Firewhirl and Firenado (noun, “FIE-er-werl” and “FIE-er-NAY-do”)
These words describe swirling columns of air that form under hot conditions. These vortices of ash, flame and debris can arise during wildfires. Firewhirls are often small — maybe a couple of meters (around 8 feet) wide. Sometimes they stretch tens of meters off of the ground. But firewhirls don’t connect to the clouds.
Firenadoes do. These wicked twisters reach from the clouds to the ground. They are rare — only two are known to have occurred. Firenadoes form from an intense inferno. The hot air rising from a wildfire carries moisture up to the sky that helps form billowing clouds. Fluffy pyrocumulus clouds and thunderclouds called pyrocumulonimbus clouds can create the right conditions for tornadoes. When these massive updrafts start to spin, they can produce powerful winds.
The firenado that blew through Redding, Calif., in July 2018 was the strongest tornado the state had ever experienced. Scientists haven’t quite figured out what set those clouds spinning. Some researchers think that a powerful updraft may have stretched winds near the ground up to the clouds. Others suspect that updrafts began to swirl inside a supercell thunderstorm.