Tom's Blog

Saturday, April 3, 2010

Fire whirl during prescribed burn

Last Monday during our big prescribed burn there was a fairly large fire whirl (also called a "dust devil") in the middle of the Pocket Prairie. I didn't see it, but Kathie and Chris did, although I have seen other ones.

The photo below is of a particularly spectacular fire whirl I found on Wikipedia.

The one in the Pocket Prairie did not have a fire component such as this photo, but was formed by black dust arising from the burn.

What causes a dust devil? They are a result of intense local heat remaining after the flaming front has passed by. This heat interacts with the air above to create a tornado-like structure which pulls the black dust up into the air. An upward spiralling motion usually results.

Although a dust devil is usually benign, dissipating quickly, occasionally flaming embers are pulled up into the air where they can be transported out of the burn unit, possibly resulting in spot fires. Thus, it is important to keep an eye on recently burned areas until they have cooled down.


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