LIGHTNING strikes!

This weather phenomenon people endure in northern KZN and across the country many times in a year, sadly often results in fatalities.

ALSO READ: Could tropical storm Eloise hit northern KZN?

While many South Africans are scared of thunder and lightning storms, there are some who relish the opportunity to gaze upon the skies during a storm, even finding it therapeutic.

So what is lightning, why does it occur and how many types of lightning strikes are there?

Lightning is a sudden, electrostatic discharge – a spark or flash – as charged regions in the atmosphere temporarily equalise themselves through this discharge.

It is the polarity of lightning discharge that can affect the way it spreads and branches in space and time.

It is this, as well as the starting and ending points and direction of movement, that give rise to different types of lightning.

Lightning can strike the ground, the air or inside clouds, but there are roughly five to 10 times more cloud flashes than there are cloud-to-ground flashes.

Typically, a lightning flash is only two to three centimetres wide.

Because lightning is the movement of electrical charges, it doesn’t have a temperature, however, resistance to the movement of these electrical charges causes the materials that the lightning is passing through, to heat up.

Air is a very poor conductor of electricity and gets extremely hot when lightning passes through it. In fact, lightning can heat the air it passes through to roughly 30 000°C (five times hotter than the surface of the sun).

Types of lightning.
Cloud-to-ground (CG) or forked lightning
In CG lightning, a channel of negative charge, called a stepped leader, will zig-zag downward in a forked pattern.
This stepped leader is invisible to the human eye and travels to the ground in a millisecond.
As it nears the ground, the negatively charged stepped leader is attracted to a channel of positive charge reaching up – a streamer – normally through something tall like a tree, a house, or a telephone pole.
When the oppositely-charged leader and streamer connect, a powerful electrical current begins flowing.

Ground-to-cloud (GC) lightning
This is a discharge between cloud and ground initiated by an upward-moving leader originating from an object on the ground.
GC lightning strikes, sometimes called upward-moving lightning, are common on tall towers and skyscrapers, and can be either positive or negative in polarity.
Lightning that demonstrates upward branching is a clear indication of a ground-to-cloud flash, though some upward-moving lightning is branchless below the cloud base.

Sheet lightning
This is a term used to describe clouds illuminated by a lightning discharge where the actual lightning channel is either inside the clouds or below the horizon (not visible to the observer).
Sheet lightning is simply any lightning that is hidden by clouds or terrain aside from the flash of light it produces.
It can also be known as heat lightning or silent lightning.

Ribbon lightning
This occurs in thunderstorms with high cross-winds and many return strokes.
The wind blows each successive return stroke sideways into the previous return stroke, causing a ribbon effect

Ball lightning
The phenomenon of ball lightning is a large, mysterious glow that appears during thunderstorms
It has generally been described as being a luminous sphere that appears during or after a thunderstorm.
Some theories suggest ball lightning is a plasma, others that it is the result of a chemiluminescent process – light that occurs due to a chemical reaction.
Scientists have been trying to figure this out for hundreds of years and now it seems they may finally be close to solving one of earth’s most intriguing natural mysteries.

Source: Severe Weather Information Centre SA

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