Tornado formation, 3D computer artwork. Tornados develop from intense thunderstorms that begin to spin because high-level winds are blowing faster and in a different direction to low-level winds. The rotation can be enhanced by the interaction of cold and warm air currents (red and blue arrows). This forms a mesocyclone, a powerful air column that moves upward at the centre of the storm. The spin then intensifies and a rotating column of air will break through the wall cloud and hit the ground (yellow arrows). Large and powerful tornados can have wind speeds of over 200 kilometres per hour, causing immense destruction. For a series showing tornado formation, see images C001/2060 - 2063.