Tornadoes are powerful and destructive phenomena created during severe thunderstorms. Tornadoes are more common in the United States, and in the United States they are common in an area called Tornado Alley. Every year, tornadoes devastate countryside, towns and even cities. The deadliest tornado in U.S. history swept through three states, destroyed 15,000 homes and killed nearly 700 people. There are only a couple of people on record who claim to have been and seen the center of a tornado and experienced it. Tornadoes also have their own rating scale, based on wind and damage level. Tornadoes are powerful vortices created during thunderstorms, are common in the United States, have their own rating scale, have been seen indoors only a few times, have the potential to demolish cities and can take lives. A tornado is a type of vortex. A vortex is essentially a rotating funnel that forms from downdrafts that drag a medium, such as air or water, downward. Tornadoes are vortices, and vortices happen in everyday life, even if you don't live in Tornado Alley. An everyday example of a vortex is when you flush a bathtub or sink drain and a rotating vortex forms. This is a whirlwind. Tornadoes occur on the same principle, but with air in thunderstorms instead of water in the bathtub. A tornado occurs during very powerful thunderstorms and usually occurs in a supercell. A supercell is a type of storm that already has a rotation inside it, called a mesocycle. A tornado begins to form when a descending air current drags the mesocycle toward the ground. A funnel begins to form and when it finally hits the ground, it officially becomes a tornado. When warm, moist air (a tornado's fuel) is drawn into the tornado, it matures... middle of paper... vice. National Weather Service Storm Prediction Center. March 4,2014 .Tega Jessa. Universe today. WordPress. March 4, 2014< http://www.universetoday.com/52055/how-tornadoes-are-formed/ >.Windows to the Universe. National Association of Earth Science Teachers. March 4, 2014. Charles W. Bryant. How things work. HowStuffWorks, Inc; Discovery. 4 March 2014 Windows on the Universe. National Association of Earth Science Teachers. March 4, 2014. John Galvin. Popular mechanics. Hearst Communication, Inc. March 4, 2014 .