Tornadoes are violent
windstorms characterized by a twisting,
funnel-shaped cloud. Tornado is a small-diameter
column of violently rotating air developed within a
convective cloud and in contact with the ground.
Tornadoes occur most often in association with
thunderstorms during the spring and summer in the
mid-latitudes of both the Northern and Southern
Hemispheres. These whirling atmospheric vortices can
generate the strongest winds known on Earth: wind
speeds in the range of 500 km (300 miles) per hour
have been estimated. When winds of this magnitude
strike a populated area, they can cause deadly destruction and great loss of life, mainly through
injuries from flying debris and collapsing
structures. Most tornadoes, however, are
comparatively weak events that occur in sparsely
populated areas and cause minor damage.
Watch Tornado Video
How Tornado
forms
Before thunderstorms
develop, a change in wind direction and an
increase in wind speed with increasing
height creates an invisible, horizontal
spinning effect in the lower atmosphere.
Rising air within the thunderstorm updraft
tilts the rotating air from horizontal to
vertical.
A tornado
usually begins in a severe thunderstorm
called a supercell. The same property that
keeps the storm going also produces most
tornadoes. The wind coming into the storm
starts to swirl and forms a funnel. The air
in the funnel spins faster and faster and
creates a very low pressure area which sucks
more air into it as tornado grows in size.
Warning
signs include:
Severe thunderstorms, with frequent thunder
and lightning.
An extremely dark sky, sometimes highlighted
by green or yellow clouds.
A rumbling sound, such as a freight train
might make, or a whistling sound such as a
jet aircraft might make. A funnel cloud at
the rear base of a thundercloud, often
behind a curtain of heavy rain or hail.
May to September are prime tornado months.
Tornadoes usually hit in the afternoon and
early evening but they have been known to
strike at night too.
What to do Before a Tornado
Be alert to the weather conditions
and frequently check weather
stations for updates.
Look for approaching storms.
Look for the following danger
signs:
Dark, often greenish sky.
Large hail
A
large, dark, low-lying cloud
(particularly if rotating)
Loud roar, similar to a freight
train.
If
you see approaching storms or
any of the danger signs, be
prepared to take shelter
immediately.
For
more info on how to save yourself
from tornadoes read
Tornado
Tips
