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How Is a Tornado Formed & How Does It Change?

Tornadoes are violently rotating columns of air that are encountered mainly in the United States, where they develop during spring and summer. These terribly destructive forces of nature occur principally east of the Rocky Mountains. The path of a tornado can extend for 50 miles and can be one mile wide. The most destructive tornadoes move with wind speeds of 250 miles per hour. Approximately 800 tornadoes are reported annually. According to the National Weather Service, a tornado in Oklahoma once transported a motel sign 30 miles to Arkansas.

Weather Patterns
- Thunderstorms, which develop in the moist and warm air that is found in front of eastward-moving cold fronts, produce tornadoes. The tornadoes that form in winter and early spring are normally associated with powerful frontal systems that have their origins in the Central states before moving east. It is not uncommon for large outbreaks of tornadoes to occur when these weather patterns are present. It is typical for thunderstorms that originate in the Central Plains during spring to form along a dry line, where dry, hot air from the west meets moist, warm air from the east. In these cases, thunderstorms and tornadoes develop as the dry line travels eastwards.
Storm Center
- Thunderstorms typically occur in the Texas panhandle and in the southern High Plains, when low-lying air flows upwards. Thunderstorms will occur at this time if other conditions, such as an increase in the wind, are also present. These storms encourage the formation of tornadoes. Tornadoes sometimes arrive with tropical hurricanes and storms that travel towards the coast. These tornadoes are visible ahead of and to the right of the storm center as it reaches shore.
Spinning Effect
- Changes in the wind direction, with an accompanying change in height and speed, cause a horizontal spinning condition in the atmosphere. As air rises within the updraft of this storm, it affects the air that is already rotating and causes it to shift from a horizontal to a vertical position. The resulting air mass, which continues to rotate, can be 2 to 6 miles wide. The most violent tornadoes develop within this rotating air mass. Tornadoes normally occur between 3 and 9 p.m. but can develop at any time, whether day or night.
Short Lifespan
- Tornadoes are transparent, but become visible as dust gathers and water from the accompanying storm condenses. The well-known funnel shape of a tornado can grow to approximately 660 feet in diameter. These violent columns of air can travel between 10 and 70 miles per hour, but normally do not get too far. Most tornadoes do not move more than six miles before they burn themselves out. About two percent of all tornadoes are termed violent, but these frequently travel for more than an hour and cause 70 percent of all fatalities.

Nature