Analyst Tries to Predict Fire’s Behavior : West: Bob Walker sees blazes as living things. Currently, he’s assigned to figure out what the fires ravaging the Pacific Northwest will do next.
It crawls. It walks. It lies down at night, then awakens by day to run through the woods. When Bob Walker describes the biggest wildfire in the West, there’s a reason it sounds like a living thing.
“It is a living thing,” said Walker, a fire behavior analyst who takes the pulse of the beast each day, seeking clues to a question on the mind of everyone here: Where will the fire go next?
The answer is critical. Across the West, heat and drought have produced some of the most volatile fire behavior ever observed--from a wind-whipped blaze in Colorado that killed 14 firefighters to a cluster of fast-spreading fires in Washington that have charred more than 190,000 acres in two weeks.
What determines whether a wildfire will creep along the forest floor or explode into the treetops? Why does it spare one canyon, only to fill the next with a firestorm of 200-foot flames?
It is Walker’s job to know. As one of the 50 fire behavior analysts assigned to the West’s wildfires, he rises each day before dawn and falls back into his tent around midnight, tracking the weather and the fire to make the dangerous work of firefighting a little safer.
He uses sophisticated computer models and detailed weather forecasts. But last week, as Walker drove up the smoke-filled Entiat River valley on a scouting mission, no high-tech gadgetry was needed to see the severity of the Tyee fire, which has burned more than 116,000 acres across the eastern slopes of the Cascade Range. It is the biggest of dozens of fires burning in the West.
Along one half-mile stretch, 200-foot flames had roared down from the ridge, turning trees into charred poles, leveling houses.
One witness saw a whole tree sucked up into the clouds, twirling in a tornado of flame. Others saw a flame tornado turned on its side by the wind, performing barrel rolls across the treetops. Walker calls that a horizontal-roll vortex. Those who saw it called it terrifying.
“It was pandemonium here,” Walker said. “This is some incredible fire behavior we’re seeing.”
Farther up the road, on a ridge the fire had not yet reached, Walker stared at a line of flame creeping across the canyon wall. The wind was relatively calm, the temperature was 92, and smoke billowed high in a brown column.
This kind of fire, known as a plume-dominated fire, worries wildfire experts even more than high winds. Wind, at least, fans flames in a predictable direction. A plume-dominated fire follows the fuel, pulsing out anywhere it finds dry vegetation, creating its own erratic winds.
Experts have just begun to understand the phenomenon, learning since 1989 that plume development often can be predicted by low humidity, high temperature and atmospheric instability, which can have an effect similar to opening the flue of a chimney.
“When that column starts defining itself, then you start walking in the other direction--real fast,” Walker said.
Walker, 45, has been a fire behavior analyst since 1987. In the winter, he works for the Deschutes National Forest in Oregon, assessing the efficiency of fire preparedness. During a parched summer like this, he goes wherever the fires are burning hottest.