References for Greek and Latin
written by Susanne M Hoffmann
Gradients in the heating and instabilities of the air flow causing upstreams of air accompanied by strong forces of wind that carry somewhat heavy material with it. The interplay of the flow and the upstream cause spiral motion of the air and the spiraling mixture of air, dust and water forms long and strong trunks.
An observer on Earth realizes the whirling structure of this wind only from small distances when the trajectories of material become obvious.
Satellite pictures from space show whirlwinds clearly as huge whirls with a central spot of calm air: the so-called "eye".