Intense, rotating low-pressure storm systems that form over warm tropical oceans, bringing violent winds, heavy rain, and storm surges; called cyclones in the Indian Ocean.
- Need warm sea-surface temperatures (above about 26 to 27° Celsius), high humidity, the Coriolis force (so they do not form right on the equator), and weak upper winds.
- Have a calm central "eye" of low pressure, surrounded by the eye-wall of the strongest winds and rain; winds rotate anticlockwise in the Northern Hemisphere.
- Called cyclones (Indian Ocean), hurricanes (Atlantic and east Pacific), and typhoons (west Pacific); cyclone names in the North Indian Ocean are coordinated through the IMD-led regional panel.
- In India, the east coast (Bay of Bengal) is hit more often and more severely than the west coast; main season is October to November (and pre-monsoon).
- Storm surge (a wall of sea water pushed ashore) is often the deadliest effect; the IMD issues colour-coded warnings (verify the latest categories).
The formation conditions, the eye and eye-wall structure, the naming by ocean, and the Bay of Bengal vulnerability link directly to disaster-management and security deployment.
Same storm, different names by region: cyclone (Indian Ocean), hurricane (Atlantic), typhoon (west Pacific); the east coast (Bay of Bengal) faces more cyclones than the west coast.
Warm-ocean rotating low-pressure storms with a calm eye; called cyclones in the Indian Ocean; east coast most affected.