Why does the Bay of Bengal generate more intense post-monsoon cyclones than the Arabian Sea? Discuss their implications for coastal States.

The Bay of Bengal produces roughly four cyclones for every one in the Arabian Sea [1], and its post-monsoon (October–December) storms are often the strongest of the year. Cyclone Arnab fits this pattern. It was a Very Severe Cyclonic Storm that triggered a red-message warning for Andhra Pradesh and south Odisha in October 2026 [2]. The ocean, the atmosphere and the shape of the coast together explain the difference.

Why the Bay of Bengal generates more intense cyclones

• Warmer sea: The Arabian Sea is relatively colder, which holds back cyclone formation and intensification. The Bay stays warm enough to keep feeding storms [1].
• Pacific remnants: Remnants of north-west Pacific typhoons move west over South-East Asia and strengthen again over the Bay [1].
• Freshwater layer: Monsoon rain and Ganga–Brahmaputra discharge leave a low-salinity surface layer. It resists mixing, so storms do not stir up cooler water from below.
• Post-monsoon atmosphere: As the monsoon retreats, wind shear weakens. Arnab was expected to intensify further as it detached from the ITCZ [2].
• Arabian Sea handicaps: Most Bay storms weaken over land and rarely cross into the Arabian Sea [1]. Drier air over the Arabian Sea also suppresses cyclones.

Implications for coastal States

• Exposure: India has about 7,500 km of coastline, and about 40% of its population lives within 100 km of it [3]. The Bay's shallow shelf and funnel-shaped head raise storm surge in Odisha, West Bengal and Andhra Pradesh.
• Economic loss: Even as deaths fall, losses rise: an estimated USD 4.2 billion from Fani and USD 14 billion from Amphan [3]. Crops, ports, fisheries and power networks are hit hardest.
• Forecasting stress: For Arnab, IMD forecast winds of 115–125 km/h two days before landfall [2]. A storm that strengthens faster than forecast leaves less time to evacuate.
• Resilience gains: NCRMP and related projects built 830 multi-purpose shelters and 33,258 resilient houses in coastal districts of AP, Odisha and Tamil Nadu [3]. Cyclone deaths fell by about 94% over two decades [3].
• Persisting gaps: The Parliamentary Standing Committee on Home Affairs (2020) found that construction had not begun on some early-warning projects commissioned in 2015 [4].
• Shifting risk: Cyclone frequency and intensity are rising over the Arabian Sea [3]. Gujarat, Maharashtra and Kerala therefore need east-coast-style preparedness.

The Bay's warm, stratified, Pacific-fed waters make it India's main cyclone hotspot, and a warming ocean raises the stakes. The next steps should be impact-based forecasting, sub-surface ocean monitoring by INCOIS, last-mile community warning and on-time NCRMP delivery. These would move coastal States from "zero casualty" towards "zero avoidable loss", in line with the National Disaster Management Plan, 2019 and SDG 13.