Author Topic: Central NSW Storms 6th - 8th Feb 2007 - Lithgow/Mudgee/Scone Supercells  (Read 115933 times)

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Offline Jimmy Deguara

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Re: Central NSW Storms 6th - 8th Feb 2007
« Reply #15 on: 09 February 2007, 06:41:11 AM »
Hi Michael,

Yes the shear on the day may not have been what one believes incredible but it was definitely sufficient and remember we were at near 1000 metres above sea level - so bases were not high. Second, the storm became anchored - I can only assume this given the storm was not moving at the same pace as others on the day in some cases with less shear. It was I believe on a triple point - something that will not generally show on our GFS resolution models (lack of data).

Also be careful when considering simply shear alone. There was meant to be high instability - you require less shear with higher instability. However, if a storm develops and anchors on a triple point - ie its existence and behaviour is dictated by the conditions near the triple point, then it has an advantage as winds from various directions can aid low level vorticity. COnsider 5th June 2005 in the US  ok 6000CAPE but less wind shear than this. However, despite the HP supercell nature of this storm it moved sharply right and also developed near the intersection of a retreating warm front, dryline  creating a triple point. This storm produced a decent tornado! The rotation was significant!

I hope that helps. This is what I mean about people acquirign ample knowledge simply by going on even one US trip!

I am still on a high with this!

Regards,

Jimmy Deguara
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Offline Michael Bath

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Re: Central NSW Storms 6th - 8th Feb 2007
« Reply #16 on: 09 February 2007, 06:53:19 AM »
Don't worry - I am not going by shear alone :)  It helps to have things explained as we use exactly the same data (low res GFS, sparse sounding network, AWS Obs, radar) to analyse other events around the country (to help determine supercells or not), so it's important to know why this stands out. Obviously photographs and video of structure and rotation are the key.

MB




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Paul Graham

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Re: Central NSW Storms 6th - 8th Feb 2007
« Reply #17 on: 09 February 2007, 07:03:23 AM »
Hi Michael,

I've estimated the mean surface to 6km shear vector to have a magnitude of around 35 kts (based on yesterday afternoon's Sydney sounding - the situation in the storm zone wind-wise probably was not too much different).  From what I understand, supercells require a value of greater than 30 kts.  So that puts yesterday's conditions within the threshold.

Cheers,

Paul

Offline Jimmy Deguara

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Re: Central NSW Storms 6th - 8th Feb 2007
« Reply #18 on: 09 February 2007, 07:17:36 AM »
Hi Michael,

Sometimes, storms become extradordinarily severe even beyond what the conditions were suggesting so that cannot be ruled out. I guess this is not about whether this storm was the most significant ever recorded or better than others in this season or other seasons, it was significant in its own right. Classic supercells are the most efficient tornado producers so naturally the rotation would be more visible. But in this case, from the updraft to the inflow and beaver tail, rotation was clearly evident in real time. But over Lithgow, the rotation over headed was as David suggested comparable to some supercells we had observed in the US.

Outflow at no point whilst we were observing cut through which was amazing in my opinion. Usually that is what I look for - what will spoil the party this time around. Take for instance the 7th December 2004 event. Rain descended from behind and the storm became HP not long after. There was no problem like this yesterday.

Regards,

Jimmy Deguara
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Offline Michael Bath

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Re: Central NSW Storms 6th - 8th Feb 2007
« Reply #19 on: 09 February 2007, 08:03:24 AM »
Paul - I'm not saying the shear plotted on GFS or the soundings did not support supercells - it certainly did support them. I was just questioning why this one became so intense with the strong rotation described by you guys who were there. Jimmy has provided some answers to that.

Regards, Michael

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Offline Michael Bath

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Re: Central NSW Storms 6th - 8th Feb 2007
« Reply #20 on: 09 February 2007, 09:00:18 AM »
Scone sure experienced a prolonged period of severe winds as that storm passed by (from 6.18 to 6.49 severe gusts) :

07/07:59pm 23.2 21.3 16.8 67 4.2 S 22 28 12 15 1004.7 1.0
07/07:03pm 24.0 23.2 16.1 61 5.2 NNE 15 57 8 31 1002.7 1.0
07/06:55pm 22.0 15.7 16.1 69 3.9 SSW 44 67 24 36 1001.7 1.0
07/06:53pm 22.3 15.6 16.1 68 4.1 SSE 46 76 25 41 1001.8 1.0
07/06:49pm 21.3 13.4 16.9 76 2.9 S 54 95 29 51 1002.0 1.0
07/06:45pm 26.5 16.1 12.6 42 8.8 S 59 95 32 51 1001.5 1.0
07/06:39pm 19.8 10.6 17.0 84 1.8 S 61 80 33 43 1002.3 0.8
07/06:34pm 20.5 11.4 16.2 76 2.8 SSW 59 113 32 61 1003.0 0.0
07/06:27pm 22.5 9.0 14.1 59 5.3 SW 78 113 42 61 1003.3 0.0
07/06:20pm 28.6 16.2 14.1 41 9.4 WSW 72 109 39 59 1001.9 0.0
07/06:18pm 30.4 22.3 14.5 38 10.4 WSW 50 100 27 54 1002.0 0.0
07/06:17pm 32.7 25.9 14.4 33 12.1 WSW 43 70 23 38 1002.2 0.0
07/06:00pm 35.4 36.0 11.8 24 15.2 CALM 0 0 0 0 999.3 0.0
07/05:00pm 36.4 34.6 12.0 23 15.8 NNW 13 20 7 11 1000.9 0.0


