Storm chaser struck by lightning

[Jeff Snyder]

I've been wondering if the "out of focus" was done as a post-production effect to prevent copying, and the actual footage is sharp?

W.

The footage contained some autofocus hunting, but usually that was on the order of <1 s (the usual "hunting"). In the case of the strike, the camera went out of focus a couple of seconds before the strike and stayed out of focus in the short time afterwards. I do think it would be very coincidental if the strike just happened to strike during a time of unusually-long "out of focus"-ness compared to all of the other time (>80%) during which the video was mostly in focus. It does look to go out of focus naturally (as in hunting), but then it locks into an out of focus position and doesn't move through the end of the video. I'm not suggesting doctoring or anything (!), but it does make one wonder as Warren did. It is possible, IMO, that the rapidly-intensifying electric field immediately preceding the strike played games with the AF. The pattern in the "out of focus" (bokeh essentially) through the strike looks the same as it did when it was focus hunting, and I don't see an abrupt change in the 'blur' to suggest post-processing.

There's such a tremendous amount of current that moves through a typical lightning channel that I still can't believe anyone survives direct strikes. I suspect that most "hit by lightning" reports are actually "lightning hit really close" reports or something similar, given the current and heat of most lightning channels.

 

[Dan Robinson]

Agreed -most lightning injuries are from the radial 'step voltage' through the ground from a close strike. Direct hits are rarely surviveable. Without knowing the details of the injury, this looks like a 'step voltage' incident. A direct strike via a split-channel (multiple ground point) CG flash would have produced burns and charred/blown off clothing, socks and shoes. I don't know if a leader strike to a person has ever been documented with certainty (I've never heard of an injury that was definitively identified as one), but I'd suspect it would still be capable of burns given any direct skin contact (direct-strike lightning channels usually travel along the surface of the skin).

 

[rdale]

Guys, I don't think rdale was actually questioning the authenticity of the video.

Correct - I'm questioning the amount of lightning flashes in that cell with the thought that an experienced storm chaser felt it was safe to be outside of his car...

 

[Warren Faidley]

I believe the shot goes out of focus due to the passing vehicle. It appears like the camera tried to re-focus when the car moved into the center of the frame, which may have activated the camera's center-weighted focus sensor. It's possible the camera was not able to re-focus after the moving vehicle passed and it used the windshield as a new point of focus. Regardless, this is why you should always shoot with manual focus set to infinity.

W.

 

[JamesCaruso]

A positive strike I got on video:

You can see the characteristic smooth channel and beaded breakup.

Is the "beaded breakup" characteristic only of positive strikes? I thought the "beaded breakup" was a visual phenomenon associated with being in relatively close proximity to ANY lightning strike...

Jim

 

[Dan Robinson]

All lightning 'beads out', but the more intense a return stroke is, the more it lingers and the easier it is to see at farther distances. Those single-return stroke positives are usually hot enough to allow the beading to be seen farther away than usual. Of the CG variants, those are the ones that I fear even being close to, let alone hit by one.

 

[JeremyS]

Aren't positive stoke lightning bolts more common with tornadic producing storms too? I swear I can remember most every tornado warned storm I've seen throwing out the positive strikes constantly, while other variety of thunderstorms don't seem to have them as much. These bolts scare me way more than other lightning. If this is true, what is the reason why?
About a month ago, I was out on my deck watching a storm put on a decent but not great light show, when out of nowhere a very close strike hit. It was close enough for me to be able to see it bead out, even though I don't think it was a positive looking strike.

 

[JamesCaruso]

What exactly is a positive strike and what are the visual criteria for identifying it?

(Apologies if there is already a thread on this somewhere...)

Jim

 

[Dan Robinson]

James, a positively-charged leader has much less visible branching (usually none at all below cloud base). They usually consist of only one very intense (and unusually bright) return stroke, and the resulting thunder sounds like a series of sonic booms.

Video clip:
https://www.youtube.com/watch?v=Sp9bKDHRfsM&t=0m58s

A little more detailed reading:
http://www.vaisala.com/Vaisala Docu...istics_from_high-speed_video_observations.pdf

 

[Mike Marz]

I absolutely love the sound of positive strikes... It sounds so much louder and more intimidating. I wish I would have been able to chase on May 31st, 2013... That supercell had so much CAPE to work with... the amount of positive strikes it spit out during it's growing stage just prior to tornadogenesis was nuts. I feel like massive CAPE values have a lot to do with positive strikes, but I could be way wrong.

