Cyclone season: Naming, formation and India's warning system
Naming, formation and the warning system are the three things UPSC asks about cyclones, timed for the post-monsoon season when the Bay of Bengal wakes up.
How cyclones form
A cyclone needs three ingredients.
Warm seas. Sea-surface temperatures around 26.5°C or higher.
Low vertical wind shear. Winds that do not tear the system apart as it builds.
The Coriolis force. The Earth's rotation effect that spins the storm. This is exactly why cyclones never form within about five degrees of the equator, where Coriolis is too weak.
The Bay of Bengal is the world's most active basin for this latitude. Warm waters, river discharge and a funnel-shaped geography concentrate systems there.
Naming
Names are drawn from rotating lists maintained by the WMO/ESCAP Panel on Tropical Cyclones. Its 13 member countries, including India, contribute names. Names suggested by India have included Amphan, Nisarga, Gulab, Tej and Remal. A name is retired when a cyclone is exceptionally deadly or costly, so that the name is never used again.
Source: IMD: Cyclone warnings
India's warning and response stack
| Element | Function |
|---|---|
| IMD advisories | Track, intensity and landfall forecasts |
| Colour-coded warnings | Green → Yellow → Orange → Red escalation |
| NDRF/SDRF pre-positioning | Rescue teams staged before landfall |
The intensity ladder and the deadliest hazard
Systems escalate from depression to deep depression, cyclonic storm, severe cyclonic storm, very severe, and extremely severe cyclonic storm.
Across all intensities, the storm surge is the deadliest hazard. It is the abnormal rise of sea water pushed ashore, amplified in shallow, funnel-shaped bays.
Climate change sharpens a further risk. Rising ocean heat content enables rapid intensification, where a system strengthens sharply in under 24 hours.
Prelims traps
| Statement | True or False |
|---|---|
| "Cyclones form within 5 degrees of the equator" | False. Coriolis is too weak there |
| "The WMO/ESCAP panel has 13 member countries" | True |
| "The storm surge is the deadliest cyclone hazard" | True |
| "Bay of Bengal cyclones are most common in summer" | False. Pre- and post-monsoon seasons dominate |
Part of: Environment and Climate, July 2024 to June 2026
Read next: Monsoon 2026 review · Ocean currents for UPSC
Source: India Meteorological Department; WMO/ESCAP Panel on Tropical Cyclones.