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In dealing with weather there are many types which can seriously cause damage to people and communities. Especially in the aviation we as pilot have to take into account many consideration in preparing for a flight. For instance, thunderstorms, icing levels, winds aloft, and visibility all play major factors in preparing for a flight. But there are some weather phenomena that can be extremely dangerous to fly into. Hurricanes, wind shear, and tornadoes are just some of the major threatening systems that can cause serious damage to people and places.
One of the most interesting systems is the tornado. So what is a tornado? A tornado is a violently rotating column of air, which is found below cumulonimbus clouds and is nature's most violent wind. A tornado is officially defined as an intense, rotating column of air extending from the base of a thunderstorm cloud to the ground. Wind speeds in tornadoes can vary from 72 to almost 300 mph. Fortunately, only 2 percent of all tornadoes have winds greater than 200 mph. When a tornado is seen and has not yet made contact to the surface this is what is called a funnel cloud. When a funnel cloud touches the ground, it becomes a tornado (Jack Williams, USA TODAY Information Network). Most tornado's range from 300 to 2,000 feet in diameters, but have been reported to extremes of one mile. Tornado's usually travel in a southwest to northeast direction at about 30 knots in the U.S. According to Peter F. Lester tornado's lifetime average only for a few minutes, but have been documented to last over three hours.
In the United States there is one particular place that seems to be more prominent to have tornado's form. The American Meteorology Society's Glossary of Weather and Climate defines Tornado Alley as: "The area of the United States in which tornadoes are most frequent. It encompasses the great lowland areas of the Mississippi, the Ohio, and lower Missouri River Valleys. According to USA today Depending on the time of year, the southern and northern borders of tornado alley extend from about central Texas to Nebraska and Iowa. This region is where tornadoes spin up most frequently and where most monster, mile-wide twisters roam. The question is why is this area so prime for tornado's to form? Thunderstorms thrive on lots of warm, humid air. And the rotating thunderstorms, called supercells, which spawn the biggest tornadoes, need low-level winds that shift direction and grow stronger just above the ground (USA weather). The Gulf of Mexico provides an abundance of tropical moisture blowing into the Plains on south and southeast winds. Meanwhile the higher and drier elevations of the Rockies allow a hot, dry layer of air to blow over the region from the southwest. (USA TODAY Chris Cappella USA weathers source). It's the unique combination of atmospheric "parameters" -- a large moisture supply, low-level wind shear, a drying and cooling middle atmosphere, and features such as the dryline and a convective cap -- that turn the Great Plains into a tornado alley.
The conditions responsible for the cause of tornado's are basically wind from the west and moister that comes from the Gulf of Mexico. The clash of warm and cold air helps supply the humidity and energy needed. Winds from different directions high above the ground help supply more energy and also give the air the turning motion needed for tornadoes. The center of the tornado's vortex is a low-pressure area. As air rushes into
the vortex, its pressure lowers, which cools the air. Cooling condenses water vapor in the air into the tornado's familiar funnel-shaped cloud. Although the air is rising in a tornado, the funnel itself grows from the cloud toward the ground as the tornado is forming. Tornadoes form in the air rising into a thunderstorm, in the updraft. The strongest tornadoes are often near the edge of the updraft, not far from where air is descending from the thunderstorms. (Jack Williams, USA TODAY Information Network). Some times tornado's can be mistaken for microburst. The difference between microburst and tornado's is that Air moves very rapidly upward around a tornado center. This distinguishes tornadoes from microburst, which often do tornado-like damage and are often mistaken for tornadoes. Microburst, on the other hand, features air blasting downward from thunderstorms.
Since each tornado that is sprung has its own different strength there is a scale to measure the intensity of each one. A scale called the Fujita scale that was developed by T. Theodore Fujita a professor at the University of Chicago measures the intensity of the tornado. The range of the scale starts at F0 which is a gale tornado with winds 40 to 72mph and cause damage to chimneys; breaks branches off trees; pushes over shallow-rooted trees; damages sign boards
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