How Does a Tornado Form?


Written by Kennedy Allen in Science
Viewed by 37 readers since 07-28-2009

A tornado is defined as a localized and violently destructive windstorm occurring over land. It is characterized by a funnel-shaped cloud extending toward the ground. Sometimes tornadoes are visible, although they have no specific color. The grey or brown hue often associated with a tornado is made up of the dust, dirt and debris collected by this very dangerous meteorological threat. Where and how does a tornado form?

Tornadoes form in all places of the world. No area or continent is completely free of the possibility. However, a tornado occurrence is most common in the United States. It is a myth that places near rivers, lakes or mountains are safe. Waterspouts are weak tornadoes that form over warm water with a cold storm, and these can make the jump onto land where they become as destructive as tornadoes that formed there originally. Expected tornado season goes from early spring to summer, although the waterspouts that eventually turn into a destructive land tornado are found in late fall and winter.

The formation of a tornado begins while a thunderstorm develops. The circumstances that cause thunderstorms are unstable atmospheric conditions, meaning that the temperature in the atmosphere decreases rapidly with height. Low level moisture also plays a part. If the air below is warm, and there is a cold front coming in from another direction, this causes the wind direction to suddenly change and increase in speed.

When a cold front meets the warm air below, it creates an invisible horizontal spinning effect in the lower atmosphere. This vortex is then pulled up into vertical position by the cooler air in the higher parts of the atmosphere, searching for more moisture. This wind tunnel now picks up speed and power as it joins the cumulus cloud of the thunderstorm, and results in a tornado.

The quickness with which a tornado forms is where the real danger lies. Also, while there are now systems implemented to send out tornado warnings to communities, they are not always fast or accurate enough. Doppler radars are in place to track air movement towards and away from the radar, so when increasing rotation is detected, a warning is issued.

While most tornado formations are of the weaker variety, this does not mean their destruction is. Weak category tornados, which make up about 69% of all tornado activity, have 110 mph winds and a lifetime of about 10 minutes. That is more than enough time for the tornado to wreak complete havoc on a community. A strong category tornado can have winds up to 205 mph and can last for about 20 minutes. Then there is the violent tornado with wind speeds capable of 300+ mph and can last for an hour or more. The horrendous after effects of said meteorological disturbances are horrendous.

A tornado is probably one of the most dangerous and damage inducing natural disasters in the world. A tornado can be so strong they have been known to drive a piece of straw through a solid tree trunk!


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