Tornadoes
Tornadoes, also known as twisters, are columns of air which rotate above the ground at speeds of up to 480kmph (300mph). They occur when cool air on top forces a layer of warm air below to rise rapidly to form a rotating tunnel. Tornadoes can travel 220km (100m) and be over 18,000m (60,000ft) high.

Tornadoes are classified by the Fujita scale, from F0 to F5, which measures the amount of damage the storm leaves in its wake. The lowest on the scale is classified as a ‘gale’ (40-72mph) and the most violent F5 tornadoes are called ‘incredible’ at 420-511 kmph (261-318mph). An ‘incredible’ tornado will cause mass destruction, uprooting homes and throwing cars up to 100m (330ft). A tornado will pick up everything not nailed down, including animals, people and debris that can cause terrible damage.

On a single day in April 1974 in the USA there were 148 tornadoes, covering 13 states. 330 people were killed, 5,000 people were injured and billions of dollars in damage was caused.

Cyclones
Cyclones are also known as hurricanes and typhoons, depending on which part of the world they occur. They form over oceans were the water temperature is 26°C (80°F) or higher. As warm, humid air rises and condenses it releases latent energy and this forms a tropical cyclone which rotates around an eye. Cyclones can be up to 22km (10m) high and 1100km (500m) wide.

Cyclones, hurricanes and typhoons are measured on the Saffir-Simpson scale and must blow at over 74mph to qualify. A grade 1 will cause crop damage, however at the other end of the scale, a grade 5 will have winds of 175mph or more resulting in severe, widespread destruction; buildings will be damaged and large dangerous airborne debris will be carried. Hurricanes are given names, which will be used just once if there is a disaster.

In 1992, hurricane Andrew killed 30 people and left 180,000 people in the USA homeless. The 1970 Bay of Bengal tropical cyclone killed about 300,000 persons, mainly by drowning.

Climate
Our climate is the production of a combination of elements. There are five different types; tropical, dry, warm temperate, cold temperate and cold. Some places will have a climate with varied weather, like parts of Europe. Others will experience regular change at around the same time each year, which results in rainy and dry seasons.

By the end of this century it is estimated that Earth will be 1.4°C to 5.8°C warmer. Some scientists believe this change is a result of human activities, due to pollution and greenhouse gases.

El Niño is thought to be one example of how the global climate has changed. It occurs due to a current of warm water which moves through the Pacific every three to seven years and is so significant that it affects the climate around the globe. El Niño has been blamed for droughts in Africa and monsoons in India which have lead to poor crops and caused the loss of thousands of lives.

Sandstorms
Sandstorms and dust storms occur most commonly in hotter places which experience drought, where there is a permanent high pressure and clear skies that yield little or no rain. High winds pick up loose sand and dust and move it a high speeds across the ground, altering the landscape and severely reducing visibility.

If you’re in an area that suffers from sandstorms it’s a good idea to wear long trousers and boots to avoid sand burn. If you get caught in a sandstorm in the open with no cover, you should dampen a cloth and hold it over your mouth. Try and find higher ground where the storm won’t be so strong, (unless it is combined with a thunderstorm due to lightning). Then lie on your side with your back to the wind and wait for the storm to pass.