Cyclones what is a Cyclone?

A cyclone is a system of rotating winds over a warm water area, spinning inward to a low pressure center and generally causing stormy weather.

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  Eye: The centre or eye of a tropical cyclone is at the area of lowest pressure and is characterized by little or no wind and often a cloudless sky. In severe cyclones the eye usually shows up as a circular hole in the central cloud mass.
  
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  Eye Wall: Surrounding the eye is a wall of dense convective cloud rising about 15 km into the atmosphere. This is the eye wall and is where the most violent winds and heaviest rainfall occur.
  
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  Spiral rain bands
  

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  North Atlantic
  
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  North-East Pacific
  
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  North-Central Pacific
  
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  North-West Pacific
  
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  North Indian Ocean
  
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  South-West Indian Ocean
  
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  Australian Region
  
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  Southern Pacific
  

Tropical cyclones which occur in the Atlantic region and affect the Caribbean and USA usually comprise less than 15% of global tropical cyclone activity. Tropical cyclones also occur in various parts of the Pacific Ocean, and can affect coastal regions of Mexico, south-east Asia, north-east Australia and the south Pacific islands. Those that form in the Indian Ocean can affect India, Bangladesh, north-west Australia, some parts of east Africa and Indian Ocean islands such as Mauritius and Madagascar.

In the northern hemisphere most tropical cyclones occur between June and November with a peak in September. However, in the north-west Pacific it is not unusual to have the occasional tropical cyclone outside of this period. In the southern hemisphere the season usually lasts from November to April. Tropical cyclones are occasionally observed in the South Atlantic, but this is a very rare occurrence. The map above shows the areas of the world affected by tropical cyclones.

How do cyclones form?

1. 
   Sea water it’s at its hottest (27º or more).
   
2. 
   Air above the sea surface is heated and the warm moist starts to rise.
   
3. 
   A deep center of low atmospheric pressure is made while the moist rises.
   
4. 
   Warm air spirals upward around the center of the cyclone, called the `eye´.
   
5. 
   Very dark and heavy clouds form and precipitate torrential rainfall while in the `eye´ the weather is calm and dry.
   

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  Water temperature at least 27º or more
  
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  Down to a depth of at least 160 ft.
  
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  Rapid cooling with height
  
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  High humidity
  
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  Low wind speed difference in a small area
  

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  A cyclone can be still powerful enough to destroy vehicles, buildings and other structures and objects.
  
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  They can even make them fly in the sky, turning loose debris into fatal projectiles.
  
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  Cyclones have caused 1.9 million deaths worldwide.
  

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  Cyclone Yasi
  

Dissipated: 3 February 2011

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  Cyclone Tracy
  

Dissipated: 26 December 1974

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  Cyclone Larry