FAQ on tropical cyclones in India

Tropical cyclones are one of the deadliest natural disasters worldwide. The word 'cyclone' is derived from the Greek word Cyclos meaning the coil of a snake. It was coined by Henry Peddington, an English sea captain who sailed in East India and China and experienced tropical storms in the Bay of Bengal and the Arabian Sea.

Cyclones are caused by atmospheric disturbances around low-pressure areas that lead to very swift and destructive air circulation, causing violent storms. This air circulation happens in a clockwise direction in the southern hemisphere and in an anticlockwise direction in the Northern hemisphere. Cyclones often bring heavy rains that can cause flooding. 

Cyclones are known as typhoons in the China Sea and Pacific Ocean, hurricanes in the West Indian islands, tornadoes in the Guinea lands of West Africa and southern USA, willy-willies in north-western Australia and tropical cyclones in the Indian Ocean.

Cyclones begin over warm tropical oceans. When sea surface temperatures rise at or above 26°C, it causes intense evaporation, sending large amounts of water vapour into the atmosphere. This vapour-rich air rises rapidly and cools as it ascends, condensing into towering, puffy, cotton-like clouds with flat bases known as cumulonimbus clouds. If the region has low atmospheric pressure, it acts like a vacuum, pulling surrounding air and clouds towards the centre. 

The Earth’s spin causes the incoming air to deflect and rotate. As more clouds form and rotation strengthens, the system may evolve into a mature cyclone. If conditions change (e.g., cooler waters or landfall), it can lose momentum and weaken.

A mature cyclone can grow in size and increase its wind speed. For a formation to be categorised as a cyclone, its average wind speed needs to exceed 63 km per hour. To be classified as severe, the average sustained wind speed needs to exceed 118 km per hour. Once a cyclone arrives over land, its strength weakens and it begins to fade out. This is due to the lack of moisture and heat compared to the ocean over which it was formed.

A fully developed tropical cyclone has a central cloud-free calm region known as the “eye” of the cyclone, with a diameter varying from 10 to 50 km. Surrounding the eye is the “wall cloud region”, characterised by very strong winds and torrential rains, which has a width of about 10 to 150 km. The winds rotate around the centre. The ‘eye’ of the storm can be circular, concentric or elliptical in shape. The peculiar feature of a mature tropical cyclone in the Indian Ocean is the presence of concentric and  highly turbulent thundercloud bands.

Landfall is the event when a tropical cyclone comes to land after being over water. During a landfall, the centre or eye, of the storm moves across the coast and can be accompanied by strong winds and heavy rains, also causing beach erosion in some cases. 

When the cyclone makes landfall, the eye closes in upon itself, and this leads to the falling down of high waves and a decrease in the wind force. A landfall is different than a direct hit, where the eyewall comes onshore but the centre of the storm may stay offshore, leading to high waves, heavy rains that may cause flooding, water build-up along the coast, coastal beach erosion, high winds, and severe weather. 

A tropical cyclone can be compared to a heat engine where its energy is derived from warm water and humid air over tropical oceans. The release of heat in the cyclone is through condensation of water vapour to water droplets or rain. A small percentage (3%) of this released energy is converted into kinetic energy to maintain the cyclone circulation. A mature cyclone releases energy equivalent to that of 100 hydrogen bombs. 

Intensity of a cyclone is the maximum wind speed around the circulating centre. 

The radius of maximum wind (RMW) of a tropical cyclone is the distance between the centre of the cyclone and its band of strongest winds. This is an important parameter used in understanding atmospheric dynamics and the forecasting of tropical cyclones. 

In India, cyclones are classified by:

• Strength of associated winds

• Storm surges

• High rainfall patterns

Cyclonic storms are categorised based on the maximum wind associated with the storm. If the maximum wind is between 34 and 47 knots (about 62-88 kmph), it is classified as a Cyclonic storm. Severe Cyclonic storm has the maximum wind speed between 48 and 63 knots (about 89-117 kmph).

If the maximum wind is 64-89 knots, it is classified as a Very Severe Cyclonic storm. If the maximum wind is 90-119 knots, it will be called an Extremely Severe Cyclonic Storm, and when the wind is 120 knots and above, it is classified as a Super Cyclonic Storm. 

The Indian Meteorological Department (IMD) classifies the low-pressure systems in the Bay of Bengal and the Arabian Sea on the basis of capacity to damage, which is adopted by the WMO.

The Indian subcontinent is exposed to nearly 10 percent of the world’s tropical cyclones with a coastline of 8041 kilometres. Five to six tropical cyclones form every year, of which two or three can become severe. 

Majority of the cyclones occur in the post-monsoon season (mid-September to December), followed by the pre-monsoon season from April to May. The post-monsoon cyclones are the most devastating, and the active zone for cyclones is the Bay of Bengal in India. 

