Cyclones in India: Formation, Naming and UPSC Notes (UPSC Environment)

Cyclones are among the most destructive weather systems that affect India. The country has a coastline of over 7,500 kilometres exposed to tropical cyclones from both the Bay of Bengal and the Arabian Sea. About 8 percent of world’s tropical cyclones originate in the North Indian Ocean basin, with the Bay of Bengal accounting for the majority. In recent years, climate change has intensified Arabian Sea cyclones, upending historical patterns. For UPSC aspirants, cyclones are a central GS Paper III theme on disaster management, geography and climate change.

What are cyclones

Cyclones are atmospheric disturbances around a low-pressure centre, distinguished by swift and often destructive air circulation. They are accompanied by violent storms, heavy rainfall and surge tides. The word "cyclone" derives from Greek "kyklos" (circle), describing the spiralling pattern of winds.

In the North Indian Ocean, cyclones are categorised by the India Meteorological Department (IMD) by wind speed:

• Low Pressure Area: up to 31 km/h.
• Depression: 31 to 50 km/h.
• Deep Depression: 51 to 62 km/h.
• Cyclonic Storm: 63 to 87 km/h.
• Severe Cyclonic Storm: 88 to 117 km/h.
• Very Severe Cyclonic Storm: 118 to 166 km/h.
• Extremely Severe Cyclonic Storm: 167 to 221 km/h.
• Super Cyclonic Storm: 222 km/h and above.

Why the Bay of Bengal is cyclone-prone

Higher rainfall and freshwater influx

The Bay of Bengal receives high monsoon rainfall and the continuous discharge of mighty rivers like the Ganga, Brahmaputra, Godavari and Krishna. This freshwater lowers surface density, keeping the surface warmer. Warm sea surface temperatures above 26.5 C provide the thermal energy cyclones need.

Lower wind velocity

Wind velocity over the Bay is lower than over the Arabian Sea. Sluggish winds do not dissipate surface heat and keep temperatures higher, favouring cyclone formation.

Recycling from the Pacific

The Bay also receives cyclones that originate over the Pacific and cross through narrow straits in Southeast Asia, getting re-energised upon reaching the Bay.

Easterly tracks

Tropical cyclones formed in the Bay move westward under the influence of easterly winds but dissipate upon reaching the Indian landmass. They rarely cross over to the Arabian Sea.

Post-monsoon peak

Post-monsoon months (October to December) see a higher number of cyclones than pre-monsoon. Summers and pre-monsoons see dry, hot air moving from north-western India towards the Bay, blocking the rise of surface air and cloud formation. This dry intrusion weakens during post-monsoon, allowing cyclone formation.

Arabian Sea cyclones: a changing pattern

Historically, the Arabian Sea has seen fewer and weaker cyclones than the Bay. That is changing rapidly.

Rising sea surface temperatures

Due to global warming, sea surface temperatures in the Arabian Sea have risen 1.2 to 1.4 C above the level of four decades ago. This warmer water supports active convection, torrential rainfall and stronger cyclones.

Favourable wind shear

The Arabian Sea now provides the wind shear conditions that tropical cyclones need for intensification. Cyclone Ockhi (2017) crossed from the Bay to the Arabian Sea via southern India and intensified.

El Nino Modoki

The occurrence of El Nino Modoki, a "pseudo El Nino," creates conditions in the Bay of Bengal that are unsuitable for cyclogenesis but favourable for the Arabian Sea.

West Wind Drift warming

Warm water flowing eastward is pushing into the Arabian Sea, creating a positive feedback that keeps sea surface temperatures high.

Major Arabian Sea cyclones in recent years include Ockhi (2017), Vayu (2019), Maha (2019), Nisarga (2020), Tauktae (2021), Shaheen (2021), Biparjoy (2023) and Asna (2024).

How cyclones are named

Cyclones across the world are named by Regional Specialised Meteorological Centres (RSMCs) and Tropical Cyclone Warning Centres (TCWCs). There are six RSMCs including the India Meteorological Department (IMD).

IMD's role

RSMC New Delhi Tropical Cyclone Centre names cyclones that form over the Bay of Bengal and the Arabian Sea when they reach the required intensity. The IMD issues advisories to 12 other countries in the North Indian Ocean region.

