IMD Forecasts a Cyclone

Context: 

Recently, the India Meteorological Department (IMD) said that the first cyclone of the year was likely to form in the Bay of Bengal by early next week.

• It will be called Cyclone Mocha.
  • Its name was proposed by Yemen.

About Cyclone:

• A cyclone is a low pressure system that forms over warm waters. 
• Essentially, it is a system of high speed winds rotating around a low-pressure area, with the winds blowing counterclockwise in the Northern Hemisphere and clockwise in the Southern Hemisphere.
• Conditions favourable for the formation of Cyclone: 

• • Large sea surface with temperature higher than 27° C
  • Presence of the Coriolis force
  • Small variations in the vertical wind speed
  • Pre-existing weak low-pressure area or low-level-cyclonic circulation
  • Upper divergence above the sea level system.

Which ocean in India sees more storms?

• 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. 

How IMD categorises cyclones?

• The core criterion for labelling a cyclonic formation as one of eight categories of cyclonic storms, in order of increasing severity, is the maximum wind speed within the cyclonic system. 
• Type of Disturbances (and Associated Wind Speed in the Circulation): 

• • Low pressure Area: <31 kmph
  • Depression: 31 to 49 kmph
  • Deep Depression: 50 to 61 kmph
  • Cyclonic Storm: 62 to 88 kmph
  • Severe Cyclonic Storm: 89 to 118 kmph
  • Very Severe Cyclonic Storm: 119 to 221 kmph
  • Extremely severe cyclonic storm: 168-221 km per hour 
  • Super cyclonic storm: 222 km per hour and higher

Four Stage Warning issued by IMD:

• First Stage warning known as “PRE CYCLONE WATCH” is issued 72 hours in advance.
  • It contains early warning about the development of a cyclonic disturbance.
• The Second Stage warning known as “CYCLONE ALERT” is issued at least 48 hrs.
  •  It contains information on the location and intensity of the storm likely direction of its movement, intensification, etc
• The Third Stage warning known as “CYCLONE WARNING” is issued at least 24 hours.
  • Landfall point is forecast at this stage.
• The Fourth Stage of warning known as “POST LANDFALL OUTLOOK” is issued at least 12 hours in advance of expected time of landfall.
  •  It gives the likely direction of movement of the cyclone after its landfall and adverse weather likely to be experienced in the interior areas.

Naming of Cyclones:

• Cyclones that form in every ocean basin across the world are named by:
  •  the Regional Specialised Meteorological Centres (RSMCs) and Tropical Cyclone Warning Centres (TCWCs). 
• There are six RSMCs in the world, including the India Meteorological Department (IMD), and five TCWCs.
• As an RSMC, the IMD names the cyclones developing over the north Indian Ocean, including the Bay of Bengal and Arabian Sea, after following a standard procedure.
• In 2000, a group of nations called WMO/ESCAP (World Meteorological Organisation/United Nations Economic and Social Commission for Asia and the Pacific), decided to start naming cyclones in the region. 
  • It comprises Bangladesh, India, the Maldives, Myanmar, Oman, Pakistan, Sri Lanka and Thailand.
  • After each country sent in suggestions, the WMO/ESCAP Panel on Tropical Cyclones (PTC) finalised the list.
  • The list of 169 cyclone names released by IMD in 2020 were provided by these countries — 13 suggestions from each of the 13 countries.

Why is it important to name cyclones?

• Adopting names for cyclones makes it easier for people to remember, as opposed to numbers and technical terms. 
• It also helps the scientific community, the media, disaster managers etc. 
• With a name, it is easy to identify individual cyclones, create awareness of its development, rapidly disseminate warnings to increase community preparedness and remove confusion where there are multiple cyclonic systems over a region.

What cyclone names has India suggested?

• The 13 names in the recent list that have been suggested by India include: Gati, Tej, Murasu, Aag, Vyom, Jhar (pronounced Jhor), Probaho, Neer, Prabhanjan, Ghurni, Ambud, Jaladhi and Vega.
• Some of the names picked by India were suggested by the general public. 

                                                                                                                                         News Source: The Hindu

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