More cyclones occur in the Bay of Bengal than in the Arabian Sea, and the ratio is approximately 4:1. This is because the surface temperature in the Bay of Bengal is higher than in the Arabian sea. In the last century, out of the 1019 cyclonic disturbances happening over the Indian subcontinent, 890 were along the eastern coast, and of these, 260 had their landfall over the Odisha coast. 

Eight states on the eastern and western coasts of India are vulnerable to cyclones, of which the eastern coastal states of West Bengal, Odisha, Andhra Pradesh, Tamil Nadu and West Bengal are the most affected. Between 1981 and 2002 these states have experienced 69, 98, 79 and 54 cyclones, respectively. The western coasts have suffered from relatively fewer cyclones and include the states of Maharashtra (13), Gujarat (28), Kerala (3), Karnataka and Goa (2 each).

Cyclonic storms can get dangerous because of very heavy rains that accompany them triggering sudden floods, strong winds and storm surges. Record rainfall in a cyclonic storm has been as low as a trace to as high as 250 cms. It has been found that the intensity of rainfall can be about 85 cm/day within a radius of 50 kms and about 35 cm/day between 50 and 100 kms from the centre of the storm. Flash floods can accompany very heavy rains. Strong winds associated with cyclonic storms (62-88 kmph) can damage kaccha houses and infrastructure and threaten lives. Winds of a severe cyclonic storm (89-117 kmph) can cause uprooting of trees, damage pucca houses and installations, disrupt communications, and destroy crucial health care facilities such as hospitals, food storage facilities, roads, bridges and culverts, crops, etc. The maximum wind speed associated with a very severe Cyclonic storm that hit the Indian coast in the past 100 years was 260 kmph in Oct, 1999 (Paradip Super cyclone).

The most severe impact of a tropical storm is the formation of tidal waves that worsen if the landfall time coincides with that of high tides and if the seabed is shallow. Storm surge as high as 15 to 20 ft. may then occur, which can inundate low-lying coastal areas, leading to an increase in salinity of land and loss of fertility. Storm surges and torrential rains that flood the lowland areas of coastal territories often lead to a high number of fatalities. 

Through early warning systems

The IMD is a nodal agency for cyclone forecasting and early warning. IMD uses Doppler weather radars, Insat satellite and ocean buoys for real-time monitoring

IMD issues five-stage cyclone alerts for Indian coasts:

• Pre-cyclone watch: It is issued 72 hours in advance, and discusses the likelihood of development of a cyclonic disturbance in the north Indian Ocean and the coasts

• Cyclone alert: Is issued 48 hours in advance of the cyclonic disturbance over the coastal areas.

• Cyclone warning: Issued 24 hours in advance of the cyclonic event over coastal areas. The location of landfall is discussed at this stage.

• Post-landfall outlook: Issued 12 hours in advance of the cyclonic event. The possible impact of the cyclone after the landfall is discussed at this stage.

Employing Disaster Management and Response Agencies

• The National Disaster Management Authority (NDMA) is India’s apex body for disaster preparedness and mitigation. It formulates policies, coordinates large-scale evacuations, and ensures that relief measures are in place before a cyclone makes landfall.

• The National Disaster Response Force (NDRF) includes specially trained teams who are equipped with search-and-rescue gear, inflatable boats, and medical kits and can help to evacuate people and provide immediate relief.

• State Disaster Management Authorities (SDMAs) work closely with the NDMA and district administrations to manage local shelters, plan evacuations, and ensure provision of timely relief materials like food, water, and medicines to the affected.

• Armed Forces play a critical role in rescuing fishermen at sea, transporting relief supplies, restoring connectivity, setting up medical camps, and reaching inaccessible and affected villages.

Common Alerting Protocol

Developed by IMD and NDMA and provides a single platform for hazard warnings such as cyclones and includes:

• Mobile SMS alerts

• Television tickers

• Radio broadcasts

• Social media alerts

Mock Drills and Community Preparedness

• Regular mock drills conducted in vulnerable villages that are led by SDMAs and NDRF 

• School safety programmes, village task forces and community-based disaster management are promoted.

Cyclone Preparedness in the Fisheries Sector

• Vessel Monitoring Systems (VMS) and Distress Alert Transmitters (DAT) are provided to fishermen for cyclone-related alerts

• Fishermen advisories are regularly provided by IMD, Coastguards and INCOIS (Indian National Centre for Ocean Information Services).

Communication and Warning Systems: How does a common person get information on cyclones

Local AIR broadcasts hourly (or more frequently) bulletins in the local language as well as in Hindi and English. These bulletins give the location of the cyclonic storm, its direction of movement, place and time of landfall and details of adverse weather expected over the areas likely to be affected by the storm. AIR, New Delhi, issues bulletins thrice in a day giving similar information. 

Cyclone warning messages are sent to the collectors of the districts expected to be in the line of the cyclone and the chief secretary of the concerned state. The state government takes necessary steps to inform the local population through their machinery, such as police wireless, etc., and arrangements for evacuation from coastal and other risk areas.

