Wildfire in the Forecast

Wildfire moves with the wind, as firefighters were grimly reminded in Arizona and Colorado last summer. New computer modeling could soon bring greater precision to the art of knowing which way the wind is blowing, potentially helping firefighters control blazes.

Computer simulations usually break down weather systems into grids of manageable cells, then calculate the interactions between adjacent cells. Most weather modeling uses a coarse grid, with cells 30 to 50 kilometers on a side. That’s fine for predicting whether it’s going to rain in your town. But when a fire is burning across complicated terrain, the ability to forecast winds, humidity and other atmospheric phenomena with a resolution of one kilometer or less could spell the difference between a fire contained and a fire gone wild. “If you want to predict the behavior of fire, you need high-resolution modeling,” says forestry researcher Mark Finney of the U.S. Forest Service’s Rocky Mountain Research Station in Missoula, MT.

In the 1990s Finney developed a model that predicts the behavior of fire on the basis of a number of variables, including weather. In Hawaii, researchers at the Maui Center for High-Performance Computing recently coupled this model, called Farsite, with atmospheric models  that provide resolutions of one to two kilometers. A supercomputer runs the weather model to churn out detailed predictions of wind, humidity, cloud cover and other weather characteristics; these data then become input to Farsite, greatly abetting its precision. Although not yet used in the field, these coupled models could significantly improve the lot of firefighters, according to the Hawaii research. “This will give us a forecast of where the fire will move over the next 24 to 36 hours,” says Duane Stevens, a meteorologist at the University of Hawaii at Manao.

Other groups are also coupling fire modeling with weather prediction. The Wildland Fire R&D Collaboratory includes about 20 organizations working to understand the interactions among fire, weather, terrain and flammable matter. Right now, the physics is too hard to simulate because of the numerous variables involved, including the type and dryness of the vegetation (known in the fire control world as “fuel”) and the length of time since the last big fire. Moreover, not only are fires driven by weather, but large infernos also influence weather on a local scale. But Rich Wagoner, a scientist at the National Center for Atmospheric Research in Boulder, CO, isn’t daunted. “We want to answer the question: what is this dance between fuel, fire and atmosphere?”