Author Topic: Melbourne area storms: December 18th 2008  (Read 9830 times)

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Offline Brad Hannon

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Melbourne area storms: December 18th 2008
« on: 19 December 2008, 03:43:00 PM »
Hi all, when I left work at 5.15pm today I sure didnt think i'd be reporting on a chase tonight :) but you just never know and I was treated to some rapid development.

I was on the western ring rd heading nth at around 5.30 and saw a very ordinary updraft trying to punch upward at what appeared from my vantage to be the southermost end of a relatively short SW/NE line that had developed moving NNE (at a guess), and on a convergence line of sorts as it appeared. As I drove I got closer and lost sight of the smallish Cu tower above me but was amazed at the rapid development of large amounts of very very low scud underneath and out towards Tullamarine/Sunbury. This was followed by rapid development of a significant rain free base on the southern/eastern side and heavy precip area on the northern side. I went east on the ring road, north to Epping and then west towards Sunbury where I had a good view of the storm.

The updraft base of the cell appeared to just about stall in this area near Sunbury for up to 30 minutes as I drove westward. It took on some impressive low level features including consolidation of the southeast part of the base into what was appearing like a precurser to a wallcloud for a moment, and two distinct inflow regions - one from the east which was dark and dense with moisture and another from the SSW which was slightly higher and less organised, but deeper.

I was on the phone talking to John Allen at this stage and I could see the northern precip area absolutely bucketing down to my NW and said I thought there would be hail - I was right! John texted me soon after (he now had radar access) to say he thought he could see evidence of a short lived vault-like feature and even a hook echo. I will leave it to him to add to these observations.

Not long after, the RFB had unfortunately turned to precip and it was obvious to me that the cell was no longer stationary but had resumed a north-easterly track. I turned north onto Oaklands Rd and drove into the core as it moved across my path, where I encountered torrential rain for several minutes, flash flooding (yes the road was covered) and pea size hail. Turning eastward onto Craigieburn Rd (I think) I managed to get onto the southern edge of the core where I got more pea size hail and more heavy rain for a few minutes before it cleared away to my north-east.

I then contently drove eastward toward home watching as the cell moved away to the NE.

Talking to John again via phone and text, he informed me that radar showed another cell had caught up to and interacted with the main cell from the SW (where I couldnt see) and this coincided with my description to him of the main cell 'dropping its guts' (when I was approaching the core). Whatever the mechanics were that appeared to be building a nasty storm were clearly affected by the second cell and outflow rain and hail was the result.

I havent seen such rapid development from an otherwise innocuous TCu in Melbourne before so i'm glad I was observant on the way home!

From what I can tell, the BOM did not issue a STW on this cell and im not really surprised because it all happened so quick. Im sure John will have some observations and possible explanations for this short and sharp event.

BTW I didnt have my camera with me (spewing) so I had to settle for a few low res shots with my phone - doh!

Brad.
hmmm June 2nd......

Offline Brad Hannon

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Re: Melbourne area storms: December 18th 2008
« Reply #1 on: 19 December 2008, 04:37:09 PM »
Interestingly, Jane O'Neill also saw this storm and quotes Clyve Herbert on the WZ forum in reply to my post there:

Jane: Clyve chased the same storm from Melton and I skirted it from the south....

Clyve (from the austpacwx list):
"Hi all....Followed an interesting storm from Melton to Sunbury this evening.....Started to form a wall cloud just east north of Melton then dropped a funnel....! I kid you not.....then a few CG's under a rainfree base....The storm really got going just west of Sunbury with a fully rotating wall cloud...I reported this to the BOM and the senior forecaster confirmed small rotation between 1 and 2.5 kilometres....near Sunbury. While all this was going on the CB tops were only getting to about 6 kilometres....The storm appeared to be a coldie maybe hybrid of some sort.....You just never know what will hang off a storm in Victoria....Yippeeee...Clyve H"

My reply to Jane in WZ:
Yep thats the one Jane. Interesting to see it from another angle and great to hear another independant confirmation of the nature of this storm from Clyve which corresponds with the behaviour I was observing.

At the time I was on the Ring Road (at the Tulla interchange) heading north I could see what looked like several small funnels but there was a lot of low cloud and scud so I wasnt and am not in a position to say whether I saw what Clyve refers to and due to my uncertainty I didnt mention it in my report. I hope he has some pics!

 
hmmm June 2nd......

