A fire tornado, also known as a fire whirl or fire devil, is a spinning column of fire, smoke, and ash. These whirlwinds incorporate flames and burning debris, creating a vortex. While they resemble meteorological tornadoes, their formation processes are distinct. They vary in size, from small, fleeting occurrences to massive, towering columns.
Essential Precursors
Fire tornado formation requires a substantial heat source, typically a large fire like a wildfire. This intense heat generates powerful updrafts. A plentiful supply of combustible material, or fuel, must be present to sustain the fire’s intensity. Oxygen is the third component, feeding combustion to achieve the necessary intensity.
The Core Formation Process
The intense heat from the fire warms the air above it, making it less dense and buoyant. This superheated air rises rapidly, forming a strong updraft. Cooler, denser air from surrounding areas is drawn inward towards the fire’s base to replace the rising air.
If there is slight pre-existing rotation or wind shear, this incoming air begins to spin as it converges. As the spinning column narrows and stretches vertically due to the updraft, its rotational speed increases, like an ice skater pulling arms inward. The rotating column then draws in flames, ash, and burning debris, making the vortex visible.
Influential Environmental Factors
Environmental conditions influence a fire tornado’s development and persistence. Wind shear, a change in wind speed or direction with height, can introduce or strengthen initial rotation. Topography, such as valleys or urban structures, can channel winds and create localized eddies, promoting rotational forces.
Atmospheric instability, where air continues to rise once pushed upward, supports sustained updrafts. A sustained heat source is also necessary for the fire to maintain intensity and feed the updraft.
Distinguishing Features
Fire tornadoes are driven by the fire’s intense heat and updrafts, unlike meteorological tornadoes which form from atmospheric pressure differences and wind shear within thunderstorms. Fire tornadoes do not require a cloud or storm system, originating directly from a ground-level fire.
They are generally smaller and shorter-lived than large meteorological tornadoes. While locally destructive, reaching heights of over a thousand feet and wind speeds exceeding 100 mph, they usually dissipate within minutes to an hour. Their core can reach extreme temperatures, sometimes over 2,000°F (1,093°C).