New Delhi: A cyclone is a large-scale low pressure system characterized by a cyclonic circulation about a definite center where pressure is lowest. Generally bring stormy weather. In the northern hemisphere, where tropical cyclones occur in the Atlantic Ocean, Caribbean, and eastern Pacific Ocean they are called hurricanes and those in the Pacific Ocean west of the 180th meridian are called typhoons. Those in the southern Pacific Ocean and Indian Ocean are simply called cyclones. Cyclone Phailin (pronounced phie-leen) is half the size of India and is strengthening quickly as it heads for land. Here we bring to you 10 facts about a cyclone: 1. Cyclones are large tropical storms caused by winds rotating around an 'eye', or central area, of low atmospheric pressure. 2. 'Cyclone' is the generic term for cyclones, hurricanes and typhoons. They are called 'cyclones' in the southern hemisphere, and they rotate in a clockwise direction. 3. In the northern hemisphere, where cyclones occur in the Atlantic Ocean and Caribbean, they are called hurricanes. 4. Cyclones in the South China Sea and regions of Asia are called typhoons. 5. Northern hemisphere cyclones rotate anti-clockwise, and are sometimes called anti-cyclones. 6. Cyclones can only form over warm waters in the tropical regions of the oceans where the sea temperatures are 26.5 degrees Celsius or higher. 7. Cyclones occur in areas of very low pressure when air that is heated by the sun rises rapidly and becomes saturated with moisture which then condenses into high thunderclouds. As the hot air rises, cooler air rushes in to fill the area left vacant by the hot air. The Coriolis effect of the Earth spinning on its axis causes the air to spiral upwards with considerable force. This in turn causes the winds to rotate faster, causing the tropical low to deepen in intensity into a tropical depression, and eventually a cyclone. 8. Cyclones can be anywhere between hundreds of kilometres to thousands of kilometres wide. 9. Although cyclones are characterised by strong winds, in their centre is a clear, calm region called the 'eye'. 10. Cyclones are named alphabetically. They used to be given female names, but now they can be given either male or female names. Cyclones (and hurricanes) are given a random name beginning with whatever letter the meteorologists (who first detect it) are up to, provided the name has not been used previously. Cyclones also tend to take on a name common to the region where they form. For example, in February 2011, Severe Tropical Cyclone Yasi was given a Fijian name because it developed in Fijian waters.