Offline Brad Hannon

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Re: Melbourne area storms: December 18th 2008
« Reply #2 on: 20 December 2008, 04:54:07 AM »
Clyve Herbert's pics (posted by Jane O'Neill) are now on WZ here:

http://forum.weatherzone.com.au/cgi-bin/ultimatebb.cgi?ubb=get_topic;f=10;t=002601;p=16

G.Sorensen (Gary I think?) was also on the storm and has added a pic too.

Certainly a unique, low-topped, shortlived event with some very interesting dynamics.  Wish I'd had my camera with me.
hmmm June 2nd......

Offline Brad Hannon

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Re: Melbourne area storms: December 18th 2008
« Reply #3 on: 20 December 2008, 06:18:58 PM »
Further info has come to hand on this storm on WZ forum.  Harald Richter has confirmed mid level convergent weak rotation, low level anticyclonic rotation and a weak echo overhang in a low topped cell of 6000m and has provided radar imagery and comment.  I can absolutely confirm from my observations that the low level inflow bands were feeding into the cell in an anticyclonic fashion (as Im used to seeing in the USA) - I had not seen this here before and I guess I assumed it was more of a visual illusion while driving and through lack of sleep.  However, with the other independant obs and my crappy res mobile phone pics I took I am very confident of what I saw and have learnt not to make assumptions!

See Harald Richter's comments in quote here and also pics that show possible RFD cuts:
http://forum.weatherzone.com.au/cgi-bin/ultimatebb.cgi?ubb=get_topic;f=10;t=002601;p=16

hmmm June 2nd......

Offline Michael Bath

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Re: Melbourne area storms: December 18th 2008
« Reply #4 on: 22 December 2008, 06:23:53 AM »
Interesting storm and some great descriptions and comment from various sources. Are you going to post any of your phone pics Brad ?

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Offline Brad Hannon

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Re: Melbourne area storms: December 18th 2008
« Reply #5 on: 22 December 2008, 07:24:55 AM »
Hi Michael,

I have problems getting the pics off my phone.  I have recieved some advice about how to go about it so I may be able to post them at some stage.  Problem is I dont have a cable to transfer the pics to PC and my Optus (work related) phone plan doesnt support sms for photos.  I will try and get a cable at work tomorrow, or a new phone :)
hmmm June 2nd......

Jeff Brislane

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Re: Melbourne area storms: December 18th 2008
« Reply #6 on: 22 December 2008, 07:33:18 AM »
Brad, does the phone have a micro SD card? If so you could stick it straight into your pc via an adaptor.

Offline Brad Hannon

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Re: Melbourne area storms: December 18th 2008
« Reply #7 on: 22 December 2008, 09:39:53 AM »
Not from what I can tell Jeff.  It is a very average looking Optus post-pay 'SB' (printed on it) card.  I think i'll be able to get a cable for it with a bit of effort though.

Thanks.
hmmm June 2nd......

Offline Brad Hannon

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Re: Melbourne area storms: December 18th 2008
« Reply #8 on: 25 December 2008, 05:08:11 PM »
Well I worked out that I can transfer images from phone to laptop with IR so I got 2 pics of this storm but they are low res and narrow angle and dont really do the inflow features justice.  This pic happens to be the same time (18.16'ish) that Clive reports seeing a rotating funnel from the wallcloud (pics on WZ) - it was a low-topped storm with anticyclonic rotation, particularly in the lower levels but the inflow bands had an anticyclonic curve and entry into the storm. The storm weakened from the time of the pic and lead to small hail and flash flooding soon after.

hmmm June 2nd......

Offline Peter J

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Re: Melbourne area storms: December 18th 2008
« Reply #9 on: 26 December 2008, 12:52:47 PM »
Brad,

I have a feeling (as I was on my way back from Heidelberg in a party coach after dropping the group I took to Kyneton that day) I actually saw that storm whilst on the Western Ring Road coming through Thomastown area - I did try to get a couple of camera-phone shots of it, as it was stranger than any other storm I'd seen of late - the eerie haze further east from it made it look more stronger. but it's hard to take pics and drive a 6 speed coach at the same time.

It certainly was darker closer to the Sunbury direction, and the storm was an isolated one at the time.

There were other storms earlier in the day around Macedon ranges, and the weather did clear (but remained quite humid and muggy) for the time I was in Kyneton, but once I dropped the group, that cell did catch my eye. Glad someone else was on it to get pics.

Big Pete
PJJ