
Since Tuesday, January 7, the flames have shown no mercy to residents and firefighters alike, claiming not only human lives but countless material damages. While some fires are now fully contained, the one in Pacific Palisades that sparked the tragedy remains highly active. So much so that yesterday, we witnessed a chilling phenomenon: a fire tornado.
What’s a fire tornado?
A fire vortex, also known as a “fire tornado”, is a rare phenomenon in which fire, under certain conditions dependent on air temperature and currents, gains vertical vorticity and forms a vortex or a vertical column of air similar to a tornado.
According to information collected by the Library of Congress, the U.S. Forest Service defines a fire whirl as a spinning vortex column of rising hot air and gases from a fire, carrying smoke, debris, and flames. Fire whirls can vary in size, ranging from less than one foot to over 500 feet in diameter.
Not all fire whirls are considered fire tornadoes, but some scientists today classify certain extreme occurrences as fire tornadoes. They are also sometimes called firenadoes.
How are fire tornadoes formed?
SkyBrary, a portal dedicated to aviation safety in general, explains that a fire whirl is made up of a burning core and a rotating column of air, with temperatures that can reach up to 1,090 °C. These whirls typically form when a wildfire, or more intensely, a firestorm, generates its own wind, creating large spinning vortices.
The biggest fire whirls usually develop from wildfires when warm updrafts and air convergence are present. They typically range from 10 to 50 meters tall, a few meters wide, and last just a few minutes. However, some can exceed 1 kilometer in height, with winds over 200 km/h (120 mph), lasting more than 20 minutes.
Fire whirls are powerful enough to uproot trees over 15 meters tall and can help spread wildfires by carrying burning debris like tree bark, which is then blown to new areas by stronger winds.
Types of fire tornadoes
There are three main types of fire tornadoes, categorized based on the nature of the whirl:
- Type 1: Stable and positioned directly over the burning area.
- Type 2: Stable or transient, occurring downwind of the burning area.
- Type 3: Steady or transient, located over an open area next to an uneven burning zone with wind.
The understanding of how Type 3 fire whirls form is still incomplete. For instance, Type 3 whirls have been seen forming over water, burning with a blue flame that indicates soot-free combustion, a phenomenon known as the blue whirl.
How common are fire tornadoes?
Fire tornadoes are rare and extreme events that don’t happen frequently. However, they are often observed during large wildfires, like the current one in Pacific Palisades.
Two notable and recent examples include an event during August 15, 2020, when the U.S. National Weather Service issued its first-ever tornado warning for a pyrocumulonimbus generated by a wildfire near Loyalton, which had the potential to produce a fire tornado. Another example is the one on July 26, 2018, when the massive Carr Fire tornado struck Redding. Both incidents occurred in California.