FUJIWHARA EFFECT

A rare meteorological phenomenon where two nearby cyclonic systems begin to rotate around a common centre due to interaction of their wind circulations.
Identified by Sakuhei Fujiwhara (1921), it occurs mostly in the tropical cyclone belt when storms are within ~1,400 km of each other.

Factors Aiding Its Occurrence:

Proximity of twocyclones within a threshold distance (typically <1400 km in the Indian Ocean).
Similar rotational direction(counter-clockwise in the Northern Hemisphere).
Favourable sea surface temperatures>26°C supporting sustained convection.
Low vertical wind shearallowing stable cyclone structure.

How it forms?

Close Formation:Two cyclones forming within ~1400 km begin influencing each other’s wind fields and natural movement patterns due to proximity.
Wind Interaction:Theirouter rainbandsand upper-level winds overlap, creating deformation zones that gradually pull the systems toward each other.
Coupled Circulation:The interacting winds generate a shared pivot point, forcing both cyclones to rotate in curved, mutually influenced paths.
Orbiting:If one storm is stronger, the weaker one revolves around it and may eventually be absorbed due to energy imbalance.
Merger:When centres move very close, the vortices fuse into a single, larger cyclone with enhanced convection and stronger winds.
Weakening:Competition for heat and moisture can deprive the weaker cyclone of inflow, triggering rapid weakening or dissipation.
Deflection:If interaction is weak, storms may push each other onto diverging paths, adding significant uncertainty to forecasts.

Fujiwhara Effect