Storm Australian Severe Weather Forum
Severe Weather Discussion => General Weather - all topics not current severe weather. => Topic started by: Mike on 10 January 2007, 12:10:26 PM
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I was pondering today and hope that some of you more experienced chasers can help me. When watching a storm come in, is the highest concentration of lightning strokes likely to be within the rainshaft(s) of the cloud or on the outer regions of the cloud? I know that it can occur at any place, but i've seen many photos of lightning from within the rain curtain(s) or in the middle of the storm per se? Also what is stattico lightning - is that just another name for CG lightning with branching? Is there a particular part of the storm that is more active during its cycle than other parts of it?
Mike
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HI Mike,
I think you are on the money here. Rain curtains tend to create a form of discharge and the onset of a rainshaft conincides with a lightning barrage. Of course this is generalised. The best concept to follow is a pattern of what you see on the day. I have found that lightning behaves similarly based on atmospheric conditions.
When you get into some of the well structured storms such as supercells or severe organised squall lines, and in very high CAPE environments, I tend to see occurrence of anvil lightning as well. These can be rather scary as they are eratic and very hard to pinpoint where they will strike or from where!
I hope this gives some insight.
Regards,
Jimmy Deguara
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Yes, for sure, Jimmy.
I think we're all in that area of the unknown. I would agree that within the rain shaft there would be some sort of additional electrical activity because as we know rain droplets do in fact cause static discharges due to friction during their updraft and downdraft phase, so that could be part of it also.
As you say, although I have not seen a single supercell in my life (yet!) but have seen discharging from the very top outer tip of an anvil right to the ground around the circumference of the cloud itself - truly one of those things that you thought didn't happen but does!
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Well I'm no expert in this area at all and must say that lightning has always puzzled me. I have noticed that quite well organised storms can sometimes have very little CG lightning where as I have seen some high based multicell storm that are quite lightning active. I think the most dramatic example I have seen of this was in Boulder, Colorado. One day some multicell storms came though and they were very lightning active (someone was killed by lightning unfortunately that day), several days later an organised isolated storm moved though that was severe and I barely saw a cg. Back to the question, I have noticed that alot of cg's can come from behind squall lines, I have only noticed this twice and would be interested to know whether this is common. Also, I think it would be nice to start a thread on lightning in general since it is so interesting, I know I have read of the polarity of CG lightning changing during tornadic storms and smoke from forest fires affecting the lightning activity of storms.
Michael
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One important aspect Michael I found are the lapse rates. Steep lapse rates can cause stronger and rapidly developing updrafts and in these cases you can get a barrage of lightning. This was certainly the case in the following event:
http://www.australiasevereweather.com/forum/index.php?topic=225.0
There were episodes of lightning barrages but to me the on that occurred during the 8pm period seem to be very lightning active.
Regards,
Jimmy Deguara
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Well Mike i'm all for continuing the topic of lightning.
I Jimmy is also correct in regards to smoke enhancing lightning because as a good example is volcano eruptions - lightning does occur with the extraordinary upward motion of the plume of ash and smoke from the cone. So it would make perfect sense to me that any particle - be in water droplets, ash or anything else that can cause friction will cause a discharge.
Those of you who have seen supercells would probably be aghast at the amount of lightning these produce, I can only imagine!. Yet on the other side of the coin, my mate in Oklahoma has seen huge tornadic supercells with little CG activity - yet others with so many you couldn't count them - yet the processes of formation are the same!
I'd like to know if any of the forum members have seen damage by CGs while they were actually observing - ie - has anyone almost been hit while observing???? I'd like to read of some.
Mike
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As an aside gentlemen, what is staccatos lightning? I've seen the photos and probably taken shots of it myself - but perhaps you could enlighten me!
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Staccato lightning are very quick highly branched lightning bolts!
I will try digging some good examples up!
Regards,
Jimmy Deguara
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I agree that steep low/mid level lapse rates are a major factor in many lightning active storms. However, to my knowledge LP supercells are not usually very lightning active and often form in areas with steep lapse rates but limited lower level moisture. In regards to smoke changing the lightning activity of storms, I think their conclusion was that the increased concentration of condensation nuclei affects droplet size and that influences the lightning activity of storms. I can dig up the references if anyones interested.
