Tornado

Lore & Background

The word tornado comes from the Spanish (meaning 'thunderstorm', past participle of tronar 'to thunder', itself in turn from the Latin tonāre 'to thunder'). The metathesis of the r and o in the English spelling was influenced by the Spanish tornado (past participle of tornar 'to twist, turn', from Latin tornō 'to turn'). A linguistically related convective wind phenomenon, that unlike the relatively small concentrated area of a tornado, is the widespread, straight-line derecho.

Reader's Guide

Most tornadoes have wind speeds less than 110 mph, are about 250 ft across, and travel several kilometers before dissipating. The most extreme tornadoes can attain wind speeds of more than 300 mph, can be more than 2 mi in diameter, and can stay on the ground for more than 100 km. Types of tornadoes include the multiple-vortex tornado, landspout, and waterspout. Tornadoes can be detected before or as they occur through the use of pulse-Doppler radar by recognizing patterns in velocity and reflectivity data, such as hook echoes or debris balls, as well as through the efforts of storm spotters.

Did You Know?

• Tornadoes most commonly occur in North America, particularly in central and southeastern regions of the United States colloquially known as Tornado Alley.
• The Fujita scale rates tornadoes by damage caused and has been replaced in some countries by the updated Enhanced Fujita Scale.
• A tornado is not necessarily visible; however, the intense low pressure caused by the high wind speeds and rapid rotation usually cause water vapor in the air to condense into cloud droplets due to adiabatic cooling.