Cyclone Arnab: Cyclone Formation, Coastal Vulnerability and Odisha’s Disaster Preparedness
Exam Relevance:
- UPSC Prelims: Physical Geography | Cyclones | Atmospheric Circulation | Disaster Management
- UPSC GS-I: Important Geophysical Phenomena | Cyclones | Coastal Geography
- UPSC GS-III: Disaster and Disaster Management | Climate Resilience
- HPAS GS-I & III: Physical Geography | Early-Warning Systems | Disaster Preparedness
Why in News?
Cyclone Arnab over the Bay of Bengal has prompted preparedness measures in Andhra Pradesh and Odisha. Forecasts issued ahead of 28 October 2026 indicated landfall along the Andhra Pradesh–Yanam coast between Bapatla and Visakhapatnam, with maximum sustained winds of 115–125 kmph, gusting to 140 kmph.
The National Crisis Management Committee reviewed preparations, highlighting the importance of evacuation, emergency coordination and protection of essential services. These are forecast conditions, not a confirmed account of landfall.
The event provides an important case study for understanding tropical cyclone formation, coastal vulnerability and the conversion of weather forecasts into timely action.
What is Cyclone Arnab?
Arnab is a tropical cyclone originating over the Bay of Bengal. It developed from a depression and strengthened as it moved towards India’s eastern coast.
| Feature | Key information |
|---|---|
| Ocean basin | Bay of Bengal, North Indian Ocean |
| Type | Tropical cyclone |
| Forecast landfall region | Andhra Pradesh–Yanam coast, between Bapatla and Visakhapatnam |
| Forecast landfall date | 28 October 2026 |
| Main hazards | Strong winds, heavy rainfall, rough seas, storm surge and flooding |
| Forecasting agency | India Meteorological Department (IMD) |
IMD’s bulletin based on observations at 8:30 p.m. on 26 October classified Arnab as a severe cyclonic storm. Subsequent reporting on 27 October described further intensification. This illustrates why cyclone reports must specify the time of observation rather than combining positions and intensities from different bulletins.
Map pointer: Yanam belongs to the Union Territory of Puducherry, although it lies within the coastal geographical setting of Andhra Pradesh.
How Did Arnab Get Its Name?
The name “Arnab” was proposed by Bangladesh and appears in the regional naming list adopted in 2020. It means sea or ocean in Bengali. Naming helps distinguish weather systems and communicate warnings clearly.
What is a Tropical Cyclone?
A tropical cyclone is an organised, rotating system of clouds and thunderstorms around a low-pressure centre, generally developing over warm tropical oceans.
Its main source of energy is the release of latent heat when moist air rises and water vapour condenses.
Conditions Required for Formation
- Warm ocean water: Usually around 26.5°C or higher, extending through a sufficiently deep layer.
- Moist atmosphere: Moisture supports sustained cloud formation and thunderstorms.
- A pre-existing disturbance: An initial low-pressure circulation helps organise the system.
- Sufficient Coriolis force: This supports rotation; tropical cyclones rarely form very close to the equator.
- Low vertical wind shear: Large changes in wind speed or direction with height can disrupt the storm.
- Upper-level outflow: Air moving away from the storm at higher levels supports continued rising motion.
Warm water alone does not guarantee cyclone formation; several atmospheric and oceanic conditions must act together.
What are the Stages of Cyclone Development?
- Initial disturbance: Warm, moist air rises around a low-pressure area.
- Organisation: Thunderstorms become more organised, surface pressure falls and circulation strengthens.
- Intensification: Continued moisture supply and heat release strengthen winds under favourable conditions.
- Mature stage: A strong cyclone may develop a distinct eye, eyewall and spiral rainbands.
- Weakening: Landfall, cooler water, dry air or strong wind shear can weaken the circulation.
Important: Every depression does not become a cyclone, and every cyclone does not reach the highest intensity category.
What is the Structure of a Tropical Cyclone?
| Component | Characteristics |
|---|---|
| Eye | Relatively calm central region, often with descending air and fewer clouds |
| Eyewall | Ring of intense thunderstorms surrounding the eye; generally contains the strongest winds and heaviest rainfall |
| Spiral rainbands | Curved bands of thunderstorms extending outward |
| Upper-level outflow | Air spreading away from the storm at high altitude |
A clearly defined eye is usually associated with a well-developed cyclone; weaker systems may not have one. The eye’s temporary calm does not mean the danger has passed, because the opposite eyewall may follow.
