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, CIRES and NOAA scientists 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 assessment of wildfire potential for every nine square kilometers of land area that is updated every hour. The frequent updates allow forecasters to see sudden changes in potential fire activity due to weather becoming more hot, dry, and windy. The tool provides more accurate and timely predictions of wildfire activity to existing weather prediction models, including the amount of emitted wildfire smoke. 

CIRES and NOAA scientists in the Global Systems Laboratory based the HWP on three years of measurements of radiant heat captured by satellites flying over large wildfires in the western United States. 

“There 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,” said Eric James, a GSL research scientist who played a key role in development of the HWP. “Applying the HWP to a weather model provides an inexpensive way to anticipate changes in fire activity without running a computationally expensive fire behavior model.”

In development since 2019, HWP is expected to be a component of the RRFS, NOAA’s 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. 

“We expect that this index can help forecasters anticipate sudden changes in wildfire activity, as well as predict wildfire smoke emissions, leading to improved decision support for fire management and enhanced communication with communities impacted by fire and smoke,” James said.   

What sets HWP apart from other established fire indices is that it’s the first index designed specifically for use with hourly, high-resolution, storm-scale weather models. The frequent updates means the index can predict changes in wildfire activity from sunrise to sunset and through the night, as well as account for the influence of weather events such as cold fronts, windstorms, and rainfall.

Real-time HWP forecasts are now being generated from operational and experimental storm-scale models covering the contiguous U.S. and Alaska, and are available on the Global Systems Lab’s DESI website.  

Besides helping land managers and firefighters anticipate changes in fire activity, the HWP can improve predictions of the amount of smoke emitted from wildfires in the coming hours and days, as well as the likely height of the associated smoke plumes. Plume height is an important factor in predicting the spread of wildfire smoke, with long-range transport generally occurring only with very high plumes. The index can also assist with planning of prescribed burns.  

The HWP Index can also help distinguish between flaming versus smoldering combustion phases in wildfires, which has important implications for the chemistry of smoke plumes including the production of ozone. Ozone is harmful for human health and has been tied to wildfire smoke plumes.