Cyclone Categorization and Naming Explained: Types, Wind Speed Scales, and Global Naming Systems
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Categorization of Cyclones
Cyclonic systems are categorized primarily by their maximum sustained wind speed, with different scales used depending on the geographical region. This categorization is crucial for forecasting, issuing timely warnings, and planning disaster preparedness.
Broadly, cyclone categorization is done in two ways,
- By Type of Cyclone – Based on the region and mechanism of formation.
- By Wind Speed/Intensity – Based on the strength of sustained winds, which indicates the cyclone’s destructive potential.
1. Categorization by Type of Cyclone
- Tropical Cyclones: These are intense, large-scale, low-pressure systems that form over warm tropical or subtropical ocean waters. They draw energy from ocean heat and moisture. Depending on the region, they are called: • Hurricanes (Atlantic Ocean) • Typhoons (Western Pacific Ocean) • Cyclones (Indian Ocean)
- Extratropical (Temperate or Mid-Latitude) Cyclones: These usually form in temperate and higher latitudes and are commonly known as frontal cyclones. Unlike tropical cyclones, they form due to interactions of different air masses and temperature contrasts along weather fronts.
2. Categorization by Wind Speed/Intensity
Once formed, cyclones are further classified by the strength of their winds. Different regions use different classification systems: (a) Cyclone Intensity Scale – India (Bay of Bengal & Arabian Sea)
India classifies tropical cyclones by their maximum sustained wind speed. In the Bay of Bengal and Arabian Sea, the IMD uses a more granular scale based on a 3-minute sustained wind average. This system provides a more detailed progression of a cyclonic system's development.
- Low-pressure area: Wind speed does not exceed 31 km/h.
- Depression: Wind speed of 31 to 49 km/h.
- Deep depression: Wind speed of 50 to 61 km/h.
- Cyclonic Storm: Wind speed of 62 to 88 km/h. Storm: Wind speed of 62 to 88 km/h.
- Severe Cyclonic Storm: Wind speed of 89 to 117 km/h.
- Very Severe Cyclonic Storm: Wind speed of 118 to 167 km/h.
- Extremely Severe Cyclonic Storm: Wind speed of 168 to 221 km/h.
- Super Cyclonic Storm: Wind speed of 222 km/h and above.
(b) Saffir-Simpson Hurricane Wind Scale (SSHWS) – Atlantic & Northeastern Pacific
This scale ranks hurricanes from Category 1 to 5, based only on maximum sustained wind speeds:
- Category 1: 74 to 95 mph (119 to 153 km/h) – Some damage expected.
- Category 2: 96 to 110 mph (154 to 177 km/h) – Extensive damage possible.
- Category 3 (Major): 1111 to 29 mph (178 to 208 km/h) – Devastating damage likely.
- Category 4 (Major): 130 to 156 mph (209 to 251 km/h) – Catastrophic damage expected.
- Category 5 (Major): 157 mph or higher (252 km/h or higher) – Widespread catastrophic destruction.
Naming of Cyclones
The practice of naming tropical cyclones was introduced to make storm identification and communication easier for forecasters, the media, and the public. A short and memorable name is far more effective than technical terms or numbers, especially in raising disaster awareness, preparedness, and risk reduction.
Global Oversight by WMO
Today, the naming of cyclones is managed by regional bodies operating under the World Meteorological Organization (WMO). Five regional tropical cyclone committees coordinate this process:
1. ESCAP/WMO Typhoon Committee
2. WMO/ESCAP Panel on Tropical Cyclones
3. RA I Tropical Cyclone Committee
4. RA IV Hurricane Committee
5. RA V Tropical Cyclone Committee
Cyclone Naming in the North Indian Ocean
For the Bay of Bengal and Arabian Sea, the naming of cyclones is overseen by the WMO/ESCAP Panel on Tropical Cyclones, which prepares and maintains the list of names summited by member countries. This panel includes 13 member countries: Bangladesh, India, Iran, Maldives, Myanmar, Oman, Pakistan, Qatar, Saudi Arabia, Sri Lanka, Thailand, United Arab Emirates, and Yemen. Once a weather system intensifies into a cyclone (reaches wind speeds of ≥ 63 km/h or 34 knots), the Regional Specialized Meteorological Centre (RSMC) in New Delhi assigns the next available name from this list.
India has contributed multiple names to the list. In 2004, names like Agni, Akash, Bijli, Jal, Lehar, Megh, Sagar, and Vayu were adopted. After the panel expanded from 8 to 13 countries in 2018, a new list was finalized in April 2020. India’s submissions to this updated list include Gati, Tej, Murasu, Aag, Vyom, Jhar, Probaho, Neer, Prabhanjan, Ghurni, Ambud, Jaladhi, and Vega.
Rules for Naming
Each cyclone name must meet strict criteria:
• It should be neutral (not linked to politics, religion, culture, or gender).
• It must be short (maximum eight letters) and easy to pronounce.
• It should not carry offensive or negative meanings.
Unlike other global basins where names are reused, in the North Indian Ocean, each name is used only once. From intensity scales to international naming conventions, we now understand the organized science used to classify and communicate the threat of these powerful storms. Knowing the difference between a 'Severe' and a 'Super Cyclonic Storm' is critical knowledge that forms the foundation of disaster preparedness. But what is the real-world impact of these categories, and what should we do when a named storm approaches? In our next post, we will explore the destructive power of cyclones and the essential measures to protect life and property. Read Next →
