My Assignment

Severe Storms – Get the Facts

For a thunderstorm to be created, it needs 3 main ingredients:

air that is moist
an atmosphere that is unstable
a weather event like a front, trough or area of low pressure.

When you mix these 3 things together, thunderstorms can develop. These storms can be moderate storms, severe storms, multicellular storms and even supercell thunderstorms.

How are severe thunderstorms created?

Thunderstorms are created when cooler air begins to push warmer humid air upwards. As the warm air continues to rise rapidly in an unstable atmosphere, the cloud builds up higher and higher and begins to spread. Thunderstorms can quickly develop when the atmosphere remains unstable or if it is able to gather additional energy from surrounding winds.

Hail

Hail as big as a tennis ball

Hail can form within the thunderstorm when the air is much cooler than the water vapours that make the cloud. This cooler air freezes the water droplets making the frozen raindrops heavier.

If the air is not warm enough to melt the ice particles as they fall from the cloud, hailstones will fall – instead of raindrops.

Hail can be as small as a few millimetres in diameter to the size of tennis balls.

Lightning

As the air becomes warmer, the cloud builds and expands in size. In every cloud there are positive and negative electrons. The positive charges are at the top of a cloud and the negative charges sit towards the bottom. As the cloud continues to grow, it creates a gap between the two charges, which causes a spark, known as lightning.

Lightning can occur inside a cloud, between clouds and between clouds and the ground.

Thunder

Thunder is caused when the lightning rapidly heats the air that surrounds it, causing an explosive effect. The air around a lightning strike can be heated to temperatures as high as 30,000°C in just a fraction of a second.

Where do severe storms occur?

Severe storms can occur anywhere in the world. It has been recorded that Uganda and the Democratic Republic of Congo, both in Africa, have the highest frequency of lightning.

Australia has several severe storms each year. Most thunderstorms in Australia occur during the months between September through to March.

This “Thunderstorm Season” is mainly caused by there being more of the Sun’s energy available, coupled with Spring and Summer weather patterns that are favourable for storms.