safety during lightning
It can turn healthy trees to matchsticks, start raging forest fires, destroy communications systems, and kill people.
The causes of lighting are still being researched, and there is more to learn.
But current scientific thinking includes collisions between different forms of ice in a storm cloud (descending small hail meeting very small ice crystals rising on warm air) creating different charges between the two crystal masses. These electrically positive (or occasionally negative) charges equalise either within the cloud (IC), between two clouds (CC), or less commonly from cloud to ground (CG). Equalising currents superheat the air, and are seen as blue lightning arcs.
In a typical cloud to ground (CG) lightning strike, a ‘leader’ forms out and down in a series of steps and branches from the cloud, while at the same time a smaller ‘streamer’ forms from the ground toward the leader. Once a continuous ionised path is formed, a much more intense cloud to ground discharge can follow.
On the ground, the streamer is likely to start from a tall structure like a building or lightning conductor however any exposed object such as a human on a beach or open ground may create the same streamer starting point.
When the lighting discharge passes down this ionised pathway, it superheats the surrounding air which rapidly expands causing thunder. The lightning also travels more readily over the surface of an object rather than through it, so people suffering lighting strike commonly suffer external burns. Often, a ripple effect occurs where the energy travels outward from the point of the strike on the ground. A person may be potentially electrocuted when lightning travels up one leg and down the other in this widening circle, even though they were not directly hit themselves. In this case, the result can include severe organ damage.
Managing the risk
The connection to the ground is the main lethal element in lightning strikes so avoid direct contact with the ground, or conductive materials like taps, electrical cables and landline phones.
Outside the home, the best place to avoid lightning is inside a car, as it is electrically insulated from the ground…just don’t touch anything metal.
Lightning can strike an aircraft or even be caused by the aircraft itself, but will generally pass along the aircraft skin and leave at the trailing edges. Careful engineering protects sensitive areas such as electronics and fuel systems.
The proximity of a lightning storm is calculated by counting the seconds between the lightning flash and the resultant thunder. Sound travels one kilometre in three seconds
If there is no thunder or hissing crack of sound, then the lightning is either a safe distance away, or of the IC or CC variety.
To avoid any risk of lightning, you should check the speed and direction of approaching storm cells where lightning is likely to occur, usually on a B.O.M. radar image. Time the distance to the strikes…often they are many kilometres away or out to sea. However, storm cells may be very wide and descend on you rapidly.
If the elapsed interval time between strike and thunder is decreasing, make a decision on the best course of action based on the options at hand.
If you are caught out in your paddlecraft in a lightning storm:
- Paddle to the bank and shelter under low foliage, but do not paddle to a beach or exposed area.
- Separate from other paddlers if you are too far from shore, so the lightning stream point size is reduced.
- Lie down in your craft to lower your exposure height, and lay your paddle flat in the water.
- Do not paddle to or shelter near tall exposed trees
- Do not seek shelter in or near metal structures like steel sheds, jetties etc
- Do not touch anything conductive, like metal poles embedded in the ground.
There are no statistics to suggest getting out of your paddlecraft is the best option. You may end up more exposed to lighting than staying in your craft and taking sensible measures to minimise your risk.
Article supplied by Tony Hystek – Chair of PaddleNSW Safety Committee