Topic: SE Aust Severe Storms (incl possible VIC tornadoes) 19 - 22 December 2007

[David C]

Some VERY nice storms down there and what about Victoria for chase country! - but a tornado in that news segment? Again form the brief footage it looks like a 'scudnado' to me - no motion evident at all. The structure looks wrong for a vortex too - what is that gap at cloud base on the right side -- while it might be a case of perspective and could be some condensing cloud jutting out towards the photographer moving in, it all looks very undynamic. There is obviously more footage of the event, and at that distance if there was clear rotation then it then it should be visible, and maybe it was.  As Michael said it would be nice to see more footage.

In fact, what are we even discussing this for. That storm is well within range of a Doppler radar Large tornadoes will not go unnoticed from around that part of the world. E-mail Harald Richter and ask him what the radar was showing at the time.

[Michael Bath]

David - Harald happened to write this on the Aussie Wx list and it corresponds to the event:


"As those folks watching the "outside world" around 2pm EDT today will have noticed,
it is rare for Victoria to achieve a juxtaposition of decent deep layer shear
and rich, deep surface moisture.  Today is an exception.
                                                                                                                               
The storms extending from Aireys Inlet to E of Skipton, however, seem to have trouble
capitalising on the deep layer shear.  Their rotational signatures are shallow and
sporadic, something I have seen a few times now with Australia's southern storms.  Maybe the
competition for "the juice" and/or the localised disruption of the wind field
by neighbouring storms is to blame.  The tail end (northern) leftmover E of Skipton
should be least affected by such competition, as evidenced in its longevity
and propagation characteristics.
                                                                                                                               
As of 3:30z we have the northern tailend storm splitting with the leftmover
quickly dominating (nice TBSS - a sign for large hail).
                                                                                                                               
On the previous scan (3:24z), the southern neighbour sported a hook echo and
low-level (< 1000m) mesocyclone - both very shortlived, though."

[Jimmy Deguara]

Hi Michael,

Is there any other indication as to whether Harold has dismissed this tornado based on doppler and radar characteristics?

Rotation sufficient to cause tornadoes is definitely noticeable from a few kilometres away. I did see only slight shelf cloud shear if any - not sufficient for a 'large tornado'. It is claimed that the tornado became rainwrapped. I would not mind seeing the 11 minutes of footage of this event.

There was a funnel cloud and then outflow is evident given the scud at the base.

Regards,

Jimmy Deguara

[Shaun Galman]

Hi guys,
Hers a couple storm images from the 12st Dec. and a couple flooding photos from 22nd Dec. to "wet" your appetite lol
21 December 2007 Upper Western. Storm Photos

Here's that impressive looking storm line you noticed Michael. This is looking north-west from town at 7:27pm. This is the beast that seemingly broke the cap twice. If only the shear was stronger we may have had a different outcome!

This is the western edge of the rain cores that formed from the storms in the panorama above. Taken at 8:18pm facing west from 3k's east of town.

Same camera position as above only looking east. It's funny, I was caught in a major dust storm on these plains just two weeks ago!

22 December 2007 Upper Western. Flooding Photos
Now for some flood shots from this morning! (22nd Dec.)

This the Castlereagh Highway turnoff to the Ridge. 5k's from town.

The entrance to town. If we get another inch or two in the coming days, the roads will be surely cut as the ground is pretty well super saturated!

This shot speaks for itself! This is typical of the surrounding plains in any direction!
Cheers guys,
Shauno

[Michael Bath]

Is there any other indication as to whether Harold has dismissed this tornado based on doppler and radar characteristics?

No - there have been no further comments that I have come across - perhaps you or David can email him ?   

Also - we now finally have some more info about what was taking place. Clyve's tornado was just before 4pm, not earlier as initially thought (why it has taken 2 days to get details is beyond me), so it is part of the line of cells on radar around 05z.  (I have extended the radar loop)

Another observer, Andre Dalton took these photos are wrote:

"I was on Thompsons Rd, about 10 ks south of Beaufort, with a mate from work - Matt Carey (Tech Officer)- saw two lowerings - the one at the far rear flank of the storm became a large wall cloud, then just dropped it.....it started feeding off the other lowering, and for a moment I thought I was looking at a wedge, it was a doozy."

"It was 1.20 pm approx - I saw the thing on the ground for a good 2-3 minutes continuously, although it skipped up and down for a good 5-6 minutes. It touched down as a rope, and became almost a stovepipe within seconds. The inflow winds were blowing at our backs from the north at a good 40 km an hour, and I'd say the tornado was located maybe 10 km to the west of Skipton, at Stockyard Hill?? Carranballac??"

http://backyardchaser.net/gallery/album114

I have asked Andre to display some closer shots so hopefully we'll see these tomorrow. It would appear two events had possible tornadoes.


Shauno, thanks for displaying those pics - amazing scenes of that storm and this morning's flooding !  Barely seen any weather here for the past 2 weeks and the next week looks very ordinary as well. 

[Jimmy Deguara]

Hi Michael,

Wow! We have even a stove pipe now? I fail to see any but I await the pictures - I would have thought they have been showed off already.

