Author Topic: Snowy Mountains severe storm: Tuesday 11th March 2008  (Read 3466 times)

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ntweather90

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Snowy Mountains severe storm: Tuesday 11th March 2008
« on: 12 March 2008, 02:35:05 PM »
According to the Canberra 256km Radar this afternoon, a massive thunderstorm roared through the section of the Snowy Mountains region within the NSW border between Bombala, Dalgety, Jindabyne and Thredbo. Going by only amateur readings of the radar image at the time, it seems the storm would've been intense enough to produce supercellular features, perhaps the likes of large hailstones and very heavy rainfall. However, because it occurred over a very isolated & remote area, rainfall observations or storm reports will be extremely difficult to come by. According to the 24 hour Flood Warning Service rainfall map, there are no stations that report through their rainfall readings on a day to day basis in the vicinity of the thunderstorm. The since 9am readings that are available show that 13mm fell at Myalla Lake, just south of Cooma, that fall coming from that other less significant cell further north. Looking at more detailed maps of this particular area of south-eastern NSW, I've plotted the storm to have passed right over Mount Alexander, 1075m above sea level & adjacent to the Little River, before continuing its path over the eastern Snowy River and weakening over the homestead of Jimenbuen, followed by the homestead of Bungarby (next to Beards Lake), Mount Rix (988m above sea level) and the homesteads of Rodney & Tombong.

If there are communities located in the approximate area in the vicinity of Mount Alexander, it would be very interesting to see the reports of what happened. It is perhaps the most isolated area in south-eastern NSW, so unfortunately we'll never know what features were apparent from the full force of the thunderstorm, unless people report through. On a different note though, was the storm supercellular? Certainly seems as though it was, as the 256km loop tends to substantially under-exaggerate intensity. On the 256km loop, the storm did indeed reach black intensity, developing in the shape of a hook as it did. Just interested me this afternoon, I'm open to any points. :)

Here is the Canberra 256km Radar loop:

---> Canberra 256km radar
« Last Edit: 13 March 2008, 02:12:58 AM by Michael Bath »

Offline Jimmy Deguara

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Re: Snowy Mountains severe storm: Tuesday 11th March 2008
« Reply #1 on: 12 March 2008, 04:30:02 PM »
Hi,

Given the short term period of high intensity alone, lack of consistent core and its relatively close procimity to the radar, I would put this at low confidence of being a supercell. I personally would take more convincing. In fact, we don't have observations of features as you suggest - so that reduces the confidence level once again. Certainly it seems to change direction but this can also occur along a boundary briefly. I have not studied the wind shear or the amount of energy available to this storm.

Thanks though for bringing to our attention. I have adjusted the title of this thread to reflect what we confidently think it may be. I am also open to other comments. as well given my current limited time to dwell into this.

Regards,

Jimmy Deguara
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Offline Michael Bath

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Re: Snowy Mountains severe storm: Tuesday 11th March 2008
« Reply #2 on: 13 March 2008, 02:34:08 AM »
The 128km radar loop also shows most of the cell in question SE of Thredbo:

---> Canberra 128km radar

GFS analysis at 06z shows shear was generally all from the W to SW between 850hpa to 200hpa and up to 30kts by 600hpa. The jet peaked about 45 knots over the area. Looking at the VIS satpics there is evidence of a surge in winds from the SE along the far South Coast. This would have played a part in improving the low level moisture over the region.

The conditions could support brief severe storm organisation - as can be seen on Canberra radar 0550z to 0640z and VIS (07z), but the windshear profile does not appear conducive to more organised thunderstorms.

Note also that the Canberra radar tends to make cells look a little better than what they probably are (IMO).

05z
06z
07z
08z

Regards, Michael

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Offline Ursula

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Re: Snowy Mountains severe storm: Tuesday 11th March 2008
« Reply #3 on: 13 March 2008, 08:35:25 AM »
Hi,

being in the Shoalhaven valley, the storm built up after lunch, had some anvils, but wasn't severe from what I could observe, later in the afternoon it built up a bit more due to easterly breezes which carried a lot of moisture and obscured any chance of taking pics, rumbling of thunder wasn't loud either, espechially as the cells hanging on the Divide, mostly on the western side, I hope this helps with your evaluation of it.

There is built up at this point in time, being late and the sea breeze kicking in I don't think it will get to much.