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It’s 4:00pm on a stinking hot day, the place is packed and squad training has just started. As usual for this time of year the clouds have really started to build. One is several kilometres across. Its base is at around 1000m altitude, while its top is up around the 6000m mark. While most of it is fluffy and white like a cauliflower, the top is grey and flattened off by wind sheer at the tropopause.

This is the notorious cumulonimbus cloud or thunderhead. Cumulonimbus can form alone, in clusters, or along cold front squall lines. These clouds are known for their lightning, hail, damaging winds and other dangerous weather.

While still watching the pool the lifeguard is also keeping an eye toward the horizon, sizing up the storm front. He knows that outdoor pools and lightning don’t mix. Add tall, metal, overhead light poles into the equation and you can really be in for some unwanted attention.

The flash to bang method for determining when to close a pool is a fair tool but often a lot more goes into the decision.

The flash to bang method involves seeing a flash of lighting and timing how long it takes to hear the thunder. Sounds travels at around 340m per second. So hearing thunder 30 seconds after the lighting strike means it was about 10kms away.

But which direction is the storm travelling? How fast is it travelling? What usually happens with a storm from that direction? Will it go around us? Will it turn and come back? What does the BOM Radar say? These days some organisations also use handheld lightning detectors to take away some of the guess work.

And mostly, lightning doesn’t strike the pool and swimmers begin to think it’s a bit of a pointless exercise. Squad coaches in particular can bemoan having to clear their lanes. Some can be seen glaring at the lifeguard. Some go as far as to add a few words of their own in an effort to influence the lifeguard’s decision. Clear the pool a couple of days in a row and see the reaction! Because, like I said, mostly it seems like a pointless exercise.

Late last year the Warrnambool Standard ran a local story about why we continue with this “pointless exercise”; www.standard.net.au/story/3515556/lightning-bolt-hits-outdoor-pool/?cs=2452

22-year-old lifeguard Tom Wilson gained his 15 minutes of fame when he decided to evacuate the outdoor pool at AquaZone in Warrnambool, Victoria just in the nick of time.

The reality is that the front of a thunderstorm is erratic and lightning can travel almost 10kms horizontally out in front of a storm. In effect seeming to come from out of the blue sky. I’ve been on deck when lightning blew a tree apart in the pool grounds well before the front arrived. There had been no thunder to that point.

Estimates put the number of people struck each year by lightning at between 6,000 and 24,000. Between 10- 30% of those are fatal. Data from the National Oceanic and Atmospheric Administration (USA) for the years 1959- 1994 shows that 93% of people struck by lightning were outside. 13% were in the water.

Next time you see the lifeguard looking to the horizon and wringing his hands, spare a thought for what’s going on in his head. He knows he’s about to bring upheaval to everyone’s afternoon and, more than likely, for no discernible reason. If the lifeguard blows his whistle, some extra piece of information has just tipped his decision and I’d get my lycra clad backside out of the pool asap.

And Tom Wilson… well done. You’re an example to lifeguards the world over. A moment later and the story in the paper could have been quite different; potentially front page the nation over.

Despite the pressure lifeguards need to weigh their options, make the call and then stick to their guns in a professional manner. Well done Tom.