Author Topic: VIC/NSW Thunderstorms ( incl Victorian tornado discussion ) 9 - 12 February 2010  (Read 34946 times)

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Offline Anthony Cornelius

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Hi John and Brad,

Thanks very much for your detailed posts and photos, it's great to finally have gotten a few more images of everything!

Ultimately, no one is here to "belittle" you or anything like that - people are just here to give their own opinion, and then it's up to others if they wish to take that on board or not.  It definitely isn't a "northerner vs southerner" thing - everyone is equally ecstatic when they see great storms (and their associated photos!) in other locations, I can vouch that I have many NSW and QLD friends who will flick me a message saying "Wow, have you seen the Vic/SA/WA/NT etc etc photos???"

From the photos you have illustrated, it is my belief that this is an outflow feature.  It appears to be a nice gust front that has developed thanks to the higher than usual humidity over Victoria.  I hope this isn't taken the wrong way...but I've seen dozens and dozens of storms like that and I'd all call it the same thing (a gust front).  There does indeed to appear to be a raised vortex though - and that would most likely be a gustnado if that's the case.  Gustnadoes can be quite exciting - I remember on one great day (a 196km/h gust was reported from one of the storms too!) that Dave Sercombe and I had to stop on the highway with our hazards on (to stop people from proceeding) as a strong and defined gustnado crossed in front of us!  We saw it from a while away too, and there were several other vorticies in the outflow push of this particular storm - there may have even been a small funnel above reported from another chaser.  I believe that gustnadoes are quite common - especially if viewed from the angle that you witnissed it.  If you think about it, if you are looking parallel to the wind motion ie:

          x              (x = your position
<----------------------  (inflow winds, 30km/h)
   O      O      O       (O = vortex rolls)
----------------------> (outflow push direction 100km/h)

From this angle, you'd see them easily (note if you were at the wrong angle, you may not witness it so easily).  Again, it even reminds me of another storm which had winds of 130km/h (and some one was killed just near us from a tree falling on their car), but the dust front/gust front had multiple vorticies on the front of the storm - many short lived, but nonetheless definied.  The above schematic could also occur on either the horizontal or vertical plane (ie, you could have tilted vorticity if the strong winds undercut the inflow, so it's inflow above and outflow below - the lifting of the warmer air on the boundary of the outflow could then tilt the horizontal vorticity and then connect the two briefly).  There are many dynamics at work here.

Also - outflow dominated storms don't necessarily die either.  And sometimes outflow dominated storms can become inflow dominated again!  They're very dynamic...other times outflow dominated storms can become "front loading" (meaning that the outflow is generating the new updrafts just ahead of it, common in squall lines).  A common feature for prolonged HP supercells in say NE NSW and SE QLD is to pulse, the outflow pushes through and the storm weakens briefly and then reintensifies again as the inflow becomes established (common near the coast with strong seabreezes, as the outflow eventually gets overcome by the stronger northerly winds).

No one's opinions should take away from your experience though!  Either way you should be excited about what you saw - and it has been great to see some photos of the storms down there!

AC

Offline Paul D

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The photos in Brads pics Post 76/77, with the initial earlier posts (post 20) I had assumed the storm was traveling left to right in the frame but reading though it appears it is right to left?? just for reference sake could you confirm what direction you were looking when taking these pics (Brad had mentioned you were looking SE to SSE?) and also direction of storm movement.
The second pic in post 77 seems to show a funnel extending from the cloud base. (I was looking upper right hand side rather than the area highlighted in your last post)
So here's my two cents worth.. I don't like the term Gustnado full stop for cloud/associated feature classification, (nado is not a word which has anything to do with weather)so the coined term should be viewed along the same lines of using a term such as willy willy.
Fully agree with John about the terms useage, if a gust front spin up shows signs of attachment to the cloud base it ceases to be a gustnado(if the term is insisted upon). If formation of tornadoes of any form, was bias toward those lacking well defined condensation funnels in Australia it wouldn't be hard to see many being incorrectly termed as gustnados.
This topic has certainly been an interesting read keep it up, As for the case being discused photos don't do justice in showing the whole processes involved/suggested, hope to see some video footage.

