Cyclone
A cyclone is a kind of storm and a storm is simply air that is moving rapidly from one place to another.
A storm starts when warm, moist air from the Equator moves northwards into the Northern Hemisphere and meets a mass of cold dry air moving southwards from the Arctic region. These two kinds of air masses do not mix. The sharp boundary that is formed where they meet is called a "front". As the air masses continue to move, the lighter, warm air climbs up over the cold air. As it is forced upwards, the warm, moist air is cooled. The moisture then condenses, forming clouds.
While all this is going on, the air pressure begins to fall at the centre of the storm. The winds begin to blow around the low pressure area in an anti-clockwise direction. Thus the warm, moist air moves northwards around the eastern side of the storm, while the cold air moves southwards around the western side.
A low pressure area is know as a "cyclone". The mass of air in such an area could vary in diameter from 400 to 1,000 miles.
Tornado
A tornado is simply a special kind of cyclone. It is also a circular storm and is confused with a cyclone. But while a cyclone is 400 to 1,000 miles in diameter, a tornado may be only 30 to 1,600 metres in diameter.
A tornado arises when the conditions that cause ordinary thunderstorms are unusually violent. There is an updraft of air. There are winds blowing in opposite directions around this rising air. This starts a whirling effect that is narrow and very violent. When this happens, centrifugal force throws the air away from the centre. And this leaves a core of low pressure at the centre.
This low-pressure core acts like a powerful vacuum on everything it passes. This is very destructive. It can actuall' suck the walls of a house outwards in such a way that the house will collapse. The other destructive thing is the high winds that may blow around the edges of a whirl. These winds can reach 300 miles per hour and nothing is safe against them .
Hurrricane
Hurricanes are storms that start in the tropics. In a hurricane, the storm area is usually from 100 to 400 miles in diameter and winds around the hurricane may reach speeds of 75 to 125 miles per hour. A special feature of the hurricane is the calm, central part of the storm which is called the "eye"- of the strom. This eye is about 5 to 15 miles in diameter. As it moves over an area, the winds become almost calm. This sometimes leads people to believe that the storm is over. However after the eye passes, the winds begin to blow with equal violence from the opposite direction. Since a hurricane is a circular storm, the winds move in a kind of circle as the storm itself moves.
Hurricanes strike the USA mainly in Gulf of Mexico area and also all along the eastern coast. When exactly the same kind of storm takes place in the East Indies and the China sea, it is called a "typhoon". A general name for both is "tropical storms" .
More about cyclones - Cyclone + Something extra on Tornado - Tornadoes + About Hurricane ( Tropical cyclone ) - Hurricane
