In the news: Extremely severe cyclonic Fani hit the Odisha coast in Puri.

More about Fani in news: 

  • The Met department has issued a "yellow warning" for Odisha, predicting heavy to very heavy rain in several areas. Tamil Nadu and Andhra Pradesh have been placed on high alert too.

A yellow warning indicates severely bad weather, warning people who are at risk to take preventive action. Yellow also means that you should plan ahead thinking about possible travel delays, or the disruption of your day-to-day activities.

  • According to the IMD, in the past 126 years (1891-2017) only 14 severe tropical cyclones have formed in April over the Bay of Bengal. Out of those, only one storm crossed the Indian mainland. The last severe cyclone 'Nargis' in 2008 devastated Myanmar.
  • With sustained winds of 240 kmph, the storm was the equivalent of a Category 4 hurricane on the Saffir-Simpson Hurricane Wind Scale.
  • Meteorologists rely on the Saffir-Simpson Hurricane Wind Scale to measure the magnitude of the hurricane’s impact. 
  • Category 4 hurricanes often include long-term power outages and water shortages lasting from a few weeks to a few months

About Cyclone Fani: 

  • The name of the Cyclone 'Fani', pronounced as 'Foni' was suggested by Bangladesh. 
  • India, Sri Lanka, Bangladesh, Maldives, Myanmar, Oman, Pakistan and Thailand send names of tropical cyclones developing in the North Indian Ocean to the regional committee. 
  • Presently, each country has suggested eight names for cyclones occurring in future. The name ‘Fani’ was decided from a list containing 64 names.
  • Cyclones emerging over Bay of Bengal in April-May are usually weaker, and often swerve away from India’s east coast.

What makes Fani unique?

  • Fani is stronger: Cyclones emerging in April-May usually are much weaker than those during October-December.Fani is not just a severe cyclone but an “extremely severe cyclone”.Cyclone Fani made a landfall in Odisha with wind speeds of more than 170 km/h.
  • Origin of Fani: 
    • The in situ cyclonic systems in the Bay of Bengal usually originate around latitude 10°, in line with Chennai or Thiruvananthapuram. 
    • Fani, on the other hand, originated quite close to the Equator, around latitude 2°, well below the Sri Lankan landmass. 
    • The forecast landfall on the Odisha coast is at a latitude of almost 20°. 
    • It has traversed a long way on the sea, thus gaining strength that is unusual for cyclones originating in the Bay of Bengal in this season.
  • Tropical cyclones over the Bay of Bengal have a lifespan of four-seven days, whereas Fani traveled long which allowed it to gather a lot of moisture and momentum, resulting in strong winds.
  • It was initially headed northwestwards, towards the Tamil Nadu coast, but changed course midway, and swerved northeast away from the coastline to reach Odisha. That has given it even more time on the sea.

Tropical cyclone:

  • Tropical cyclones are violent storms that originate over oceans in tropical areas and move over to the coastal areas bringing about large-scale destruction caused by violent winds, very heavy rainfall and storm surges.
  • Tropical cyclones originate and intensify over warm tropical oceans.
  • The conditions favourable for the formation and intensification of tropical storms are: 
    • Large sea surface with temperature higher than 27° C
    • Presence of the Coriolis force
    • Small variations in the vertical wind speed
    • A pre-existing weak low-pressure area or low-level-cyclonic circulation
    • Upper divergence above the sea level system
  • The energy that intensifies the storm, comes from the condensation process in the towering cumulonimbus clouds, surrounding the centre of the storm. With continuous supply of moisture from the sea, the storm is further strengthened. 
  • On reaching the land the moisture supply is cut off and the storm dissipates. The place where a tropical cyclone crosses the coast is called the landfall of the cyclone.
  • The cyclones, which cross 20o N latitude generally, recurve and they are more destructive. 
  • During these periods, there is an ITCZ in the Bay of Bengal whose southern boundary experiences winds from west to east, while the northern boundary has winds flowing east to west. This induces the anticlockwise rotation of air. 
  • The Indian subcontinent experiences cyclones from two basins: the Bay of Bengal basin and the Arabian Sea basin.