 

[Jon Strebler]

I absolutely love the sound of positive strikes... It sounds so much louder and more intimidating. I wish I would have been able to chase on May 31st, 2013... That supercell had so much CAPE to work with... the amount of positive strikes it spit out during it's growing stage just prior to tornadogenesis was nuts. I feel like massive CAPE values have a lot to do with positive strikes, but I could be way wrong.

I remember reading about the Plainfield tornado and the positive lightning that preceded it. That was definitely a day with extreme CAPE. My understanding is that almost all the positive strikes occurred before the tornado formed and then it was all negative strikes after the tornado dissipated. I wish I could find the write up on this because it was a really interesting read.

Edit: I found the study, written by Anton Seimon. Here's a link if anyone is interested although I'm sure many of you have read it before.

http://journals.ametsoc.org/doi/pdf/10.1175/1520-0477(1993)074<0189:ACTGLI>2.0.CO;2

 

[Jeff Duda]

The folks at the University of Alabama - Huntsville have been heavily involved in a lot research linking lightning flash activity to severe weather. A few years ago there was an entire sub-conference at the annual AMS meeting about lightning and severe weather, most of it presented by UAH people. The big thing I remember hearing about is a "lightning jump" - basically a significant increase in lightning flashes just before a supercell produces a tornado, followed by a relative lull in lighting flash activity while the tornado is in progress.

Here's an example link: http://www.uah.edu/news/research/li...e-warning-of-violent-weather-before-radar-can

 

[Todd Rector]

Very interesting, Jeff - Thanks for sharing that link!
(I am trying to imagine 16.3 MILLION lightning strikes during a storm - incredible!)

 

[Paul Knightley]

I hope Danny is continuing to recover.

Two quick points regarding comments already made:

I have to agree with Dan R about the step-voltage/side strike possibilities here - it may seem somewhat academic to discuss it when someone has clearly been (sadly) injured - however, I think it's a valid point that many lightning incidents involving people (and probably animals too) are where the strike has occurred a short distance away, the the person/animal has been affected by the step-voltage effect (one reason for keeping your legs together when lightning's about). Of course, what it then highlights is that you don't need to be directly struck by lightning to get affected by it - indeed, if you're close to a wire fence, for example, you might be affected by a strike some distance away.

The second point regards +ve strikes. As I'm sure many here know, these *tend* to emanate from the top of the storm, often the anvil (or at least, areas of the storm an higher altitudes, where +ve charges is collecting at the top of the updraught). One case where +ve strikes seem to outnumber -ve ones (which is, on average, the opposite to 'normal') is shallow, winter-time convection, especially that of maritime origin. The whole storm is shorter than a summer/'warm' storm, and so the anvil is nearer the ground - also, they contain a lot of ice material (colder airmass), hence the +ve charge region may be larger. Here in the UK, I've noted quite a high percentage of +ve strikes as a function of all strikes in polar airmasses which have been warmed/destabilised by the surrounding seas.

Another case seems to be (as has been mentioned) developing supercells prior to tornadogenesis - one could speculate that the very powerful updraught of a supercell puts huge amounts of ice material at the top of the storm very rapidly, building a very large +ve charge region - with upper flow blowing this downshear of the mesocyclone, many of us will bear witness to the intense CGs which can occur just ahead of the meso, and sometimes some distance downshear - worth noting when jumping out the car 10 miles ahead of the wall cloud, to start timelapsing! As the intense rotation builds down to lower levels, via the ingestion of high-vorticity low-level inflow along the forward flank, perhaps the amount of cloud material being lifted to very high levels starts to decrease, with the updraught at altitude not being quite so strong - thus, the positive charge region at the top of the storm may become smaller/weaker, and lead to a decrease in the number of +ve CGs as the low-level updraught increases.

A few thoughts, anyway, and perhaps not quite as quick as I suggested above!

 

[Mike Smith]

Danny is having a lot of trouble. His nerve system has apparently been damaged and strong pain killers have not been enough, so far.