Topic: Melbourne Severe Storms - 4 Feb 2008

[Brad Hannon]

Hi all, I ran into John Allen today (on my turf!) and we saw some very interesting events to Melbournes W and NW.  I posted this very brief obs report on the WZ forum hoping someone else saw this event this arvo:
(pics to come)

WALL CLOUD AND FUNNELS?

Hi all, I just returned from 5 hours up at Mt Cooper in Bundoora which has a fantastic view of the western skies well beyond the airport. I ran into 'Severely Tall' from this forum and we watched the initial large cell move over the NW suburbs. This cell had a large anvil, developed a shelf cloud feature and a very impressive rain foot as well as some visible CG activity. But the best part was to come!

Another cell formed somewhere between Geelong and Ballarat (I estimate) and followed a similar but slow path as the earlier cell. It exhibited similar structure and features but the updrafts appeared stronger with pileus cloud forming consistantly. We noticed a large (wide) base structure emerging from the hazy conditions and thought it may have been a shelf cloud or scud but it persisted and persisted and...the northern end was particularly interesting.

Then we began to note that it was far more organised than we thought and my guess at a shelf cloud may have been wrong. We believe we were looking at a persistent wall cloud which went on to spawn several funnels one in particular that looked large and persisted for several minutes.

This event was a long way from our location (Bundoora)- I would estimate somewhere behind the airport toward Ballan perhaps at a guess.

I will review my pics and video and post some shots. Hopefully someone else saw this event from a closer vantage.

The evening finished with an explosive updraft to the North, some mammatus and also directional shear through the levels resulting in some beautiful cloud formations at sunset. All in all it was a great chase (read slow drive 5mins from home [Smile] )

Photos to come.

Brad.

[Peter J]

Hi Brad,

I think you're vantage point was much better than mine - however I will agree with you - when I was driving (at work on a school bus) through East Burwood in the mid afternoon - I could have sworn I saw a small funnel protuding from one of the W-SW storms - it wasn't very big, and I didn't get a clear enough view for a camera-shot from my camera-mobile phone, or else I would have posted it here. Definetly an interesting storm - and it (the storm) did linger around the northern region of Melbourne for at least an hour or so  - but when I got home, there was no rain in the gauge here, and the storms were to the N and SE of my place, and it was very Humid (about 92% RH), but no storms or rain here - I am mystified by this, why some would get the rain and others don't - if anyone else has had this experience - maybe good for another thread?

Big Pete

PS 5th Feb - got some drizzle here today, not enough to even make a dent in the raingauge (maybe a mil or so).

[Brad Hannon]

Hi Pete, yeah they were very slow moving cells thats for sure.  Our vantage was good and quite elevated, however the distance to the storms was significant, possibly 70km's.  Despite the distance we had a westerly view, hence the low sun provided some good back-lighting and contrast at times.

Below is a series of cropped and enhanced (contrast and gamma) photos that show the features of the storm that moved North through the areas west of Melbourne such as Ballan around 6-6.30 on Monday evening.  (This storm followed behind a larger storm that was lightning active with visible CG's and a shelf cloud)


After the first storm had moved north and weakened John Allen and I had almost decided to leave the location when I noticed what appeared to be a VERY low cloud feature below a storm that could barely be made out through the hazy moisture-rich conditions out west.  Within seconds it became clearer and was becoming more substantial even to the naked eye (despite the distance).  We started taking photos straight away and discussed what the feature was but adding to the dilemma was the mid level cloud and anvil from the first storm that was blocking our view of the updraft towers connected to this new storm.  At first I thought it was scud, then it looked way more substantial like a funnel, then I thought surely its only a shelf cloud feature.  But over the next 10 minutes or so, the cloud base took on the appearance and behaviour of something more dynamic than a uni-directional shelfcloud.  We saw funnel shaped lowerings of different sizes and shapes and several lowerings that appeared to be a wallcloud or wallclouds forming from scud.  Based on the distance and several Qantas jets I captured in the foreground of my shots it can be said that the base features were certainly large. 



Finally the mid level cloud cleared enough to show the towers above and there were multiple pulse updrafts with impressive pileus on each.  One secondary overshoot was observed on one of the first pulses after several new pulses had already gone up behind it and John noted that there was obvious opposing flow through the low and mid levels and directional shear was probably quite good.  The large lowering took on a cone shaped funnel appearance at this stage.



As this cone dissipated, several substantial and persistant semi-horizontal features (funnels?) became prominent and scud or the like appeared to be drawn in from right to left and it appeared a wallcloud was forming.  You can see a Qantas jet landing at Tullamarine Airport in the foreground of one of the pics for some perspective.



By this stage the upper levels of the storm as well as the base were clearly in view and it was quite impressive - see the updrafts and the pileus below.  Also note the opposing wind flow at different levels as indicated (approx).



The base feature (wallcloud?) persisted as the storm moved slowly north, grew in length (north-south) and then another funnel shape emerged from the base as can be seen below



We observed the updrafts had stopped pulsing and the storm weakened from this point before we were treated to some mammatus at sunset.

So there you go.  Now I will check my video and if there is anything of note I will post some stills.

Brad.