Nomenclature rules

• The WMO maintains rotating lists of names for each Tropical Cyclone basin. Panel member names are listed alphabetically by country.
• Names are used sequentially column-wise.
• The first name starts from the first row of column one and continues sequentially to the last row in column thirteen.
• Names of tropical cyclones over the North Indian Ocean are not repeated. Once used, a name retires.
• A proposed name must be new and must not exist in any current RSMC list worldwide.
• A cyclone from the South China Sea that crosses Thailand and emerges into the Bay of Bengal retains its original name.
• Proposed names are provided with pronunciation and voice-over.

Panel member countries

Panel members of RSMC New Delhi are 13 countries: Bangladesh, India, Iran, Maldives, Myanmar, Oman, Pakistan, Qatar, Saudi Arabia, Sri Lanka, Thailand, UAE, Yemen.

Impacts of cyclones

• Coastal flooding from storm surge and heavy rainfall.
• Wind damage to buildings, trees and power infrastructure.
• Loss of life, especially among fishing and farming communities.
• Agricultural losses from salinity and waterlogging.
• Disruption of transport, communication and power.
• Ecosystem damage to mangroves, coral reefs and coastal wetlands.
• Economic losses, particularly for insurance, tourism and fisheries.

India's cyclone preparedness

• India Meteorological Department (IMD): Forecasting, early warning, naming.
• Indian National Centre for Ocean Information Services (INCOIS): High-energy swell wave warnings for coastal states.
• National Disaster Management Authority (NDMA) Cyclone Guidelines: Risk mapping, shelter construction, evacuation protocols.
• National Cyclone Risk Mitigation Project (NCRMP): Cyclone shelters, coastal embankments, early warning infrastructure.
• Coastal Disaster Risk Reduction Project: World Bank-supported programmes in Odisha, Andhra Pradesh and Tamil Nadu.
• Sagarmala and Blue Economy framework integrating coastal resilience.

Latest developments (2024-26)

• Cyclone Biparjoy (June 2023): Hit Gujarat with minimal casualties thanks to mass evacuation of over 1 lakh people.
• Cyclone Remal (May 2024): Severe cyclonic storm that hit West Bengal and Bangladesh; improved early warning limited casualties.
• Cyclone Asna (August 2024): Rare off-season Arabian Sea cyclone, reflecting climate-changed patterns.
• Cyclone Dana (October 2024): Made landfall on Odisha coast; Odisha's cyclone preparedness again reduced fatalities.
• Cyclone Fengal (November 2024): Affected Tamil Nadu and Puducherry, causing severe rainfall.
• Arabian Sea intensification: Research papers in 2024 confirmed a statistically significant increase in Arabian Sea cyclone frequency and intensity.
• COP29 Baku (2024): India highlighted cyclone-attributable Loss and Damage in its adaptation narrative.
• BBNJ Treaty signed September 2024 is linked to cyclone-related marine pollution and coastal vulnerability.
• Disaster Management (Amendment) Bill 2024 clarifies cyclone response coordination.

UPSC Relevance

Prelims focus

• IMD categorisation of cyclones by wind speed.
• RSMC New Delhi: Naming Bay of Bengal and Arabian Sea cyclones; advisories to 12 other countries.
• 13 panel member countries.
• Bay of Bengal vs Arabian Sea cyclone patterns.
• Recent cyclones: Ockhi (2017), Amphan (2020), Tauktae (2021), Biparjoy (2023), Remal, Dana (2024).
• INCOIS, NCRMP, NDMA Cyclone Guidelines.

Mains focus (GS III)

Typical question framings examine why cyclones are more frequent in the Bay of Bengal, the changing pattern in the Arabian Sea due to climate change, India's cyclone preparedness, and the Loss and Damage Fund for climate-attributable disasters. Strong answers cite specific cyclones, climate science, NDMA guidelines and international frameworks.

Linkages

Cyclones connect to the Sendai Framework for Disaster Risk Reduction, SDG 11, SDG 13, SDG 14 (Life Below Water), India's updated NDCs after COP29, the Loss and Damage Fund, the Coastal Regulation Zone notifications, the BBNJ Treaty, and the Disaster Management Act 2005.