Cheers
Paul
   
« Last Edit: 18 February 2010, 06:54:20 AM by Paul D »

Offline James

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Our problem here is that people are judging the storm purely on one feature which was clearly not the feature that caused the extended damage tracks...the damage was caused 10km earlier, and you can see behind the feature upon you are so fixated a defined tailcloud and a dark shape with quite hard edges in the murk. The tail cloud alone suggests this thing may have had a wall cloud....and this would be reflective of all the other storms we have shown prior to this image, which display wall clouds, and some also produce tails.

I still have a problem with the discussion of the "gustnado" against the nomenclature...given...the minute it reaches the cloud it is no longer a gustnado by definition...and yet noone has offered comment or even tried to say anything here...its just being ignored. If it was a gustnado then why were there associated funnels...not small ones, but ones that were miscoloured by the ingestion of dust? Why also did these features extend from the cloud...only to retract thereafter?
And an annotated point to so look at the the correct bit. We have the remenants of the prior funnel to the right, and an extended vortex tube which is discoloured by the dust and is contacting the ground. Can we please explain this...see the images either side of this blowup for evolution, noting the pin-funnel following this object.



Great discussion so far!

John with regards to your above image I have noted you have outlines in red what you believe is the vortex and associated debris underneath (Correct me if I am wrong). I believe what you have outlined in your photo are two separate features. I will explain using my dodgy photoshop skills below.



The above image comprises 3 images taken in sequence of the proposed tornado. The last photo above is pretty much taken at the exact time your coloured example above is (just not as contrasted). A couple of thoughts on this below

- The arrow above shows the leading edge of a gust front (which your calling a tail cloud) however in the last photo the way that the dust and leading edge are lined up looks like they are connected. Clearly from the first two photos they are not

- Using the mountain in the background the gust front (which your calling a tail cloud) is moving away (or out) from the main storm as the photos progress.

- In my opinion the dust cloud in the first of those three pictures does not line up underneath the darker "tail cloud" you are talking about. The dust cloud is  or so away whilst the "tail cloud' looks to be 2-3km away

- The discolouring you talk about in the third photo is the top of the dust plume in the second photo being pushed out by outflow winds so it is located in front of the leading edge of the guster (or tail cloud). It looks a little dusty but its not. That dust is still a km or two in front of that feature.

- I can see the little funnely notches you are talking about however there is no connection in any of those photos that link the dust debris cloud to the cloud base (besides I believe the notch to be further back than the dust - see above)

Those above to me (plus seeing these sort of features so many times over my 11 years chasing) show clear evidence that it is purely outflow in those photos. I have also pasted a reference below of wall cloud/shelf cloud definitions taken from the NSSL (Keeping in mind the sloping edge of the guster [what you refer to as a tail cloud] in the above pictures as it moves away from the rain on the right  - http://www.nssl.noaa.gov/primer/tstorm/tst_detecting.html

To tell the difference between wall clouds and shelf or roll clouds, remember a wall cloud 1) suggests inflow and an updraft, 2) maintains its position with respect to rain, and 3) slopes upward away from the precipitation area. In contrast, shelf clouds 1) suggest downdraft and outflow, 2) move away from rain, 3) slope downward away from the precipitation area.

Offline Anthony Cornelius

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Hi John,

In reference to your photo I largely have to agree with James' summary.  It is perhaps that that photo is in the right place at the right time to capture an outflow prong with the dust vortex.  I've also been chasing for 11 years, I've chased with quite a few people on this forum also (Jimmy, James, Macca etc) - especially back in the late 90s/early 2000 days.  And I remember us all getting very excited when we saw dust etc rise up, and we'd then go back and have to examine the video footage and we'd look for movement etc.  Much of it came to it being some of our first adventures, and us being very excited and eager to see (find?) tornadoes.  But later inspection (especially with current knowledge) pretty much all suggests the same - that many (although not all) were not tornadoes, but they certainly looked the part for a brief period.

The features you have illustrated in photos are very common in NE NSW/SE QLD storms - and when I see them I often think outflow.  I have seen wall clouds turn into gust fronts, and even gust fronts become remodified into wallclouds too!  Weather is certainly very dynamic that's for sure.  Hopefully as you become more experienced at chasing, you'll understand a bit more about what some of the comments have been said.  That's one of the great things I love about chasing, it doesn't matter how long you chase for, there's always something new to be learnt!

