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.
Of the 193 million acres it manages, the Forest Service thins out the undergrowth in two million to three million acres every year, primarily through controlled burns or by laboriously chopping down and removing smaller trees and shrubs. (In a few places, it employs low-tech innovations like goats, which eat shrubs.)
Weather satellites high overhead capture thunderstorms as they form, giving hints of the gusty winds that often accompany them. Remote-controlled unmanned aircraft, flying over a blaze for hours at a time, can take infrared photographs that show its shifting edges.
Those images could be beamed to iPads and Android tablets carried by the firefighters.
"That information could all be available on mobile devices in real time so folks could reference that periodically as they're out in the field fighting the fire," said Tim Sexton, who manages the Forest Service's Wildland Fire Management Research, Development and Application program.
This summer, in a pilot program, the Forest Service, is testing out Android tablets. Last year, the agency tested iPads and smartphones.
"They exceeded expectations," Laura L. Hill, an information technology strategic planner for the Forest Service, said of the iPads. "People found utility for them in their jobs."
The Forest Service is using a mix of off-the-shelf software and custom apps tailored to the needs of firefighting. Ms. Hill said the agency also hoped to take advantage of commercially available distributed computing -- so-called cloud services -- to make some of the computer models and databases more readily available.
But burning forests often have no cellphone towers. "The real big stumbling block we've got right now that we've got to solve is how to get Internet connectivity to every fire every time," Mr. Sexton, of the wildland fire-management program, said.
Sometimes the Forest Service can set up a mobile cellphone tower, or a microwave connection to the local telephone company that allows firefighters to use small antennas to communicate with one another.
Ms. Hill said another possibility was a "mesh network" -- an ad hoc computer network that allows firefighters to share information. If for example, the leader of the crew had Internet connection via satellite, he would be able to download information and share it. Even if the Internet connection failed, the crew members could still share information with one another.
Such technology is already used by the military, the Homeland Security Department and the Federal Emergency Management Agency, she said.
Another challenge is gathering more complete knowledge about a fire.
Currently, for the larger fires, aircraft with infrared sensors fly over the fire at night, producing a map first thing in the morning for the commanders on the ground. Updates during the day are based on incomplete and inexact visual reports.
An unmanned aircraft can remain aloft over the fire for hours at a time. NASA collaborated with the fire service in 2007, providing its Ikhana aircraft, a modified version of the Predator drone fitted with infrared sensors instead of missiles, that flew out of the space agency's Dryden Flight Research Center in California.
The infrared sensors kept track of the movement of the fires that would otherwise have been obscured by smoke.
"It was great information," Mr. Sexton said. "The technology was there."
Robert Roth, an aviation management specialist for the Forest Service, said there were no immediate plans to deploy more drones, but instead the Forest Service was trying to figure out what exactly it would need and then analyze the risks and costs of various approaches.
Predators are expensive, but smaller, lighter unmanned aircraft may not be able to fly through the shifting winds of the smoke columns. Existing airplanes with a flight crew aboard may turn out to be an option.
"We didn't jump and pick an airplane," Mr. Roth said. "We're going to determine the missions that we need to fly first, and then see what aircraft can meet those mission requirements."
Mr. Roth said there was no firm date for carrying out better aerial reconnaissance. "We should probably have a good idea where we want to go next year," he said.
Mr. Sexton said he imagined that in the future people in the command post would be able to see the precise position of each firefighter, via a GPS receiver, as well as the current spread of the fire. They would also have access to information like calculated safe zones to which firefighters could retreat and the time it would take to get an injured firefighter to medical care.
"We could remotely look at the locations of firefighters in relationship to where the fire is and the heat signature that it's producing, and perhaps anticipate movement of the fires before it reaches the crews," Mr. Sexton said. "Sometimes it comes over a ridge, and the crews can't see it coming."
This article originally appeared in The New York Times.