One of the most powerful of all weather systems, hurricanes are powered by the heat energy released by the condensation of water vapour. However, the conditions have to be exact for a hurricane to form, with the seas surface temperature being above 26.5C.

　　How Hurricanes Happen

　　Air above warm tropical water rises quickly as it is heated by the sea. As the air rises it rotates or spins creating an area of low pressure, known as the eye of the storm. The eye can be clearly seen on satellite pictures, and is usually eerily calm.

　　The hurricane only moves slowly at speeds of 20-25mph bringing torrential rain and thunderstorms and very strong winds. However, they also cause flooding on low lying coastlines with a phenomenon known as a storm surge.

　　Storm Surge

　　This is caused by the intense low pressure at the eye of a hurricane, combining with the effect of strong winds. The sea rises 1cm for every millibar of pressure - if the pressure is 930 millibar, the sea surge will be about 80 cm. Hurricanes can raise the seas surface by as much as 4m.

　　The hurricane winds push the surge along in front of its path. When this surge hits low-lying coasts, the effects can be devastating. In addition to the sea surge, flooding can also result from torrential rain falling from the storm clouds.

　　Once it reaches the mainland, a hurricane may cause widespread damage for a few days, but with no warm water to supply heat, they quickly die out.

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