Tornadoes are violent storms that strike as a powerful rotating mixture of wind and thunderstorm clouds, extending from the clouds to the ground in a funnel shape. They are known to be the most powerful and destructive atmospheric generated phenomena (wind systems), and are very common in the USA, particularly from the middle belt extending to the east coast. They come in all shapes and sizes.
The largest and most destructive tornadoes are released by incredibly strong thunderstorms known as supercells. These supercells contain a deep and persistent rotating updraft known as mesocyclone. Supercell thunderstorms can last for several hours only and only if the environment is favourable.
Generally, most tornadoes are formed during supercell thunderstorms. However, not all supercell thunderstorms produce tornadoes. If we talk about extreme cases, supercells can generate tornadoes that can easily reach 2 miles wide with winds over 483 kmph.
For a tornado-producing supercell to develop initially, moisture, instability, vertical forcing and wind shear are the main four ingredients needed to be present in the atmosphere.
On the contrary, not all the four ingredients are needed for a thunderstorm to develop. However, in the absence of any of these ingredients, a storm may not reach severe levels.
Usually these four ingredients come together during spring in the central and southeastern United States. That is how the nicknames of Tornado Alley and Dixie Alley have been earned.
The risk of severe thunderstorms expands during the summer, extending northward into Canada and all the way to the east coast of the United States.
Every thunderstorm has a column of rising air, known as updraft. The stronger the updraft, the more intense a storm becomes. For the development of tornado, air needs to rotate horizontally near the ground. This rotation is caused by wind shear. When this rotating air is drawn into the updraft, it becomes titled vertically.
This is just one of several factors that play a role in tornado development.
It is believed that when the rapidly descending downdrafts are enhanced by the overall spin of the thunderstorm, tornadoes take a shape.
Image Credit: Time Magazine
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