How do tropical storms form?
Tropical storms occur between 5* and 30* north and south of the equator. Find out how they form below.
Tropical Storms start between 5º and 30º north and south of the equator where surface sea temperatures reach at least 26.5ºC.
Air is heated above the surface of these warm tropical oceans. The warm air rises rapidly under low-pressure conditions.
The rising air draws up more airing large volumes of moisture from the ocean, causing strong winds.
The Coriolis effect (spinning movement of the Earth) causes the air to spin upwards around a calm central eye of the storm.
As the air rises, it cools and condenses to form large, towering cumulonimbus clouds which generate torrential rainfall. The heat is given off when the air cools powers the tropical storm.
Cool air sinks into the eye, therefore, there is no cloud so it is drier, clear and much calmer.
The tropical storm travels across the ocean by the prevailing wind.
When the tropical storm meets land it is no longer fuelled by the source of the moisture and heat from the ocean so it loses power and weakens.
The weather system generates heat which powers the storm, causing wind speeds to increase. This causes the tropical storm to sustain itself. Tropical storms rely on plenty of warm, moist air from the sea – this is why they die out over land.
What is the structure of a Tropical Storm?
The central part of the tropical storm is known as the eye. The eye is usually between 30-50km across. It is an area of calm, with light winds and no rain. It contains descending air. Large cumulonimbus clouds surround the eye. These are caused by moist air condensing as it rises. Wind speeds average 160km per hour around the eye.
1. Hurricane Katrina – America’s costliest hurricane.
2. Hurricane Andrew – 1992 America’s second-costliest hurricane
4. Indian ‘Super Cyclone’ 1999 Orissa cyclone – The strongest and deadliest cyclone in the region since the Bangladesh cyclone of April 1991
5. Cyclone Eline – 2000 The cause of the major disaster in Mozambique
For more information on current hurricanes visit the US National Hurricane Centre website.
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