazard, including the official Fire Danger Rating issued by operational agencies. While its use in this context is no longer recommended, FFDI remains a widely recognised fire weather metric that is commonly understood and informs jurisdictional policies and building standards. All these characteristics result in datasets that are a significant advancement in defining extreme fire weather, surpassing previous approaches and offering a robust foundation for informed decision-making in managing and mitigating Australia’s growing bushfire risks in a changing climate.