What are Cyclones: Types, Causes and Effects


What are Cyclones - Types, Causes and Effects

By 23 October, 2016, even as the country was gearing up to celebrate a bright and colourful Diwali, the India Meteorological Department pulled a major dampener when it announced that a deep depression had been intensifying along the eastern coast of the country, over the Bay of Bengal. Fears were that a cyclone would hit the state of Odisha and move up to West Bengal over the Diwali weekend. By 26 October, however, it started to seem unlikely that the Cyclone Kyant would make a landfall, despite the heavy showers it would bring in Tamil Nadu, Andhra Pradesh, and Odisha. What the announcement of a cyclone, however, has done is put the people of the coastal regions on high alert.

What is a Cyclone?

Tropical Cyclones (TC) are intense low pressure systems that develop over the seas or oceans in the tropical and subtropical regions. The IMD says, “A tropical cyclone is an intense low pressure area or a whirl in the atmosphere over tropical or sub-tropical waters, with organised convection (i.e. thunderstorm activity) and winds at low levels, circulating either anti-clockwise (in the northern hemisphere) or clockwise (in the southern hemisphere)” Typically tropical cyclones are accompanied by gale force winds that average a speed of about 63 kilometre per hour. According to modern convention, a Cyclone that forms over the Indian Ocean is referred to as Cyclone, but is called Hurricane if it forms over the Atlantic Ocean and Typhoon if it forms over the Pacific Ocean.

How Are Cyclones Named?

During World War II weather forecasters took to naming storms using female names. By 1953, the American weather service had put together a list of names (from alphabets A to W) that were used to name the storms that formed. By the late 1970s this list grew to include male and female names. Compared to the system of naming storms and hurricanes, naming tropical cyclones is a rather recent convention. By the year 2004, eight countries located in the Indian Ocean region agreed upon a naming convention that could help identify tropical cyclones affecting the region. Bangladesh, India, Maldives, Myanmar, Oman, Pakistan, Sri Lanka, and Thailand agreed to contribute a list of names each thus developing a pool of names. Cyclones developing in the region are now named sequentially from this pool.

Categories of Cyclones

Cyclones are categorized according to wind speeds and the damage they cause.

Category 1 Cyclone: Wind speeds between 90 and 125 kilometres per hour, some noticeable damage to houses and trees.

Category 2: Wind speeds between 125 and 164 kilometres per hour, damage to houses and significant damage to crops and trees.

Category 3: Wind speeds between 165-224 kilometres per hour, structural damage to houses, extensive damage to crops and uprooted trees, upturned vehicles and destruction of buildings.

Category 4: Wind speeds between 225 and 279 kilometres per hour, power failure and much damage to cities and villages.

Category 5: Wind speeds over 280 kilometres per hour, widespread damage.

Worst Affected Regions in India

Last year the India Meteorological Department (IMD) published the results of a study conducted on some 96 districts of the country. Among these, about 72 are coastal districts while the rest are close to the coastline. According to the IMD, 12 districts of the country stand to be affected most by cyclones. These districts are classified as “very highly prone” and all 12 are in the eastern coastal belt. These include Yanam district in Puducherry, East Godavari, Krishna, and Nellore districts in Andhra Pradesh, Balasore, Bhadrak, Jagatsinghpur, and Kendrapara districts in Odisha, Medinipur, Kolkata, and North and South 24 Parganas in West Bengal.  Apart from these there are about 41 districts which are classified as “highly prone”.  30 districts are “moderately prone” and the remaining 13 are “less prone”.

The IMD also said that while all 13 states and Union Territories that are located along the coast are vulnerable but Tamil Nadu, Pondicherry, Andhra Pradesh, Odisha, West Bengal, and Gujarat are most prone to damages from cyclone. Only about 7 percent of the tropical cyclones in the world originate in the Arabian Sea and Bay of Bengal but these are some of the most devastating and damaging, says the IMD.

Worst Cyclones of Recent Times

Two cyclones – Cyclone Phailin and Cyclone Hudhud caused extreme damage to life and property in India in recent times.

Cyclone Phailin was one of the most intense and most destructive cyclones to make landfall in the country in recent times. The cyclone hit India in October 2013and caused pronounced destruction to many villages in Odisha. It prompted one of the largest evacuations in the country in decades. Over 550,000 people were evacuated and moved to cyclone shelters. Over 30 lives were lost due to the cyclone.

The next year in 2014, Cyclone Hudhud made landfall near Vishakapatnam in the state of Andhra Pradesh and caused extensive damage to coastal regions. Total damages due to Hudhud were estimated to be about INR 21,908 crore. Some 124 deaths were also recorded due to the cyclone. Nepal also suffered from the effects of this cyclone which triggered an avalanche in the country.

Cyclone Warning System in India

The Indian Meteorological Department is responsible for forecasting the occurrence of cyclones, for estimating and categorizing them, and for issuing warnings when necessary. Cyclones in the Bay of Bengal and in the Arabian Sea are predicted by the Area Cyclone Warning Centres (ACWC) and the Cyclone Warning Centres (CWC) departments of the IMD respectively. The National Cyclone Warning Centre (NCWC) in New Delhi acts as a coordinator between the two. In 2014, the IMD launched an SMS based cyclone warning system that shall enable the masses to stay alert and prepared in the event of an approaching cyclone. From time to time the Indian Army and the Indian Air Force have also been roped in to rescue Indians from the devastation caused by tropical cyclones. Apart from this the National Disaster Response Force (NDRF) is responsible for relief operations.

View All Hurricanes and Tropical Cyclones:

Cyclone Kyant
Cyclone Hudhud
Cyclone Roanu
Cyclone Komen
Cyclone Ashobaa
Cyclone Nilofar
Cyclone Phailin
Cyclone Prone Areas in India
SMS-Based Cyclone Warning System Launched in India