A Tornado Made of Fire. Bonus: Flying Tumbleweeds.

Bad Astronomy
The entire universe in blog form
March 30 2014 7:30 AM

A Vortex of Fire. Bonus: Tumbleweedocalypse.

fire tornado
I'd probably just stand there and gape at it, too.

Photo by Thomas Rogers, from the video

On March 14, 2014, just a few weeks ago, firefighters began a “controlled burn” at Rocky Mountain Arsenal, a wildlife preserve between the city of Denver and the Denver airport. This is done (generally in cooler times of the year) to prevent the buildup of weeds and other plants that can fuel much larger fires once the weather gets hotter and drier.

On that day there were shifting winds, and a sudden change in the direction of the wind created—get this—a fire tornado! I’ve written about these spectacular events before (see below), but this time it has the added bonus of hundreds of tumbleweeds caught in the vortex, producing one of the more awe-inspiring displays of natural forces at work:


Yegads! I can only imagine what it must have been like to stand there and watch this ridiculously over-the-top phenomenon unfold. I hope they all had a change of underwear.

What causes a fire tornado? Well, it’s not actually a tornado by definition, since tornadoes descend from the bottoms of clouds. A fire tornado is pretty much a dust devil with fire added. As I wrote in an earlier post about a fire tornado:

Imagine: a fire starts. As the air is heated above the fire, it rises, and the upward motion can be very strong. This leaves a lower pressure spot at the fire, and the air from outside the fire rushes in to fill the gap. The air is very turbulent, and as the inward-moving air from one side hits air coming in from the other, swirls can form. These get amplified by the constant gale of air, and rotation on a larger scale can get started and sustained. The whirlwind gets pumped by the hot air rising, and the next thing you know you've got a full-blown tornado of fire. 

In general dust devils don’t have a lot of power; the rotation is rather weak and the wind isn’t blowing terribly hard. But their strength depends in part on how quickly the warm air in the middle rises, and when there’s fire in there, well, that adds a bit of a kick to it. In this case, the wind was enough to draw in all those tumbleweeds. Mind you, tumbleweeds have evolved to be picked up by wind; that’s kinda their whole point. Still, it does make for a jaw-dropping scene!

Tip o’ the firefighter helmet to Ed Yong.

Related Posts

Phil Plait writes Slate’s Bad Astronomy blog and is an astronomer, public speaker, science evangelizer, and author of Death From the Skies!  



The Irritating Confidante

John Dickerson on Ben Bradlee’s fascinating relationship with John F. Kennedy.

My Father Invented Social Networking at a Girls’ Reform School in the 1930s

Renée Zellweger’s New Face Is Too Real

Sleater-Kinney Was Once America’s Best Rock Band

Can it be again?

The All The President’s Men Scene That Captured Ben Bradlee

Medical Examiner

Is It Better to Be a Hero Like Batman?

Or an altruist like Bruce Wayne?


Driving in Circles

The autonomous Google car may never actually happen.

The World’s Human Rights Violators Are Signatories on the World’s Human Rights Treaties

How Punctual Are Germans?

  News & Politics
Oct. 22 2014 12:44 AM We Need More Ben Bradlees His relationship with John F. Kennedy shows what’s missing from today’s Washington journalism.
Oct. 21 2014 5:57 PM Soda and Fries Have Lost Their Charm for Both Consumers and Investors
The Vault
Oct. 21 2014 2:23 PM A Data-Packed Map of American Immigration in 1903
  Double X
The XX Factor
Oct. 21 2014 3:03 PM Renée Zellweger’s New Face Is Too Real
  Slate Plus
Behind the Scenes
Oct. 21 2014 1:02 PM Where Are Slate Plus Members From? This Weird Cartogram Explains. A weird-looking cartogram of Slate Plus memberships by state.
Brow Beat
Oct. 21 2014 9:42 PM The All The President’s Men Scene That Perfectly Captured Ben Bradlee’s Genius
Oct. 21 2014 11:44 PM Driving in Circles The autonomous Google car may never actually happen.
  Health & Science
Climate Desk
Oct. 21 2014 11:53 AM Taking Research for Granted Texas Republican Lamar Smith continues his crusade against independence in science.
Sports Nut
Oct. 20 2014 5:09 PM Keepaway, on Three. Ready—Break! On his record-breaking touchdown pass, Peyton Manning couldn’t even leave the celebration to chance.