Typhoons and Hurricanes
- What is a hurricane?
- How does it form?
- The eye of the storm
- How do we name them?
- Tracking the hurricanes
- A trail of destruction
- Building defenses

A hurricane is a large spinning wind system which develops over warm seas near the Equator. These areas are known as the tropics. Technically hurricanes are called tropical revolving storms, but they also have local names. They are called hurricanes when they occur over the Atlantic Ocean, typhoons in the Far East and cyclones in the Indian Ocean. So by definition, all are characterised by rotating winds, which exceed speeds of 120 km/h on the Beaufort Scale.

How does a Hurricane develop?

It is not fully understood why a hurricane develops, as moist air is always rising above warm seas, but it is thought that an "extra" low pressure area moving in over the sea may set them off. >> A diagram of a hurricane's formation.

As the pressure falls rapidly, strong surface winds area formed as air is sucked in towards the centre of the low. At the centre, the air speeds up and spirals upwards. Vast quantities of water vapour in the rising air condense to form massive cumulonimbus clouds. As the water vapour condenses, enormous amounts of heat are given out which makes the air rise even faster, and in turn increases the speed of the surface winds moving in.

A hurricane will usually last for two or three days and then take about four to five days to die out.

The eye of the storm

Down the centre of the storm there is a column of air 30 to 50 km wide, called the eye. The air is slowly sinking and the wind are light. As the eye passes overhead, the wind and the rain stop for a short time only to start again as the other side of the hurricane passe over.
>> An example of an eye of a hurricane.

Did You Know?
If all the energy from one hurricane in a single day could be converted into electricity, it would be enough to supply the whole of the USA for three years. This is equivalent to the amount of energy needed to power 1 095 cars an incredible 36 000 times around the world.

I name you

The first hurricane of the season is given a name beginning with A, the next one with B, and so on. This makes them easier to identify. The names are alternately male and female and come from lists approved by the World Meteorological Organisation.

>> A satallite image of Hurricane Gilbert.

Tracking hurricanes

Like all storms, hurricanes do not stay in one place, but travel away from the sea where they form. Their path is influenced by the movements of high- level winds and the direction of warm sea currents. A hurricane dies out when it reaches an area when there is no longer the necessary warmth and moisture, such as when it reaches a cool sea, or land.
>> Inside the weather station, meteorologists using satellite images to locate the storms.

Satellite images are used to detect where a storm may develop into a hurricane. Meteorologists try to predict the path which a hurricane may take, and issue warnings to people who are at rish from the storm.

A trail of destruction

A trail of destruction

Over land hurricanes do tremendous damage, destroying trees and crops and wrecking buildings. On coasts they whip up huge waves which smash on shore, where they cause flooding and kill many people.

>> This is photo of a region after being destroyed by a hurricane.

5 of the worst recent hurricanes:

Sea walls are the best protection for towns near the sea. Some walls have tops that curve outwards so that the waves are turned back on themselves as they break against them. Others have teeth or ridges which are designed to break up the wave and reduce its impact. When floods do occur, efficient pumping stations needed to get rid of the water quickly. Shutters can be used to protect windows from smashing. Windows can also be covered with strips of tape to stop it from shattering.

>> These people in Bermuda were putting boards over their windows to protect them from the winds of Hurricane Felix when they were hit by a huge storm wave, in August 1995.

>> Tape is sticked on the window, so to prevent the windows from cracking when the wind is too strong.

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