Close encounters of the 300MV kind

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I was just west of the summit of ZL3/WL-318, mid afternoon Monday. Known locally as Ridgeline this summit is the southern peak on the sometimes knife-edge ridgeline between the Lake Greaney basin and the deep depths of the Waiatoto valley, a 1500m stone’s throw to the east.

Weather was light whispy clag, the sun almost visible through the haze, temperatures in the mid 30’s on the coastal plain 1500m below, and still hot and humid even at this altitude. I stopped for no more than 2 minutes, stowing tools in my pack and taking a much needed swig of water.

When I looked up the bright hazy day had turned black. Goosebumps were already prickling on my sweat-soaked skin as the temperature plummited. I grabbed my pack and proceeded to get outa there! No easy task on a knife-edge ridgeline where the only safe options were a cautious scramble along the crest.

5 minutes later saw me 250m from the summit and maybe 80m below it, focussed on the tricky descent.When three things happenned in rapid succession.

  1. Someone punched me. Simultaneously, over the full length of my body.
    I had time to think ‘what the …’
  2. I was aware of an intense flash of light
  3. Maybe a second later the deafening clap of thunder followed.

The lightning appeared to have hit the summit, maybe 300m away.

I spent the next 30 minutes cowering under a seriously inadequate outcrop of rock until the heavens ceased hurling 20mm hailstones at me, and mentally filling in the ‘near miss’ report form.

====

Now, I assume the sensation of being punched was my body forming the secondary winding to the transformer the lightning path had just created the primary of. But does that stand up mathematically, over that distance?

What puzzles me is the sequence of perceived events. In my perception, the punch came first. I had time to question it’s cause before I sensed the flash. This could just be delays in perception, but if so it seems back to front: it’s more usual to see injuries happen and have time to anticipate the pain before it arrives.

Or is there an electrical / physics explanation? A delay between the current flow and the ionisation of gasses that causes the flash.

Answers, musings and digressions appreciated.

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I think I remember reading somwhere that the flash in a lightning strike is the return stroke. So the punch you felt first might have been the initial charge movement along the ground to the point of the strike. I’m sorry I can’t quote all the details, maybe someone else will have detailed scientific explanation.
Glad you got far enough away in time though.
Andy
MM7MOX

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Glad, you’re well, Matt. Even after two days, if you feel your heart misses a beat, see a doctor!
I guess you experienced step potential / step voltage, the reason you should always keep your feet close together near thunderstorms.

Ahoi
Pom

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Mine is, I’m so glad you’re here to write about it!

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I went off searching about lightning strikes and found this which is interesting and may help explain.

I’ve been on a summit (VHF/UHF contesting) when there was a hit on a comms tower (Cyrn-y-Brain GW/NW-043). We’d decided the storms were getting nearer so it was time to pack up and everything was stowed into the cars, probably 10 of us and 7 cars, it was still dry. It took about 45mins to rapidly disassemble and pack away.

The strike took place when everyone was getting into their cars. I remember it as a shrieking noise, a blinding white flash and a noise like a whip crack but very loud. I think I couldn’t see properly for a few seconds from the flash. A scramble for the cars and then the rains started. But there were no more strikes closeby.

The strike had hit the BT Type 8 tower which we were nearby. There was more room to setup and it was further from the BBC VHF tower which has about 20kW on Band II into a fair amount of antenna, so best to be just a few hundred metres further away :wink:

This link shows 2 of the masts on site: mb21 - The Transmission Gallery I was there with Brian G4ZRP (SK) and he was keen on Ornithology so he had binoculars with him. We studied the 4 lightning conductors on the top of the BT tower and it looked Stevie Wonder and Ray Charles had been practising welding on them! Large amounts of blobs of metal and they looked very beat up from previous strikes.

We felt quite safe as we were sure any unexpected strikes would go to the towers which had lightning protection and would be properly earthed. But as the storms got nearer we took the wise decision to leave. You can question the wisdom of staying so long or going in the first place. Well we were convinced the towers afforded us protection and we were younger. It was 30 years ago and whilst the indestructibility beliefs of a teenager / twenty-something man had almost left, I still felt it would be OK to be there.

Almost a Darwinian Award moment. I have a very different view of sparks from the sky after that nearby strike. I like to be a long way away from summits and exposed places nowadays!

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Glad you are able to pose us questions!

I agree with Andy mox and sure Andy fmf’s article will explain it.

Does your rig still work?

