How ISRO Satellites and INSAT Data Warn Indian Fishermen Before a Cyclone Hits the Coast

About 7 percent of the world's tropical cyclones form in the Bay of Bengal, but that basin accounts for a disproportionate share of cyclone deaths globally. The geometry is partly to blame: the bay is shaped like a funnel, and storms that form in its southern reaches have nowhere to go but north, straight toward the densely populated coasts of Odisha, Andhra Pradesh, West Bengal, and Bangladesh. For the fishing communities that work these waters, the difference between a warning and no warning is not inconvenience. It is survival.
India has roughly 7,500 kilometres of coastline and over four million registered fishermen. On any given morning during the pre-monsoon or post-monsoon season, thousands of boats are at sea before dawn. The question that has occupied ISRO engineers and IMD meteorologists for decades is a practical one: how do you get reliable, actionable information to a fisherman who is 80 kilometres offshore with no internet connection and a patchy mobile signal?The INSAT series, operated by ISRO, is the backbone of India's weather satellite infrastructure. INSAT-3D and INSAT-3DR, both geostationary satellites, carry imaging and sounding payloads that scan the Indian subcontinent and surrounding ocean every 15 to 30 minutes. Geostationary means they sit at roughly 36,000 kilometres above the equator, moving at the same speed as Earth's rotation, so they always watch the same patch of sky and sea.
The imaging payload captures the ocean surface and cloud formations across multiple spectral bands, including infrared and water vapour channels. The sounder reads vertical temperature and humidity profiles through the atmosphere, layer by layer. Together, these instruments give meteorologists at the India Meteorological Department a continuous, high-resolution picture of how a low-pressure system is organising itself over the Bay of Bengal or the Arabian Sea. When cloud tops start cooling rapidly and the circulation tightens, the data shows it hours before any surface observation could.
INSAT-3DR, launched in 2016, added a Data Relay Transponder that receives transmissions from Automatic Weather Stations and ocean buoys scattered across remote areas. Those buoys measure wave height, sea surface temperature, and wind speed at the water's surface. The satellite collects that data and relays it to ground stations, filling in the gaps that no land-based radar can reach.The chain from raw satellite data to a warning in a fisherman's hands runs through several institutions. IMD processes the INSAT imagery and model output to track and forecast cyclone intensity and track. INCOIS, the Indian National Centre for Ocean Information Services based in Hyderabad, translates that into ocean-state forecasts and fishery advisories specifically aimed at coastal communities.

INCOIS runs a system called the Potential Fishing Zone advisory, which tells fishermen where fish are likely to be concentrated based on sea surface temperature and chlorophyll data derived from satellites. The same infrastructure that delivers that advisory also delivers the cyclone warning. When IMD upgrades a depression to a cyclonic storm and issues a colour-coded alert, INCOIS pushes SMS messages in regional languages to registered fishermen. The messages specify the expected landfall zone, the wind speed category, and the number of hours remaining before conditions become dangerous at sea.
Coastal district administrations, the Indian Coast Guard, and state fisheries departments reinforce the message through loudspeakers at harbours, VHF radio, and direct outreach to fishing cooperative leaders. The system is deliberately redundant because no single channel reaches everyone.Cyclone Fani made landfall near Puri, Odisha, in May 2019 as an extremely severe cyclonic storm with wind speeds around 175 kilometres per hour. It was the strongest storm to hit India's east coast in roughly two decades. The Indian government evacuated approximately 1.2 million people in the days before landfall, one of the largest pre-cyclone evacuations in the country's history. The death toll, which would have been catastrophic under earlier warning systems, was contained to around 64 in India.

The satellite-driven warning chain was central to that outcome. INSAT-3D and INSAT-3DR tracked Fani's intensification as it crossed the warm waters of the Bay of Bengal. The track forecast, issued days in advance, gave state governments in Odisha and Andhra Pradesh enough lead time to move people out of low-lying coastal areas. Fishermen had been warned off the sea well before the storm reached dangerous proximity to the coast.
The contrast with Cyclone 1999, which struck nearly the same stretch of Odisha coastline and killed close to 10,000 people, is a measure of what the satellite infrastructure has changed. The 1999 storm arrived with far less warning time, and the communication systems to reach fishing villages and coastal hamlets simply did not exist in their current form.Satellite data is powerful but not the whole picture. Cyclone intensity forecasting remains harder than track forecasting. A storm can intensify rapidly over warm ocean water in a matter of hours, and even the best satellite sounders and numerical weather models can underestimate the speed of that jump. Rapid intensification, defined as a wind speed increase of at least 55 kilometres per hour in 24 hours, is the forecast problem that keeps IMD scientists working on improved algorithms.

The reach of SMS warnings also has a hard floor. Fishermen without registered numbers, boats that go out before a warning is issued, and communities with poor network coverage remain vulnerabilities. ISRO and IMD have been working on satellite-based direct-to-device communication systems that could eventually bypass terrestrial mobile networks entirely for emergency alerts.
What the INSAT constellation has already done is compress the warning lead time problem from days of uncertainty to hours of precision. A fisherman who gets an INCOIS alert in Tamil or Odia with a specific harbour-return deadline is working with information that, two decades ago, no technology could have produced at all. The satellite does not stop the cyclone. It changes the calculation of who has time to get out of its way.