Winds can play a major role in wildfire behavior
Wind plays a large role in how fast a wildfire spreads and in what direction it goes.
Central Oregon Fire Management Service Fire Information Officer Lisa Clark said fires move exponentially faster with the wind.
Clark said the wind pushes flames forward, which creates radiation and conduction that heats the fuel ahead of the fire. Heat then transfers faster.
A fire that is traveling uphill, with the wind behind it, will travel even faster, which makes it difficult and dangerous for firefighters to get out ahead of it.
One of the most dangerous challenges a firefighter can face while battling a wildfire is the wind directions.
“(…) When it is blowing one direction, you can plan for it, prepare for it, put your firefighters on the safest side of the fire,” Clark said Tuesday.
“If a thunderstorm moves over, you get a downdraft of wind from that thunderstorm and it changes the direction of the fire. You have to really keep your eye out for firefighters, and be really prepared to respond to that weather change because it can blow the fire back on them. With the Cemetery Fire (…) that is burning in the Maury (Mountains), we actually had two 180-degree wind changes as the thunderstorm moved across.”
Firefighter safety is a priority, and wind shifts can put their lives at greater risk. The wind is most dangerous at the start of a fire, which limits suppression efforts during the first few hours of a fire.
Something like a cheatgrass fire can move at 8 moh, but it doesn’t take much to put it out. A forest fire might be slow to start, but once it’s going, it’s harder to suppress.
Firefighters can take advantage of the wind by lighting back-burns that help control a fire. A wildfire draws air in because it needs oxygen, and that causes an indraft.
“What we try to do with a back-burn is set a fire a little bit away, and as that main fire is drawing in that oxygen and that air, it’s actually going to pull our back-burn towards it, and as that back-burn burns closer and closer, it’s also burning the fuel between those two fires,” Clark said.
“When they come together, you have removed all the fuel between your back-burn and the main fire. (There’s) nothing left to burn — you’ve removed all the fuel.”
Another helpful and natural element is when the sun goes down. Fire temperatures generally go down, winds taper off and humidity or moisture levels go up. That gives firefighters a chance to get closer to the fire and battle it through the night.
Here’s a link to a graphic that explains wind-driven fires.
