Fire Tornado A fire tornado or fire whirl is just like a tornado but made of fire. email to friend
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When you picture a tornado, most of us imagine a whirling column of air poking down from the clouds. But this tornado-like effect is not limited to just the air. A fire tornado or fire whirl is just like a tornado but it's made of fire. As the heated air from the fire rises, strong air currents (often whipping through the trees) cause the air molecules to spin (often referred to as angular or rotational momentum) which shapes the flame into the shape of a tornado.

Materials

Lazy Susan (rotating tray)
Metal screen - the size will depend on the size of your Lazy Susan
Wire or staples
Glass or metal dish
Pieces of sponge
Lighter fluid
Safety glasses
Fire extinguisher

Experiment
Video

ADULT SUPERVISION REQUIRED! This demonstration write-up is provided for educational purposes only and should only be performed by properly trained science demonstrators.

Roll the wire screen into a cylinder about the diameter of the Lazy Susan. Fasten the ends of the cylinder using wire or staples. Find a way to temporarily secure the screen to the Lazy Susan so that the screen does not fall over when the tray spins. You'll want to be able to quickly remove the screen in order to extinguish the fire.
Place the glass or metal dish in the middle of the Lazy Susan (tray). It is best to find a small square of fire resistant material (a small plate or saucer) for the dish to sit on so as not to damage the Lazy Susan.
Cut up several pieces of sponge and place them in the dish. Soak the pieces in lighter fluid.
Put on your safety glasses. Light the fire but leave the mesh screen off of the Lazy Susan for now and gently spin the tray. Notice how the fire spins, but no tornado effect is created. Extinguish the fire by covering it with a small plate.
Re-ignite the fire and place the wire screen cylinder on the Lazy Susan. Gently spin the tray and watch as the fire twists into the shape of a tornado. The fire tornado will rise as the tray spins faster and faster.
Remove the screen cylinder from the tray and extinguish the fire.

How does it work?

The fire tornado phenomenon occurs when certain conditions (depending on air temperature and currents) acquire a vertical vorticity and form a whirl, or a tornado-like effect. Fire tornadoes may be whirlwinds separated from the flames, either within the burn area or outside it.

The reason for the flame to be shaped like a tornado is the direction from which the air feeding the flame has to come. Because of the rotating screen around the flame, the air molecules are given an initial spin (called angular momentum or rotational momentum). The rotating air molecules collide with the hot air rising from the fire and the flame twists into the shape of a tornado.

The rotating metal screen is a simple way to illustrate the way winds whip through the trees in the forest and collide with the warm updraft from the wildfire. These so-called fire tornadoes can measure 30-50 meters tall (100-200 feet).

Most of the largest fire tornadoes or fire whirls are spawned from wildfires. They occur when a warm updraft and convergence from the wildfire are present. They are usually 10-50 meters (30-200 ft) tall and only a few meters wide, but some of the largest fire tornadoes have measured more than a kilometer in height. It's easy to see how the rising column of twisting fire can dance along the tree tops, causing the fire to spread easily.