How Does IMD Classify Cyclonic Disturbances?
IMD classifies systems using maximum sustained surface wind speed, rather than the strongest short-duration gust.
| Category | Wind speed in knots | Approximate wind speed in kmph |
|---|---|---|
| Depression | 17–27 | 31–49 |
| Deep Depression | 28–33 | 50–61 |
| Cyclonic Storm | 34–47 | 62–87 |
| Severe Cyclonic Storm | 48–63 | 88–117 |
| Very Severe Cyclonic Storm | 64–89 | 118–165 |
| Extremely Severe Cyclonic Storm | 90–119 | 166–221 |
| Super Cyclonic Storm | 120 or more | 222 or more |
The knot thresholds provide the clearest category boundaries; some publications show slightly different rounded kilometre-per-hour equivalents.
Exam clarification: The reported landfall forecast of 115–125 kmph spans the severe/very severe boundary. A 140-kmph gust must not be used by itself to assign the intensity category.
A super cyclone is the highest intensity category within this classification, not a separate mechanism of cyclone formation.
Tropical Cyclones, Temperate Cyclones and Anticyclones
| Feature | Tropical cyclone | Temperate or extratropical cyclone | Anticyclone |
|---|---|---|---|
| Central pressure | Low | Low | High |
| Main setting | Tropical and subtropical oceans | Mainly middle and higher latitudes | Various latitudes |
| Main mechanism | Heat and moisture from warm oceans | Contrasts between air masses and associated atmospheric disturbances | Descending air and outward surface flow |
| Fronts | Usually absent in the tropical stage | Commonly associated with warm and cold fronts | Not a defining feature |
| Northern Hemisphere rotation | Anticlockwise | Anticlockwise | Clockwise |
| Typical weather | Strong winds and heavy rain | Widespread cloud, rain or snow | Often clearer and more stable conditions |
An air mass is a large body of air with broadly similar temperature and moisture characteristics. A front is the boundary between contrasting air masses. Fronts are particularly important in extratropical cyclone development.
Why are Odisha and the Bay of Bengal Coast Vulnerable?
1. Exposure to Cyclone Tracks
Cyclones developing over the Bay of Bengal can move towards India’s eastern coast. Odisha’s location exposes it to both direct landfall and the rainfall and winds of nearby systems.
2. Low-Lying Coastal Areas
Coastal plains, river mouths and deltaic areas can be inundated by seawater and heavy rainfall. Flooding may become worse when high coastal water levels obstruct river drainage.
3. Coastal Shape and Shallow Waters
Shallow continental shelves and the shape of bays and estuaries can amplify storm-surge impacts. Actual flooding depends on the storm’s size, track, wind direction, tide and local topography.
4. Concentration of People and Livelihoods
Fishing settlements, farms, roads, ports and power infrastructure create significant exposure. Weak housing and limited household resources can increase vulnerability.
Mains insight: Disaster risk results from the interaction of hazard, exposure and vulnerability, shaped by the capacity to prepare and respond.
What are the Major Hazards Associated with Cyclones?
- Destructive winds: Damage to buildings, trees, electricity lines and communication networks.
- Heavy rainfall: Urban flooding, river flooding and, in hilly areas, landslides.
- Storm surge: An abnormal rise of seawater above the predicted astronomical tide, mainly driven by winds pushing water towards the coast.
- High waves and rough seas: Risks to fishing vessels, ports and offshore operations.
- Agricultural damage: Crop lodging, waterlogging, livestock losses and saltwater intrusion.
- Cascading disruption: Interruptions to transport, healthcare, drinking water and electricity.
Storm surge is different from a tsunami. A surge is weather-driven; a tsunami is generally produced by sudden displacement of a large volume of water, commonly following an undersea earthquake.
Cyclone-related rainfall and flooding can continue after landfall and after wind speeds weaken.
