26.11.2025

Fujiwhara Effect

Subject: Geography

Context

Two cyclones forming in the Bay of Bengal may undergo the Fujiwhara Effect, where nearby storms interact and rotate around a shared center, altering their paths, speeds, and intensities.

What is the Fujiwhara Effect?

• Identified by Sakuhei Fujiwhara in 1921, it describes how two cyclonic systems within about 1,400 km begin orbiting a shared pivot as their circulations interact.
•  In the Northern Hemisphere, they rotate anti-clockwise around this common center, deviating from normal trajectories.
• Depending on strength, one storm may be drawn into and absorbed by the stronger system, both may merge into a larger cyclone, or they may repel each other into diverging tracks, making predictions difficult.

Key Features

• Mutual rotation around a shared center with altered motion and speed.
   
• Possible energy or moisture transfer, with stronger systems influencing weaker ones.
   
• Greater uncertainty in track and intensity forecasts, affecting preparedness.
   
• Potential merging into a larger, more destructive storm.
   
• Cyclones may slow or stall, increasing rainfall duration and flood risk.
   

Formation Factors

• Cyclones must be within ~1,400 km.
   
• Same rotational direction (counter-clockwise in the Northern Hemisphere).
   
• Warm sea surface temperatures above 26°C and low wind shear that maintain storm structure.
   

Implications

• Forecasting becomes difficult due to disrupted steering winds.
   
• Potential for intensification and prolonged rainfall over Tamil Nadu, Andhra Pradesh, Odisha, Bengal, Sri Lanka, and Myanmar.
   
• Higher likelihood of storm surges, severe winds, and coastal damage if systems merge or strengthen.
   

Conclusion

The Fujiwhara Effect highlights the complexity of cyclone dynamics, increasing prediction challenges and risk levels for coastal regions. Continuous monitoring and timely alerts are essential for protecting vulnerable communities during interacting cyclone events.