This week's death of young American Sam Beattie after a lightning strike while camping at the top of Mount Warning in northern NSW was a tragic reminder of nature's awesome and fickle power.
How does lightning form?
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The science of lightning has advanced far since Frenchman Thomas-Francois Dalibard pipped Benjamin Franklin by a month in his experiment to use conductive materials to attract lightning (and doubts remain whether the American ever flew his famous kite into a thunderstorm).
A charge builds up within storm clouds as water droplets borne higher by the strong updraft smash into ice crystals, generating a static electricity that is ultimately released – mostly between clouds – but also as bolts or even balls that reach the ground. Reaching temperatures several times hotter than the surface of the sun, the burst of energy produces the shock wave we hear as thunder.
As seen this past week, lightning can cause death, although as many as 90 per cent of human victims survive.
According to Risk Frontier's PerilAus data, lightning ranks fifth among fatalities from natural hazards, with 85 people killed between 1900-2011, or about one-fiftieth the largest killer – extreme heat – blamed for 4555 deaths over that time.
Where are the lightning hotspots?
The areas with the most thunderstorms are, not surprisingly, the most active for lightning strikes. Such regions typically are found in the tropics.
A NASA satellite has been studying lightning for 18 years, and pinpointed the spot in Venezuela where the Catatumbo River enters Lake Maracaibo. Dubbed the "Beacon of Maracaibo" and even "the playground of Zeus", the region counts as many as 158 lightning strikes per square kilometre from its 260-300 storms per year.
According to Andrew Dowdy, a senior researcher at the Bureau of Meteorology, the NASA data identified Australia's most dense lightning regions – in the Kimberley and north-west Northern Territory – to count about 20-30 lightning flashes per square kilometre. (See map below.)
"During the cooler months of the year a maximum in lightning activity for the Australian region occurs near the central east coast of Australia, potentially associated with East Coast lows," Dr Dowdy said.
Other factors, though, can play a role. As storm chasers well know, the continental US, for instance, has much more severe weather than Australia although of a comparable size. Along with lightning, Americans cop more tornadoes and hail too.
While NASA's new GOES-R satellite will study lightning, its stationing over the US means its information will have limited value for Australia. However, China will launch an advanced geostationary satellite later this month, the Fengyun-4A, which will have a lightning sensor that may be able to be used over Australia in the summer months, Dr Dowdy said.
What do I do during a storm with lightning?
Cars are usually a safe space to shelter from lightning. Photo: Nick Moir
If inside a house, it's best to avoid rooms with pipes – such as kitchens or bathrooms – that could serve as current conductors. Likewise, landlines with their copper cables, should be avoided and electrical appliances without surge protectors turned off, he says. Areas with windows should be avoided as much from threat of being smashed by fallen tree branches as the consequence of a strike.
Cars are usually a safe place to shelter, with windows up and, if possible, without touching metal objects. Vehicles act as a so-called Faraday's cage, named after the English scientist, with the lightning charge dispersed.
If in the open, put down metal objects such as golf clubs and chainsaws. People should crouch down – even lie flat – and also spread out if in a group, Mr Campbell said.
If people are boating, swimming or surfing, they should leave the water.
How often does lightning strike?
Weatherzone has created a Total Lightning Network of 90 sensors around the country to provide earlier warning of the potential for lightning strikes by detecting cloud-to-cloud lightning before strikes reach the ground.
The Bureau has about 20 sensors at some airports. Users include airlines looking to get ground staff to safety quickly and mining companies keen to ensure those working with explosives especially are out of harm's way.
The number of strikes can also be counted. For instance, there were 3560 ground and cloud strikes in Sydney during Thursday night's storms within 35 kilometres of Parramatta, Weatherzone said. (See chart below.)
Interestingly, although rain is likely to fall about as much on land as over the oceans, about 94 per cent of lightning occurs over land, Steve Sherwood, a cloud specialist at the University of NSW, said.
A simple guide used by many people is the so-called 30-30 rule. By this widely used gauge, if thunder is heard 30 seconds after lightning is seen, the storm cell is about 10 kilometres away – and it's a good time to seek cover. Sporting teams often wait 30 minutes after a storm passes before resuming play. That delay makes sense, says Rob Sharpe, a Weatherzone meteorologist.
While the great bulk of lightning is from negatively charged particles, lightning can also be discharged from the tops of clouds as so-called positive lightning. That can occur even under blue skies after the worst of the storm has apparently passed – hence the phrase "bolt from the blue", Mr Sharpe said.
Does climate change affect lightning?
A storm off the Central Coast . Photo: Nick Moir
As with most meteorological processes, warming the planet by pumping more greenhouse gases into the atmosphere is likely to have some impact on lightning too.
The bureau's Dr Dowdy said the influence of global warming on thunderstorm activity in Australia is currently not well understood. Still, research projects an increase in the frequency of potential severe thunderstorm days in eastern Australia, with rise of about 30 per cent for Sydney and 14 per cent for Brisbane.
He and Professor Sherwood noted studies such as one by American scientist David Romps, which indicated a possible increase in global thunderstorm activity, especially in the US.
"In terms of mechanisms, as humans continue to increase the amount of greenhouse gases in the atmosphere, this is causing an increase in the maximum amount of water vapour that can be present in the air," Dr Dowdy said. "This is one mechanism that could cause thunderstorms to become stronger in the future, given that thunderstorms can get energy to develop from the amount of water vapour available in the air."
Professor Sherwood said it may be that storms under climate change get longer to develop before releasing their rain, hail or lightning – with the delay likely to produce more fierce tempests.