Check the Newcastle loop for matching radar:
http://australiasevereweather.com/storm_news/2007/radar/20070207/newcastle128.htm

Also a couple of soundings for reference:

http://australiasevereweather.com/storm_news/2007/soundings/2007020704sydney.png

http://australiasevereweather.com/storm_news/2007/soundings/2007020700williamtown.png


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Paul Graham

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Re: Central NSW Storms 6th - 8th Feb 2007
« Reply #21 on: 09 February 2007, 09:03:07 AM »
Hi Michael - Sorry for the confusion.  Yes, it was an awesome sight to witness and reminded me of the video clips I've seen of storms in the US.  I wonder if in addition to instability, topography may have also had an enhancing effect, at least to the lower levels of the storm?
Cheers,
Paul

Offline David C

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Re: Central NSW Storms 6th - 8th Feb 2007
« Reply #22 on: 09 February 2007, 09:16:01 AM »
Nice photos everyone.

Hi Paul, yes they are video frames. Your report at blogspot is excellent too, hope everyone takes a read of it!

Not surprised at the winds from the storms further north based on photos and radar -- high-based with lots of dusty outflow evident.
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Offline Jimmy Deguara

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Re: Central NSW Storms 6th - 8th Feb 2007
« Reply #23 on: 09 February 2007, 11:35:56 AM »
Hi Rodney,

Those gustnadoes were awesome - very tight circulations! And so was the storm structure. I recognise the locality of those undulating hills.

Rodney, does anyone have some pictures of the storm when it was in its classic stage? Ben suggested classic supercell tending to HP supercell? I can only see HP structure from the pictures.

Regards,

Jimmy Deguara
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Offline pingtang

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Re: Central NSW Storms 6th - 8th Feb 2007
« Reply #24 on: 09 February 2007, 01:02:21 PM »
Good afternoon.

I dont think anybody was chasing the South Coast and ajacent ranges. Some intense echoes were picked up on the ranges west of Moruya yesterday afternoon. It might be worth posting the Canberra radar loop as well. It was very interesting down that way!

 We chased the Goulburn/Taralga area yesterday.Some high based scraps brought some suprise close CGs quite early in the day.These cleared off towards the coast leaving us with clear blue skies. Strong development could be seen to the far south but this was 3 hours away. More activity could be seen to the north towards Lithgow. At about 3PM we met up with Michael Thomas at a servo in Goulburn. By now a very solid anvil could be seen to the distant north spreading to the NE probrably over Sydney. 5PM,and we finially saw updrafts to the northwest of town.These built very quickly and before we knew it we had a storm. This storm pumped out some nice CGs before moving away to the southeast,this was when Michael Thomas left us.Soon afterwards another dark base developed rapidly overhead letting out a few flangs. This was the start of the storm which moved through Bungonia and Nerriga maintaining black echoes for a good hour.



Some of the updrafts at the back of the storm were quite explosive. I have some footage of this storm and the powerful updrafts but unfortunatly no timelapse. The storm moved towards the southeast quite quickly moving into unaccessable bushland. Heres a few more pics of the storm.





The Bungonia storm was definatly the highlight of my day. Its just unfortunate the action was so shortlived.






Offline Michael Bath

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Re: Central NSW Storms 6th - 8th Feb 2007
« Reply #25 on: 09 February 2007, 01:48:10 PM »
Location: Mcleans Ridges, NSW Northern Rivers
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Offline Jimmy Deguara

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Re: Central NSW Storms 6th - 8th Feb 2007
« Reply #26 on: 09 February 2007, 02:28:43 PM »
Pintang,

I actually quite like the storms you have chased here. The region you were in was in a slightly better environment for upper level cooling thence the explosive development. I could see some of those storms further south. For me it was game over to get to them from Lithgow. Some powerful updrafts as you suggest and you can see a distinct lowering in the second photograph.

I found it interesting how there were weaker storms in a line and then suddenly they decided to venture another level into the atmosphere. This on the sounding was the most unstable component of the trace and it is great to see things in action.

Regards,

Jimmy Deguara
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Offline Jimmy Deguara

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Re: Central NSW Storms 6th - 8th Feb 2007
« Reply #27 on: 09 February 2007, 06:21:27 PM »
I did a rough edit video timelapse of this supercell linked here:

http://www.australiasevereweather.com/video/movies/2007/classic_supercell_rotation_february_7_2007.wmv

Regards,

Jimmy Deguara
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Offline Rodney Wallbridge

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Re: Central NSW Storms 6th - 8th Feb 2007
« Reply #28 on: 09 February 2007, 07:43:04 PM »
Hi Jimmy re other pictures of the Storm in its more classic form... I have lots of pictures but at some stage we may have missed the inflow dominate stage.I'm yet to look at all of my pictures to see if I could produce anything close to those requirements as it was inside my comfort zone a lot of the time .....Clearly a few of us were all taking pictures so may be able to complete  a well documented angle as the next few days pass.

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Re: Central NSW Storms 6th - 8th Feb 2007
« Reply #29 on: 10 February 2007, 02:14:13 AM »
loved the timelapse  jimmy. and well done to all chasers on the lithgow and mudgee storms
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