Lightning occurs with every thunderstorm and can be expected as soon as thunderstorms form. The most lightning occurs between clouds, but it is the ground strikes that are most dangerous. Your chances of being struck by lightning are estimated to be 1 in 350,000 but could be reduced by following some safety rules.

South Africa is one of the top three countries with the highest death rates from lightning and is responsible for up to 300 deaths a year. The statistics may be higher as these are only the number recorded by Health Institutions and mortuaries after persons are struck by lightning. Regrettably, these numbers may be even higher, since no complete database exists, and numerous deaths are probably not reported. This is true for most countries, and especially for developing countries.

Lightning is one of the leading causes of natural deaths in South Africa. if the population size of South Africa is taken to be 50 million, this means that between 75 and 440 people are killed by lightning annually.

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Early Warning Systems:

  • A lightning activity profile can be obtained through the SA Weather Services Lightning detection network. (Ref: http://www.weathersa.co.za)
  • Risk assessments can be compiled to determine the regularity and intensity of cloud-to-ground lightning activity in the area of your project.
  • Where the location is identified as a high-risk area; early warning systems are available on the market which when link to a cell phone give early warning information via an SMS. User defined buffer zones can be set up based on the established risk.
  • Alternative methods include visiting the SA Weather service web site on a daily basis to get up to date weather forecasts.

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This is the lightning flashes per year in South Africa in the year of 2008 issued by the University of Washington (Ref: http://www.weatherphotos.co.za/lightning.html ).

Emergency Procedures:
Site procedures must describe action to be taken in the event of an approaching electrical storm. This may include:

  • establishing effective communication systems, e.g. “air raid” type siren
  • an evacuation plan for work areas that may be affected by the storm
  • identifying locations and requirements for safe shelters for workers
  • indicate response times necessary for all workers to reach safe shelters

Action to take if caught outside in a thunderstorm:

There is no safe place outside during a thunderstorm and it is important to get into a safe place at the first sign of a thunderstorm. If a safe building cannot be reached immediately; these tips will reduce the odds of being struck by lightning.

  • A construction worker standing on a roof or a ladder on the ground is a prime target for lightning. Immediately get off ladder, scaffold, roof, etc. and remove all metal objects including your safety harness and your tool belt
  • Do NOT seek shelter under tall isolated trees. The tree may help you stay dry but will significantly increase your risk of being struck by lightning.
  • Do NOT seek shelter under partially enclosed buildings
  • Stay away from tall, isolated objects. Lightning typically strikes the tallest object which may be you in an open field or clearing.
  • Know the weather patterns of the area. For example, on the Highveld and in mountainous areas, thunderstorms typically develop in the early afternoon.
  • Monitor the weather forecast. Where there is a high chance of thunderstorms, plan construction activities accordingly.
  • Metal is an excellent conductor so stay away from metal objects, such as fences, poles and metal tools. The current from a lightning flash will easily travel long distances
  • If lightning is in the immediate area, and there is no safe location nearby, stay at least 5m apart from other members of the group so the lightning won’t travel between you if hit.
  • Keep your feet together and sit on the ground out in the open. Sitting or crouching on the ground does not guarantee your safety and should be a last resort if an enclosed building or vehicle is not available.

Interesting Facts about lightning:

  • On average lightning strikes the earth 100 times per second.
  • 3 p.m. is the most dangerous time of day, it is five times more dangerous than 9 a.m.
  • Men account for 84 percent of lightning deaths, women 16 %
  • Number of thunderstorms occurring at any given moment: 2000
  • Number of lightning strikes round the world per day: 8 Million
  • Number of VOLTS in a lightning flash: 1 Billion
  • Number of AMPS in a lighting flash: between 10,000 and 200,000
  • The average lightning flash would light a 100 watt light bulb for 3 months
  • The heat generated by the electrical discharge is about 20,000 0C (3 times the temperature of the
    surface of the sun).
  • Days of week of most incidents = Sun./Wed./Sat.
  • Time of the day for most lightning incidents = 2 PM to 6 PM.
  • Number of victims = One (91%), two or more (9%).
  • Lightning tests confirms that even indirect strikes can cause surges on lines with horizontal arcing in excess of 40m.
  • The chances of being struck by lightning is estimated at 1 in 700,000

Refences:

http://www.lightningsa.org.za/lightning-research/
http://www.weathersa.co.za
http://www.liveline.co.za/lightning-stats.php www.noaa.gov/ (National Oceanic and Atmospheric Administration)