What is a Tornado? |
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A tornado is a violent rotating column of air extending from a thunderstorm to the ground.
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The most violent tornadoes are capable of tremendous destruction with wind speed of up to 300 mph.
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The word tornado comes from Spanish language and means to twist or turn.
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A tornado is a whirlwind produced by atmospheric conditions, mainly extremely low pressure, during a severe thunderstorm. Tornadoes usually turn counterclockwise.
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They appear as funnel shaped columns of violently rotating winds that reach down from a storm and touch the ground.
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Although a tornado is not always visible to the eye, tornadic conditions can still be picked up on radar, or the tornado may become visible once debris and dirt are pulled into it.
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Fujita Scale |
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The Fujita Scale measures the strength or intensity of tornadoes and uses five categories to determine how damaging each storm is.
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Watch this Video |
Formation of Tornadoes |
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Most tornadoes form from thunderstorms.
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When two air masses like warm, moist air from the Gulf of Mexico and cool, dry air from Canada meet, they create instability in the atmosphere.
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A change in wind direction and an increase in wind speed with increasing height create an invisible, horizontal spinning effect in the lower atmosphere.
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Near the ground, there's a layer of warm, humid air and strong south winds. In the upper atmosphere, we'll find colder air and strong west or southwest winds.
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The air near the surface is much less dense than the cold, dry air aloft. This condition is called instability.
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It means that if the warm, moist air can be given an initial push to move upwards, the air will keep on rising, sending moisture and energy to form a tornado's parent thunderstorm.
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When a thunderstorm high in the atmosphere moves east and begins to lift the layers, it begins to build severe thunderstorms that spawn tornadoes.
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As it lifts it removes the cap, setting the stage for explosive thunderstorms to develop as strong updrafts form.
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If the rising air encounters wind shear, it may cause the updraft to begin rotating, and a tornado occurs.
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A Funnel Cloud |
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A funnel cloud is a rotating cone-shaped column of air extending downward from the base of a thunderstorm, but not touching the ground.
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Tornadoes can appear as a traditional funnel shape, or in a slender rope-like form.
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Some have a churning, smoky look to them, and other contain "multiple vortices", which are small, individual tornadoes rotating around a common center.
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Even others may be nearly invisible, with only swirling dust or debris at ground levels as the only indication of the tornado's presence.
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Losses due to Tornado |
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Tornadoes can happen at any time of the year and at any time of the day.
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In the southern states, peak tornado season is from March through May.
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Peak times for tornadoes in the northern states are during the summer.
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A few southern states have a second peak time for tornado outbreaks in the fall and can cause major damages.
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