Tornado

Tornado, violent whirlwind cloud of small diameter, extending downward from a convective cloud in a severe thunderstorm, generally funnelshaped. Air rises rapidly in the outer region of the funnel, but descends in its core, which is at very low pressure. The funnel is visible owing to the formation of cloud droplets by expansional cooling in this low-pressure region. Very high winds spiral in toward the core. There is almost total devastation and often loss of life in the path of a tornado, which may move at speeds up to 656 ft (200 m) per sec. Though generally rare, tornadoes occur worldwide, especially in the United States and Australia in spring and early summer.