Cyclone

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.

What is a Cyclone?

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

What Causes a Cyclone?

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—

  • Speed of the wind
  • The direction of the wind
  • Temperature
  • Humidity

Classification of Cyclones in India

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.

  • Tropical 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.

  • Extratropical Cyclones

Also known as temperate cyclones, extratropical cyclones develop in middle or high latitude regions and in areas having horizontal temperature variations called frontal zones.

Understanding Anticyclones

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.

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FAQs on Cyclone

Q.1. Which was the biggest cyclone in India?

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.

Q.2. Which states were affected by Cyclone Amphan?

Cyclone Amphan occurred in May 2020 and severely affected the states of West Bengal and Odisha.

Q.3. Which are the most cyclone-prone states/areas in India?

Tamil Nadu, Andhra Pradesh, Orissa, West Bengal, Puducherry, and Gujarat are more vulnerable to cyclone hazards.

Q.4. Which cyclone occurred in India in 2021?

Cyclone Tauktae struck the Indian states of Maharashtra and Gujarat in May 2021.