Unusual Warm Weather Prompts First Burn

​The unseasonably warm weather created a flurry of activity to prepare the fire equipment in anticipation of the weekend's controlled burn. Nachusa burns typically begin in March.

Dave

Mike

With the staff committed to speaking engagements, much of the prep work fell on long–term and dedicated volunteers, Dave Crites and Mike Carr. This past week, the men worked hard and swiftly to prepare for the possible weekend burns, loading all the various equipment and pumps to the vehicles.

The burn begins, as the crew uses drip torches to ignite the grass. 

Water pumpers follow the igniters and extinguish any fire that burns back toward fire breaks.

The crew has the fire well underway.

Crew members dedicated to fire suppression, put out any unwanted fire, such as around this brush pile (it will be burned later, when there is more time to watch over it).

A dust devil!

A dust devil was observed during the burn. What causes a dust devil? McKinnon (2014) explains the interesting science:

If a column of hot air rapidly rises inside a pool of cool air and picks up a bit of rotation, the column pulls in and up, lengthening as it spins faster and faster through the conservation of angular momentum. More hot air is pulled horizontally along the ground, drawing in at the base and feeding the dust devil. The hot air cools as it rises, loosing buoyancy until the now-cool air descends along the outside of the tower. The combination of a steady supply of hot air rushing in at the base and the descending cool air stabilizing the tower creates a self-sustaining system.

​On hot, barren, flat surfaces, the hot air supply can be enough to sustain the dust devil for minutes. When cold air is sucked in, the temperature differential is broken, and the dust devil dissipates. Dust devils are fragile structures that form in calm conditions. A bit of wind will disrupt the stabilizing rotation, blowing the dust devil apart.
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The controlled burn is typically set in a "ring" by starting at one point and sending two crews in opposite directions, working into the wind. Near the end, the blackened area is wide enough to allow the two crews to meet up in the middle of the wind side. All the "sides" of fire meet up, and with no more fuel, the flames go out!

After the burn is complete, the Project Director leads a debriefing to go over the events of the day. What did we do well? Where can we improve?

February 19, 2017 Burn Crew

Here is a short video detailing some typical events that occur during a controlled burn at Nachusa. For more information, visit Nachusa's webpage about controlled burns.
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Today's author is Dee Hudson. Joe Richardson, Charles Larry, Kirk Hallowell, and Bill Kleiman provided the images for this post; John Schmadeke created the video.
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References
McKinnon, Mika, (March 30, 2014).
Science of the Fiery Dust Devil Spawned by a Controlled Burn