Michael
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I think dry air at a certain level plays a big part, but not really sure what level exactly and it would depend if it's a day of high temps (say mid 30s) and high based cells or warm temps (high 20s) and lower bases. Two recent examples on the Northern Rivers with an extraordinary amount of lightning were 28th Nov 2006 (hot day, high based) and 15th December 2006, very warm day, low bases. Of course the lack of soundings close to where these storms were observed and near to convection time makes it very hard to know what are good conditions for high CG rates.
MB
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Michael,
The following explanation I suggest is pure speculation I guess.
Of course the lack of soundings close to where these storms were observed and near to convection time makes it very hard to know what are good conditions for high CG rates.
Based on behaviour I have observed with storms over the years, lightning behaviour in certain atmospheric profiles tend be fairly similar. So I personally don't think you being close to Brisbane would have much of a difference in the behaviour of the lightning as if you had taken a sounding nearby particularly if there is no reasoning for their to be much of a difference.
When you compared the two cases you mentioned low based case as compared to high based, and you suggested both were lightning active, would you suggest:
- CAPE was resonably high say around the 2000 mark
- lapse rates were steep?
What do others think from their personal experiences?
Regards,
Jimmy Deguara
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I mean a Brisbane sounding 8-10 hours prior to storms 200-300km away is not much help in analysis.
CAPE was approaching 2000 in both cases. I have the GFS analysis runs for 06z that can be posted if that is any help.
regards, Michael
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Greetings guys (and gals)
Just on lightning again; I have read from forum members when chasing storms that when they see 'anvil crawlers' that they move on to another location. Now, is it the case that this sometimes is the precursor to the storm dying out?
I guess that I've seen lots of storms with crawlers but never really took much notice of 'when' it is occurring per se - so after all the CG activity is diminished, is this an indication of the storm becoming spent?
It seems the more I'm learning from the forum the more I'm observing storms first rather than taking photos and you see 'that' strike or anvil crawler and you think there will be more, but no more appear and you've missed the moment!
cheers.
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Hi Mike,
My understanding from experiences in the field is that anvil crawlers occur in a region mostly where the updraft is weakening and becomes elevated. The storm or main updraft may still be severe but the remnant anvil is what may produce the anvil crawlers.
Regards,
Jimmy Deguara
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So that would explain why most of the crawlers i've seen have been on the back end of the storm as i'm watching it moving away from me. ah ha, now i see. Yes and also that the storm could be still severe or strengthening also - it's just that the storms i've seen of late with this activity may be because i've gotten to observe them late from the back end - as there were no crawlers to the front of the storm/anvil. I guess it's like when you see the storm coming, you see the rainshaft, the CGs, the gust of wind and once the storm passes you still get the CGs - although diminishing - and then you get a sort of lull in the drama and then there's a whole host of crawlers on the backside of the storm - so that's why i was asking, but yep makes sense to me.
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Another question re lightning activity:
I have a collection of DVDs from storm chaser Mike Hollingshead from USA and on some of the supercell video there's these huge bolts that emit from the side of the structure (mothership) but are what he describes as 'super bolts' Now, i don't know if this is something that he's just tagged because there is no description for them, but the lightning is twice as bright and twice as lethal. So have you, Jimmy or other more experience observers ever seen this type of activity?
Viewing them they just look so sureal - absolutely massive flashes from the storm that eclipse other strong CGs striking and they are not CC flashes either - these are single strikes that don't even ground to earth - they just come out of nowhere!
cheers.
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Mike,
US storms are always full of surprises. Once you have a very organised supercell, you will realise its energy!
For some more samples of superbolts - try the sequence from this violent mothership supercell - go down to 27th May 2001:
http://www.australiasevereweather.com/video/tornado_alley_videos.htm
This is available on the Tornado Alley 2001 DVD (http://www.australiasevereweather.com/video/dvd_videos.htm)
Regards,
Jimmy Deguara
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Hi everyone
A couple of post back you were talking about anvil crwlers.
I was just wondering what an anvil crawler is.
Thanks
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Anvil crawlers are lightning that crawl along the anvil or base of a storm usually in its weakened state. Here are a couple of examples I took in the US.
