30th May, 2020
As Cyclone Amphan approaches close to the Bay of Bengal, millions of lives are at risk. Higher than normal temperatures in the Bay of Bengal region is triggering ‘super cyclones’
- Cyclone Amphan made landfall in West Bengal, India, near the Bangladeshi border. Amphan became the strongest storm ever recorded in the Bay of Bengal.
- The super cyclonic storm got this name from Thailand even before it had formed. It was proposed back in September 2004 for storms over north Indian Ocean.
- In the Indian Ocean region, eight countries (India, Pakistan, Sri Lanka, Bangladesh, Maldives, Myanmar, Oman, and Thailand) started the process of giving the naming cyclonic storms since 2004.
- 'Amphan' was the last name in the current list and was supposed to be taken up as the name of the first cyclone to occur in the region in 2020.
- The word 'Amphan' (pronunciation: Um-pun), means sky.
- It is the first tropical cyclone of the 2020 North Indian Ocean cyclone season, Amphan's origins can be tracked back to a low-pressure area situated over the Bay of Bengal on April 29.
What is Amphan?
- Super cyclone Amphan is the strongest storm to have formed in the Bay of Bengal.
- This is only the second super cyclone to form over the Bay of Bengal in two decades. In 1999, a super cyclone killed about 10,000 people as it slammed into Odisha.
- Amphan, which means "sky" in Thai, currently packs the punch of a Category 5 hurricane.
- Cyclone Amphan intensified from a category-1 cyclone to category-5 in 18 hours, an unusually quick evolution.
- Last year Fani, a category 4 cyclone, which swept through the Odisha coast, was again fuelled by high temperatures in the BoB.
What is Tropical Cyclone?
- A tropical cyclone is a rapid rotating storm originating over tropical oceans from where it draws the energy to develop.
- It has a low pressure center and clouds spiraling towards the eyewall surrounding the "eye", the central part of the system where the weather is normally calm and free of clouds.
- Its diameter is typically around 200 to 500 km, but can reach 1000 km.
- A tropical cyclone brings very violent winds, torrential rain, high waves and, in some cases, very destructive storm surges and coastal flooding.
- This weather phenomenon is named with different terms depending on the location.
- In the Caribbean Sea, the Gulf of Mexico, the North Atlantic Ocean and the eastern and central North Pacific Ocean, such a weather phenomenon is called "hurricane"
- In the western North Pacific, it is called "typhoon"
- In the Bay of Bengal and Arabian Sea, it is called "cyclone"
- In western South Pacific and southeast India Ocean, it is called “severe tropical cyclone”
- In the southwest India Ocean, it is called “tropical cyclone”
- The term "storm surge" refers to rising seas whipped up by a storm, creating a wall of water several metres higher than the normal tide level.
- The surge can extend for dozens of kilometres inland, overwhelming homes and making roads impassable.
- A storm surge is shaped by a number of different factors, including storm intensity, forward speed, the size of a storm and the angle of approach to the coast.
Classification of Cyclones:
Cyclones are classified on the basis of the wind speed:
- Depression: The lowest official classification used in the North Indian Ocean is a Depression, which has wind speeds of between 20–31 mph (31–49 km/h).
- Deep Depression: If the depression intensifies further then it will become a Deep Depression, which has speeds of between 32–38 mph (50–61 km/h).
- Cyclonic storm: If the Deep Depression develops gale force wind speeds of between 39–54 mph (62–88 km/h), it is called a Cyclonic storm.
- Severe Cyclonic Storm: Severe Cyclonic Storms have storm force wind speeds of between 55–72 mph (89–117 km/h).
- Very Severe Cyclonic Storm: Very Severe Cyclonic Storms have hurricane-force winds of 73–102 mph (118–166 km/h).
- Extremely Severe Cyclonic Storm: Extremely Severe Cyclonic Storms have hurricane-force winds of 166–221 km/h (104–137 mph).
- Super Cyclonic Storm: The highest classification used in the North Indian Ocean is a Super Cyclonic Storm, which have hurricane-force winds of above 138 mph (222 km/h).
Why Cyclones are so frequent in India?
- Cyclones affect the entire coast of India the East Coast is more prone compared to the West Coast.
- India's eastern coast and neighbouring Bangladesh, a low-lying delta nation, are routinely hit by bad storms between April and December that cause deaths and widespread property damage.
- Bangladesh is vulnerable to cyclones due to its location at the triangular-shaped head of the Bay of Bengal, the geography of its coastal area and its high-population density,
- India’s 13 coastal states/UTs encompasses 84 coastal districts which are affected by cyclones almost every year.
- India’s four major states, Andhra Pradesh, Odisha, Tamil Nadu, and West Bengal and one UT, Pondicherry on the east coast and Gujarat on the west coast are more vulnerable to cyclonic disasters.
- 40 percent of the country’s total population lives within 100 km of coastline.
Why tropical cyclones formed in BoB are destructive?
- Tropical cyclones are less likely to form in the Indian Ocean than in the Atlantic or Pacific basins.
- But storms that do form in the warm, shallow waters of the Bay of Bengal have a reputation for being unusually destructive.
- That’s in part because the Bay is semi-enclosed, so storms that form there are likely to strike land because they have not outlet for moving back out to sea.
- Also, much of the coastline is densely populated and low-lying, so damage tends to be considerable when storms make landfall.
What role does the warm water play?
- Many factors determine whether a tropical system intensifies or weakens. One of the primary factors is sea surface temperatures.
- Cyclones gain their energy from the heat and moisture generated from warm ocean surfaces.
- Warm water temperature: While water temperature alone does not govern whether a storm will intensify or weaken, warm water temperatures can be indicative of an environment that can provide energy for a developing system.
- Warm climate: A warming climate could bring more destructive cyclones as there would be extra heat in the oceans and atmosphere, although such systems could also become less frequent.
- Rising sea levels: Rising sea levels could boost storm surges from cyclones, making them even more deadly and destructive.
While tropical cyclones in Bay of Bengal are a typical feature of the summer months and play a role in aiding the arrival of the monsoon, warming around India is not longer restricted to just the BoB but also the Arabian Sea and the Indian Ocean. The situation is becoming scary which needs urgent attention and effective steps.