Tropical cyclones are largely confined to South China Sea, Bay of Bengal and Gulf of Mexico. Why? (UPSC 2014)

Tropical cyclones need warm, deep water, enough Coriolis force, moist air and low vertical wind shear. The South China Sea, Bay of Bengal and Gulf of Mexico provide this combination more often than most other ocean areas.

• Semi-enclosed basins: These seas trap heat, so surface waters stay above 26.5°C for long periods.
• Shallow shelves: Limited deep mixing prevents cold water from rising and weakening storms.
• Freshwater input: Large rivers create a warm surface layer and barrier layer, which helps storms keep drawing energy.
• Favourable latitude: They lie far enough from the equator for Coriolis force to initiate rotation.
• Seasonal monsoon setting: Low pressure, high humidity and pre-existing disturbances support cyclone formation.

Thus, these basins act as natural breeding grounds for tropical cyclones, while many open oceans lack the same heat retention and atmospheric support.