Don Sweeney, Vincent Moleski
The Charlotte Observer
A dramatic U.S. Forest Service video shows a firenado form in the 10,000-acre Tennant Fire in Siskiyou County, California.
Smoke and flames whirl behind firefighting equipment in a grassy field in the June 29 video, posted to Twitter by the National Weather Service.
The weather service office in Medford, Oregon, picked up the firenado on radar, another Twitter post shows.
The Tennant Fire has scorched 10,614 acres in the Klamath National Forest near Yreka and the Oregon border, the U.S. Forest Service reported. The wildfire, which began June 28, is 71% contained as of Wednesday and crews are continuing mop-up efforts.
How do firenadoes form?
A fire-fueled thunderstorm cloud can form on top of a wildfire’s smoke plume, allowing the plume to grow vertically very quickly, Neil Lareau, a scientist and professor at the University of Nevada, Reno, told The Sacramento Bee in 2018.
When the plumes grow, a wind condition called shear happens near the ground. Shear is a wind pattern in which wind is blowing in two opposite directions very close to each other – Lareau compared it to a busy freeway with a center divider.
The wind blowing in opposite directions is what formed the tornado’s spin, Lareau said. He said it’s similar to how a paddle wheel, placed in the center divider of the busy freeway, would begin to spin rapidly.
©2021 The Charlotte Observer. Visit charlotteobserver.com. Distributed by Tribune Content Agency, LLC.