Naming of tropical cyclones

Topic: Air Masses, Fronts, Cyclones and Thunderstorms · NCERT: Beyond NCERT

Meaning

Naming of tropical cyclones in the north Indian Ocean is the system where RSMC New Delhi, run by the IMD, gives a storm over the Bay of Bengal or the Arabian Sea a name once its maximum sustained surface wind reaches 34 knots (62 km/h), which is cyclonic-storm strength [1]. The name comes from a fixed list of 169 names, 13 from each of the 13 WMO/ESCAP Panel member countries, and each name is used once and never again [1][2].

This matters because a short, simple name helps people spot a storm quickly. Warnings also spread faster and further. A name also avoids confusion when two storms are active at the same time in the same region [1][2].

Explanation

When a storm gets a name

• IMD classification: the India Meteorological Department (IMD) puts every low-pressure system over the Bay of Bengal and the Arabian Sea into a category.

• The category depends on the maximum sustained surface wind. This is the wind speed near the surface, averaged over 3 minutes.

• The first three stages get no name:

• Low-pressure area: wind below 31 km/h (below 17 knots).
• Depression: wind of 31–49 km/h (17–27 knots). The isobars (lines on a weather map joining places with equal pressure) are closed, meaning they form full rings around the centre.

• Deep depression: wind of 50–61 km/h (28–33 knots).

• Naming starts at "cyclonic storm": this is the stage when wind reaches 62–88 km/h (34–47 knots) [1].

• Every stronger stage also uses the name. These stages are severe cyclonic storm, very severe cyclonic storm, extremely severe cyclonic storm and super cyclonic storm (222 km/h or more).

• How a system reaches naming strength:

• Warm sea water heats the air above it. The warm, moist air rises, and pressure at the surface falls.
• The Coriolis force (the turning effect of the Earth's spin on moving air) makes the inflowing air spin anticlockwise in the northern hemisphere.
• Condensation releases heat, which makes the system stronger. When winds cross 34 knots, the storm gets the next name on the list.

Who names the storms

• Around the world, 6 RSMCs (Regional Specialised Meteorological Centres) and 5 TCWCs (Tropical Cyclone Warning Centres) give cyclone advice and name tropical cyclones [1].
• RSMC New Delhi is one of the six. It gives cyclone and storm-surge advice to the 13 WMO/ESCAP Panel member countries [1].

• Storm surge means sea water that a storm pushes onto land.

• WMO/ESCAP Panel on Tropical Cyclones (PTC): a regional body of the World Meteorological Organization (WMO) and the UN Economic and Social Commission for Asia and the Pacific (ESCAP). It agrees on the list of names.

• Special rule: a cyclone that forms in the South China Sea, crosses Thailand and enters the Bay of Bengal keeps its old name. It is not renamed [1].

How the lists grew

• 2000: at its 27th session in Muscat, Oman, the Panel agreed to name storms [1].
• September 2004: the first list began. It had 64 names from 8 countries: Bangladesh, India, Maldives, Myanmar, Oman, Pakistan, Sri Lanka and Thailand [1].
• September 2018: at the 45th session in Muscat, the Panel decided to make a new list. Five new members joined: Iran, Qatar, Saudi Arabia, UAE and Yemen [1].
• September 2019: the rapporteur's report was presented at the 46th session in Nay Pyi Taw, Myanmar. The rapporteur was Dr Mrutyunjay Mohapatra (IMD). A rapporteur is the person who brings members together and finalises the list [1].
• April 2020: the new list was adopted by consensus (everyone agreed). The WMO announced it on 1 May 2020 [1][2].
• Amphan (2020) was the last name on the 2004 list. The new list started after it [1].

How the 2020 list works, and the rules for a name

• Size: 169 names, 13 from each of the 13 members: Bangladesh, India, Iran, Maldives, Myanmar, Oman, Pakistan, Qatar, Saudi Arabia, Sri Lanka, Thailand, UAE and Yemen [1][2].
• Order of use:
• The countries are listed in alphabetical order [1].
• Names are used in turn, column by column. The list starts at the first row of column 1 and ends at the last row of column 13 [1].

• Column 1 begins: Nisarga (Bangladesh), Gati (India), Nivar (Iran), Burevi (Maldives), Tauktae (Myanmar), Yaas (Oman), Gulab (Pakistan), Shaheen (Qatar), Jawad (Saudi Arabia), Asani (Sri Lanka), Sitrang (Thailand), Mandous (UAE) [1].

