October storm in Bay of Bengal after 3 years: When, where it is likely to hit

Subject : Geography

Context-

The first tropical cyclone of the post-monsoon season of 2022 is likely to form in the Bay of Bengal on October 24.
If realised, this will be the first cyclone to develop in the Bay of Bengal in October since 2018, and will be called Sitrang, as named by Thailand.
The last October cyclone in the Bay of Bengal was Titli in 2018.

Why storms in October-

After the withdrawal of the Southwest monsoon, there is a rise in ocean heating, which leads to rise in sea surface temperature over the Bay of Bengal.
The atmospheric moisture availability over the ocean region, too, is higher.
So, when remnant systems from the South China Sea reach the Bay of Bengal, they get conducive conditions, aiding the formation and intensification of cyclones in October.
The months of October-November and May-June see storms of severe intensity develop in the North Indian Ocean — comprising the Bay of Bengal and the Arabian Sea — with an average of five developing in a calendar year.
In the past 131 years,October saw 61 storms develop in the Bay of Bengal, according to the Regional Specialised Meteorological Centre (RSMC).
The east coast, notably Odisha, has faced many of its severest storms in October, including the Super Cyclone of 1999.
In some years, ocean-atmospheric factors hinder this phenomenon.
For instance, in 2020, weak La Nina conditions along the equatorial Pacific Ocean prevented a cyclonic formation near India’s coasts.

Cyclone Sitrang

The name Sitrang (read Si-trang) has been given by Thailand, and features in the list of tropical cyclone names prepared by the RMSC being followed since April 2020.
The IMD is one of the world’s six RMSCs mandated to provide cyclone advisories and alerts to 13 member countries — Bangladesh, India, Iran, Maldives, Myanmar, Oman, Pakistan, Qatar, Saudi Arabia, Sri Lanka, Thailand, United Arab Emirates and Yemen.

How the cyclones are named and what are the guidelines on adopting their names?

In 2000, a group of nations called WMO/ESCAP (World Meteorological Organisation/United Nations Economic and Social Commission for Asia and the Pacific), which comprised Bangladesh, India, the Maldives, Myanmar, Oman, Pakistan, Sri Lanka and Thailand, decided to start naming cyclones in the region.
After each country sent in suggestions, the WMO/ESCAPPanel on Tropical Cyclones (PTC) finalised the list.
The WMO/ESCAP expanded to include five more countries in 2018 — Iran, Qatar, Saudi Arabia, United Arab Emirates and Yemen.
The list of 169 cyclone names released by IMD in April 2020 were provided by these countries — 13 suggestions from each of the 13 countries.

Which states are likely to be affected ?

As the storm is expected to come close to Odisha shores, heavy to very heavy rain (64.5 to 204.4mm in 24 hour) would lash over during October 22-25.
The IMD has issued a ‘yellow’ for coastal districts of Puri, Jagatsinghpur and Kendraparha.
Once the cyclone develops, heavy rainfall is likely to lash Mayurbhanj, Baleshwar, Bhadrak, Jajpur, Cuttack, Khorda, Nayagarh, Puri, Kendraparha and Jagatsinghpur districts on October 24 and all these districts are on ‘yellow’ alert.

Colour- Coded Weather Warning-

It is issued by the IMD whose objective is to alert people ahead of severe or hazardous weather which has the potential to cause damage, widespread disruption or danger to life.
Warnings are updated daily.
The IMD uses 4 colour codes are:
- Green (All is well): No advisory is issued.
- Yellow (Be Aware): Yellow indicates severely bad weather spanning across several days. It also suggests that the weather could change for the worse, causing disruption in day-to-day activities.
- Orange/Amber (Be prepared): The orange alert is issued as a warning of extremely bad weather with the potential of disruption in commute with road and rail closures, and interruption of power supply.
- Red (Take Action): When the extremely bad weather conditions are certainly going to disrupt travel and power and have significant risk to life, the red alert is issued.
These alerts are universal in nature and are also issued during floods, depending on the amount of water rising above land/in a river as a result of torrential rainfall.
- For instance, when the water in a river is ‘above normal’ level, or between the ‘warning’ and ‘danger’ levels, a yellow alert is issued.

Cyclones in the Arabian Sea-

In comparison with the Bay of Bengal, only 32 storms have developed in the Arabian Sea in October since 1891.
Climatologically too, the IMD states that of the five storms formed in the North Indian Ocean in a calendar year, four are in the Bay of Bengal and one in Arabian Sea.

Reasons for more tropical cyclone originate in Bay of Bengal :

The vast low pressure created by the warm water of the ocean.
The Bay of Bengal shaped like a trough that makes it more hospitable for storms to gain force.
The high sea surface temperaturetriggers high intensity storms.
Bay of Bengal gets more rainfall with sluggish winds and warm air currents around it that keep temperatures relatively high all year.
The constant inflow of fresh warm water from the perineal rivers like Bramhmaputra, Ganga, etc makes it further impossible to mix with the cooler water below.
The absence of air movements from north-western India towards the Bay in the post-monsoon phase is also another reason for the chances of cyclones in the Bay of Bengal.
Remnant of tropical cyclones from the Pacific