I cannot believe that these people are for real. But this is the same disease being spread across the board.

It is extremely important that we are able to debate observations to better our understanding and not make dubious claims as has been done in the past. Not on this forum by the way.

We may have to start another thread to discuss this component so please stick back with the topic of discussion.

Regards,

Jimmy Deguara

[Macca]

Hi all,

I've had a bit of a read of all and sundry posted to the events which unfolded in Vic on Thursday and here is what I have been able to dicipher from this...

Andre Dalton is indicating he saw something which he believes may've been a tornado near Skipton in central western Vic at sometime around 2pm on Thursday.  He has posted photos (see earlier posts for links).  It appears to show a fairly strong storm with a thick anvil and some scud of some description under the base.  There is also a photo which shows what *could* be a funnel/tornado but without seeing motion or a closer image, it would be difficult to confirm based on this image alone.  The radar around this time indicated a strong storm with a nice "shape" on radar and movement to the left of the mean storm flow.  Harald Richter makes comment of this cell in his post which Michael kindly posted for us.  Harald says "As of 3:30z we have the northern tailend storm splitting with the leftmover
quickly dominating (nice TBSS - a sign for large hail)".  He mentioned nothing about a meso on this storm being evidenced on radar.  I can't recall exactly but I do remember looking at that area on radar and thinking to myself at the time that there could've been a meso based on the doppler imagery at the time.  That's all I can add about that cell.

Another tornado has been reported at just before 4pm from the same area by Clyve Herbert.  The images (in this thread earlier) shown on Ch7 news are what Clyve saw.  A second-hand description of the event states "Looking towards the main inflow area Clyve was north of it at the time looking SE (it was a tail end Matilda storm). It generated a thick thumb shaped funnel then a separate rope funnel then the tornado was in between the 2 of them. The tornado appeared out of the rain area, moving northeast. Moved fairly steadily northeast while the area of convergence at the rear of the storm remained almost stationary. The tornado became rapidly rain wrapped in the later stages & pushed out a very strong cool outflow".  It is difficult to pinpoint the radar imagery which correlates directly to the report as we don't have a specific time at this stage and there are several storms/line of storms in the vicinity of Skipton at the time (ie within 10-15km E and W of Skipton).  Without knowing the exact position and time of the report, it makes it difficult to assess the radar imagery.   I think seeing more of the video and possibly more photos of the storm, as well as further details on location, time and any damage observed will help clarify what exactly happened in this case.  Oh - and the doppler imagery (and hi-res radar...lol...am I asking for too much?)  I'm sure those involved will get this information online as soon as they have time (we are only 3 days out from Christmas and I'm sure we all have plenty of other committments at this time of year). 

Conditions on the day were quite good with the sounding showing 25-30knts in the lowest 100mb from the N and this was overlayed with a 35-40knt westerly at 700mb (and continuing to strengthen up through the atmosphere).  Surface winds based on the obs at various AWSs around the area show a general NE'ly surface flow of around 15knts, gusting up to 25knts at times.  That's pretty decent shear in my book.  Obs in the *general* area indicate surface temperatures in the early afternoon being around 26-28C with DP's in the 16-18C range.  Plotting an average temp/dp combination of 27/17 from that area onto the sounding posted by Michael in this thread earlier on gives LI's of about -6 and an estimated CAPE in excess of 2000j/kg.  Given these observations, supercells would not be out of the question.  As for tornadoes, it really depends on the conditions in the direct vicinity of the storms (ie whether there was a boundary of some sort present, etc). 

I eagerly await further details on this interesting day (hopefully from the BoM who I assume will do damage assessments for these reports).  I'm also still waiting in hope for more reports to come of the two supercells over the far northern part of Vic which then turned sharply left and ventured into NSW.  (Hail up to 3 inches was reported from Deniliquin from one of these cells!).

(As was feared, yesterday clouded over rapidly over the entire state (of VIC) with the only chaseable area pushing into S NSW around Hay where there was a massive storm...and I didn't want to venture that far so stuck it out at home...good thing too...we got 15mm in 10mins last night and our kitchen flooded...hehe). 

Macca

[David C]

Hi Michael,


I cannot believe that these people are for real. But this is the same disease being spread across the board.


Jimmy Deguara

Let's wait and see what eventuates, since, and as Macca suggested above, supercells and possibly tornadoes are not out of the question given the kinematic wind fields and thermodynamic conditions. A storm with nice structure like that is wonderful in it's own right IMO and some of these were nice supercells. 

BTW, the pics form the other link Michael posted show a wall cloud, possibly, but no tornado.

[post edited: parts of my post were out of context and not directed at Clyve in anycase, so I have deleted them. Apologies to any Vics who thought they were being targetted ! ]

[James]

Just further to my rant on the Deniliquin supercell (Thursday, page 1 of thread). Macca sent me a link to some photos taken in Deniliquin itself of the hail and what looks to be some really nice cumuliform anvil structure. These images were taken by a Weatherzone Member called Dusty Plains who is based in Deniliquin. I have asked to see if he has any more photos, video or information on the storm. His comments on it so far "received 24.5 mms in 10 mins averaging golf ball sized hail with stones up to 3". man there's some damage here".