• Rules for a name:

• It must be neutral towards politics and political figures, religious beliefs, cultures and gender [1][2].
• It must not hurt any group of people anywhere in the world. It must not be rude or cruel [1].
• It must be short and easy to say, and must not offend any member [1][2].
• It can have at most 8 letters [1][2].
• It must be sent with its pronunciation and a voice recording [1].
• It is never repeated: "once used, it will cease to be used again." It must also be new to the lists of every other RSMC in the world [1][2].

• The Panel can reject a name that breaks these rules [1].

• India's names: members of the public sent suggestions, and an IMD committee picked India's names [1]. India's first names are Gati, Tej, Murasu and Aag [1].

Where it occurs

• Area covered: the north Indian Ocean, meaning the Bay of Bengal and the Arabian Sea. Storms here are named by RSMC New Delhi (IMD) [1].
• Member countries (13): from the Gulf (Iran, Oman, Qatar, Saudi Arabia, UAE, Yemen), through South Asia (India, Pakistan, Bangladesh, Sri Lanka, Maldives), to Southeast Asia (Myanmar, Thailand) [1][2].
• Named storms that hit India:
• Fani (2019) hit Odisha. It was a name from the 2004 list.
• Amphan (2020) hit West Bengal and Bangladesh. It reached super cyclonic storm strength over the Bay of Bengal, and it was the last name on the 2004 list [1].

• Biparjoy (2023) formed in the Arabian Sea and made landfall in Gujarat (Kutch). The name came from Bangladesh, in column 2 of the 2020 list [1].

• The world: the same kind of storm has a different name in each ocean. It is a cyclone in the Indian Ocean, a hurricane in the Atlantic and eastern Pacific, and a typhoon in the western Pacific. Each region has its own naming centre among the 6 RSMCs and 5 TCWCs [1].

Don't confuse with

• Depression / deep depression: these are never named. A storm gets a name only at 34 knots (62 km/h). An IMD "depression" warning usually means a rain alert, such as for monsoon depressions over the head of the Bay of Bengal, not a named cyclone.
• Saffir-Simpson Hurricane Wind Scale: this is a 1–5 intensity rating used by the US National Hurricane Center. It is based only on wind, averaged over 1 minute [3]. It measures strength. It does not name storms.
• 2004 list vs 2020 list: the 2004 list had 64 names from 8 countries and ended with Amphan. The 2020 list has 169 names from 13 countries and starts with Nisarga [1].
• Cyclone / hurricane / typhoon: these are regional names for the same type of storm in different oceans. They are not personal names given to individual storms.

Prelims Hooks

• The IMD names a north Indian Ocean storm only when it reaches cyclonic-storm strength: 34 knots / 62 km/h [1]. Depressions and deep depressions are not named.
• Naming was agreed at Muscat, Oman (2000) and began in September 2004 with 64 names from 8 countries [1].
• 2020 list: 169 names = 13 members × 13 names. The five new members are Iran, Qatar, Saudi Arabia, UAE and Yemen [1][2].
• Amphan was the last name of the 2004 list. Nisarga (Bangladesh) was the first name of the 2020 list [1].
• Biparjoy (2023) was proposed by Bangladesh. Gati, Tej, Murasu and Aag were proposed by India [1].
• Trap: a name can have at most 8 letters, and a used name is never repeated. A storm from the South China Sea that crosses Thailand into the Bay of Bengal keeps its old name [1][2].

Mains Points

• Naming helps risk communication (GS-III, disaster management):
• Short, neutral, never-repeated names help the media, disaster managers and the public follow a storm [1][2].
• This matters most when the Bay of Bengal and the Arabian Sea have storms at the same time, because names remove confusion [1][2].

• Named, category-based warnings helped Odisha evacuate people before Fani (2019) and Gujarat before Biparjoy (2023).

• Regional cooperation and India's role:

• The WMO/ESCAP Panel grew from 8 to 13 members, and an IMD rapporteur finalised the 2020 list [1].

• As RSMC New Delhi, India provides cyclone and storm-surge advice to countries from the Gulf to Southeast Asia [1].

• A name is only a label:

• The name says which storm it is, not how dangerous it is.
• Disaster plans must still weigh the IMD category, storm surge, rainfall and how exposed the coast is.
• The Saffir-Simpson scale, for example, ignores storm surge and rain [3].

Related concepts

• Depression
• IMD classification of cyclonic disturbances
• Saffir-Simpson scale

Read more

• Classifying and naming cyclones