Topic: NSW Storms 6 December 2007

[Michael Bath]

Bit of action around the state already with a number of flash flooding warnings issued by the BoM.

[Shaun Galman]

G'day Michael,

Conditions are certainly looking ok out here for possible storms. The temps are climbing nicely, currently 32.8 (12pm). DP is sitting at 19.3 and the humidity is 62% and boy does it feel like it too!

We had a few storms over the past few nights and the shear seemed ok as they remained stable throughout the duration of their cycle (some took on a quite severe look, but just a little too distant from us here). One formed 40k's out towards Walgett around 6pm on Monday (3rd Dec) evening that was in good form with crisp anvil, flanking line and very CG active. It finally approached town from the south after heading west with a southerly windshift around 9:30pm (could this be classed as a left mover?) It had a very heavy dust squall preceding. Russ and I headed out into it but the drops of rain were large and coming in horizontal, making photography almost impossible. Seems as though you were very correct in saying the shear would improve. It certainly has and it is great to see long-lived storms once again!

We'll see what eventuates as today progresses? Expecting to see the temps up in the 35-38º range this afternoon.
(Looks like an interesting and quite active line approaching through SA and the NT today, I hope it keeps it up over NSW & QLD)
Take care if out chasing!
Shauno

 

[Richary]

Bit of action around the state already with a number of flash flooding warnings issued by the BoM.

Unluckily they didn't issue one for my house! Was woken about 4:40am by the storm, so went to the toilet. Sat down and found I was getting rained on. So was the washing machine in the adjacent laundry. It's an area at the back of this rented house that has obviously been added on to. So moved the washing machine out the way and went back to bed listening to the thunder.

About 50mm again from that in the morning, to go with the 50mm that we got yesterday here in the mid morning downpour.

Went onto the roof tonight but can't see anything obvious where the water is getting in. Gutters at that point look OK, no broken tiles and so on. Time to ring the estate agent!

[David Brodrick]

Along with everywhere else this week.. there has been some serious left-moving storms around the QLD/NSW border between Boomi and Tenerfield on the Moree RADAR today and yesterday.

At 8:40pm tonight there is one cell heading north from Inverell and there was one near Boomi around 5pm this afternoon. A different cell that didn't look nearly as menacing on RADAR gave 93km/h gusts at Moree at 6:10pm.

Yesterday a good one went over Texas and another over Boggabilla/Goondiwindi. Plus there have others around.

It would have been nice to take a closer look. I hope someone was there.
Cheers,
  Dave

[Shaun Galman]

December 6. 2007 Upper Western Pulse Storms, Report & Photos
Hi guys,
We had an afternoon line of pulse storms to our east-south east kicking off around 3pm, possibly stretching off towards Collarenebri and linking up with the storms you mentioned above David? I don't know what it is with the area between here and Walgett, but it must have something going for it as it seems to be a storm magnet!

They seemed to grow and dissipate fairly rapidly but showed real nice formation with the largest (visible from here) settling down at 5:30pm, I couldn't see any lightning but would imagine there may have been a few strikes on the LT? Most of these storms had a small confined rain core just under the towers behind the anvil. This storm weakened around 9:30pm as another tower shot up in it's place, put on a nice forward shearing anvil and dissipated not long after.

I had a nice clear view from my yard so I kept an eye out but nothing eventuated other than a clear, very warm night with plenty of stars unfortunately?


The shot above was taken at 7:47pm. This was the largest cell I could see clearly around this region.

It made for a great afternoons viewing and it is good to see some nice development around! (yep, that is an old Richmond Rattler train in the photo, they convert them into camps here for some reason? If you ever wondered where they end up, look no further lol they look quite odd sitting out here as there is not a piece of track to be seen, not real good in the 40+ summer temps either!)

Cheers guys,
Shauno

[David C]

Along with everywhere else this week.. there has been some serious left-moving storms around the QLD/NSW border between Boomi and Tenerfield on the Moree RADAR today and yesterday.

