A cyclone is formed over tropical seas. Winds from opposite directions meet. This air is heated by the warm seas and so evaporates moisture from the ocean. This warm air rises up rapidly, cools and condenses to form clouds and produces an area of very low pressure. When moisture and air mix, it makes a collection of thunderstorms from which a cyclone can develop. Water needs to be at least 26 degrees warm so a tropical cyclone can develop.
More air is sucked in to take its place, and it too is heated and rises rapidly. This sucking in and risins movement of the air produces spiralling clouds. Eventually, an enormous storm system is built up, which can spread over two hundred kilometres. Heavy rain falls from the clouds. There is much thunder and lightning and the fast winds whip up the waves of the ocean.
In the middle of this system, air moves down. This produces a patch of drier, calm weather with few clouds. It is called the 'eye' of the storm and can last for an hour before the fierce winds and torrential rainstorms sweep in again. When the cyclone hits land, it soon weakens as there is no warm, moist air to 'feed' the storm.
