Lightning in NZ
Forum rules
These topics are a read-only archive and may be subject to out-of-date information.
For today's weather discussion head to: New Zealand Weather & Climate
These topics are a read-only archive and may be subject to out-of-date information.
For today's weather discussion head to: New Zealand Weather & Climate
-
- Posts: 2
- Joined: Fri 08/05/2009 09:28
- Location: Auckland
- Has thanked: 0
- Been thanked: 0
Lightning in NZ
My friends and I are wondering why the incidence of Fork lightning (or cloud to ground lightning) is relatively rare in NZ, compared to somewhere like Australia. The majority of lightning here seems to be sheet lightning. Any facts or theories appreciated.
I'm thinking it's related to land mass
I'm thinking it's related to land mass
- Vertigo
- Posts: 1184
- Joined: Sun 09/12/2007 23:50
- Location: Henderson, Auckland
- Has thanked: 0
- Been thanked: 12 times
Re: Lightning in NZ
hi keith,
good question. but lets get the terminology right before we start, just to be as accurate as possible. sheet lightning is called intra-cloud lightning, or IC - it looks like the cloud is lighting up, but its still just a bolt inside it. fork lightning is when the bolt exits the cloud and hits the ground, and is called a cloud-to-ground strike, or CG.
nothing wrong with your terms btw, its just the the right terminology lends a hint as to the nature of the different forms.
good question. but lets get the terminology right before we start, just to be as accurate as possible. sheet lightning is called intra-cloud lightning, or IC - it looks like the cloud is lighting up, but its still just a bolt inside it. fork lightning is when the bolt exits the cloud and hits the ground, and is called a cloud-to-ground strike, or CG.
nothing wrong with your terms btw, its just the the right terminology lends a hint as to the nature of the different forms.
- Vertigo
- Posts: 1184
- Joined: Sun 09/12/2007 23:50
- Location: Henderson, Auckland
- Has thanked: 0
- Been thanked: 12 times
Re: Lightning in NZ
IC and CG lightning have different radio signitures, which can be picked up on and plotted by lightning trackers, such as the Stormvue that a lot of us here use, so theorizing that they are formed in very different ways is no doubt plausible.
there are general attributes that are well known, however. both IC and CG come in positive and negative flavours, depending on the height that the lightning originates at (correct me if im wrong here, someone). IC tends to be produced when a storm is weaker, tho it can be observed in a storm of any strength. CG bolts are produced as a storm grows in strength, with negative strikes originating at lower levels, and positive strikes originating from the top of storms. therefore, to reach the ground, positive strikes tend to be more energetic - they have to be to even reach the ground. positive strikes can also loop back and re-enter the cloud near the bottom, where the charge is predominently negative.
so going by that, i would say that our thunderstorms tend to be much weaker than those observed overseas, and this is why we dont see as much CG lightning. this agrees with upper atmospheric data, which shows that we dont get nearly the levels of CAPE that Aus and the mid-west US get (our CAPE tends towards 1000J/kg, max, whereas the US can regularly get above 3000J/kg).
there are general attributes that are well known, however. both IC and CG come in positive and negative flavours, depending on the height that the lightning originates at (correct me if im wrong here, someone). IC tends to be produced when a storm is weaker, tho it can be observed in a storm of any strength. CG bolts are produced as a storm grows in strength, with negative strikes originating at lower levels, and positive strikes originating from the top of storms. therefore, to reach the ground, positive strikes tend to be more energetic - they have to be to even reach the ground. positive strikes can also loop back and re-enter the cloud near the bottom, where the charge is predominently negative.
so going by that, i would say that our thunderstorms tend to be much weaker than those observed overseas, and this is why we dont see as much CG lightning. this agrees with upper atmospheric data, which shows that we dont get nearly the levels of CAPE that Aus and the mid-west US get (our CAPE tends towards 1000J/kg, max, whereas the US can regularly get above 3000J/kg).
