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PHOTO: Maine Forest Ranger Jeremiah Burch investigates and maps the aftermath of a wildfire in Greene in early April. The Maine Forest Service warns that fuels are drying out, and Mainers should be careful with any outdoor burning. (Maine Forest Rangers Facebook photo)
By Vicki Schmidt
We all know it when we feel it – the bitter chill from winter wind is identical to the wind that cools and refreshes us in the summer. We can’t see it, hold it or touch it, and as gentle or fierce as wind can be, it’s merely the interaction of the sun’s energy on air, relative to the Earth’s surface. Wind can be our friend or foe, especially with regard to the phenomenon of wind-driven fires.
Recalling our grade school geography, there are three major wind systems that form the Earth’s atmosphere: the Polar Easterlies, the Prevailing Westerlies, and the Trade Winds. To look at how it affects fire, let’s break it down into the smaller ones that we experience daily in Maine. All wind patterns are the result of constant changes in atmospheric pressure which are because of temperature differences caused by the sun’s heat as it reaches the Earth. The difference in air temperature moves air from higher pressure areas to lower pressure areas, allowing us to experience winds of various speed and direction.
So, if wind is pure air, and air contains oxygen, which is one of the components that sustains fire, it’s not hard to imagine how dramatically wind can have an impact on fire. Structure fires that your local fire department responds to, along with wildland and naturally caused fires, such as those from lightning storms, are all dependent on air if they are to keep burning. In Maine we are used to seeing dramatic wind-driven wildfires in the western U.S., which burn so intensely that their all-consuming heat creates and sustains its own local wind system, known as a firestorm. Luckily, Maine has experienced very few wind-driven wildland fires, but Marc Veilleux, a supervisor with Maine’s Fire Marshals Office, recalls several wind-driven structure fires during his tenure as Sabattus fire chief. Not only can the heat from wind-driven fires spread to nearby buildings, the wind feeds the internal flow path of the fire within the structure.
Veilleux states that “the velocity of the gusty winds made a wind-driven fire a formidable force. I was thankful for my mutual aid departments.”
Advanced training for both structure and wildland firefighters involves learning about what impact wind has on fire, and what tactics and strategies can be deployed to control it. While we can’t see the wind we can see its impact on other items. Flags are a top indicator that show the direction and speed of the wind. A flag that is barely moving indicates calmer wind of less than 10 mph, lightly flapping is about 10-20 mph, moving over its entire length is close to 20-25, and a fully stretched flag flapping in the wind indicates wind over 25 mph.
Firefighters feel the wind, note its direction and see things in the wind, such as smoke. Smoke that is rising straight up as opposed to billowing or moving away from an area gives us information on where to position and attack a fire. In fact, “The Art of Reading Smoke,” by David Dodson, is one of the most valued training sessions that firefighters and commanding officers attend.
Along with learning to read smoke there is another way firefighters use wind that helps us fight fire. A breeze (4-7 mph) wind becomes the friend of firefighters working a prescribed burn to reduce wildland fuels (dried grass, shrubs, and wood debris) that burn during a wildfire. This breeze allows the fire to gently creep over the land, consuming what easily burns to reduce the wildland fuel load, yet allowing other more solid wood and greenery to survive and thrive.
The most destructive and deadly wind is known as “critical wind.” This is wind that dominates the fire environment and easily and quickly overrides, not only the local wind and its influences, but also the resources and firefighting capacity of those attempting to fight the fire. The Santa Ana winds of Southern California are one of the most well-known critical winds. In Maine, thunderstorm wind, and to a lesser but growing threat, frontal wind, is the critical wind we most experience. While to date, these and other storm-force types of wind have not caused significant damage, death or destruction; climate change is increasing wind speed and many now report that Maine is experiencing more frequent and gustier storm wind patterns.
Every year Maine proclaims the third full week of April as Wildfire Awareness Week. With luck, the most you’ll ever experience for a windy impact on a fire is the gentle flickering of your campfire. If you happen to notice strong wind on a warm dry day, take note, as Maine may issue a red flag warning. Realize too that wind-driven fires of any type can happen any time of year, especially when there is no snow or heavy moisture covering the land.
To learn about the science behind wind-driven fires, visit the website of the National Wildfire Coordinating Group at nwcg.gov.
Most of all, keep fire safe with any activity involving any type of heat or fire. Thank you from your local first responders!
— Vicki Schmidt is a Maine state fire instructor and volunteers with the Buckfield Fire Department, as well as several regional and state fire training organizations.
