| Cyclones
are large revolving tropical storms caused by winds
blowing around a central area of low atmospheric
pressure. In the southern hemisphere these tropical
storms are called cyclones and rotate in a clockwise
direction, while in the northern hemisphere cyclones
are called hurricanes or typhoons and rotate in an
anti-clockwise direction.
Cyclones develop over
warm waters in the tropical regions of the oceans
where areas of very low pressure are created by air
being heated by the sun. This causes the air to rise
very rapidly and becomes saturated with moisture that
condenses into large thunderclouds.
Cool air rushes in to
fill the void and is bent inwards and spirals upwards
with a great force caused by the coriolis effect of
the earth spinning on its axis. The result of all this
is - the winds begin to rotate faster and form a large
rotating weather system, in some cases up to several
thousand km in diameter. In the centre of this system
there usually is a cloudless, calm area called
"The Eye", with no rain and very light
winds.
|
Tropical
cyclone "John" December 14th 1999 off the
coast of Western Australia.
A
map showing the tracks of cyclones in Australia over the past 70
years. (~400 have crossed the Australian coast in this
period).
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