Depending on air currents and temperature, the rotating vortex from which an ordinary tornado forms can suck up fire and anything burning, resulting in the phenomena you can see in these pictures.
In 1923, a fire tornado sucked up not only fire and burning embers, but also killed 38,000 people within 15 minutes.
Lightning can often be the source of the fire after it strikes something flammable like a pool of gasoline or oil storage tanks. With the right wind speeds, the fire may soon become part of a tornadic vortex that can burn or level anything in its path.
These dangerous fire tornadoes, or fire whirls, as they are sometimes called, have the power to uproot trees 49 feet tall – the equivalent in height of a five-story building. Fire tornadoes tend to be 10 to 15 meters tall and a few feet wide, though they may last only a few minutes, according to this source.
The core of the fire tornado is an invisible pocket of oxygen that feeds the eddie. At the core, there may be temperatures of at least 2,000 degrees Farenheit. Wildfires are usually the spark that allow these types of tornado to form.