are intense low-pressure weather systems that develop in the tropics.
they begin in an area of low pressure, caused by surface heating, into which warm air is drawn in a spiralling manner.
small-scale disturbances enlarge into tropical depressions with rotating wind systems.
these may continue to grow into a much more intense and rapidly rotating system.
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conditions for them to occur
an oceanic location with sea temperatures above 27 degrees - provides contiuous source of heat to maintain rising air currents.
ocean depth of at least 70m - moisture provides latent heat, rising air causes moisture to be released by condensation - this drives the system,
location at least 5 degrees north or south of the equator in order that the coriolis force can bring about the maximum rotation of air.
low-level convergence of air in the lower atmospheric circulation system - winds have to come together near the centre of the low pressure zone.
rapid outflow of air in the upper atmospheric circulation - this pushes away the warm air, which has risen close to the centre of the storm.
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distribution
occur between latitudes of 5 and 20 degrees north and south of the equator - once generated they tend to move westwards and are at their most desructive:
caribbean sea/gulf of mexico area where they are kown as hurricanes.
western side of central america
Bay of Bengal wher they are known as cyclones
off southeast asia where they are known as typhoons
off madagascar
in northwestern australia, where they are known as willy willies.
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