Dramatic video of a fire tornado emerged from the Woolsey Fire in California over the weekend. The blaze had killed two people, destroyed more than 400 structures and charred more than 96,000 acres by Tuesday morning. The video, which shows a rapidly rotating funnel of flames, illustrates how devastating this wildfire has been to the communities around Thousand Oaks and Malibu.

The vortex spun up in the western suburbs of Malibu along the coast Friday morning. It snapped power lines and lofted debris hundreds of feet into the air. It had the look and power of a tornado, but was it technically a twister?

In most cases, firewhirls — small spouts of spinning air akin in strength to a dust devil — can be classified as tornadoes. However, Friday’s episode may walk the lines of what could be classified as a true tornado.

The National Weather Service defines a tornado as “a violently rotating column of air, usually pendant to a cumulonimbus, with circulation reaching the ground.”

The rapacious winds were probably 80 or 90 mph, based on the debris and damage shown in the video. The fire’s heat carried stormlike plumes of ash towering to 18,000 feet, with updrafts snaking high into the sky. But the circulation appears to be shallow. Looking at the strongest rotational signature of the day (possibly responsible for spawning this twister), it extends to about 4,000 feet — vs. 20,000 feet or more for a traditional tornado.


A 3-D radar image of the fire tornado near Malibu on Nov. 9. (Matthew Cappucci)

The rotation — which showed up on radar at a strength commensurate with most EF-0 or EF-1 tornadoes — was anticyclonic, or clockwise. Even though that’s not evidence the whirl didn’t come from a storm (which can rotate in either direction, though less commonly clockwise), it suggests the rotation developed near the ground, rather than being rooted in the clouds.

In the case of the Carr Fire tornado in July, the entire storm cloud was rotating, and it behaved like a supercell thunderstorm. In Malibu on Friday, that wasn’t the case.

The vortex probably developed in response to local forces. A swirl that started weak probably stretched high into the air and strengthened, which would make it the equivalent of a landspout. That’s the closest cousin of a tornado. Regardless, it was powerful enough to whip leaves, trees and building supplies into its circulation.

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