Descriptionary

hurricane a massive, cyclonic storm system that forms in tropical waters and, rotating clockwise in the Southern Hemisphere and counterclockwise in the Northern Hemisphere, produces torrential rain, high waves, sustained winds reaching 155 miles per hour (249 km/hr) or more, and dangerous storm surges that can flood entire cities. Hurricanes feed on heat from rising, moist air and lose their strength as they travel over land. Hurricanes spawn thunderstorms and can even produce tornadoes. Also known as a cyclone, tropical cyclone, or a typhoon.

jet stream strong winds beginning at 30,000 feet and increasing in velocity (up to 200 miles per hour or more) at 35,000 to 40,000 feet.

khamsin hot, dry southerly wind in Egypt in spring.

landspout slang for a characteristically smooth and tubular tornado, similar to a waterspout in appear­ance. Unlike normal land tornadoes, they form without mesocyclones and are generally smaller and weaker. Also known as a dust-tube tornado.

macroburst a powerful downdraft that is at least 2.5 miles (4 km) across, lasts from five to 20 minutes, and can cause as much destruction as an F3 tornado.

mesocyclone difficult to see with the naked eye and often only perceived on radar, an area of strong rota­tion, generally from 2 to 6 miles in diameter, and from which tornadoes may be spawned.

microburst a powerful downdraft less than 2.5 miles (4 km) wide that lasts less than five minutes and can create dangerous wind shear situations, a hazard to aircraft.

mistral stormy, cold northerly wind that blows down from the mountains along the Mediterranean coast.

monsoon seasonal wind that blows along the Asian coast of the Pacific from the Indian Ocean; the sum­mer monsoon is characterized by heavy rains.

multiple vortex tornado any tornadic storm having two or more funnel or debris clouds appearing simul­taneously and usually revolving around one another.

nor'easter a powerful storm that brings heavy snow and sometimes hurricane-force winds along the north­east coast of the United States and Canada.

rope a thin, tubelike tornado that is weakening and dissipating.

roping out slang for the narrowing of a funnel cloud as a tornado weakens and dissipates.

Saffir-Simpson Hurricane Wind Scale a measure of a hurricane's strength, given on a scale of 0 to 5, and used to predict the level of damage and danger to be expected as the storm passes. Category 1 has wind speeds of 74-96 miles per hour (119-153 km/hr) and a storm surge 4 to 5 feet above normal, while Cat­egory 5 has wind speeds greater than 155 miles per hour (249 km/hr), with a storm surge 18 feet (5 m) above normal.

satellite tornado any smaller, weaker tornado revolving around a larger one.

shamal a northeast wind of Mesopotamia and the Persian Gulf.

simoon scorching hot, dry wind of Asiatic and Afri­can deserts.

sirocco warm winds blowing from northern Africa to the Mediterranean area.

snow devil a waterspout that forms under a snow squall.

squall a sudden violent burst of wind, usually accompanied by rain.

stovepipe see wedge.

tehuantepecer powerful northerly wind of the Pacific off southern Mexico and northern Central America, occurring during the cold season.

tornado an extremely dangerous spinning column of air spawned from a thunderstorm, especially a supercell. Most tornadoes form when a layer of cold, dry air overlies a layer of warm, moist air. As the ground heats up during the day, the moist air rises, forming thunderstorms. Above and below the storms, opposing winds create wind shear, rolling and spin­ning the rising air, which can then rotate into a tor­nado. Tornados can create winds that whirl at 300 miles per hour (500 km/hr), strong enough to com­pletely flatten entire towns.

tornado alley in the United States, a broad, flat area from west Texas to North Dakota, where dry, cold air from Canada and the Rockies sweeps down and meets with warm, moist air from the Gulf of Mexico, resulting in the creation of more tornadoes than any other location in the world, especially in the month of May.

trade wind a consistent wind of 10 to 15 miles per hour.

tropical depression a cyclonic storm forming in tropical regions and not quite achieving hurricane status, with sustained winds of less than 39 miles per hour (62 km/hr). Tropical depressions sometimes evolve into hurricanes.

veering wind a wind that gradually shifts clockwise through the compass; the opposite of a backing wind.

waterspout a tornado, which may or may not be associated with a mesocyclone, that appears over a body of water, characterized by a vortex made up of water. The most typical waterspout is unassociated with a mesocyclone and is generally weaker than most other types.