UPSC Mains 2026 | General Studies Paper 1 | Geography | 10 Marks | 150 Words
What is the Fujiwhara effect? Explain its impact on the movement and intensity of tropical cyclones.
Model Answer
The Fujiwhara effect refers to the interaction between two nearby tropical cyclones, whereby they begin to rotate around a common centre due to their mutual circulation. The phenomenon was studied by Japanese meteorologist Sakuhei Fujiwhara.
Impact on movement:
– The cyclones can orbit each other, causing changes in their normal tracks.
– Their movement may become erratic, curved or looping, making forecasting difficult.
– A stronger cyclone may draw the weaker one towards itself, sometimes resulting in partial or complete merger.
Impact on intensity:
– Interaction can cause deformation and weakening of the weaker cyclone.
– In some cases, partial or complete merger may produce a larger and potentially stronger system.
– Thus, the effect can alter both cyclone trajectory and intensity.
Conclusion:
The Fujiwhara effect demonstrates the complex interaction of tropical cyclones and highlights the need for continuous satellite monitoring and improved forecasting for effective disaster management.
1. Decode the Question: What is UPSC Asking?
The question has three clear demands:
Define the Fujiwhara Effect
Explain what happens when two tropical cyclones come sufficiently close.
Explain its impact on movement
Show how mutual interaction changes the track, direction and speed of cyclones.
Explain its impact on intensity
Discuss how interaction can lead to weakening, deformation, absorption or merger.
Best approach: Definition → Mechanism → Movement → Intensity → Conclusion.
2. How to Approach the Answer
For a 10-mark, 150-word answer, avoid spending too many words explaining cyclone formation.
Use this structure:
Introduction
→ Define Fujiwhara Effect
Body
→ Mutual interaction
→ Impact on movement
→ Impact on intensity
→ Possible outcomes
Conclusion
→ Forecasting + disaster management
This ensures that every part of the question is directly answered.
3. What is the Fujiwhara Effect?
The Fujiwhara effect is a binary interaction between two nearby tropical cyclones.
When sufficiently close, the cyclones’ circulation fields interact and they tend to rotate around a common midpoint or centroid. NOAA describes it as two nearby tropical cyclones rotating cyclonically around each other.
The interaction becomes more significant as the distance between the systems decreases.
Key Concept
Two nearby cyclones
↓
Mutual interaction of circulation
↓
Rotation around common centre
↓
Track & intensity changes
4. Impact on the Movement of Tropical Cyclones
The Fujiwhara effect can significantly disturb the normal movement of cyclones.
Major effects:
– Change in direction: A cyclone may deviate from its expected path.
– Change in speed: Movement may accelerate or slow down.
– Curved/looping tracks: Mutual rotation can produce unusual trajectories.
– Orbital movement: Cyclones may revolve around a common centre.
– Deflection and absorption: A weaker cyclone may be drawn towards a stronger one.
Therefore, the phenomenon can increase uncertainty in cyclone-track forecasting.
5. Impact on Cyclone Intensity
The Fujiwhara interaction does not always produce the same intensity outcome.
Weakening
Strong interaction can deform the weaker cyclone and disrupt its circulation.
Partial Merger
Part of the weaker vortex may be incorporated into the stronger system.
Complete Merger
Two systems may eventually combine into a single, larger cyclone in certain situations.
Possible Intensification
In rare cases, the combined circulation can produce a stronger system rather than simply weakening both storms.
Important UPSC point:
Do not write that the Fujiwhara effect always intensifies cyclones. Its impact depends on the relative size, strength, distance and environmental conditions of the interacting systems.
6. Exam-Ready Flowchart
Two nearby Tropical Cyclones
Fujiwhara Interaction
Mutual Rotation around Common Centre
Movement Effects
Track Deflection → Curved/Looping Path → Speed/Direction Changes
Intensity Effects
Deformation → Weakening → Partial Merger → Complete Merger
Greater Forecasting Uncertainty
Need for Better Satellite Monitoring & Early Warning
7. Value Addition for UPSC
Use these keywords to make the answer more geographical and analytical:
Fujiwhara Effect
Binary Cyclone Interaction
Common Centroid
Mutual Rotation
Track Deflection
Cyclone Merger
Straining-Out
Cyclone Intensity
Forecast Uncertainty
Satellite Monitoring
Example for extra value:
The interaction between Hurricane Hilary and Hurricane Irwin in the eastern Pacific in 2017 is a documented example of the Fujiwhara effect.
8. Fujiwhara Effect vs Normal Cyclone Movement
Normal Cyclone Movement| Fujiwhara Interaction
Mainly controlled by environmental steering winds| Strong mutual interaction between cyclones
Relatively predictable track| Track can become highly variable
One dominant circulation| Two interacting circulations
No mutual orbital movement| Cyclones may rotate around a common centre
9. Previous UPSC PYQ Connection
The question fits directly within UPSC GS Paper 1’s Geophysical Phenomena portion of the syllabus.
UPSC has repeatedly tested tropical cyclones through different dimensions, including:
– 2024: Sea-surface temperature rise and tropical cyclone formation
– 2022: Colour-coded weather warnings for cyclone-prone areas
– 2026: Fujiwhara effect and cyclone movement/intensity
The pattern shows that UPSC can move from basic cyclone formation → forecasting → specialised cyclone interactions.
10. Syllabus & Topic Linkage
UPSC GS Paper 1 – Geography
Syllabus:
Important geophysical phenomena such as earthquakes, tsunami, volcanic activity, cyclone etc.; geographical features and their location.
Topic:
World Physical Geography → Geophysical Phenomena → Tropical Cyclones → Cyclone Interaction → Fujiwhara Effect
11. Mains Takeaway
The key to this question is not merely defining the Fujiwhara effect.
A high-scoring answer must clearly connect:
Interaction → Movement Changes → Intensity Changes → Forecasting Challenges
Remember:
Fujiwhara Effect = Two nearby cyclones + Mutual rotation + Track alteration + Possible intensity change
This makes the answer conceptual, analytical and directly aligned with the question demand.
