When the winds change, a ferocious forest inferno can make a sharp turn, and the fire crews battling it may need to depend on their eyes and instincts to tell them whether they are in danger.
Sometimes, as appears to be the case in the deaths of 19 elite firefighters in Arizona, it is already too late.
Of course, the best way to fight catastrophic fires is to keep them from growing to catastrophic scale. But that is becoming more and more difficult as global warming raises the likelihood of fires, especially in Western forests. By 2050, the annual extent of forests burned is predicted to rise by 50 percent or more.
So officials and experts are increasingly relying on technology both high and low to counteract the trickery of raging wildfires.
In computer simulations, the United States Forest Service sets tens of thousands of virtual fires — factoring in different weather patterns, topography, vegetation and historical weather patterns. “You would sort of get a map that depicts a likelihood of fire occurrence,” said Elizabeth Reinhardt, an assistant director of fire ecology and fuels for the Forest Service.