Historic Fire Weather Indices: Development and Implementation

Over the last six decades, many fire scientists have developed and implemented fire weather indices. Their efforts have produced numerous tools designed to assess the potential for meteorological conditions to affect the initiation and evolution of a wildland fire. Some fire weather indices have been implemented as elements of fire danger and/or fire behavior prediction systems, which combine information about the state of the weather and the state of the fuels to diagnose and predict certain fire characteristics. Other fire weather indices have been put forth as stand-alone products that are intended to inform the user about the potential for the atmosphere to affect the evolution of a fire without direct reference to the state of the fuels. The manner in which meteorological conditions are employed in these indices varies widely dependent upon the spatial and temporal scales considered by their parent research studies. Likewise, there is considerable variability in the extent to which the indices have been adopted by the operational community.

This presentation consists of an overview of fire weather indices that have been developed in the past. The research studies that contributed to the formulation of the indices are described followed by an assessment of how the indices are designed to be applied, either as a component of a larger fire danger or fire behavior prediction system or as a stand-alone tool. Whether or not the indices and the prediction systems in which they reside have been adopted locally or widely for operational use is discussed. Where possible, the reasoning behind why a given index is or is not commonly employed is identified, and for indices that are widely used we assess whether they are used in a manner consistent with the publications that document their development.