Tropical cyclones originate and intensify over warm tropical oceans. The conditions favourable for the formation and intensification of tropical storms are:
- Large sea surface with a temperature higher than 27° C;
- Presence of the Coriolis force;
- Small variations in the vertical wind speed;
- A pre-existing weak low-pressure area or low-level-cyclonic circulation;
- Upper divergence above the sea level system.
When the air rises up and away from the ocean surface, it creates an area of lower air pressure below. It causes the air from surrounding areas with higher pressure to move towards the low-pressure area which further leads to warming up of the air and causes it to rise above. The moist air rises and cools the water in the air forming clouds. The complete system of clouds and wind spins and grows. More air rushes to the centre and this cycle is repeated. The chain of events ends with the formation of a very low-pressure system with very high-speed winds revolving around it. It is this weather condition that we call a cyclone.