Gav from The Slow Mo Guys combined a mix of chemicals that burn in different colors then lit them in front of a circle of fans to create a fire tornado. The colorful plume of fire forms a surprisingly smooth gradient it rises from the barrel below. The top-down views are particularly captivating.
TheBackyardScientist shares a simple way to create a small fire tornado with no moving parts. The trick is to split the glass receptacle in half and place each half around the flame slightly off center. The wind that comes in through the gaps will create the tornado effect.