Which Boonah storm are you talking about?  Is this the storm last Monday?  If so - I don't believe this to be a supercell?  I even mentioned that in my posts on the Weatherzone Forum, a few people argued that it was a supercell and I disagreed with them.  See: http://forum.weatherzone.com.au/ubbthreads.php?ubb=showflat&Number=833017&page=11 and then page 12 for more discussion, and page 10 for the photo.

AC

Offline dann weatherhead

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Hey everyone

Thought i would weigh in at this point with nothing more than to say that the discussion as been great so far - and that I support the comments from my esteemed colleagues above (Macca, James, AC). These matters are difficult - ones diagnosing skills are honed after years of chasing and questioning - most oft in the lamenting the big day that didn't quite fire - or that day where the cyclical meso developed a plethora of funnels but not that cherished tornado.

Being on the ground, in the environment - you eye and experience captures more than even the best photograph or video (Wingle angle HD or not) can. However endeavours of weather and chasing exist in the realm of science - and thus supportive evidence and the methods must be followed to support our aims and claims. The process of discussion and openess should be cherished and encouraged in all forums. The open ended question is oft of more benefit than the closed focused conclusion.

Great work in the documentation of these storms and damage surverys.

D.

Offline Macca

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The only way which this will be resolved one way or another is to see the video.  Obviously many of us are struggling to visualise what John and Brad are referring to in the still images.  Personally, even with the red drawings showing the said funnels, etc, I'm still struggling to determine whether these are in fact rotating funnels or just scud features (commonly referred to as scudnadoes) - again this will come down to the video and what can be seen in terms of motion.  

Until then, this debate seems somewhat fruitless.  Any arguments to the contrary of this being a tornado are being shot down with lengthy repeated comments which all the seem to be doing are increasing the length of this thread.  Whilst I enjoy the debate and discussion, its getting a little tedious.  

The features in the photos suggested to be "wall clouds" are again hard to assess in still images.  Wall clouds are usually associated with strong updrafts (again which I suggested in an earlier post were unlikely given the situation on the day).  

There is definitely no doubt that Victoria gets a pretty decent number of non-supercellular tornadoes/funnels (of which I've seen plenty and have seen photographic evidence of plenty).  Perhaps this is where we should be looking to categorise this event (as opposed to the short, low topped supercells referred to by John). To me, this environment is not one that could've or should've produced a supercell - whether it had tops of 50,000ft or 15,000ft.

I *eagerly* await this video.  In the mean time, I'm off to look at photos of the tornado from the Atherton Tablelands from yesterday - definitely no doubt about this one (the question is, was it a supercell...).

Macca    

Offline Jimmy Deguara

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Hi John,

Quote
So hang on...does this mean you are contesting this as being an inflow feature.

Yep - shelf cloud to me.

Sorry I am exhausted. I am not going to comment any more until more funnel related pictures are presented or video of rapid rotation like I see with tornadoes. Excuse my narrow mindidness but count me out of the topic discussion. Brad thanks for posting your excellent pictures - they really show a very nice high contrast shelf cloud. Perhaps there were connection with gustnado at some point - perhaps not. I wasn't there you guys were. Unfortunately when you have to go to the trouble of enhancing and enlarging and annotating, the evidence is unfortunately poor to convince others who were not there. Maybe you did see a tornado - can't rule out the possibility. What I see is at least gustnado. At least we all tend to agree with that. I have seen several potential Australian tornadoes - I have only really claimed one! US tornadoes not a problem.

Thanks for all others for your comments and feel free to keep posting. John, please get Harald Richter to send actual comments of radar and so forth that points the wind shear couplets suggesting shear profiles of a tornado and low topped supercell conditions. To me the storms were much higher than that from what I could see. Like Anthony said, we have chased and observed these type of features many times before.

Regards,

Jimmy Deguara
« Last Edit: 20 February 2010, 01:00:28 AM by Jimmy Deguara »
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Offline Brad Hannon

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« Last Edit: 19 February 2010, 12:54:40 AM by Jimmy Deguara »
hmmm June 2nd......