(http://australiasevereweather.com/photography/photos/2006/0603jd15.jpg)
Sometimes the anvil crawler also puts down a cloud to ground lightning bolt. Also I note that this storm had the anvil crawlers along the front part of the anvil - the storm itself was strong to severe!
(http://australiasevereweather.com/photography/photos/2006/0528jd37.jpg)
Regards,
Jimmy Deguara
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So, if it doesn't put down a CG stike, it is classed as a cloud-cloud strike, right?
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Orage, you're right. (correct me if i'm at all wrong anyone)
You can have what looks like CC lighting but was actually a CG. especially at night when you can't see the storm(s). They could be side by side, behind or hidden from your view. CC lightning is also referred to as intra-cloud lightning because it's just electrical activity from within the cloud itself and also from discharges from one cloud to another.
CGs don't necessarily have to come from the base of a storm - as in the rain shaft - they can come from the circumference of the cloud from the anvil to the ground, from within or beneath. Remember that you have positive and negative charges throughout the cloud and around and beneath it, so lightning can emit from anywhere - that's why it's so unpredictable!
When you see a thunderhead lit up like a light bulb it's more than likely CC. even between storms you see CC discharging as it leaps from cloud to cloud to find a connection. However, you can have CC lightning that can discharge as a CG at the same time if it finds a conductive path! It all depends on the maturity, structure, atmosphere of the storm and its surrounds.
In short, yes you're right. There's literally millions of paths electricity can choose from. I hope I explained that in layman's terms - makes sense to me!
Mike
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Here's another question for you. Is there a particular name for the storm cell or cells that continually discharge CC lightning many times per second continuously for hours on end with occasional CG strikes?
We've had them for the past several days in the rural area - long line of them just going off!
Mike
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Mike,
Acording to my knowledge thus far, I don't know of any attmepts to ctaegorise storms according to lightning behaviour - moreso based on severe weather potential. Having said this, one can sometimes get a feel for the type of lightning behaviour a storm will sometimes exhibit.
Regards,
Jimmy Deguara
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Thanks Jimmy, i suppose what i really should have asked is what conditions present in the storms discharging this much activity favour such activity? Perhaps it's just a decent amount of generous indices favouring them. (We've got more about an hour away this evening in the rural area heading our way, so I'm off to check them out about 30km down the track. )
The storms aren't overly huge, very low level ones in fact and not huge towers with large anvils as the norm here - they're just a grouping of middle level storms moving slowly and at times almost stationary for one to two hours before shifting.
Frankly with this amount of lightning activity one should not question why, but just enjoy! Just interested to see if certain conditions favoured these storms.
Mike :)
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In my opinion, as I would have alerted in a previous discussion, each storm event has conditions that exhibit specific lightning behaviour. CC lightning usually becomes particularly active in very unstable conditions with high CAPE but also can be present with rapid destabilisation. Not necessarily do you require the whole atmosphere to be very unstable - mid level instability can also be favourable for active cloud to cloud lightning.
Regards,
Jimmy Deguara
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Generally speaking, Lightning will always follow the path of least resistance.
The presence of a rain curtain, or shaft will probably indicate the likelihood of lightning occurring there, this is simply because air is quite a good insulator, then again I have noticed on the storms I have observed when there is a rain column this is usually in a part of the cloud where there is less electrical activity.... then again you will often see lightning strikes occur just ahead of rain, it really seems to be down to the atmospheric conditions on the day, but water being a much better conductor of electricity than air would seem to be the most likely area for lightning to occur, this may be why much more lightning is sheet lightning then CGs
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Re staccato lightning: Is there a reason why this type of lightning is so quick and branched? Believe it or not i've only seen one this year as we were chasing a storm into town and saw it in front of us. Is there a reason why they're not 'the norm' and are there specific conditions that assist in this type of lightning or is it just one of those things that one is lucky to capture on video or camera at the time?
Mike
Edit: Corrected the spelling of staccato:)
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I can't find much info on the subject from a couple of Google searches. However, it would appear quick to the eye as it consists of only one return stroke.
MB
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Mike,
Staccato lightning from what I have observed are more likely in drier atmospheric conditions and also higher based storms. One would assume that electrical potential in the staccato case of lightning would not be as high? High energy lightning often exhibits multiple pulsing bolts discussed in another thread.
Regards,
Jimmy Deguara