Cyclones in India: Patterns and Preparedness

Every year between April and December, India’s coastline watches the sky with a mix of familiarity and dread. Swirling systems of wind and water build up over the warm waters flanking the subcontinent, and somewhere between a depression and a full-blown storm, they earn a name. For millions living along the 7,500-kilometre coastline, cyclones are not distant news stories but lived realities that shape how homes are built, when fishing boats go out, and where evacuation routes are drawn. Understanding how these storms form, where they strike, and why preparedness has become a matter of life and death is central to grasping the country’s disaster profile.

Why Indian coasts sit in the path of cyclones 🔗

The North Indian Ocean, which includes the Bay of Bengal and the Arabian Sea, is one of the warmest tropical ocean basins on the planet. Although the region contributes only about seven percent of the world’s tropical cyclones, the storms it produces are among the deadliest, largely because they strike densely populated coastlines. In fact, seven of the ten deadliest cyclones recorded between 1970 and 2019 by the World Meteorological Organization formed in this basin.

Tropical cyclones need a specific recipe to form: sea surface temperatures above roughly 26.5°C, enough moisture in the lower atmosphere, low vertical wind shear, and some initial rotation. The waters around India tick most of these boxes during two clear windows each year, giving the country what meteorologists call a bimodal cyclone season.

The two cyclone seasons 🔗

Unlike the Atlantic or Pacific, which have a single prolonged cyclone season, the North Indian Ocean has two distinct cyclone seasons: the pre-monsoon phase from April to early June and the post-monsoon phase from October to December. During the southwest monsoon months themselves, strong vertical wind shear tears apart developing systems before they can mature, which is why July to September is comparatively quiet.

The post-monsoon window tends to produce the more intense and destructive storms. By October, the sea has absorbed heat all summer, upper-atmosphere conditions become favourable, and the monsoon trough shifts south, creating a conducive environment for cyclogenesis.

Bay of Bengal versus Arabian Sea: a lopsided story 🔗

Although cyclones can form on either side of the Indian peninsula, the two basins behave very differently. The Bay of Bengal is by far the busier of the two. For every cyclone that forms in the Arabian Sea, roughly four develop in the Bay of Bengal, according to the Regional Specialised Meteorological Centre of the India Meteorological Department. Between 1990 and 2020, the Bay of Bengal recorded 190 tropical cyclones compared to just 73 over the Arabian Sea.

What makes the Bay of Bengal so cyclone-prone 🔗

Several factors explain the Bay’s disproportionate share. First, the bay is semi-enclosed by land on three sides, which traps heat and keeps sea surface temperatures unusually high. Freshwater discharge from the Ganga, Brahmaputra, Godavari and Krishna rivers lowers surface salinity, keeping the top layer warm and stratified, which provides sustained thermal energy for cyclones.

Second, the bay receives low-pressure remnants from the Pacific that cross through Southeast Asia and get re-energised over its warm waters. Third, wind speeds over the Bay tend to be lower, so heat is not efficiently dissipated from the surface. The combined result is a basin almost perpetually primed for cyclone formation during the pre- and post-monsoon windows.

The Arabian Sea: historically calmer, now changing 🔗

The Arabian Sea was traditionally considered a quieter basin. It produces an average of about 1.3 cyclones a year, accounting for roughly three percent of the global total. Cooler sea surface temperatures, higher salinity, and stronger wind shear historically suppressed cyclogenesis there.

That pattern, however, is shifting. Changes in ocean and atmospheric warming are producing more frequent and severe tropical cyclones in the Eastern Arabian Sea, adjacent to India’s west coast. Cyclones like Ockhi (2017), Tauktae (2021), and Biparjoy (2023) have underlined this trend, putting states like Gujarat, Maharashtra, Goa, Karnataka and Kerala on higher alert than before.

The states in the firing line 🔗

Cyclone exposure in India is heavily concentrated along the east coast. Four states – Andhra Pradesh, Odisha, Tamil Nadu and West Bengal – along with the Union Territory of Puducherry are the most vulnerable to cyclone disasters. An analysis between 1891 and 2000 found that 308 cyclones affected the east coast, of which 103 were severe, while only 48 cyclones crossed the west coast during the same period.

Odisha, in particular, sits at the top of the exposure list. The state has faced more than a hundred cyclones since 1891, and cyclonic storms are almost an annual occurrence there. Andhra Pradesh, with its 972-kilometre coastline and nine coastal districts, is similarly exposed, having weathered over 62 cyclones in the past four decades alone.

How the IMD classifies cyclones 🔗

The India Meteorological Department uses a graded classification system based on sustained wind speeds. A low-pressure area is the weakest system, followed by a depression and a deep depression. Once winds cross 62 km/h, the system becomes a cyclonic storm and earns a name. Higher categories include severe cyclonic storm, very severe cyclonic storm, extremely severe cyclonic storm, and finally super cyclonic storm, with sustained winds above 221 km/h.

Names for cyclones in the region are drawn from a rotating list contributed by member countries of the RSMC New Delhi panel, which includes India, Bangladesh, Pakistan, Sri Lanka, Myanmar, Maldives, Oman, Thailand, Yemen, UAE, Iran, Qatar and Saudi Arabia.

The devastating footprint of a cyclone 🔗

When a cyclone makes landfall, the damage comes in three broad forms: strong winds, heavy rainfall, and storm surge. Of these, storm surge – the abnormal rise of sea water pushed ashore by winds – is historically the biggest killer. The 1999 Odisha Super Cyclone remains a grim benchmark, with sustained winds of 260-270 km/h and nearly 10,000 deaths, many caused by a massive surge that inundated villages kilometres inland.

