A tropical cyclone is a severe storm which takes place largely in South Asia, South-East Asia, Northern Australia, South America and the south-eastern part of North America. In South Asia, it is referred to as the cyclone, in South-East Asia as the typhoon, in Australia as the willy-willy, and in America as the hurricane.
Although cyclones generally reach speeds of 160 to 240 kilometers per hours, some of them have attained even higher speeds. The power of the cyclone is derived from the latent of evaporation (the heat released after water vapor is changed into water droplets). A single storm has so much stored energy that, if harnessed, it is powerful enough to supply Pakistan with electricity for several years to come. The cyclone usually originates over the sea, thus harnessing the energy stored in the water vapor which rises from the sea. It takes several days to mature. During that time, it whirls round and round without any forward movement. Once it is fully developed, it moves forward, first moving north-westward and then taking a north-easterly turn. Many cyclones die before reaching the coast. If they attack the coast, they cause heavy damage to life and property, particularly because of the large waves they generate.
Much more damaging is the cyclone surge is a moving wall of water about 3 to 8 meters high underneath the eye of the cyclone. The eye of the cyclone has a radius of 15 to 50 kilometers. Here, air pressure is at its lowest, calm prevails and there are no clouds. Outside the eye of the cyclone, the cyclone rages in its full fury. This is the main storm. The outer edge of the cyclone is called the eye wall where the wind speed is the highest and rainfall the heaviest. At the periphery of the storm, the wind speed slows down.