What is cyclone(definition)

A  cyclone is a relatively small, intensely developed low pressure cell that usually occur over warm oceans. Its diameter can range between 200 and 2 000 km. It is characterized by a warm centre, very steep pressure gradients and strong cyclonic (clockwise in the southern hemisphere) winds near the Earth's surface. 

Cyclones with a maximum wind speed of less than 60 km/h are called tropical depressions; when the maximum wind speed ranges between 60 and 110 km/h, they are tropical storms, and when the maximum wind speed exceeds 110 km/h, they are called tropical cyclones.

The process by which a disturbance in the pressure pattern forms and subsequently strengthens into a tropical cyclone depends on at least three conditions:

1. Developing tropical cyclones gather heat and energy through contact with warm ocean waters. This usually happens between 5 and 20 North and South.

2.The addition of moisture by evaporation of sea water from the sea surface powers them like giant heat engines, i.e. it draws its energy from the evaporation of sea  water under the storm.

3.A wind pattern near the ocean surface that spirals air inward, is also necessary.

The net result of these processes is a towering column of spiralling air with an intense low pressure in its centre. Bands of thunderstorms form, allowing the air to warm further and rise higher into the atmosphere.