1
How a tornado is formed
Although no two tornadoes are the same, they need certain
conditions to form - particularly intense or unseasonable heat.
A storm quickly develops - there may be rain, thunder
and lightning.
Tornadoes are among the most violent storms on Earth,
with the potential to cause very serious damage.
As the ground temperature increases, moist air heats and
starts to rise.
2
How a tornado is formed
When the warm, moist air meets cold dry air, it explodes
upwards, puncturing the layer above. A thunder cloud may
begin to build.
A storm quickly develops - there may be rain, thunder
and lightning.
3
How a tornado is formed
Upward movement of air can become very rapid. Winds from
different directions cause it to rotate.
A visible cone or funnel drops out of the cloud towards
the ground.
4
How a tornado is formed
The vortex of winds varies in size and shape, and can be
hundreds of metres wide. A tornado can last from several
seconds to more than an hour and may travel dozens
of miles.
5
How a tornado is formed
Winds within the tornado may be so fast they cannot be
properly measured. Instead, the Fujita damage scale is used
to estimate speed.
F0 (0-73mph) - Light damage: Some damage to chimneys.
Branches broken from trees and some trees blown over.
F1 (73-112mph) - Moderate damage:
Moving cars blown off
roads, mobile homes overturned, or pushed off
their foundations.
F2 (113-157mph) - Considerable damage: Mobile homes
demolished, large trees snapped or uprooted, cars lifted off
the ground.
F3 (158-206mph) - Severe damage: Trains overturned, most
trees uprooted, heavy cars thrown, walls of homes destroyed.
F4 (207-260mph) - Devastating damage:
Well constructed
buildings destroyed, large objects thrown.
F5 (261-318mph) - Incredible damage: Cars thrown more
than 100 metres, strong buildings swept away.