Fire tornadoes form when combustible gases ignite in windy conditions. According to the Mother Nature Network, most fire tornadoes spawn from wildfires. The center of a fire tornado is a column of flaming gas up to 9 feet in diameter. A whirling column of fresh air circulates around the fiery core, feeding it fresh oxygen and sustaining the blaze.
About.com expert Rachelle Oblack explains that fire tornadoes are most likely to form when ambient wind speeds are mild. Once the tornado forms, however, its winds gain speed. Although most fire tornadoes are smaller than tornadoes, they are dangerous and capable of inflicting fire and wind damage. According to Fox6Now.com, fire tornado winds often equal those of mid-size tornadoes and are sufficiently powerful to knock down small trees, destroy power lines and damage buildings. Items touched by the flame column frequently burst into flames and become secondary sources of fire damage.
Fire tornadoes fall into one of three categories. Type One fire tornadoes have an obvious fire source and do not depart from it. Type Two fire tornadoes are slightly mobile and travel downwind from their source. Some do not move at all and appear directly downwind of their source, which is usually a wildfire. Fire tornadoes classified as Type Three have powerful winds, are highly mobile and travel through open areas. These are the most dangerous fire tornadoes because of their speed and ability to spread fire throughout grasslands, wooded areas and housing developments.