Late last week the Carr Fire, the largest of 17 major wildfires currently burning across California, jumped the Sacramento River and began burning in the city of Redding. As residents evacuated, a scene out of a disaster movie unfolded: a massive tornado of smoke and fire expanded in size, reaching up to 18,000 feet high as it moved through parts of Redding for almost an hour, blowing at nearly tornado-strength speeds, reports Allie Weill at KQED. Images of the so-called firenado have haunted social media ever since.
So what, exactly, is going on in the apocalyptic scene, and what is a “firenado?” There are many names for the whirling masses of ash, dust and live flame. In general, they are known as fire whirls but are also called fire devils, fire twisters or fire tornadoes, though experts discourage that name since they are not formed in the same way as tornadoes. Tornadoes pop into existence when conditions are just right as warm moist air near the surface of the Earth rises into the cooler air above. If that updraft is set spinning by strong winds and is then tilted vertically by a thunderstorm, it can spawn a tornado.