Answer: Cyclones are caused by atmospheric disturbances around a low-pressure area distinguished by swift and often destructive air circulation. They are usually accompanied by violent storms and bad weather. The air circulates inward in an anticlockwise direction in the Northern hemisphere and clockwise in the Southern hemisphere. Based on the position of occurrence of cyclones, they are categorized as tropical (10-30 degrees N and S of the equator) and temperate (35-65 degrees N and S of the equator) cyclones. Various conditions favorable for the formation of tropical cyclones are:

• Large sea surface provides a supply of moist air which helps form clouds.
• A temperature higher than 27° C is needed for tropical cyclone formation. The high temperature provides the required heat for the cyclone.
• The presence of the Coriolis force is necessary for tropical cyclones so that air starts and continues spiraling around a center.
• Small variations in the vertical wind speed are necessary for the maintenance of the airflow system.
• A pre-existing weak or low-pressure area attracts the flow of moist air to the center.
• Upper divergence above the sea level system is necessary so that the low-pressure system is maintained at the center.

Differences between Tropical and Temperate Cyclones:

It is projected that with ongoing climate change, there is a greater likelihood of a future increase in tropical cyclone precipitation rates; tropical cyclone intensity, and an increase in the frequency of very intense tropical cyclones.