Mocha Cyclone

Cyclone Mocha was an ‘extremely severe’ tropical cyclone that ripped through the Bay of Bengal in May 2023, causing significant damage in Bangladesh and Myanmar. This powerful storm, with winds exceeding 168 kmph, impacted not only these two countries but also parts of India and other South East Asian nations. The World Bank estimated the total damage caused to be around $2.24 billion.

The term "cyclone" comes from the Greek word "cyclos," as when they approach they look like "coils of a snake". The ocean is filled with warm water. This warm water heats up the air above it, causing it to rise. This rising air is like a hot air balloon, filled with water vapor that it collected from the ocean. As the warm air rises, it leaves a low-pressure zone behind at the ocean's surface. This zone tries to suck in more air. Cooler air rushes in to fill this low-pressure vacuum. However, due to the Earth's rotation, this rushing air doesn't just fill the hole straight down. Instead, it starts to spin, creating a swirling vortex. This is why the winds look like a coiling snake.

The Mocha Cyclone rapidly intensified from a depression to a storm impacting the Indian States of Mizoram, Tripura, Assam and Nagaland along with the Andaman & Nicobar Islands. It led to displacement of people in the Bay of Bengal region and heavy losses to property, life, agriculture and vegetation in the area.

The cyclone was characterised by the following:-

• Rapid Intensification: The Mochan cyclone rapidly intensified within a few weeks from a mere depression to a cyclone, catching the forecast agencies by surprise. Rapid intensification is when the speed of a cyclone increases by 55 kmph in 24 hours. This is because of the warm waters of Bay of Bengal.
• Extremely severe cyclone: is a tag given by the Indian Meteorological Department (IMD). It is the 4th out of the total 5 categories characterised by wind speeds between 168 to 221 kmph.
• Weakened before Landfall: The Cyclone weakened right before meeting land because of cool local conditions and being cut off from warm ocean water supply. The rugged terrain ensured that it dissipated very quickly after moving inland.
• Strongest Cyclone in Northern Indian Ocean since 1982. It was not affected by the western disturbance which arrives from the Mediterranean Sea.
• Eyewall Replacement or Concentric Eyewall Cycles: An eye develops when there are very strong winds around the centre. The eye is the point of maximum intensity. However, in the Mocha Cyclone, due to rapid speeds and a weaker inner eye, another wall of strong circulating thunderstorms formed which eventually replaced the eye at the centre. This is called eyewall replacement. This naturally occurs in intense tropical cyclones with winds greater than 185 km/h. During this process of replacement, the intensity of the cyclone dips, but then again gains momentum.

• Impacted Areas: While Myanmar and Bangladesh were the main countries affected by the cyclone, North Eastern parts of India, and other South East Asian countries were also impacted.
  • There was intense rainfall in Andaman and Nicobar Islands, Tripura, Mizoram, Nagaland, Manipur and south Assam.
  • Many refugee camps of the Internally Displaced refugees (Rohnigya Community) in Myanmar and Bangladesh were hit by Cyclone Mocha, robbing the most marginalised groups of even the makeshift roof over their head. This is an example of the impact climate change has on the most vulnerable people.
• Mitigation Measures
• Evacuation of people from low-lying areas. Bangladesh relocated 5 lakh people while Myanmar evacuated 1 lakh people. In the state of Mizoram around 600 people were shifted to shelters.
• Advisory for Agriculture: Directions to immediately harvest mature crops and to not spray fertilisers or pesticides. Also ensuring clear drainage for the crops and postponing sowing activities was also advised.

Cyclones are classified into two main types:

extra-tropical and tropical.

• Tropical cyclones develop in the regions between the Tropics of Capricorn and Cancer. They are large-scale weather systems that form over tropical or subtropical waters.
• The air of the cyclone circulates inward in an anticlockwise direction in the Northern hemisphereand clockwise in the Southern hemisphere.

1. Cyclones are caused by atmospheric disturbances around a low-pressure area, which has strong and oftendestructive winds. Over warm ocean waters, low pressure system forms due to rising hot air.
2. This air contains water content as it is rising from the Ocean. This leads to formation of thunderstorms. These thunderstorms, in the right condition cluster and get strengthened with continuous supply of water from the ocean.
3. When this developing storm reaches land (landfall), it ends because it no more has the ocean supply from the water.

• Defining Tropical Cyclone: The World Meteorological Organization (WMO)uses the term "tropical cyclone" to describe weather systems with winds exceeding 63 kilometers per hour.
• Regional Centres: WMO has six regional specialised meteorological centres (RSMCs) and five regional Tropical Cyclone Warning Centres (TCWCs) across the globe to monitor cyclone formation, issue advisories and name cyclones.
• The Indian Meteorological Organisation (IMD): is the RSMC in the Northern Indian Ocean. It provides advisories to 13 countries in the north Indian Ocean basin: Bangladesh, India, Iran, Maldives, Myanmar, Oman, Pakistan, Qatar, Saudi Arabia, Sri Lanka, Thailand, United Arab Emirates and Yemen.

Naming the Cyclone: WMO names cyclones through suggestions from countries in the region.

• In 2020, the latest list was released which includes 13 names for cyclones, each contributed by one of the 13 member countries, for a total of 169 names. The names from India include Gati, Tej, Murasu, Aag, Vyom, Jhar, Probaho, Neer, Prabhanjan, Ghurni, Ambud, Jaladhi, and Vega.
• The name Mocha was given by Yemen. Some of the most important criteria for naming cyclones are that the names should be politically and culturally neutral, not rude or cruel, and short and easy to pronounce. The maximum length of a cyclone name is eight letters.

Reason for Intense and Frequent Cyclones in Indian Ocean: Normally, the season of cyclones is either before (April-June) or after (October to December) the monsoon season in India. While the number of cyclones in Bay of Bengal has reduced, their intensity had increased.

• Climate Change: This is due to temperature increase in the Indo-Pacific which is faster than the global average. This has led to many unpredictable weather events like heatwaves, floods and droughts. This is causing approximately $780 billion loss annually to the countries in the region causing death, displacement, disease and pushing millions into poverty. It is the small island states and the marginalised people who face the maximum risk.
• Greenhouse Gas Emission: While the Asia-Pacific region is developing rapidly it is also generating more than half of the world’s greenhouse gas emissions.

Cyclone Mocha is not an anomaly, instead due to the climate change there are more such disaster headed for the region. It is necessary that steps are taken to not only adapt, but also mitigate climate change disasters. Decarbonizing should be the priority of the countries in the region. With immense renewable energy potential, cross-border electricity grids are needed to maximise and reduce losses.

The rich civilizational history of the Bay of Bengal region nudges local solutions for the problems. This can be done by integrating climate considerations into regional trade agreements and encouraging private sector as well to undertake clean operations. The Bay of Bengal Initiative for Multi-Sectoral Technical and Economic Cooperation (BIMSTEC)is a regional organisation uniting the countries to tackle climate change while meeting development and energy needs of the region sustainably.

It is important to understand the science behind tropical cyclones so we can develop effective strategies to forecast and manage them. Improve dissemination of information to the last peson is also important. By combining scientific knowledge, international cooperation, and community involvement, we can work towards a future where the impact of these natural disasters is minimized, and the well-being of vulnerable communities is protected.