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The Fujiwhara effect


The United States west coast recently witnessed Hurricane Hilary (a sub-tropical storm by the time it hit the US), prompting the National Hurricane Centre (NHC) to issue its first ever tropical storm watch for parts of Southern California. This was the latest incident in a string of unusual weather phenomena in the region.

  • In one of these storms, two small areas of low pressure were drawn together in a ‘dance’: instead of merging together, the stronger low pressure area became the dominant one in the system – displaying, for a brief moment, what is known as the ‘Fujiwhara effect’.


GS I: Geography

Dimensions of the Article:

  1. Fujiwhara Effect
  2. Impact and Increasing Occurrence of Fujiwhara Effect

Fujiwhara Effect:

  • The Fujiwhara effect refers to the phenomenon in which two cyclones (hurricanes or typhoons) that are spinning in the same direction come close to each other and engage in an intricate dance around a common center of rotation.
  • Interaction and Outcomes:
  • When two cyclones approach each other closely, their interaction can lead to distinct outcomes based on their relative intensities.
  • If one cyclone is more powerful, it can dominate and absorb the smaller cyclone into its vortex.
  • In cases where cyclones are of similar strengths, they might orbit around a shared center, and their paths could merge temporarily or lead to separate trajectories.
Mega Cyclone Formation:
  • In rare situations, if both cyclones are sufficiently intense, they might merge, resulting in the formation of a single, more powerful cyclone. This mega cyclone can pose a serious threat to coastal areas.
Origins and Discovery:
  • The Fujiwhara effect is named after Sakuhei Fujiwhara, a Japanese meteorologist.
  • It was first mentioned in a paper published in 1921 by Fujiwhara.
  • The phenomenon was observed in 1964 when Typhoons Marie and Kathy merged over the western Pacific Ocean.

Impact and Increasing Occurrence of Fujiwhara Effect:

Effects of the ‘Dance’:
  • The Fujiwhara effect can lead to powerful winds and weather disturbances, as observed in different incidents around the world.
  • In March 2023, the Bay Area and parts of California experienced strong winds causing damage to property and disruptions to power supply.
  • The effect contributed to peak gusts of up to 60 to 75 mph in the Santa Cruz Mountains and 50 to 60 mph winds across Santa Cruz and Santa Clara counties.
  • The interaction of cyclones can lead to the merging of systems or intensification of primary circulation due to the influx of heat, moisture, and vorticity.
Instances and Climate Impact:
  • In 2022, typhoon Hinnamnor and tropical storm Gardo engaged in the Fujiwhara effect, with Gardo being absorbed by Hinnamnor. This led to heavy rainfall and casualties in South Korea.
  • Similar interactions were observed in the past, such as hurricanes Hilary and Irwin in 2017, which merged over the eastern Pacific Ocean.
  • Experts point out that the Fujiwhara effect is becoming more frequent, attributed to a warming climate and increasing ocean temperatures.
  • Rising ocean temperatures contribute to the intensification of cyclones, making them more powerful and increasing the chances of such interactions.
  • The occurrence of the Fujiwhara effect adds complexity to cyclone prediction, as each interaction is unique and challenging to forecast within current climate models.
Climate Change Connection:
  • Climate researchers highlight the connection between the Fujiwhara effect and climate change, particularly the warming of the world’s oceans.
  • Rising ocean temperatures lead to stronger cyclones, creating conditions conducive to the Fujiwhara effect.
  • Ravi Shankar Pandey, a research scholar, noted a 35% increase in the strength of typhoons hitting Taiwan between 1977 and 2016, linked to a rise in sea surface temperatures.
  • The effect reflects the broader impact of a warming climate on extreme weather events and atmospheric dynamics.

-Source: Indian Express

February 2024