Daily UPSC Mains Question - GS 3 - 3rd November 2025
- TPP
- Nov 5
- 3 min read
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QUESTION
Discuss the meteorological conditions that lead to the formation of tropical cyclones. Why does the Bay of Bengal often witness cyclones?
Answer: A cyclone is a large-scale atmospheric system that rotates around a low-pressure centre, characterized by strong spiralling winds, heavy rainfall, and storm surges. According to the National Disaster Management Authority (NDMA), cyclones rotate anticlockwise in the Northern Hemisphere and clockwise in the Southern Hemisphere.
Tropical cyclones—called hurricanes or typhoons in other regions—are among the most destructive natural hazards, particularly affecting coastal regions of the Indian subcontinent.
1. Meteorological Conditions for the Formation of Tropical Cyclones
Tropical cyclones typically form over warm tropical oceans between 5° and 20° latitude in both hemispheres. Their formation depends on specific atmospheric and oceanic conditions:
Condition | Explanation |
1. Warm Ocean Surface Temperature (≥ 26.5°C) | Provides necessary heat and moisture through evaporation; fuels the cyclone’s energy. |
2. Coriolis Force | Essential for initiating and maintaining the cyclone’s rotation; absent near the Equator, hence cyclones rarely form within 5° latitude. |
3. High Humidity in the Troposphere | Supports condensation, releasing latent heat of condensation, which drives vertical convection and intensifies the low-pressure system. |
4. Atmospheric Instability | Allows warm moist air to rise, causing cumulonimbus cloud formation. |
5. Low Vertical Wind Shear | Ensures that developing storm clouds are not disrupted by strong winds at different altitudes. |
6. Pre-existing Low-Pressure Disturbance | Acts as a seed around which the cyclone can develop. |
Mechanism:
As per the National Oceanic and Atmospheric Administration (NOAA), tropical cyclones derive energy from latent heat released during condensation of moist air. Thunderstorm activity intensifies near the cyclone’s eye, forming a warm core system, unlike extratropical cyclones, which form in temperate regions and have a cold core.
2. Why the Bay of Bengal Often Witnesses Cyclones
India experiences cyclones mainly in the pre-monsoon (April–June) and post-monsoon (October–December) seasons. The Bay of Bengal (BoB) witnesses a higher frequency and intensity compared to the Arabian Sea due to multiple interconnected factors:
(a) Oceanic and Meteorological Factors
High Sea Surface Temperature: The BoB maintains surface temperatures above 28°C, providing abundant latent heat.
High Evaporation Rate: Due to freshwater inflow from major rivers (Ganga, Brahmaputra, Mahanadi, etc.), surface salinity is low, allowing easier warming and evaporation.
Frequent Low-Pressure Systems: The region is a breeding ground for depressions during both monsoon transitions.
Coriolis Effect: Stronger deflection due to location between 10°N–20°N enhances cyclone formation.
(b) Geographical and Topographical Factors
Funnel-Shaped Coastline: Concentrates wind and water movement, amplifying storm surges (up to 10–15 metres in severe cases).
Complex Coastal Geometry: As per the 2020 study “Effect of landfall location and coastal topography on surge response in the Northern Bay of Bengal”, estuaries, deltas, and shallow continental shelves amplify the destruction caused by storm surges.
Long Coastline Exposure: Eastern coastlines of Odisha, Andhra Pradesh, West Bengal, and Tamil Nadu lie open to direct impact.
(c) Atmospheric Circulation Factors
Inter-Tropical Convergence Zone (ITCZ) Migration: Shifts northward during monsoon onset, favouring cyclonic disturbances.
Easterly Waves: Originating from the South China Sea often move westwards, entering the BoB and intensifying into cyclones.
Climate Change Influence: Warmer oceans and changing wind patterns have increased frequency and intensity in both BoB and the Arabian Sea in recent years.
3. Cyclone Seasonality (Data Insight)
IMD Norms: On average, 5–6 tropical cyclones form annually over the North Indian Ocean, of which 4 occur over the Bay of Bengal and 1–2 over the Arabian Sea.
Peak Months: October–November witness maximum activity due to favourable SSTs and weak vertical shear.
4. Naming of Cyclones
Cyclones in the North Indian Ocean are named by the WMO/ESCAP Panel on Tropical Cyclones, comprising 13 member countries (e.g., India, Bangladesh, Oman, Sri Lanka, etc.).
In 2020, the India Meteorological Department (IMD) released a list of 169 names, each country contributing 13.
Naming helps in public communication, scientific tracking, and disaster management preparedness.
Tropical cyclones are complex meteorological phenomena driven by oceanic warmth, atmospheric instability, and global wind patterns. The Bay of Bengal’s warm waters, unique topography, and favourable climatic conditions make it especially vulnerable. Strengthening early warning systems (IMD, INCOIS, NDMA), coastal resilience measures, and climate-adaptive disaster management strategies are vital to mitigate their socio-economic and environmental impacts.
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