By : Neha Dhyani
Updated : Mar 16, 2022, 13:46
The Indian subcontinent has a coastline of 8041 kilometres. The majority of the cyclones in India originate in the Bay of Bengal and move towards the East coast of India. On average, the Indian subcontinent is hit by at least five to six tropical cyclones every year, out of which two or three could be severe.
Based on the Indian Meteorological Department (IMD) analysis, more cyclones are formed in the Bay of Bengal than the Arabian Sea, with an approximate ratio of 4:1.
A cyclone is a large mass of wind caused due to atmospheric disturbances around a low-pressure area. This large air mass circulates a low-pressure area and rotates inwards in a counterclockwise direction north of the Equator and clockwise in the Southern hemisphere. Cyclones are usually associated with violent storms and bad weather.
IMD has classified cyclonic disturbances as follows -
Type of disturbance | Associated maximum sustained wind |
Cyclonic Storm | 34 to 47 Knots (62-88 kmph ) |
Severe Cyclonic Storm | 48 to 63 Knots (89-117 kmph ) |
Very Severe Cyclonic Storm | 64 to 90 Knots (118-167 kmph ) |
Extremely Severe Cyclonic Storm | 91 to119 Knots (168-221 kmph |
Super Cyclonic Storm | 120 Knots and above (≥222 kmph ) |
Tropical cyclones are known by various names over the world -
Region | Name |
Indian Ocean | Tropical Cyclones |
The Pacific Ocean and the China Sea | Typhoons |
The Caribbean Sea, West Indian islands, and the Atlantic Ocean | Hurricanes |
The Guinea lands of West Africa and Southern USA | Tornados |
North-western Australia | Willy-willies |
Cyclones occur due to atmospheric disturbances in a low-pressure area. Violent storms and bad weather usually accompany these swift and destructive air circulations.
Some of the factors that cause a cyclone include—
Depending upon the strength of the winds, storm surges or tidal waves, and heavy rainfall, cyclones in India are classified as tropical cyclones and extratropical cyclones.
Based on the definition given by the World Meteorological Organization, the term tropical cyclone describes a wind system that exceeds a minimum of 34 knots or 63 kph. Tropical cyclones develop over warm tropical and sub-tropical oceans and are associated with high-velocity winds, heavy rains, and storm tides. Storm surges are the greatest hazard caused by a cyclone.
In India, tropical cyclones occur in the months of May-June and October-November.
Also known as temperate cyclones, extratropical cyclones develop in middle or high latitude regions and in areas having horizontal temperature variations called frontal zones.
As the title suggests, an anticyclone is the opposite of a cyclone. As opposed to a cyclone's inward spiralling action, anticyclones flow in an outward motion, which is the opposite of that of cyclones.
Furthermore, the winds of an anticyclone rotate clockwise in the Northern Hemisphere and counterclockwise in the Southern hemisphere. Winds of anticyclones are usually not as strong as those of cyclonic winds.
To implement a holistic approach to disaster management in India, the National Disaster Management Authority (NDMA) came into existence through the Disaster Management Act on December 23, 2005. It is headed by the Prime Minister of India and creates policies on disaster management as per the national plan.
The biggest recorded cyclone in India was the Bhola Cyclone which occurred on November 11, 1970, in the Bay of Bengal. It was one of the deadliest tropical cyclones known to have caused 5,00,000 fatalities.
Cyclone Amphan occurred in May 2020 and severely affected the states of West Bengal and Odisha.
Tamil Nadu, Andhra Pradesh, Orissa, West Bengal, Puducherry, and Gujarat are more vulnerable to cyclone hazards.
Cyclone Tauktae struck the Indian states of Maharashtra and Gujarat in May 2021.