Trace how India's cyclone early warning system has evolved from port signals to impact-based forecasting. What gaps remain?

On 15 October 1976, a Bay of Bengal deep depression was moving towards Madras. IMD's main warning then was to hoist Local Cautionary Signal No. III at every Tamil Nadu port [1]. Since then, warnings have moved from saying what weather is coming to saying what it will damage, district by district. Gaps remain all the same.

Evolution of the warning system

• Port-signal era: IMD used graded port signals and special bulletins. In 1976, a night bulletin forecast 48 hours of heavy rain and squalls above 65 km/h [1]. The warnings were meant for ports and fishermen.
• Track and landfall forecasting: Bulletins now give a landfall window. For example, Fengal (2024) was forecast to cross between Karaikal and Mahabalipuram [2]. Bay of Bengal cyclones peak in October–November, and IMD runs a dedicated forecast project for them [9].
• Impact-based forecasting (2020): IMD started dynamic, district-specific warnings that say what damage to expect, not just how strong the wind will be [3]. It has issued colour-coded district forecasts since 2020 [4].
• Decision support: An indigenous multi-hazard DSS has given district-level risk-based warnings on a GIS platform since 2023 [4]. A Cyclone and Marine DSS (October 2026) adds a cone of uncertainty and district rainfall warnings [5].
• Last-mile delivery: Under NCRMP, run by NDMA with World Bank support, coastal states have built systems to send out warnings [6].

Port signals → Landfall bulletins → District IBF → GIS-based DSS
 (ports)        (coastline)          (collector)    (risk-based)

Who receives the warning has shifted from ports to district administrations

Gaps that remain

• Rain is the blind spot: Tamil Nadu's 2025 northeast monsoon was rated "Normal". Yet it had 29 very heavy and 7 extremely heavy rain days, and Cyclone Ditwah caused widespread damage [7]. Warnings built around wind miss rain that comes in bursts.
• Storms that never make landfall: Only one cyclone crossed India's coast in 2025. Westward-moving low-pressure systems still brought a large share of the season's rain [7].
• Declared vs actual onset: IMD declared the 2020 onset on 28 October. Widespread rain began only around 12–13 November [8]. This can mislead SDMAs and agriculture departments, which use these reports [7].
• Reaching people: NCRMP treats warning delivery and community response as separate objectives [6]. A district warning works only if it reaches the village and gets people to act.

India has moved from flags at ports to district-level, GIS-based risk warnings. The next steps are impact forecasts that put rain and floods first, objective rules for declaring onset, and warnings that reliably reach the last mile. That would bring India closer to the Sendai Framework goal of multi-hazard early warning for all.