Cyclones in India: Formation, Naming and Early Warning Systems

Core Concept

A tropical cyclone is a low-pressure weather system that draws its energy from the latent heat released when warm, moist ocean air rises and condenses. Over the Bay of Bengal and the Arabian Sea, favourable conditions typically develop during the pre-monsoon (April-June) and post-monsoon (October-December) months, outside the main monsoon-trough period. The India Meteorological Department (IMD), as the Regional Specialised Meteorological Centre (RSMC) for the North Indian Ocean, tracks, classifies and names these systems, and issues warnings to protect life and property along India's roughly 7,500 km coastline.

Key Points

• Formation conditions: sea-surface temperature above roughly 26.5°C up to a depth of about 60 m, low vertical wind shear, a pre-existing weak low-pressure disturbance, sufficient Coriolis force (hence cyclones rarely form within about 5° of the equator), and upper-tropospheric divergence to pull air upward and sustain the system.

• IMD intensity scale: systems are graded from low-pressure area to depression, deep depression, cyclonic storm, severe cyclonic storm, very severe cyclonic storm, extremely severe cyclonic storm, and (rarely) super cyclonic storm, based on maximum sustained surface wind speed.

• Naming authority: cyclones in the Bay of Bengal and Arabian Sea are named under the WMO/ESCAP Panel on Tropical Cyclones (PTC), whose 13 member countries — Bangladesh, India, Iran, Maldives, Myanmar, Oman, Pakistan, Qatar, Saudi Arabia, Sri Lanka, Thailand, UAE and Yemen — each contribute names to a shared, rotating list used column-wise regardless of where a storm actually forms; names must be short, easy to pronounce, and free of political, religious or gender bias.

• A system is "named" only once it qualifies: a depression is formally named only when it intensifies into a cyclonic storm (sustained winds of at least 62 km/h) — a weaker system that dissipates as a depression or deep depression never receives its reserved name, even if that name is already circulating informally in media reports.

• Institutional architecture: IMD's Cyclone Warning Division, backed by Doppler Weather Radars, INSAT meteorological satellites and numerical weather prediction models, issues staged warnings (Pre-Cyclone Watch, Cyclone Alert, Cyclone Warning, Post-Landfall Outlook); the National Disaster Management Authority (NDMA) and National Disaster Response Force (NDRF) coordinate the ground response, under the broader National Cyclone Risk Mitigation Project (NCRMP) framework and India's commitment to the UN's 'Early Warnings for All' target of 2027.

Memory Trick

Remember the escalation ladder as "D-D-C-S-V-E-S" — Depression, Deep depression, Cyclonic storm, Severe cyclonic storm, Very severe, Extremely severe, Super cyclonic storm — rising steps on a staircase of wind speed. For naming, recall "13 countries, one shared list": no single nation "owns" a storm's name, which is why Bangladesh can contribute a name for a system that eventually crosses the Andhra Pradesh-Odisha coast.

Current Relevance (2025-2026)

On 12 October 2026, IMD dedicated a new Cyclone Warning and Marine Weather Services Decision Support System (DSS) to the nation, timed to the pre-cyclone exercise meeting for the October-December 2026 post-monsoon season chaired by Director General Mrutyunjay Mohapatra and attended by officials from NDMA, NDRF and over 30 organisations. The WebGIS-based public platform overlays cyclone tracks, forecast intensity, a "cone of uncertainty," storm-surge estimates and district-level rainfall warnings on an interactive map, and had already been demonstrated to more than 650 stakeholders and media representatives on 9 October 2026. This followed a season in which, in September 2026, a Bay of Bengal system intensified only to deep-depression strength before crossing the coast near Kalingapatnam — so it never earned its reserved name, "Arnab" (contributed by Bangladesh) — a useful illustration of the naming rule above. A year earlier, Cyclone Montha (named by Thailand) had threatened Andhra Pradesh, Odisha and Tamil Nadu in late October 2025, prompting high alerts across all three states.