[Jimmy Deguara]

Brad,

Thanks for the extensive report. Before I go on, I would like to check video if possible of this event and the feature - hopefully timelapsed as well. Yes there are what seems to be "funnels" but the duration of these features are also important.

I will show you this storm event from January 30 1999 taken from near Gunnedah. The storm will have passed through Boggabri as microburst damage occurred there. It was all outflow driven.






Also from early December 2007




Regards,

Jimmy Deguara

[Brad Hannon]

Hi Jimmy, im going to look at my video tonight and see what it has but it was secondary to my photos so there is no tripod timelapse    It certainly could be outflow driven in this case too as the storm certainly died off very quickly after the last series of pics.  Your pics certainly have similar features - your memory cracks me up!  I guess because the storm was slow moving, the downdraft could cause it to become outflow dominant but then seeing the wide pics the updraft towers and rain are a long way behind the front of the base due to the northerly mid level winds.  I'm interested to know if a storm can still become outflow dominant to the forward flank where the base features are in this case?

[Jimmy Deguara]

Brad,

The contrast of the pictures of updrafts make it very difficult to develop some form of perspective. Was it a line of updrafts and was there a high base shelf developing along it?

Regards,

Jimmy Deguara

[Brad Hannon]

Hi again,

there was a series of pulse updrafts going up in roughly the same area because the storm was hardly moving.  I didnt see a shelf but thats not to say there wasnt one.  It was very hazy and the sun was streaming in (which was pretty but not very helpful!).  The pics below were taken after the others i've already posted and show the series of updraft towers a bit better (numbered, although there may have been more before that became part of the anvil) and their orientation to the base lowering as well as the storm's orientation behind an earlier storm.  The last updraft was the weakest by far so it was obvious to us that the storm may be weakening at this point.





Interested to know if you can gather anything more from this.

Brad.

[Jimmy Deguara]

John,

I can say little about any feature at this distance. I belief though is if you can see a base at 70km from a storm, it is likely higher based. Probability of wall clouds in a higher based storm is much lower. I don't believe that overshoot constitutes to anything based on pileus - it just means there is ample moisture in the mid-levels and you are seeing more development as air flow passes over successive rising updrafts. Pileus usually gives some indication or a measure of the rate aat which updrafts are rising.

My belief based on high bases is that the storm has developed and is firing along some form of convergence which locally can enhance moisture locally and produce lower bases. This could also account for the differing movement and consequent change in behaviour around sunset...

But as they say, you guys were there and have to communicate what you saw. I can only say that it is important to get close to storms otherwise it is always difficult to draw conclusions.

Regards,

Jimmy Deguara

[Peter J]

John, Jimmy and Brad,

Nice pics of the storm - what got me about it, and with other storms in Melb, is that most of them (even if it is very few compared to other States) occur in the SW, W, NW and far NE, E regions. Not so many in the S and SE regions - and of these the W,SW, & NW get the most. Maybe coz of the flat lands out that way before the GDR (great dividing range) and its associated mountains.

I don't get to see many of these storms where I live (in the fringe outer-ENE), but can watch them from a distance. I must admit that it is a fallacy if there are people who don't think that tornadoes or such type storms can't occur in Melb, its just that the air system here just doesnt conduce it.

Anyway - thats my opinion.

Big Pete

Just edited the word supercellular in this case:)

[Michael Bath]

Some data for the events of 4th February starting with the Melbourne radar loop.

---> Melbourne radar loop


Melbourne 00z

Melbourne 12z

Pete - there were forum issues due to database problems.

MB

[Peter J]

Thanks for that Mike, wondering if the problems Jimmy highlighted might have been at fault.

Anyway, my dad said that yesterday 11/2 there was a water spout in Port Phillip Bay region. Anyone else able confirm this sighting?

Big Pete

[Brad Hannon]

I don't know exactly where 70km came from but I can assure you this storm was far closer than that

Hi John, the 70km (or thereabouts) reference came from comments I made.  Looking at the 128km BOM radar loops it can be seen that the cell we were watching was located between Meredith and Ballan which is more than 50km from the Melb AP radar site which in turn is a good 20kms from our location at the time.  Hope that clears that up.

Brad.

[Brad Hannon]

Hi all, Thanks for the data Michael.  I have recieved a message from a member of the weatherzone forums suggesting I track down (if possible) the doppler wind loop for the evening of the 4th Feb.  Here is the message:
_________________________________________________________________________

Well Done Brad,

You might want to try and get a copy of the radar and doppler wind from then if you can. it showed a really clear and thin reversal of the winds out near Ballan.

I made a mental note at the time to see if anyone reported a funnel etc and sure enough you have at the exact place and time.

Cheers
_________________________________________________________________________

I have searched for archives of doppler wind (incl StrikeOne but I cant find any) so does anyone have any ideas?

PS still yet to review my video to see if theres anything good on it - perhaps tonight.

Thanks, Brad.

[Michael Bath]

John - the instability was fairly impressive though the shear on both those Melb soundings is very light until the mid levels. It will be interesting to see if you can get hold of some better radar and thoughts from Harald as the BoM web radar does not resolve what is going on too well.

[Mike]

Very informative discussion here. I won't comment on such things due to inexperience.  Certainly further investigation would be most welcome. I'm enjoying the technical discussion all...