Cyclone Fani

A powerful cyclonic storm named fani is headed towards the odisha coast.
It is not just a severe cyclone but an extremely severe cyclone.
Expected to generate storms with wind speeds as high as 200km per hour, it has the potential to cause widespread damage in odisha and neighbouring states.
The last time such a powerful cyclonic storm had emerged in the bay of bengal at this time of the year, in 2008. it has killed more than 1.25lakh people in myanmar.
However india has impressively managed disasters caused by cyclones, most remarkably during cyclone phailin of 2013, which was even stronger than the approaching fani.
Fani is , thus , unusal and that is mainly because of the place it originated, very close to the Equator and the long route it has taken to reach the landmass.

How are they formed?

Cyclones are formed over slightly warm ocean waters.
The temperature of the top layer of the sea, up to a depth of about 60 metres, need to be at least 28*c to support the formation of a cyclone.
This explains why the April-May and October-December periods are conducive for cyclones.
Then,the low level of air above the waters needs to have an anticlockwise rotation( in the northern hemisphere; clockwise in the southern hemisphere).
During this periods,there is a 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.
Once formed, Cyclones in this area usually move northwest.A it travels over the sea, the cyclone gathers more moist air from the warm sea, and adds to its heft.

What's unusual with fani?

The in situ cyclonic systems in the bay of bengal usually originated around latitude 10*, in line with chennai or Thiruvananthapuram.
Fani,on the other hand originated quite close to the equator, around latitude2*, well below the sri lankan landmass.
The forecast landfall on the odisha coast os at a latitude of almost 20*.
It has travelled a long way on the sea, thus gaining strength that is unusual for cyclones originating in the bay of bengal in this season.
It was initially headed northwestwards,towards the tamil nadu coast, but changed course midway and swerved northeast away from the coastline to reach odisha.
If it had remained on its original course, and made a landfall over the tamil nadu coastline, fani would only have been a normal cyclone it has now become.

Grading of cyclones:

Tropical cyclones in the bay of bengal are graded according to maximum wind speeds at their centre.

At the lower end are depressions that generate wind speeds of 30 to 60 km/hour, followed by:

1) Cyclonic storms - 61 to 88 kph

2) Severe cyclonic storms- 89 to 117 kph

3) Very Severe cyclonic storms- 118 to 166 kph

4) Extremely Severe cyclonic storms- 167 to 221 kph

5) Super cyclones- 222 kph or higher

ANUKUL