Atmosphere And Weather

How Tornadoes Form



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Tornadoes are formed when a cool dry air mass collides with a warm moist air mass. As the warm layer of air forces its way up through the cool layer of air it creates a powerful and unique updraft. If the collision of these polar air masses continues over an extended period of time the atmosphere becomes increasingly unstable and a series of unique and specific weather events occur that foster the formation of deadly tornadoes.

The continual collision of opposing updrafts and down drafts creates a unique horizontal wind funnel which can quickly be forced into a vertical position. The result is a dangerous vortex that is referred to as a tornado.

Tornadoes are often associated with severe thunderstorms referred to as supercell thunderstorms. A supercell thunderstorm is no ordinary storm. It is a long lasting mega storm with continuous and steady growth. When a supercell thunderstorm experiences an equally strong and simultaneous collision of unstable updrafts and downdrafts a massive funnel of rotating air will result.

As the wind speed increases and moves in varying directions the updraft forces the funnel to rise from a horizontal to vertical or angular position. The funnel will continue to rotate at incredible speeds, generating self sustaining power and gaining momentum. Eventually, the funnel extends in length stretching from the cloud base of the thunderstorm to the ground below. When one end of the funnel is connected to the cloud base and the other end of the funnel makes contact with the ground it becomes classified as a tornado.

As a tornado gains in speed and strength it picks up debris, water, and foliage making it a visible vortex moving across the ground. Tornadoes vary greatly in both size and strength but are on average 1 mile wide with the rotating winds that can reach up to 300 miles per hour. A tornado can occur quickly without advanced notice and travel unpredictably across the land at a speed of 30-70 mph. They have been known to move forward several miles and then backtrack in a random fashion. The average lifespan of a tornado is approximately 10 minutes. However, the lifespan can vary anywhere between 3 seconds to over one hour in duration.

In the United States tornados most commonly occur between the months of March and May when the cold dry air from the Canadian Rockies and the warm moist air from the Gulf of Mexico move steadily towards one another eventually coming into contact. The southern states are most commonly affected with numerous tornado watches occurring on a regular basis during tornado season.

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