73

Alan

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You bring up a very interesting topic…
https://www.weather.gov/safety/lightning-struck

My guess is you were far enough away not to be affected by the ground current mentioned in this linked topic (unless you also felt tingling). The energy in the lightning strike causes the air around it to be heated very rapidly so it expands very rapidly over a wide area. It might have been the very strong force of the air (effectively an explosion) that gave you the all-over-body punch.

In that distressing situation it might be hard to recollect in which order you felt the body blow and saw the flash.

I can’t think how your body-as-transformer secondary windings theory would work. Animals and people in the ground current zone are usually killed by the potential difference between one leg and another causing high currents to flow through the body.

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Glad you got away with it. It certainly makes you feel very small and insignificant to nature.

I experienced a strike somewhat closer, with virtually instantaneous “flash to bang” on GW/NW-050 Gyrn Ddu. I was sat activating in light to moderate cloud cover, when it suddenly went much darker, the wind picked up and then hail started. I was just thinking “I wonder if this is a storm” when… BANG!

No shock feeling, just ringing ears. I went QRT, dropped the 2m antenna flat, then sat still in the recommended position, until at least 20 mins had gone by between hearing thunder. Then initiated a rapid descent.

I’d not heard any thunder beforehand. Lightning was not in the weather forecast. It was winter time (not our peak lightning season - spring and summer). I’d been operating on 2m FM and not heard any “odd” noises (at other times I’ve heard static crashes on HF SSB and they are quite noticeable).

As per G8CPZ
“My guess is you were far enough away not to be affected by the ground current mentioned in this linked topic (unless you also felt tingling).”

I do recall a group of 3 people on an Eryri (Snowdonia) summit getting a much closer strike. They called for mountain rescue reporting they all had “broken legs”. In fact it turned out to be temporary paralysis due to the ground current.

It’s an occupational hazard. The more time in the mountains, the more likely you are to get unlucky. We Activators increase our chances by sitting close to summits, sometimes for extended periods. It’s still remarkably rare to get this close to a strike though, especially if you take note of weather forecasts. I still work on the basis that I’m more likely to die on the drive to and from the mountain, than by being struck by lightning when out walking!

On that cheery note… I’ll sign off :blush:

PS some good simple advice.

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Thanks for all the replies. Response to a few points:

I’m musing that ground current is the most likely explanation - but can find no indications online as to how far away the effect can be felt. I was descending steep terrain using an ice-axe and if this was ground current then probably flowing in via the axe and out via my feet which would give it a reasonable distance over which the PD could occur.

This was my initial thought too - but in that case that shock wave would have to be travelling many times the speed of sound. Does it? And would such a shock wave be silent?

This is close to, but narrowly misses the point I was trying to make myself. The internal narration of the events I give above is the exact narration that occurred in my head as I experienced the strike. So, no - it is not hard to recollect what order I felt the events, I suspect it will take a long time to forget that sequence.

However, the order in which I experienced the events need not be the order in which they actually occurred. The brain is effectively a complex multi-threaded processor, with different experiences being processed simultaneously in parallel. The order in which multi-threaded code returns results can often bear little resemblence to the order in which the processes were started. Even limiting ourselves to visual queues, different brain processes analyse different parts of what you are seeing separately, in parallel. The brain is then tasked with piecing them all back together afterwards into a single narrative.

I read a summary of a study many years ago looking at the reliability of witnesses to describe the order of events in a crime. Witnesses were shown video (or maybe it was a reenactment) of a violent crime occurring, and asked to describe the order in which events occurred. The conclusion of the study was that you should never trust the order in which a witness describes a rapid sequence of events - even where they remember the incident clearly, they describe events in the order in which they became aware of them, not the order in which they actually occur. Interesting this applied equally to ‘trained witnesses’ such as police officers, and despite people involved in the study knowing what the point of the study was.

So yes - I also acknowledge that the order in which I experienced the events, and the order in which they occurred may not be the same!

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Holy Moley, what an experience.
I’m glad to see you’re writing about it !
It reminds me of one time as a teenager some thunder went off right over head. It was the loudest thing I ever heard and knocked me to the ground. I don’t know if it was the force of the clap or my nervous response, but it’s something I’ve never forgotten.

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Well done Matt for taking appropriate measures as soon as it became evident that the storm was on its way. It is scary how quickly the weather can change. I’m sure a lack of understanding of the forces of nature results in many deaths.

