where we hope you learn about the fascinating weather that affects us day to day. This is a great learning resource for parents and teachers.
What is a hurricane?
A hurricane is the most violent storm known on Earth.
- Hurricanes are tropical storms. They take place between the Equator and the Tropic of Cancer to the north, or between the Equator and the Tropic of Capricorn to the south.
- Hurricanes form at sea and cause dangerous, stormy seas.
- Some hurricanes reach the land and can destroy buildings and trees.
- A hurricane can blow high waves onto the land and cause flooding.
- The Atlantic hurricane season lasts from the beginning of June until the end of November.
- There are usually between four and six hurricanes in a year that will cause some destruction on land.
The winds in a hurricane do not blow from west to east or north to south. They blow round in a circle.
- A hurricane is like a spinning top.
- The winds in a hurricane blow in a circle.
- North of the equator the winds in a hurricane blow in an anticlockwise direction.
- South of the equator the winds blow in a clockwise direction.
- The winds in a hurricane blow at a speed of at least 74 miles an hour. Their speed is often much more than this.
Hurricanes can be seen from space. This photograph from space shows Hurricane Ivan hitting the coast of America.
- Hurricanes form a thick mass of swirling cloud which can be seen from space.
- A hurricane can be six miles high and 400 miles wide.
- An area of calmer weather lies in the centre of the hurricane. This is known as the ‘eye of the storm’.
Why does a hurricane move in circles?
Hurricanes form their circular, swirling movement because of the spinning of the earth on its axis.
- If the earth did not spin, we would have very strong winds from the tropics to the poles and back.
- Because the earth spins, the spinning movement causes the wind to go to the right. Try this yourself. If you keep turning to the right, you will go round in a circle.
- The force that makes the wind turn to the right is called the Coriolis Force.
- The Coriolis Force does not affect winds above the Equator.
- Hurricanes never form on the Equator itself.
What causes a hurricane?
Hurricanes form in areas of low pressure. When meteorologists (scientists who study weather) talk of low pressure, they mean warmer weather, storms and rain.
- In the tropics there is a broad area, or zone, of low pressure on either side of the equator.
- Inside the area of low pressure the ocean is warm and heats the air above it.
- The warm air rises until it cools and forms thundery clouds.
- As the air rises, more air moves in to replace it.
- As more and more clouds form and more warm air is pushed upwards, the clouds join together and begin to spin.
- This is the beginning of the hurricane.
Hurricanes, typhoons and cyclones
Hurricanes, typhoons and cyclones are the same thing.
- These destructive, swirling storms are known scientifically as tropical cyclones.
- The cyclones are called typhoons in the north-west Pacific.
- They are called hurricanes in the Atlantic and north-east Pacific
- The word ‘hurricane’ is taken from the name of the Carib Indians’ storm god, Hunraken.
The names of hurricanes
Meteorologists (scientists who study weather) know when tropical storms are about to happen. The meteorologists give names to all the tropical storms, hurricanes, typhoons and cyclones.
- The first storm of the year begins with the letter ‘A’.
- The names are male and female in order. For example in 2011 the names of the first six Atlantic tropical storms were:
- The names are reused every six years, so in 2017 Arlene and Bret will reappear.
- If a storm causes terrible destruction and loss of life, the name is not used again.
- Following the destruction caused to New Orleans in American by Hurricane Katrina in 2005, the name Katrina was taken off the list.
- Hurricane Katrina was a category 5 hurricane.
- Category 1 hurricanes have wind speeds of 74 to 95 miles per hour and cause small damage.
- Category 2 hurricanes have wind speeds of 96 to 110 miles per hour and cause moderate damage.
- Category 3 hurricanes cause damage to roofs and trees and have wind speeds of 111 to 130 miles per hour.
- Category 4 hurricanes are likely to cause some deaths and extreme damage to buildings and trees. They have wind speeds of 131 to 155 miles per hour.
- Category 5 hurricanes cause death and dreadful damage. They have wind speeds of over 155 miles an hour. The result of a category 5 hurricane is often a disaster.
An oil rig damaged in a Category 4 hurricane