Indian National Centre for Ocean Information Services (INCOIS): INCOIS provides specialised ocean forecasts such as storm surge warnings, high wave alerts, and potential coastal flooding zones crucial for fishermen and coastal authorities.

Use of Technology and Innovation

The India Meteorological Department (IMD) has a network of Doppler weather radars, ground stations, and advanced satellite data from the INSAT series to monitor storm formation, intensity, and movement.

The Indian Space Research Organisation (ISRO) helps by providing high-resolution satellite imagery through its INSAT and Oceansat satellites. These satellites help track cyclone eye formation, rainfall patterns, and wind speeds. 

In recent years, private companies and AI research labs have also been helping to forecast by using advanced models.

Aurora: Microsoft's Atmospheric Foundation Model

Aurora is an AI model that can predict severe weather events with high resolution and speed. 

GraphCast: Google's AI-Driven Forecasting

GraphCast, an AI-based weather model, has the capacity to generate medium-range forecasts with remarkable accuracy and can generate a 10-day forecast in under a minute, thus reducing computational energy costs.

Skymet Weather

Skymet Weather Services is a leading private company in India that provides weather forecasts and climate-related services using over 5,500 automatic weather stations, satellite data, and proprietary forecasting models to monitor and predict severe weather events such as cyclones across India. 

Regulations and plans

National Cyclone Risk Mitigation Project (NCRMP) 

A World Bank-assisted programme for implementation by NDMA for mitigating risks of cyclones in eight (08) cyclone-prone coastal States. The scheme has the following components:

• Improved early warning systems

• Construction of cyclone shelters

• Strengthening embankments and constructing mangrove bio shields

• Capacity building of local communities

National Disaster Management Plan (NDMP), 2016

• Emphasises risk reduction, resilient infrastructure and community preparedness for cyclones

Integrated Coastal Zone Management (ICZM)

• Launched by MOEFCC

• Aims to protect coastal communities and ensure security of their lives and livelihoods, protect coastal ecosystems such as mangroves, sand and sand dunes and wetlands that offer natural cyclone protection and promote sustainable development.

Coastal regulation zone notification

• Enacted by MOEFCC in 19191 (Revised in 2011 and 2019)

• Objective: Restrict unplanned development along the coastline, protecting ecologically sensitive zones like mangroves and sand dunes that act as natural barriers against storm surges.

India has thus significantly improved its cyclone preparedness in the past two decades. The death toll in earlier cyclones was very high, such as in the case of the 1999 Odisha Super Cyclone that killed nearly 10,000 people. However, recent cyclones of similar intensity—such as Fani (2019) and Amphan (2020)—have seen fewer casualties.

The NDMA has issued some do’s and don’ts in times of cyclones

When the cyclone starts

• Listen to the radio (All India Radio stations give weather warnings).

• Monitor warnings

• Pass the information to others.

• Ignore rumours to avoid panic situations.

• Stay alert, as a cyclone alert can mean that the threat remains for 24 hours.

When your area is under cyclone warning

• Get away from low-lying areas or areas close to the coast to high grounds or shelters

• Take shelter in the safe part of the house, but evacuate as soon as possible if you get instructions

• Take protective measures like putting storm shutters in place and providing suitable support for outside doors. Ensure that you have enough stocks of food and water and medicines, etc., for vulnerable members of the family like children and the elderly.

• Move valuables to prevent damage due to floods if you need to vacate the house.

• Ensure that you have torches or other emergency lights that are in working condition and keep them handy.

• Store small and loose things, which can fly in strong winds, in safe places.

• Look out for a door or window on the opposite side of the storm in case you need to make an exit.

• Switch off the electrical mains in your house and remain calm

During a cyclone

Do not go out in the open even when the winds are low, as the 'eye' of the cyclone might be passing. Wait for official announcements, as winds might intensify again and cause damage. 

In case of evacuations

• Pack all essentials for yourself and your family to last a few days. These should include medicines and special food for babies, children or elders.

• Move towards shelters or evacuation points indicated for your area, and do not roam around.

• Remain in the shelter and move out only after you are directed to do so

Post-cyclone measures

• Remain in sheltered, protected areas until you are asked to go home.

• Get inoculated against diseases immediately.

• Avoid any loose and dangling wires from lamp posts.

• Clear debris from your premises immediately.

• Report losses to appropriate authorities.

Cyclones will continue to pose serious risks as climate change warms oceans and alters storm behaviour, increasing the likelihood of rapid intensification and heavy rainfall. But India’s experience over the past two decades shows that strong institutions, reliable early-warning systems, trained response forces and community awareness can save thousands of lives. From Doppler radars and satellite monitoring to local shelters, coastal regulation and mangrove restoration, the country has steadily built resilience.

Still, preparedness begins at home. Following official warnings, storing essentials, securing homes, and participating in community drills remain critical steps for reducing harm. As coastal populations grow and weather extremes become more unpredictable, understanding cyclones is no longer optional—it is essential knowledge for safeguarding lives, livelihoods and the fragile ecosystems that protect our coasts.