Cyclone
Cyclones are caused by atmospheric disturbances around a low-pressure area distinguished by swift and often destructive air circulation. Cyclones are usually accompanied by violent storms and bad weather. The air circulates inward in an anticlockwise direction in the Northern hemisphere and clockwise in the Southern hemisphere. Cyclones are classified as: (i) extra tropical cyclones (also called temperate cyclones); and (ii) tropical cyclones. The word Cyclone is derived from the Greek word Cyclos meaning the coils of a snake. It was coined by Henry Peddington because the tropical storms in the Bay of Bengal and the Arabian Sea appear like coiled serpents of the sea.
Classifications
Cyclones are classified as extra tropical cyclones (also called temperate cyclones); and tropical cyclones.
The World Meteorological Organisation (WMO, 1976) uses the term 'Tropical Cyclone’ to cover weather systems in which winds exceed ‘Gale Force’ (minimum of 34 knots or 63 kph). Tropical cyclones are the progeny of ocean and atmosphere, powered by the heat from the sea; and driven by easterly trades and temperate westerlies, high planetary winds and their own fierce energy.
In India, cyclones are classified by:
- Strength of associated winds,
- Storm surges
- Exceptional rainfall occurrences.