-
- Posts: 2
- Joined: Fri 08/05/2009 09:28
- Location: Auckland
- Has thanked: 0
- Been thanked: 0
Re: Lightning in NZ
Ok, so it's related to the energy present in the atmosphere during the storms? ( also, what is CAPE?)
Is this because of the general relative atmospheric pressure?
I guess I'm really wondering if it's because the large land masses of places like AUS and USA tend to lend more energy back to the atmosphere via heat etc, than NZ does?
All good stuff by the way. Just trying to get a definitive reason why.
Is this because of the general relative atmospheric pressure?
I guess I'm really wondering if it's because the large land masses of places like AUS and USA tend to lend more energy back to the atmosphere via heat etc, than NZ does?
All good stuff by the way. Just trying to get a definitive reason why.
- Vertigo
- Posts: 1184
- Joined: Sun 09/12/2007 23:50
- Location: Henderson, Auckland
- Has thanked: 0
- Been thanked: 12 times
Re: Lightning in NZ
CAPE is, if you want to get technical, the integral of the differential from observered ambient temp to parcel lapse rate, from the cloud base to the cloud top. for the rest of us, it is a measure of the energy density in a storm, measured in Joules per kilogram of air.
CAPE is measured computationally generally, but when you get familiar with reading upper atmosphere soundings (also known as skew-t diagrams), you can see the overall energy in the atmosphere at a glance. i cant really go into it in this thread, but there are websites around to learn how to read a skew-t diagram. the terminology is the hardest part, the actual diagrams are quite simple (they dont look it tho!).
CAPE is measured computationally generally, but when you get familiar with reading upper atmosphere soundings (also known as skew-t diagrams), you can see the overall energy in the atmosphere at a glance. i cant really go into it in this thread, but there are websites around to learn how to read a skew-t diagram. the terminology is the hardest part, the actual diagrams are quite simple (they dont look it tho!).
- DT-NZ
- Posts: 1010
- Joined: Mon 09/02/2009 10:55
- Location: Northland, NZ
- Has thanked: 0
- Been thanked: 0
Re: Lightning in NZ
Hi Vertigo
Appreciate your insights and thoughts ... ( thank you ) absorbing... taking it all in... learning... take care.
Appreciate your insights and thoughts ... ( thank you ) absorbing... taking it all in... learning... take care.
Lightning in NZ
The right terminology lends a hint as to the nature of the different forms.
A Vertigo Quote.
The right terminology lends a hint as to the nature of the different forms.
A Vertigo Quote.
-
- Posts: 435
- Joined: Wed 02/05/2007 08:27
- Location: Parkdale, Tokoroa
- Has thanked: 0
- Been thanked: 0
- Contact:
Re: Lightning in NZ
Thanks Vertigo! So with high lapse rates, ie steeper temperature gradients than expected for rise in elevation, ie greater temperature extremes from below at ground level to above where a very cold air stream or jet-stream may exist, contrary to what is happening at or just above ground level, then you can get very volatile air masses rising and "boiling". The greater the temperature differences, then the greater the velocity and tumbling and energy involved. Hence with the air masses moving and static electricity being generated then we expect the strongest lightning is associated with the highest extremes in temperature differences and the greater heights that the Nimbus forms are created.
Hence, I surmise then that Keithmeister's assumption about land mass is probably correct, where you can get the greatest heating with large flat land masses and the high level airstreams do not mix so much with the mid level atmospheric clouds - the landforms are flatter and less inter cloud level mixing occurs. So the thunderstorms can gather more heigfht and more enerrgy and greater temperature differences. The perceived temperature lapse rate could be greater than that generated by elevation alone and ehence more velocity and turbulence...
All just postulated with an enquiring mind... Moisture content must come into this as well, increasing the air mass and "energy capacity" of the air and probably decreasing the path resistance for lightning to move?
Graeme
Hence, I surmise then that Keithmeister's assumption about land mass is probably correct, where you can get the greatest heating with large flat land masses and the high level airstreams do not mix so much with the mid level atmospheric clouds - the landforms are flatter and less inter cloud level mixing occurs. So the thunderstorms can gather more heigfht and more enerrgy and greater temperature differences. The perceived temperature lapse rate could be greater than that generated by elevation alone and ehence more velocity and turbulence...
