Congrats to all who chased Saturday with some amazing photos across various forums which contain almost anything anyone could want on a chase (note the term almost).
There are some pretty nice hail photos (on another forum) showing 4-5cm hail with a wide spread cover of 2-3cm hail with those larger stones and more recently reports of much larger hail! Very nice indeed (I’m a hail fan so kudos to that particular chaser).
There are also some AWESOME structure photos showing near text book supercell structures (particularly the Echuca (?) storm from later). The updraft photos from Jane/Clyve are some of the best I’ve seen in a long time (from anywhere) and the radar imagery clearly shows strong left movement from the initial storm over north central Victoria. In fact I think these are probably the storm/s of the year/season for the whole of eastern Australia.
What I’m going to say now is no doubt going to make me more enemies than friends and I’m not posting this through jealousy (although I’m spewing I wasn’t there) or any sort of interstate rivalry (I’m a Victorian a heart although I now live in Queensland and still dislike NSW when it comes to sporting events).
I think there is some confusion about who has dubbed what a tornado and also some inconclusiveness as to whether and what is a tornado. This is in reference to the first storm (the earlier left mover).
In Rikki’s chase report, there are three photos which are described as being a tornado (“The speed in which was moving was very surprising and I had to get out of there quick smart. I am 100% sure that is a Tornado. No ladspouts, no Scud, a fully fledged tornado.”). This is a text book RFD and associated clear slot wrapping around a wall cloud which is hugging the ground. It is quite plausible that there was a tornado in/under that wall cloud and a damage assessment in this area would reveal whether/where a tornado occurred if this was the case (more on the damage assessment later).
http://i14.photobucket.com/albums/a318/rikjpool/storm2feb27th08_1.jpgSlightly after this, there is the next series of photos/video grabs from Rikki and Jane/Clyve (and associated videos from Rikki which are both from this phase). These photos seem to be when the storm is in a weakening/outflow dominated phase – as was stated by Rikki in his chase report. I’m not sure if this dusty phase is what Jane and Clyve are referring to as the tornado that they saw – perhaps they could clarify? If so, the photos of the “tornado” don’t look quite right to me – the dust seems to be kicking up on the RFD outflow area as opposed to where the RFD is interacting with the updraft/inflow area. I’ve tried to put together a rudimentary diagram over the top of the imagery to depict what I mean – I hope this helps explain what I’m getting at here.
http://macca.bsch.au.com/gallery2/d/5642-1/270210jon385tv2.jpgThe video grab also doesn’t look quite right with the “funnel” appearing somewhat ragged. Nearly every example I’ve seen (in photos and personally) of tornadoes, the funnel has been a very sharply defined on its edges (due to the steady state of the near tornado environment). A very similar feature also appears to be in one of Rikki’s photos from a more “front on” angle – refer below again for more rudimentary drawings. Without seeing any motion, they both just look to be some interestingly shaped scud as opposed to a genuine funnel.
http://macca.bsch.au.com/gallery2/d/5647-2/2702corop01v.jpghttp://macca.bsch.au.com/gallery2/d/5652-2/storm2feb27th03_1.jpgThere is definitely clear evidence of a supercell and there is definitely clear evidence of a mesocyclone (both through Doppler radar imagery and through the photos provided) but there is no clear evidence that there is a tornado. Conditions were not unfavourable nor favourable for the development of tornadoes but without further video evidence showing rapid organised rotation or video/photographic evidence showing a more defined funnel, this would have to go down in my book as a “maybe”.
To further support this, the damage assessment done has revealed very little damage (although has potentially uncovered some massive hail). Shear was definitely adequate for supercells but tornadoes...I’m not so sure.
The early images posted by Rikki (first link above) are similar to plenty of supercells I’ve seen (again personally and in photos) from the USA which have produced tornadoes, but without someone being in there under that mess, it makes it hard to conclude. The later images are similar to plenty of supercells I’ve seen here in SEQ and in northern NSW (and southern NSW and Victoria for that matter) – outflow dominated but just not as much dust – probably due to not having been in a drought for 10 years.
Like I said at the start, this has/will probably make me more enemies than friends but I think its really important that this discussion takes place – for several reasons. Firstly to discuss and investigate and arrive at a conclusion as to what has happened here after taking out the emotion associated with such an awesome, high-paced chase, and secondly (and probably more importantly), to assist people who read the forum and aren’t able to chase (and even those who are) to better understand the dynamics associated with supercell thunderstorms and tornadoes. I’m happy to be shown more evidence that this was in fact a tornado (and looking at the structure – particularly of the Echuca cell – it probably deserves one) but until then, this/these tornado claims are a “maybe” in my book.
Again I want to re-iterate what I said at the start of my post – I think this is one of, if not THE best storm day/storms of the season for the whole of eastern Australia and no matter the outcome of this discussion, my opinion of that will not change.
Macca
