downburst

An intense downward current of air originating within a cumulonimbus (storm cloud) which, upon striking the ground violently and spreading outward - in all directions - generates very strong winds with devastating consequences. Three types of downbursts have been catalogued: 1) warm downburst (heat burst), one that causes a marked warming of the air and a sharp drop in ambient humidity near the Earth's surface; 2) wet downburst, so called because it is accompanied by precipitation (thunderstorm showers). The dragging of cold air by falling raindrops and/or hailstones is the main cause generating the downward current; and 3) dry downburst, without precipitation. In this last case, the rain, snow or hail evaporates/sublimates before reaching the ground.