Tornado -an overview (description)

Description

A tornado is a type of intense rotary storm. According to the Glossary of Meteorology, a tornado is- "a violently rotating column of air, in contact with the ground, either pendant from a cumuliform cloud or underneath a cumuliform cloud, and often (but not always) visible as a funnel cloud."

The image “http://www.cimms.ou.edu/~doswell/a_tornado/Laverne.JPG” cannot be displayed, because it contains errors.

A funnel cloud, which
is a type of
condensation cloud, is
practically
funnel-shaped in
structure and extends
down from a cumuliform
cloud by a rotating
column of air towards
the ground. It may or
may not touch the
ground. If it touches
the ground it is called
a‘tornado’.The associated
rotating column of air
http://www.cimms.ou.edu is a ‘vortex’.

This diagram shows a funnel
cloud that does not touch
the ground.

Tornadoes are much stronger than dust devils, hurricanes or mid-latitude cyclonic storms. Practically it is the most violent of all the vortex storms we see in nature. Storms are marked by disturbance and strong wind in the atmosphere. When the storm accompanies thunder and lightning, it is called thunderstorm.

In a tornado, a strong up drift of air exists and the pressure remains very low at the core. So, if it is strong enough, it can suck in (up) almost everything that comes into it’s path. The tornado is not always visible but the circulation of debris around the funnel makes it visible.

                                       http://www.cimms.ou.edu
                                         A funnel cloud that is
     almost invisible.

In a small scale, tornado is the most violent atmospheric phenomenon. The vortex of a tornado is only a few hundred meters wide on an average. The wind speed inside a tornado normally ranges from 40 mph to as high as 300 mph. Speeds higher than this are actually rare. Depending on its speed, tornadoes are rated using F-scale.

Tornadoes may rotate both cyclonically or anti-cyclonically, but cyclonic rotation is most common. It can be mentioned here that if a wind swirl is counter-clockwise in the northern hemisphere and clockwise in the southern hemisphere, it is called cyclonic. But contrary to a common belief, coriolis force or earth’s rotation has no role in the direction of rotation of a tornado.