Massive Single Lightning Strike Heard From 30+ Miles Away?

[willgtl]

Last night there was a lightning strike, I caught the flash out of the corner of my eye through my window blinds. The thunderclap proceeded a second or two later and was incredibly loud. So loud it set off my car alarm and shook my house. There were no storms reported in the area except rain, and over 30 miles away friends heard the lightning strike with the same intensity. But I was under the impression that thunder can really only be heard from at most 10 miles away. It also wasn't warm. It was about 35°F and there was only one lightning strike.

How does lightning like that happen? Thanks!

 

[Doug Huffman]

First of all, sound travels at about 1100 feet/second, so if the flash and bang were indeed associated, then the flash was only a couple thousand feet away.

While distance does diminish the intensity of the sound, lightning forms channels that direct the sound pressure more or less effectively.

My go-to on practical lightning is Mountaineering: Freedom of the Hills by The Mountaineers.

 

[berkeman]

The thunderclap proceeded a second or two later

As Doug says, count 3 seconds per kilometer or 5 seconds per mile.

 

[Teen4Ideas]

Are you sure it was not cloud to cloud lightning, just a release of energy, thus no need for rain or ground strike?

 

[DaveC426913]

How can you know which lightning strike your friends heard?

Even if you were on the phone with them, you wouldn't be able to coordinate. They are 150 seconds away at the speed of sound. A hypothetical lightning strike between you could be out of sync by 2.5 minutes either way.

 

[willgtl]

After some e-sleuthing I found people talking about it on public pages. Local meteorologists say it was an instance of thunder being trapped by temperature inversion. The thunderclap was directed downward instead of radiated outward, which caused it to bounce around and be intensified by the lack of vegetation. Apparently it was heard as far as 60 miles away. The strike occurred at 9:11:07pm (Timestamp on my camera) in the next town over (My timing must've been off (I was drinking), as the reported area is 3.8 miles away). The rumbling of the thunderclap must've lasted at least 30 seconds after the initial bang, if not longer. It had to be the most powerful and loudest thunderclap I've ever heard. Just found it a bit perplexing that there was only 1 lightning strike and it was that intense. Apparently there was a thunderstorm embedded in the rain clouds, but only 1 bolt was actually cloud-to-ground, which was the one in question.

Or as the meteorologist put it, nature turned on Dolby Digital surround sound and cranked the subwoofer to max for that strike.

Thanks for the help figuring it out.

 

[Doug Huffman]

The rumblings are reflections. I live among islands 45°22′37″N 86°53′47″W that cause some amazing rumbles.

 

[Mark44]

My go-to on practical lightning is Mountaineering: Freedom of the Hills by The Mountaineers.

I have the 2nd ed. of this book, which I bought in 1971 for all of $7.50.

 

[rootone]

Lightening can 'happen like that' when it wasn't really expected.
You do need a cumulonimbus cloud to get the electric charge build up, but these clouds can arise quite suddenly and unpredictably where the weather is generally rainy and unstable.
I think the particularly loud thunder was probabaly an artifact caused by the geography of your area, echos on top of echoes etc.

 

[Baluncore]

Maybe I can recount a similar observation.

A few years ago, I was on the phone to a “nervous woman” in the city 20 km down the valley from me. There was a low overcast with a very flat cloud base at about 1000 feet. There was no wind. It was good visibility and quite clear below the overcast.

Suddenly my room was lit by a flash of lightning from outside, there was a synchronous instant single “click” on the phone from the magnetic pulse, then an immediate yelp/scream by the woman in the suburb 20 km away, followed at about one second by the crack of the strike. This was followed by rumbling that became progressively more complex and lower in frequency as it continued for over 45 seconds.

On that occasion, a Chemist/Electronics Engineer in the city was on the phone to an Electronics Engineer with a mobile phone at a beach 35km south of me. They reported identical observations, apart from the woman's scream. All reported only one flash, followed by a single crack of thunder about one second later.

None of us was struck by lightning. We all saw the light from a lightning flash below the cloud. None observed any following strikes. All our phone landlines are underground except for within the structure of a building.

So how can it all be explained?
After much discussion, my hypothesis, was that the electric charge had built up between the Earth and the cloud base. When an initial strike occurred, the UV flash triggered a synchronous ionisation and breakdown of a great many other points in the valley below the cloud. That UV propagated at the speed of light and so had the effect of triggering all the pending strikes throughout the volume of the valley. What was observed can be described in the same terms as the UV flash triggering of the spark gaps in a Marx generator.

The 45 seconds of rumbling can be explained by the propagation at the speed of sound of all the synchronous strikes to the observers. The lowering of the rumble frequency with time corresponds to the frequency dependent attenuation of sound with time from the multiple synchronous strikes.

What is not explained is the electrostatic interface between the valley walls and the cloud base. We were unable to observe if there was another cloud layer above the overcast.

While being struck by lightning is often a "once in a lifetime" event, observation of these synchronous discharges must also be very rare.