I experienced what the article describes as “objects like trees and bushes and buildings start sending up sparks to meet it.” while driving through the night in France. It was a strange phenomenon and I didn’t really know what to make of it until the connection was made and then the road lit up with the strike hitting less than half a kilometre away. It made me wonder how safe it was to be in vehicle. I had been told as a child that in a vehicle was the safest place to be, but that may not actually be the case. I was also told that if I was caught out in a storm to go and lie in a ditch which perhaps makes sense when you live in the flatlands of Middle England, but ditches don’t usually exist on a mountain.

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Explosive gas expansion is supersonic and the wave front would sound like a short bang were it coming from a point source like one of the military jets that frequently fly low over my village and elsewhere in G/LD land. But, not only being massively louder, I imagine – your having been so close – that there were multiple shock wavefronts coming from different directions and distances.

Maybe I didn’t word it clearly enough but this is exactly the point I was trying to make. Research shows that we humans are notoriously prone to misinterpret our senses. I was trying to say this is particularly true when the events happen in very rapid order (e.g. less than 1s apart) and when those stimuli are overwhelming the senses or distressing the body.

For instances, most of us are kilometres away from the lightning so can distinctly separate the flash and the thunder sound. In your case, being only about 300m away from the source they would have been less than a second apart (esp. as the sound is supersonic that close). It’s also complicated by the fact the brain processes different senses with different latencies. Vision is by far the slowest, with a latency of approximately 200 ms. Both touch and audition are much faster.

Much safer than outside. The advice is that you wind up the windows and stay inside your car. This is because in the vast majority of cars with a metal roof and frame, the frame will act as a conductive Faraday cage, passing the current around the passengers inside and on to the ground. Passenger aeroplanes are designed to withstand a direct lightning strike - although it probably doesn’t help if the strike hits an engine and causes it to drop off.

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When I was about 14 years old, I had a strike drop about 150M in front of me, and it was pretty much as you described! A whole body punch, followed by a flash and a HUGE bang… and tingling, lots and lots of tingling! It knocked me to the floor aswell… next thing i remember was about 4 or 5 mins later coming round in a daze with a couple of guys who stopped thier cars to make sure I was ok! I was… trip to A&E and a check over, and other than being sore for a day or 2 after I was as right as rain! Lightening is definately not to be messed with…

Glad you are ok!

Alan

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Phew! A lucky escape.

In your case it sounds like you probably were in the ground current zone and knocked to the ground by being electrocuted (or by the explosive air expansion, or both). And if so, it would definitely have happened much faster than your senses could react.

A lightning strike in its simplest form is like a DC circuit. Most of us were taught incorrectly (or not at all) at school or college how electrical energy [not the current] gets to the ‘load’. It’s not via the charge carriers (e.g. electrons) whose drift velocity is typically ~1mm/s but rather via electric and magnetic fields close to and around (but not inside) the conductor and energy being transferred by the E-M fields at the speed of light.

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I always suspected it was the explosive rush of air if im honest… but yea! VERY lucky! ill never forget the smell after I came too, It was wierd, i think its Ozone you can smell… like sticking your nose in a hot CRT tv!

Alan

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Yes, caused by the super heating of the air. Apparently the human nose is extremely sensitive to ozone and can detect it in minute concentrations.

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Hi Matt,

I shall refrain from mentioning your post to Angelina.

We were paddling across Manapouri, well out in the middle, perhaps crossing South Arm, and lightning struck the lake. My memory was of a sizzling sound, then flash and the bang within perhaps 2-300ms of the flash. We were surrounded by strong ozone smell for 200m or so.
I remember thinking (later) that it was odd that I heard the sizzling sound, and the actual flash and bang part happened a quite discernible 100’s of ms later. This implied that the initial electrical discharge was well separate in time from what or where the flash and bang happened. The main flash and bang might have been coming from a different location e.g. higher up, than the sizzling. The small pause between the flash and bang told me it was very close to us. I don’t recall feeling any electrical effects.
We were pretty happy when we got back to the side, and there was something higher than us.

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You might like this.

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My first time watching this video, very enjoyable. Richard Hammond has made many ‘science can be funny’ videos. Plot Spoiler alert! Interesting that not only was he fine afterwards, but the car, car radio, etc were fine too. Physics works!

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Lightning strikes start from both ends so to speak. The charge builds up in the clouds but also on the ground. The result is a column of charged particle rise up from the ground which meets a stream of particles coming down from the clouds. A path of ionised air is created when they meet and initially negatively charged particle flow down to Earth but then this reverses and a massive current flows the other way which we call lightning which counterintuitively is from Earth to sky.

I suspect any sensations felt before the strike are either due to static or the build-up of ionisation rising up from the ground.

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