All just postulated with an enquiring mind... Moisture content must come into this as well, increasing the air mass and "energy capacity" of the air and probably decreasing the path resistance for lightning to move?
Graeme
A Father can have a hobby because he is the Transport, Referee, Manager, Committee Member Dad!!
LaCrosse WS-2308CH, Sharp VideoCam, ULD Lightning Radar
http://www.inmanavenue.com/
LaCrosse WS-2308CH, Sharp VideoCam, ULD Lightning Radar
http://www.inmanavenue.com/
- Dale
- Posts: 1070
- Joined: Sun 27/07/2008 08:59
- Location: Greymouth - Feral Coast.. NZ
- Has thanked: 0
- Been thanked: 0
Re: Lightning in NZ
Sort of related & reading through a couple of above posts.. this may come in very handy if you have a couple of spare hours to digest.. there is a lot of reading involved but it is a tool that my mentor & very close friend, Anthony Cornelius.. put together a few years back now.
Note: it has been more or less written for Australian conditions, but the principals are very much the same.
http://www.downunderchase.com/storminfo/stormguide/
AC's guide to forecasting your own thunderstorms (and potential.)
Note: it has been more or less written for Australian conditions, but the principals are very much the same.
http://www.downunderchase.com/storminfo/stormguide/
AC's guide to forecasting your own thunderstorms (and potential.)
-
- Posts: 435
- Joined: Wed 02/05/2007 08:27
- Location: Parkdale, Tokoroa
- Has thanked: 0
- Been thanked: 0
- Contact:
Re: Lightning in NZ
Thanks
A Father can have a hobby because he is the Transport, Referee, Manager, Committee Member Dad!!
LaCrosse WS-2308CH, Sharp VideoCam, ULD Lightning Radar
http://www.inmanavenue.com/
LaCrosse WS-2308CH, Sharp VideoCam, ULD Lightning Radar
http://www.inmanavenue.com/
-
- Posts: 435
- Joined: Wed 02/05/2007 08:27
- Location: Parkdale, Tokoroa
- Has thanked: 0
- Been thanked: 0
- Contact:
Re: Lightning in NZ
I didn't see any mention of forest fires (caused by lightning or otherwise) being a generator of lightning conditions, and also volcanoes, (perhaps I have not read far enough into it...) which I have seen evidence of both creating lightning. A good thorough read though - really enjoyed the links. I have to read through further yet, and I'll probably save the pdfs and file away and hand read. Thanks.
- 03Stormchaser
- Moderator
- Posts: 4428
- Joined: Tue 09/12/2003 12:11
- Location: Prebbleton
- Has thanked: 104 times
- Been thanked: 184 times
- Contact:
Re: Lightning in NZ
The number of cgs I saw last night is probably more than I have seen altogether since chasing storms in NZ... helps to be in bangkok though! lol
NZ Largest Storm Chasing Facebook Pagehttp://www.facebook.com/nzstormchasers
NZ Largest Storm Chase Community https://www.facebook.com/groups/NZStormchasersGroup
NZ Stormchasers TV https://www.youtube.com/@NZStormchasers
NZ Largest Storm Chase Community https://www.facebook.com/groups/NZStormchasersGroup
NZ Stormchasers TV https://www.youtube.com/@NZStormchasers
- Lacertae
- Posts: 754
- Joined: Thu 06/11/2008 06:12
- Location: Waimairi Beach, Christchurch
- Has thanked: 0
- Been thanked: 0
Re: Lightning in NZ
I would say the most important thing on this website is this chart :Note: it has been more or less written for Australian conditions, but the principals are very much the same.
http://www.downunderchase.com/storminfo/stormguide/
AC's guide to forecasting your own thunderstorms (and potential.)
The Earth has music for those who listen.
- NZstorm
- Posts: 11333
- Joined: Mon 10/03/2003 19:38
- Location: Grey Lynn, Auckland
- Has thanked: 342 times
- Been thanked: 361 times
Re: Lightning in NZ
I would change that chart to
60% Models
10% Instinct
The world of forecasting has changed dramatically in the last couple of decades, the performance of the weather forecasting models has greatly improved.
