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A recent news story from Sydney told a sad tale of a diver who died during a lightning storm. Although all the facts of the incident are not all available this is a sad reminder of the potential dangers of lightning. Our thoughts are with the family and friends of the diver.
What is lightning? Thunderstorms cause turbulence in the atmosphere which leads to the formation of positive and negative charges. The positive charges form at the top of storm clouds and negative charges at the bottom. Lightning is the result of induced areas of positive charge on the earth connecting to the negative charges at the bottom of clouds.
The susceptibility of lightning strike is determined by three factors: height; isolation; and shape. And just to clear it up: lightning can strike the same place twice.
Staying indoors is one of the easiest ways to be safer during a thunderstorm. If you are unable to stay indoors one of the safest places to shelter, contrary to popular belief, is in a car with the windows up. The science behind this is that the metal of the car conducts the lightning around the outside and that the rubber tyres cannot provide sufficient insulation to stop a 30,000 amp lightning strike.
If you are on a boat, go into the cabin. It is also suggested to lower all raised objects, if possible. Also remove yourself from connection to raised objects, such as not holding the radio handset with an antenna raised.
Overall, if you can avoid diving or being in the water during a storm, do so. If you are on the surface you are likely to be the highest point around and current can travel long distances over a water surface. Staying underwater, as lightning does not penetrate that deeply, is an option, but generally impractical in most situations.
If you find yourself surfacing in a storm, Alert Diver’s recommendation is to stay below water at 6 to 10 metres if you are far from your boat or are able to stay under the water as you believe the storm will be short lived or will lose intensity quickly. Getting out of the water is the best option if you can do so safely.
Plan your dives around weather forecasts and if possible do not dive when a storm is forecast.
The original article ‘Lightning’ by Alert Diver is available here.