Beyond the immediate impact 🔗

The secondary effects often outlast the storm itself. Saltwater intrusion destroys farmland and contaminates freshwater sources. Embankments in deltaic regions like the Sundarbans break, allowing brackish water into villages and ruining livelihoods based on fishing and farming. Public health crises frequently follow. After the 1999 Odisha cyclone, outbreaks of diarrhoea and cholera spread through displaced populations.

Infrastructure damage – collapsed homes, snapped power lines, ruined roads – can set back a coastal economy by years. The climate change dimension is making this worse. The frequency of very severe cyclonic storms has increased by about one per decade over the past two decades, even as the overall number of cyclones has declined, meaning fewer but more intense storms.

Building preparedness: from the 1999 wake-up call to today 🔗

India’s cyclone management architecture has transformed dramatically since the 1999 Odisha tragedy. The National Disaster Management Authority (NDMA), set up under the Disaster Management Act of 2005, is the apex body for laying down policies, plans and guidelines for disaster management in the country. Headed by the Prime Minister, it works in coordination with state and district authorities.

Early warning systems 🔗

At the heart of the modern cyclone response is a robust early warning system. Seven cyclone warning centres have been established by the IMD, which has developed state-of-the-art tools providing critical information on cyclones, their intensity, likely point and time of landfall, associated rainfall, winds and storm surges. Warnings are issued in a four-stage colour-coded scheme – green, yellow, orange and red – depending on severity and how close the storm is to landfall.

The National Cyclone Risk Mitigation Project 🔗

Much of the on-ground resilience has been built under the National Cyclone Risk Mitigation Project (NCRMP). The project covers six coastal states with an outlay of INR 2,059 crore and has funded structural interventions like multi-purpose cyclone shelters, coastal embankments, saline embankment strengthening, and underground cabling of power lines in vulnerable zones.

Evacuation: where preparation pays off 🔗

The starkest proof that preparedness works comes from comparing two cyclones that struck Odisha twenty years apart. The 1999 super cyclone killed over 10,000 people. In 2019, Cyclone Fani, another extremely severe storm, hit the same coast. Odisha’s preparedness, efficient early warning system, timely action, and well-planned large-scale evacuation strategies helped 1.2 million people move safely into nearly 4,000 cyclone shelters, and the death toll was kept to just 64 in Odisha. Andhra Pradesh showed similar success with Cyclone Hudhud in 2014.

The United Nations Office for Disaster Risk Reduction has repeatedly praised these efforts as a global model of how an emerging economy can combine forecasting, community mobilisation, and political will.

The gaps that still need closing 🔗

Despite the progress, challenges remain. Even with advances in forecasting, the precise impact of a cyclone can usually only be determined within a short window of 36 to 60 hours before landfall, which puts pressure on evacuation logistics. Inadequate last-mile communication, especially to remote fishing hamlets and island communities, continues to cost lives.

Coastal infrastructure also needs continual reinforcement. Mangroves, coral reefs and sand dunes are the first natural line of defence against storm surges, yet they continue to be lost to construction and aquaculture. Balancing coastal development with ecological protection is one of the hardest policy puzzles along the Indian shore.

The climate change overlay 🔗

Every trend in cyclone behaviour today is being reshaped by climate change. Human-induced climate change is contributing to the intensification and higher frequency of cyclones in the Arabian Sea, putting the densely populated coast from Gujarat to Thiruvananthapuram at higher risk of strong winds, storm surges and heavy rainfall. Warming sea surface temperatures are also enabling rapid intensification, where a cyclone jumps several categories in a matter of hours, compressing the time available to warn and evacuate.

This makes adaptation non-negotiable. Coastal zone regulations, climate-resilient housing, early warning dissemination through Direct-to-Home broadcasts and mobile networks, and regular community drills must all scale up if the next decade’s storms are to cause fewer losses than the last.

What do you think? Given that the Bay of Bengal has historically borne the brunt of cyclones but the Arabian Sea is rapidly catching up, should cyclone preparedness policies for the west coast be redesigned from scratch rather than adapted from east coast models? And how can coastal communities balance the short-term economic costs of evacuation with the long-term imperative of saving lives?

References

1. https://en.wikipedia.org/wiki/North_Indian_Ocean_tropical_cyclone
2. https://www.tandfonline.com/doi/full/10.1080/1755876X.2024.2444753
3. https://www.ipeglobal.com/why-the-bay-of-bengal-is-more-prone-to-cyclones-than-the-arabian-sea/
4. https://anantamias.com/cyclones/
5. https://www.drishtiias.com/daily-updates/daily-news-analysis/more-frequent-cyclones-in-eastern-arabian-sea
6. https://testbook.com/question-answer/identify-the-state-most-affected-by-cyclone-in-ind–60a502b2aa7f54cb9f8f5bcf
7. https://ndma.gov.in/sites/default/files/PDF/Reports/IMD.pdf
8. https://www.ceew.in/publications/how-can-india-strengthen-climate-disaster-preparedness-with-multi-hazard-effective-early-warning-systems
9. https://edurev.in/t/178500/Laxmikanth-Summary-of-National-Disaster-Management
10. https://www.drishtiias.com/daily-updates/daily-news-editorials/india-s-cyclone-preparedness