Meet the dust devil's more dangerous cousin. A Missouri woman captured a picture of this pillar of fire as she was driving down a road in the town of Chillicothe on Sunday. It's since been dubbed the "firenado."
Janea Copelin explained on her Instagram account that a farmer was burning off his field when the firenado appeared.
How common is this kind of fire devil? Pretty common, as it turns out. We talked to Jeremy Sullens, a fire behavior analyst at the National Interagency Fire Center (NIFC), about the fire whirl — its correct name.
Sullens explained what happens: an area of intense heat from the fire causes an eddy of wind that spins and tilts vertically. This creates a vortex which sucks the fire into it, and then all it takes is the right kind of instability in the atmosphere.
Greg Carbin of the National Oceanic and Atmospheric Administration (NOAA) Storm Prediction Center explained this instability in depth:
The atmosphere has ambient rotations in it that occur in a horizontal plane. As you go above the ground, the air and wind increases with height, which sets up horizontal air tubes that you can’t see — the air is rolling horizontally. But when you introduce a fire into the environment, things change. The fire is transferring mass and pulling air in around it. The heated air is rising vertically so the fire is both removing air where it’s burning and pulling air in. It entrains ambient horizontal tubes of the atmosphere into it.
Very large fire whirls are not common, although they do occur. But smaller ones like this one are more frequent, and are a sign to firefighters that the environment around the fire is unstable.
Often when farmers burn their fields, Sullens says, they will try to light a fire quickly in a corner to force the fire to burn to the center of the field — minimizing fence damage and the potential spread of the fire. When a fire is started it draws in air from the outside, which creates that vertical push that lets flames stand. When a farmer lights the fire quickly, it creates a lot of heat into the center of the field and a lot of vertical movement — prime conditions for the fire whirl.
"I would say it’s not uncommon to see whirls in that scenario," Sullens says.
The fire whirl was first officially documented by scientists in Canberra, Australia in 2003. Researchers confirmed the phenomenon from analysis of evidence seen in the Canberra fires in January 2003.
The fire whirl was described as "pyro-tornadogenesis" by the lead researcher and Australian Capital Territory (ACT) Emergency Services authority, Rick McRae. His findings and research were published in Natural Hazards.