60% Models
10% Instinct
The world of forecasting has changed dramatically in the last couple of decades, the performance of the weather forecasting models has greatly improved.
- Michael
- Posts: 7210
- Joined: Thu 27/03/2003 12:04
- Location: Rainy Manurewa, Auckland - "City of Gales"
- Has thanked: 0
- Been thanked: 1 time
- Contact:
Re: Lightning in NZ
Means the other 30% simply looking out the window
NZstorm wrote:I would change that chart to
60% Models
10% Instinct
The world of forecasting has changed dramatically in the last couple of decades, the performance of the weather forecasting models has greatly improved.
-
- MetService Meteorologist
- Posts: 283
- Joined: Sat 15/03/2003 10:59
- Location: Upper Hutt, NZ
- Has thanked: 3 times
- Been thanked: 0
Re: Lightning in NZ
Personally, as an operational thunderstorm forecaster, I would change that chart to...
80% Forecasts and models
19.9% Experience
0.1% Instinct
80% Forecasts and models
19.9% Experience
0.1% Instinct
- Lacertae
- Posts: 754
- Joined: Thu 06/11/2008 06:12
- Location: Waimairi Beach, Christchurch
- Has thanked: 0
- Been thanked: 0
Re: Lightning in NZ
Sorry guys, I didn't precise that this chart is more for forecasting while chasing ...
The Earth has music for those who listen.
-
- Posts: 9907
- Joined: Sun 29/06/2003 22:39
- Location: Mt Eden Auckland
- Has thanked: 839 times
- Been thanked: 866 times
Re: Lightning in NZ
I still think instinct plays a very small part if any, experience helps alot.Sorry guys, I didn't precise that this chart is more for forecasting while chasing ...
- NZstorm
- Posts: 11333
- Joined: Mon 10/03/2003 19:38
- Location: Grey Lynn, Auckland
- Has thanked: 342 times
- Been thanked: 361 times
Re: Lightning in NZ
I agree an operational weather forecaster shouldn't really be using instinct for forecasting but storm chasers certainly do use a bit of it in their forecasting. I do think the experience part of the equation would be reasonably high though. For example models can have a lot of difficulty with the mesoscale aspect of thunderstorm development but the experienced forecaster will possibly be better at resolving those issues. The mesoscale environment that led to the severe thunderstorms in the BOP on Monday were not detectable in the modelling. All the modelling was showing was an unstable environment over a wide area of the upper North Island.
-
- Posts: 9907
- Joined: Sun 29/06/2003 22:39
- Location: Mt Eden Auckland
- Has thanked: 839 times
- Been thanked: 866 times
Re: Lightning in NZ
A personal thing I guess .instinct for forecasting but storm chasers certainly do use a bit of it in their forecasting.
- Dale
- Posts: 1070
- Joined: Sun 27/07/2008 08:59
- Location: Greymouth - Feral Coast.. NZ
- Has thanked: 0
- Been thanked: 0
Re: Lightning in NZ
Lets not forget the guide was put together many years ago now... things have improved since then.
Not only model wise, but experience wise.. and this is the view of 1 person.
Not only model wise, but experience wise.. and this is the view of 1 person.
-
- Posts: 18488
- Joined: Wed 12/03/2003 22:08
- Location: Raukapuka Geraldine
- Has thanked: 1769 times
- Been thanked: 1412 times
Re: Lightning in NZ
Some 'sheet' lightning lashing away to the west tonight.
JohnGaul
NZThS
JohnGaul
NZThS
JohnGaul
NZThS
NZThS
-
- Moderator
- Posts: 5121
- Joined: Fri 10/02/2006 15:14
- Location: Halswell, Christchurch
- Has thanked: 717 times
- Been thanked: 923 times
Re: Lightning in NZ
Yep...been seeing the same John. Good display tonight. Between rugby games.
Christchurch Rocks