GCSE Geography | Where do Tropical Storms Form and Why? (Weather Hazards 3)

Why do most tropical storms happen close to the equator? Latitude is the most important influence on global variation in climate.

Tropical storms occur in the tropics, between the Tropic of Cancer and the Tropic of Capricorn - between 5° and 30° north and south of the Equator. The equator receives much more solar radiation (insolation) that the other latitudes due to the curvature of the earth. The sun’s rays hit the equator directly so they are more concentrated, whereas towards the poles the rays hit at an angle so the radiation is spread out more. This means that air along the equator gets heated more. That heated air is less dense so it rises up, forming an area of low pressure and the formation of clouds that are a vital ingredient of tropical storms. After rising the air begins to spread out and flow towards the poles. The poles are areas of high pressure as they receive less solar radiation to make air rise.

The reason that tropical storms occur where they do is they need a certain combination of conditions to form. They need a sea temperature of at least 27°C, to a depth of around 60-70m - this provides the heat and moisture needed to make warm air rise and then release latent heat, which powers the tropical storm.

Tropical storms usually form during summer and early autumn when it is warmest and there is low wind shear - this is important as it enables the storm clouds to form without being torn apart by wind.

Many people think that tropical storms occur along the Equator - this is not true as the Coriolis Effect here is too weak to cause the wind to bend.

Tropical storms have different names depending on the where they are in the world - hurricanes form in the Atlantic and Eastern Pacific Oceans; typhoons form in the west of the North Pacific Ocean; and cyclones form in the Indian and South Pacific Oceans.