What is IMD’s Four-Stage Cyclone Warning System?
| Warning stage | Lead time | Main purpose |
|---|---|---|
| Pre-Cyclone Watch | About 72 hours before expected adverse coastal weather | Early information about a developing disturbance and possible threat |
| Cyclone Alert | At least 48 hours before expected adverse coastal weather | Likely affected areas, movement, intensification and preparedness advice |
| Cyclone Warning | At least 24 hours before expected adverse coastal weather | More specific landfall, wind, rainfall and storm-surge information |
| Post-Landfall Outlook | At least 12 hours before expected landfall | Likely inland movement and adverse weather after landfall |
Prelims trap: The Post-Landfall Outlook is issued before landfall, despite its name. It anticipates the cyclone’s subsequent effects.
What Can India Learn from Odisha’s Disaster Management Approach?
The 1999 Super Cyclone prompted major institutional changes. Odisha established its disaster management authority in December 1999 to develop a more systematic approach to risk reduction.
Key Elements
- Dedicated institutions: Coordination through the state disaster management system and district administrations.
- Multipurpose shelters: Safe buildings linked with evacuation routes and local management arrangements.
- Community participation: Volunteers, local representatives and shelter committees support preparedness.
- Mock drills: Repeated practice helps people understand warnings and evacuation procedures.
- Specialised response capacity: ODRAF, fire services and supporting national agencies assist rescue and relief.
- Early evacuation: Moving exposed populations before conditions become dangerous.
- Advance resource planning: Preparing food, water, medicines, transport and restoration equipment.
Odisha’s shelter programme emphasises community involvement and maintenance, demonstrating that infrastructure works best when supported by local institutions.
Remaining challenge: Reducing deaths must be accompanied by protecting livelihoods, maintaining shelters and restoring essential services quickly.
How Does Cyclone Management Relate to the Sendai Framework?
The Sendai Framework for Disaster Risk Reduction 2015–2030 identifies four priorities:
| Priority | Application to cyclone management |
|---|---|
| Understanding disaster risk | Hazard mapping, exposure assessment and public awareness |
| Strengthening disaster risk governance | Clear responsibilities and coordination |
| Investing in disaster risk reduction for resilience | Shelters, resilient housing, drainage and reliable infrastructure |
| Enhancing preparedness and Building Back Better | Evacuation, effective response and safer reconstruction |
Its approach shifts attention towards preventing and reducing risk, alongside emergency response.
Way Forward
- Turn forecasts into action: Link warning thresholds with specific evacuation and preparedness decisions.
- Strengthen last-mile communication: Use local languages, accessible messages and multiple communication channels.
- Protect vulnerable groups: Plan assistance for children, older people, persons with disabilities and pregnant women.
- Build resilient infrastructure: Improve housing, drainage, power distribution and communication redundancy.
- Restore natural coastal buffers: Protect suitable mangrove and wetland ecosystems alongside engineered measures.
- Prepare for compound hazards: Plan for rainfall, river flooding, storm surge and infrastructure failure occurring together.
- Protect livelihoods: Support farmers, fishers and small businesses through recovery assistance and risk financing.
- Review performance: Update evacuation routes, shelter maintenance and response plans after every event.
Key Prelims Takeaways
- Tropical cyclones: Low-pressure systems powered by ocean heat and moisture.
- Eye: Relatively calm centre; eyewall: zone of intense winds and rainfall.
- Coriolis force: Helps explain why cyclones rarely form near the equator.
- Intensity classification: Based on sustained winds, not gusts.
- Super Cyclonic Storm: Sustained winds of 120 knots or more, approximately 222 kmph or more.
- Post-Landfall Outlook: Issued before expected landfall.
- Yanam: Part of Puducherry Union Territory.
- Sendai Framework: Covers 2015–2030 and has four priorities.
Conclusion
Cyclone Arnab highlights the close connection between physical geography and disaster governance. Effective risk reduction requires accurate forecasts, trusted communication, timely evacuation, resilient infrastructure and community participation. Odisha’s experience offers useful lessons in making preparedness a continuous public responsibility.
Mains Practice Question:
“Accurate cyclone forecasting reduces disaster losses only when supported by effective local preparedness.” Discuss with reference to coastal vulnerability and Odisha’s disaster management approach. (250 words)