Wildfire was once a seasonal concern primarily for the western United States and Great Plains. It has now become a year-round threat in many parts of the country, devastating communities, impacting air quality, and reshaping landscapes. In the face of the escalating risk, scientists at NOAAโs Global Systems Laboratory (GSL) in Boulder, Colorado continue to develop sophisticated tools to give forecasters, land managers, emergency response officials, and firefighters improved situational awareness of rapidly developing wildfire hazards.
One of their latest innovations is the Hourly Wildfire Potential Index (HWP), an experimental application of NOAAโs revolutionary High-Resolution Rapid Refresh forecast model (HRRR) and the next-generation Rapid Refresh Forecast System (RRFS), developed by GSL and the National Weather Serviceโs Environmental Modeling Center. HWP provides an assessment of wildfire potential updated every hour based on model-predicted weather conditions. The frequent updates allow HWP to forecast sudden increases or decreases in potential fire activity due to changing weather conditions, providing more accurate and timely predictions of wildfire activity including the amount of emitted wildfire smoke.
The HWP index was created by a team of scientists from GSL and the University of Colorado cooperative institute CIRES, based on three years of measurements of radiant heat captured by satellites flying over large wildfires in the western United States. HWP incorporates predicted winds to estimate fire spread and intensity, humidity to estimate influence of atmospheric dryness on fuel moisture, and soil moisture derived from the HRRRโs advanced land surface model to predict the response of flammable vegetation to precipitation and drought.
โThere are lots of existing fire weather indices, but the novel thing here is to be able to predict hourly variability in fire activity related to the weather conditions,โ said Eric James, a GSL research physical scientist who played a key role in development of the HRRR. โApplying the HWP to a weather model like the HRRR provides an inexpensive way to anticipate changes in fire activity without running a computationally expensive fire behavior model.โ
In development since 2019, HWP is expected to be a component of the RRFS, NOAAโs next generation high-resolution weather model, which is being evaluated for use by the National Weather Service. A new paper published in the journal Weather and Forecasting describes how the index was developed, reports on test cases where it was verified, and identifies potential applications for the wildfire response community.
