Cyclone Fani- Why it was Unusual & how it formed | Bomb Cyclone

Cyclone Fani 

  • A very powerful cyclonic storm named Fani had hit the Odisha state recently in the month of May.
  • Cyclone of this intensity is rare and unusual in bay of bengal in this season of April- May.
  • Cyclone Fani is categorized as an “extremely severe cyclone”.
  • This super cyclone Fani caused widespread damage in Odisha and neighboring states.
  • With the help of India’s weather department, the state has impressivley managed the disasters caused by Cyclone Fani.
  • Fani is unusual because of its place of origin, which is very close to the Equator and the very long route it took to reach the landmass.

How do Tropical Cyclone form

  • Formation of Cyclones depends on the temperature of the top layer of the sea water, up to a depth of 60 metres.
  • For the formation of Cyclones the top layer of the sea water should warmer which is 28°C or above.
  • These conditions are exacerbated by global forcing mechanisms including El Niño and the Indian Ocean Dipole, which concentrates warm ocean waters in smaller geographic areas.
  • That is the reason we experience cyclones in the month of April-May & October-December.
  • Second and important reason for the formation of cyclones is the low level of air above the waters needs to have an ‘anticlockwise’ rotation in the northern hemisphere and vice versa.
  • During the periods of April-May & October-December, there lies the Inter-Tropical Convergence Zone (ITCZ) (a low pressure zone) in the Bay of Bengal region, which gets shifted with the seasons.
  • The Northern boundary of the zone experiences winds from east to west and southern boundary of the zone experiences winds from west to east.
  • The Inter-Tropical Convergence Zone (ITCZ) and the resultant wind pattern induce the anticlockwise rotation of air.
  • After formation cyclones in this area usually move northwest.
  • Since the cyclones travels over the sea, the cyclone  gathers more moist air  rising from the warm sea, and it gets added to its strength.

Cyclone Fani formed

Tropical cyclones in India

Formation of Cyclones are a normal event in the eastern coast of India.

Every year, on an average five to six significant cyclonic storms emerge in the Bay of Bengal region.

The prime seasons for tropical cyclones are

  1. Warmer Months of April and May, just before the start of the summer monsoon.
  2. October to December, immediately after the end of the summer monsoon.

Generally April-May Cyclones are weaker compared to that of October- December season. This is mainly due to the fact that the summer season just starts in these months and it takes time for the water of the sea surface to rise.

Why October-December Cyclones are stronger

  • More the time cyclones spends over the open sea more is their strength and stronger they becomes gaining moisture from the warm sea water.
  • For example the Hurricanes(another name for Cyclone) which forms near the USA originates in the vastly open Pacific Ocean and hence they cause much destruction.
  • And those Hurricanes are usually much stronger than the tropical cyclones in the Bay of Bengal, a relatively narrow and enclosed region.
  • Cyclones in October-December in India are usually remnants of cyclonic systems that emerge in the Pacific Ocean.
  • They manage to come to the Bay of Bengal, considerably weakened after crossing the Southeast Asian landmass near the South China Sea.
  • However, these systems already have some energy, and gather momentum as they traverse over the Bay of Bengal.
  • But the cyclones in April-May originate in situ in the Bay of Bengal itself.
  • And the Bay of Bengal  being only few hundred kilometres from the Indian landmass, and hence the cyclones are relatively weaker.

 

Measuring intensity of the Cyclones

Intensity of Tropical Cyclones is classified according to the Saffir Simpson scale.

Categories are measured on the basis of the sustained wind speed and the storm’s central pressure.


Why the Cyclone Fani is different & Unusual

Tropical cyclones in the Bay of Bengal are graded according to maximum wind speeds at their centre as follows:

  1. depressions – 30 to 60 km per hour (kph)
  2. cyclonic storms – 61 to 88 kph
  3. severe cyclonic storms – 89 to 117 kph
  4. very severe cyclonic storms – 118 to 166 kph
  5. extremely severe cyclonic storms – 167 to 221 kph
  6. super cyclones – 222 kph or higher

Cyclone Fani comes in the category of  “extremely severe cyclone”.

With wind speeds as high as 200 km per hour, a Cyclone of this nature is unusual for April- May cyclones in India.

Cyclone fani is different mainly on  account of its place of origin, and the route it has taken.

Origin of Cyclone Fani

  • In situ (in situ means locally) cyclone in the Bay of Bengal usually originate around latitude 10° N (in line with Chennai).
  • Contrary to this Cyclone Fani originated near to the Equator that was well below the landmass of Sri Lanka.
  • Since it originated near to the Equator, it  took a long route to reach the landmass.
  • Due to which the Cyclone spent most of its time on the sea and thus gained great strength.

Route

Cyclone Fani initially headed towards Tamil Nadu coast (north westward given its point of origin i.e, near to the Equator).

But right in the midway this cyclone changed its course and started moving towards northeast to reach Odisha.

And due to the recurve the Cyclone Fani took, gave it much more time over the sea and thus ensured that it gains unusual strength & power to wreak destruction.

 

How Cyclone Fani got its name?

Cyclone Fani pronounced as Foni name was suggested by Bangladesh. It means ‘Snake’ or ‘hood of snake’.

Areas of Concern

South Indian Ocean is warming rapidly.The regions of the South Indian ocean which previously experienced the temperatures of 26.5°C which facilitated tropical cyclone formation are now experiencing warm temperatures to the degree of 30-32°C.

Due to which stronger cyclones are getting formed which cause heavy destruction when they reach near the coastline.

 

What’s the difference between hurricanes, cyclones and typhoons?

Hurricanes, cyclones and typhoons are all tropical storms. They are all the same thing but are given different names depending on where they appear.

When these storms reaches populated areas they bring with them very strong wind and rain that causes  lot of damage.

Hurricanes are tropical storms that form over the North Atlantic Ocean and Northeast Pacific.

Cyclones are formed over the South Pacific and Indian Ocean.

Typhoons are formed over the Northwest Pacific Ocean.

What is a Bomb cyclone?

Meteorologists uses this term to indicate a mid-latitude cyclone that intensifies rapidly.

A bomb cyclone happens when atmospheric pressure in the middle of the storm drops at least 24 millibars over 24 hours, quickly increasing in intensity. The lower the pressure, the stronger the storm.

The bigger the pressure drop, the stronger the cyclone, and greater the wind speed associated with it.

How it works?

When a region of warm air meets one of cold air a deep drops in barometric pressure occurs. Rising movement of the air coupled with the rotation of the earth creates a cyclonic effect.

The direction is counterclockwise in the Northern hemisphere leading to winds that come out of the northeast.

 

Before & after Photo of Odisha  shared by an Instagram user after Cyclone Fani

 

Cyclone Fani

 

Cyclone Fani  Odisha

 

Cyclone Fani  Odisha

 

 

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