Cyclones: forecasting and evacuation in India

Tropical cyclones form over warm oceans, gather energy from heat and moisture, and strike coasts with high winds, heavy rain and storm surge — a rise in sea level pushed ashore by the storm. India's two cyclone coasts face different seasons and risks: the Bay of Bengal produces more frequent and often more intense cyclones than the Arabian Sea, though Arabian Sea activity has drawn increased attention in recent years. The Odisha coast and the Andhra Pradesh coast are among the most exposed stretches.

Forecasting has improved dramatically. The India Meteorological Department issues track, intensity and landfall forecasts, storm-surge warnings and colour-coded alerts, using satellites, radars, buoys and computer models. Longer lead times and better track accuracy allow state governments to move people before landfall, which is the main reason cyclone deaths in India have fallen sharply compared with disasters such as the 1999 Odisha super cyclone, in which official estimates put deaths at about 10,000.

Evacuation, however, is a social operation, not only a forecast. It needs cyclone shelters that are maintained and accessible, transport for people with disabilities and livestock, food and water at shelters, and trust: people will not leave homes and belongings unless they believe the warning and the shelter. After landfall, restoring power, water, roads and communications, and preventing disease in crowded shelters, determines whether a successful evacuation becomes a successful recovery.

The remaining risk is shifting. Stronger rainfall, higher seas and rapid intensification — a cyclone strengthening quickly before landfall — can surprise even a good forecast system. Building codes for coastal housing, protection of mangroves and embankments, and insurance for fishers and farmers are therefore part of cyclone policy, not afterthoughts. Maintaining shelters between cyclones — for water, sanitation and roofs — matters as much as opening them in an emergency, and stocking them with food, water and medicines before the cyclone season begins.