Flash,
bang, wallop! Thunderstorms!
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| A
stormy sky |
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Warmer
weather over the last couple of weeks has triggered off a few thundery
downpours across the county.
Thunderstorms can have a dramatic and devastating effect on the county.
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|
|
|
Warmer
weather over the last couple of weeks has triggered off a few thundery
downpours across the county.
Thunderstorms can have a dramatic and devastating effect on the county.
Here is an essential guide to thunderstorms:
Thunderstorms are one of our most exciting types of weather.
A big thunderstorm has as much energy as ten atomic bombs and a bolt
of lightning may deliver a million volts of electricity.
But why do they happen?
In a big shower cloud, known as a cumulonimbus, the temperature is
below
0 Celsius. The top of the cloud may be as cold as Minus 20 Celsius.
Not
surprisingly, much of the cloud is made up of ice and hail. As these
particles rub together inside the cloud they produce electrical charges,
positive and negative. Lightning is simply the discharge of the electricity
inside the cloud.
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| Richard
Angwin - Wiltshire weather is his expertise. |
People
often talk about forked or sheet lightning. These are really the same
type of lightning. Most lightning has a forked appearance.
Although we are familiar with lightning striking the ground, most
lightning strikes are between, or even within, thunder clouds. This
lights up the clouds.
Lightning can be very dangerous. A million volts of electricity can
kill. The temperature in a lightning bolt is about 30000 Celsius!
Thunder is harmless of course. It is simply the noise made as the
lightning heats the air very rapidly causing it to expand.
You can tell how far the thunderstorm is from where you are. Simply
count the time between the flash of lightning and the rumble of thunder.
Every three seconds you count means the thunderstorm is 3 kilometres
away from where you are. After each flash of lightning repeat your
count. If you can count longer and longer you know that the storm
is moving away from you.
You may have heard the expression that "lightning doesn’t strike twice
in the same place". This is not true. The Empire State Building gets
hit by lightning around 20 times each year.
In our part of the world there are only 5 to 10 days with thunderstorms
each year. But the island of Java, which is part of Indonesia, has
around 220 days with thunder.
Across the world there are 44,000 thunderstorms each day. On average
there are 100 lightning strikes per second.
If you are outside in a thunderstorm then you should be very careful.
Do NOT shelter under a tree. Lightning will often strike the highest
object around and many people have been killed by lightning flowing
through the ground around trees or by the trees falling on them.
Instead you should crouch down to make yourself as small a target
as possible. Keep away from water.
A car can be a good place to sit out a thunderstorm (as long as it
is not near trees or overhanging branches). This is because a car
is insulated from the ground by its tyres.
But thunderstorms are not all bad. They fertilise the soil by washing
nitrogen out of the air. And the air after a thunderstorm can be really
fresh and clear.
So whilst we should treat thunderstorms with the respect they deserve
they can be really exciting to watch.
Richard Angwin
Points West Weatherman
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