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East_England_Stormchaser91

How far away can you actually observe lightning?

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Thought I would start a thread regarding the furthest distance lightning can really be observed from.

Ive read a few times this past summer, during the storms of this year in particular including myself of observing and witnessing the flickering of lightning from well in excess of 100 miles away, perhaps nearing or exceeding 150 miles! 

I myself can certainly say that up here on the lincs/Cambs border have witnessed regular flashes from storms as far away as Wiltshire and Dorset, and more recently as far as the IOW! 

Someone on another forum claimed that they had witnessed from Suffolk flashes from storms as far away as the Dutch/German border! And flashes over Belgium from Northamptonshire!!! 

Any takes on this folks? 

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Google informs me up to 100 miles away and it's difficult to hear thunder beyond 15 miles. Living near the Atlantic I have often seen lightning at night when it's clear and heard no Thunder. My Granny used to call it openings ha

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Yeah I've read 'up to' 100 miles away on google. But my own eyes have told me that it is definitely further than that! The Isle of Wight from here is over 150 miles as the crow flies! Maybe because of the flat landscape of the fens, it gives massive unimpeded views around here. 

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1 minute ago, East_England_Stormchaser91 said:

Yeah I've read 'up to' 100 miles away on google. But my own eyes have told me that it is definitely further than that! The Isle of Wight from here is over 150 miles as the crow flies! Maybe because of the flat landscape of the fens, it gives massive unimpeded views around here. 

I tend to agree, EES. I'm sure that (unless my eyes were deceiving me) I could see lightning in MK, all the way from over here...The air was exceptionally clear at the time, mind you.

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I've seen it from the best part of 100 miles away in the states of a night.

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I once saw lightning in Bristol from a storm and I was in West London... 

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From my old house I could see Humber bridge on a chrystal clear day,that is over 70 miles away so I do not see why you cannot see lightening at night at conciderably further !

 

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I know this is an older thread, but I thought I'd give a solid theoretical answer to this question based on some over-estimating assumptions.

 

Given the curvature of the earth, you can use geometry to find the maximum distance for which you could see lightning. We can use the following formula:

d = (2RH + H2 - 2Rh - h2)1/2

where H is the height of the clouds, d is the distance, h is your height, and R is the distance to the center of the earth. This formula makes the assumption that the earth can be approximated as a sphere, and it assumes that the angle between your line of sight to the lightning and the line from the center of the earth through your body is 90 degrees (a reasonable assumption since the earth is approximately flat over short distances). My use of the formula assumes the topmost cloud layer is 49,000 feet high (based on wikipedia's info on the height of clouds from which lightning originates), the distance to the center of the earth is about 4000 miles and the height of the observer is 6 feet. Using those numbers, the approximate theoretical furthest distance you can see lightning from is:

 

d = (2*4000 miles*49,000ft +  (49,000 ft)2 -(2*4000 miles*6ft) - (6 ft)2)1/2 ≈ 273 miles.

 

So there you have it folks ;). In theory you could see lightning from a lot further away than what everyone was guessing. Of course, these assumptions make this the MAXIMUM POSSIBLE that you'd be able to see just the top part of it, and that's assuming that you even see it at it's origin point. So this is probably an overestimation. But at least we can be confident that the limit is about from this distance.

 

*as far as accuracy for these estimations, before I did this I also did a more simplified calculation in which your height was zero, which gave the formula d = (2RH + H2)1/2. This formula gave 272 miles, so you can see the other terms that depend upon your own height don't really matter.

 

Regardless, this is an estimation, but you can see that it's on the order of 2.5 to 3.5 hundred miles. If you use the law of cosines and solve for that distance, the angle differing from 90 degrees by 1 degree or so makes a difference, but really, 90 degrees is a solid estimation given the large distance, since the replies in this thread give values ranging of around 150 miles, which would correspond to an angle of about 92 degrees rather than 90. So I think an assumption of 90 degrees gives a reasonable guess for the MAXIMUM distance you could see.

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Good reply, but just a couple of thoughts. The height of cumulonimbus clouds are restricted by the tropopause, where the cloud spreads out forming the characteristic anvil shape. There can be a degree of overshoot, but cumulonimbus don't reach 49,000 feet over the UK so lowering the estimated distance. However on the other hand, at night in particular, high cloud layers can reflect the light from the lightning which may otherwise be over the horizon.

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