Offline Jimmy Deguara

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Hi Brad,

Quote
Video was a low priority at the time...

Video unfortunately would have gone a long way to consolidating the argument. Even badly shot video would have shown rotation of a vortex. Make it a priority in the future.

Regards,

Jimmy Deguara
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Offline Macca

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Brad,

I still don't think I'm clear which photos you are referring to regarding the smooth-edges thingy looking towards Avenel.  I've been back through the photos again just now and used the most rudimentary (paint) way of doing something...

Is what I've circled the feature you are referring to?

(no idea if I've attached the photo correctly).

Macca

Offline Paul D

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Managed to get some depth (stereo view)out of photos "IMG_1208_contrast" &" IMG_1209_contrast" certainly looks far more impressive viewed in 3D. Haven't worked out the exact position the photos were taken from - no street view on Google maps on that particular road, but either way, the rotating area of dust at ground level appears to be app 150m across and has a nice structure.
It also seems to support a connection at that time to a vortex as outlined by John in post 86 (image 2). Having said that, one would require higher resolution and probably better parallax to conclusively state on the basis of those 2 images alone (without video or actually witnessing the event) that it is connected, and also a further sequence of photos(hence video is best, bigger sequence)to give an indication of rotation of the vortex.

Cheers
Paul

Offline David C

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John, Brad,

Briefly off-topic, I have already clarified the reason for the brevity of my two posts offline with John (ie I'm just way too bust to spend the time that I would otherwise like to in reading and contributing to the forum, Jimmy would vouch for that), so I wont go into that aspect much more, other than to say there is no malice in it and, I guess I can be abrupt in my posts.

The bowl lowering that Macca has captioned above could well be a large bowl funnel based on it's appearance in that pic (and I have not gone through the preceding posts in  detail to gain a perspective from different photos), there's no question of that. If the shelf / collar at the front was part of a broader scale circulation and if the bowl was clearly rotating, case closed. On the other hand if the shelf was pushing out and that feature was going with the flow so to speak, and if rotation was not discernible to either of you, I would be fairly confident in saying that it is just a non-descript lowering... a tornado wanna be. When chasing, large rotating lowerings of that size, which are indicative of a low level mesocyclone, are unmistakable even from some distance -- since they are basically a pivot  - your eyes are drawn to them even if they are moving as part of the storm, in that all the other cloud base elements appear to converge on them and move around them...it really is an unmistakable process visually.  SO like I said, if that is what you saw then it is what it is.  I'll offer comments on the dusty tornado later, but reasoning was pretty  much what has been covered. If there are more pics now available of that phase, ie zoomed out etc etc, I'll look at those and give my own thoughts.

I was trying to find a good example of a similar cloud structure that is tornadic and one that is not....I'll have to use my own examples as I think White Deer had an excellent bowl lowering prior to tornadogenesis being fully realised.

I thought this (Booleroo) might be a good example, but after looking at it, thought no. Nice tornado nonetheless. btw I don't agree with it being multi-vortex....as is/was claimed ....that's scud appearing to break up the single tornado vortex.

This is the Booleroo tornado taken in 1992 referred to above.
 
« Last Edit: 20 February 2010, 12:50:15 AM by Jimmy Deguara »
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Offline Brad Hannon

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« Last Edit: 19 February 2010, 08:13:20 PM by Brad Hannon »
hmmm June 2nd......

Offline Brad Hannon

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Ok here are some pics re-posted with some brief annotation as to what I was seeing at the time and what I am seeing in the pics.  I may be wrong so let me know what you think if I am.

Considering the sustained, defined cone shaped edges and low bases in the area of the confirmed damage path, apparent inflow features initially feeding in from the west and then later from the east and below and behind the other clouds, definate presence of RFD in the area of the circulation and another RFD later at our position, the lack of any outflow and the fact that dusty vortices were produced afterwards in my pics leads me to believe there was at least a tornado between Avenel and Locksley and that new areas of circulation responsible for the dust vortices built on the northern flank as it approached Longwood while RFD cut around and wrapped the tornadic circulation to the south.

Thats my conclusion.

Brad.

hmmm June 2nd......

Offline Brad Hannon

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and a few more shots showing both the close and wide views of these features:



hmmm June 2nd......