Cheers,

James

[James]

Part 2 to my above message - some more detail on the storm hitting Deniliquin. "The structure looked like normal convection for about 45 mins then a lot of low level scud formed and the middle of the cell turned green that's when we decided to go home but only got 500 meters up the road when the gust front with golf ball sized hail hit, mixed in with it where stones 3" across. over 30 homes were de roofed in what i think was a microburst , lots of signs ripped off poles and tree damage, broken windows and cars dented ."

Also stumbled on this picture taken near Bendigo on the ABC news website. Unfortunately it doesnt have a date stamp with it so I cant confirm if its from Thursday or Friday. Im thinking more Thursday than Friday as some chasers were in the area and didnt get any structure on the Friday.

http://www.abc.net.au/reslib/200712/r213389_823116.jpg

[Jimmy Deguara]

James,

Your description of the Denliquin supercell and it seems Bendigo are large fat HP supercells. Very nice indeed.

Regards,

Jimmy Deguara

[Jimmy Deguara]

I just got off a call from Clyve Herbert who suggests he did see a tornado and it was the largest he has seen in this country. It achieved wedge status and he has 11 minutes of video of the event. At one stage it had a bell shape and then became rainwrapped. He suggests the Bureau confirmed a mesocyclone at the time but I asked Clyve to determine whether there was a TVS signature? I explained to Clyve that a meso is not verification of a tornado - merely that there was a rotating updraft. I assume at that distance the angle would have the beam pointing to the upper portions of the updraft. I guess we have to wait for this evidence as it would make an interesting case study.

I did ask Clyve to suggest whether he could tell if there was 'rapid rotation' even from 8 to 12 km out? It seems not. A large tornado of the size Clyve is suggesting has to have had significant rotation sufficent to be observed on zoomed in video.

We look forward to seeing this 11 minutes of footage as it will help solve the puzzle hopefully of such a significant event.

Regards,

Jimmy Deguara

[Brad Hannon]

Thursday 20th December 2007

Hi all, certainly an interesting thread this one  In the arvo I headed from Melb down the Princes Hwy toward Geelong to intercept some very low and intense multi-cells moving SE from Ballan/Ballarat.  I was treated to two seperate cells with wall clouds moving through the same area within 1hr of each other.

Wallcloud One
As I passed through Laverton I could cleary see directly in front of me in the vicinity of the Brisbane Ranges/Avalon a defined lowering in the cloud base.  This feature persisted for well over 20mins as I drove (excitedly) toward it and was accompanied above by what appeared to be inflow bands feeding into an updraft from the Northern side.  I have photos which show these observations and I will post these tonight.  Unfortunately the atmosphere was so dense with moisture that I never got a good view of the upper levels or overall storm structure, nor any evidence of a corkscrew updraft but from my (limited) experience (thanks to Jimmy in the US ) I was confident that I was observing a well organised wall cloud.  I did not observe any rapid rotation or funnel but visually the shape of the wall cloud appeared to be influenced by some rotation.  Sadly, as I got closer I could see the feature was occluding, not surprisingly in the competitive environment the cell was in.  Not long after this I spoke to a friend who advised me that chatter on the WZ forums was discussing a possible tornado up near Ballarat and possible supercells up north. 

Wallcloud Two
I pulled over near the Brisbane Ranges and watched for a while as another cell moved SE through the area.  It had a very low cloud base to begin with and a ragged scuddy area and was clearly forming a wall cloud (approx 1km away from me) with inflow from the east condensing into the updraft base.  I observed weak rotation and some isolated upward motion.  I began taking pics with my 17-40mm lens as it became a little more organised.  A small funnel began forming in the centre of the feature.  I raced to my car to get my long lens because the wide angle simply wouldnt do the job. Some 20-30secs later I snapped some pics with the long lens.  The V shape funnel was visible to the naked eye but now embedded in heavy rain and had next to no back-lighting.  There was no evidence of a tornado.  I intercepted the cell as it moved across the Princes Hwy but it had fallen apart as expected.  Meanwhile, Melbourne's East and Sth East was being belted by severe storms and torrential rain leading to floods and floating cars.  I've toyed with the question - would I prefer to have witnessed the rain and floods or the wall clouds?  I'll take the wall clouds thanks

Photos of these events to come tonight.

[Jimmy Deguara]

Brad,

I watched the cell approaching Ballan on radar and it had an interesting structure based on radar including a possible hook echo on one frame.

I am very interested in seeing the structure it exhibited.

Regards,

Jimmy Deguara

[Brad Hannon]

Hi Jimmy,

Firstly, I'm pretty certain the cell you are referring to came through after the two I have described.  It was significantly larger and more intense from the description I was given over the phone at the time.  I attempted to get in position for it but it took a more E and NE track than the earlier cells.  The multicellular activity cleared to the SE and I was able to watch (as I drove thru peak hour traffic) the larger cell drift across the Northern suburbs and out to the Ranges where it had weakened as I witnessed on radar when I got home.

Anyhow, here are the pics I promised in my previous post.

1st wall cloud - looking South, Princes Hwy south of Werribee, near the Brisbane Ranges