At 8:40pm tonight there is one cell heading north from Inverell and there was one near Boomi around 5pm this afternoon.
Cheers,
  Dave

Not implying anything with respect to Dave's post, as there were some strong storms around, but more as a general reminder;  in these rather weak shear situations don't read to much into storms that deviate to the left or right of the mean flow. It often means that the storms is locked into a boundary and while this in-itself will help the storm along, it does not suggest that the storm is particularly intense or is a supercell. On the otherhand, in strongly sheared environments, the left (or right) bias of supercells results from the generation of positive and negative vertical vorticity centres on the north and south flank of the updraft. The vertical pressure perturbation gradient results in low pressure and hence favoured updraft development to the north of the cyclonic circulation and to the south of the anti-cyclonic circulation. In the southerm hemisphere, typically it is the north, cyclonic updraft that would be favoured for longevity.

[Harley Pearman]

Storms Thursday 6 December 2007

Hello

The Thursday morning storm over western Sydney took my interest and I decided to track it from 3.30 am to 5 am. At 7.40 am, a second storm developed over Burwood, Strathfield and Homebush Bay before it moved onto Auburn. The storm weakened over the Auburn / Silverwater region. The event was over prior to 9 am.

From 3 am, a small cluster of storms (Being 3 cells) developed over north central and northern Sydney and moved very slowly south and by 4 am there were two moderate to intense cells which had merged into one multicell. By day break the storms tracked south towards Campbelltown and weakened. The storm stretched from about Doonside to Lidcombe (In Width).

This storm produced some 270 lightning flashes of which a majority was within the cloud but it was the rainfall that caught my attention. In particular:-

Parramatta - 68 mm
Granville Shell Refinery - 99 mm
Northmead and Pennant Hills figures reached 70 to 80 mm.
An isolated fall of 66 mm fell at Liverpool.
There was 17 mm at my place.

A second stationary thunderstorm developed over central west of Sydney from 7.30 am centered firstly on Burwood, then Strathfield and moved onto Auburn. This storm dumped more significant rain on suburbs such as Strathfield, Lidcombe, Auburn and Homebush Bay.

Council Drainage Engineers were called out to address flash flooding issues and observed and photograped flash flooding in Joseph Street (Roadway in Lidcombe), Duck River (The weir overflowed upstream) and significant water rises in Haslams's Creek. There was also inundation of other roads in Lidcombe.

Auburn Council has a rain gauge linked to the BOM network at its Golf Course and there is one at the nearby Strathfield Golf Course and we analysed part of the network of gauges at Potts Hill, Homebush Bay, (Council's own gauges) and found some interesting facts:-

a) The second storm (Being the 8 am storm) over Potts Hill had a peak intensity of approximately 108 mm / hour when a peak intensity of 4.2 mm of rain fell in 1 minute and 54 seconds.

b) Lidcombe and in particular the golf course in Nottinghill Road was hit by a 1 in 5 year thunderstorm when 39 mm fell in a 60 minute period. The mathematics of it shows this as a 1 in 5 year event.

c) The 109 mm (Total) observed at Granville Shell Refinery was split into a 99 mm fall over a 24 hour period and another 10 mm from the second storm. Yet this only rates as a 1 in 2 year event.

d) Auburn had 52 mm from the two storms with 20 mm falling from the second storm but can only be rated no more than a 1 in 2 year event.

e) Falls approaching or up to 100 mm fell in Silverwater (Being next to the Shell Refinery but part of Auburn Council's jurisdiction).

There was flash flooding on Parramatta Road. I observed significant rises in Duck River myself.

The storms developed and dumped over small areas and the second one dumped onto Auburn / Lidcombe and Strathfield causing some havoc to Council. After dumping it's rain load, the storm weakened.

The flash flooding caused several roads to be closed for a while.

I noted another line of storms developing thereafter but off the coast. Presumably they died after dumping their rain loads.

Harley Pearman

[David Brodrick]

North West Slopes, Thurs 6th Dec

There was no action near Narrabri but some great action on the Moree RADAR on this day. The attached photo was an attempt to capture some very powerful updrafts just as they were reaching the equilibrium level and the anvil began forming. The photo is from Narrabri and the Nandewar Ranges (Mt Kaputar) is in the foreground. I recall this storm was actually over Inverell, several hundred km away!

David C, good point, advice noted and taken on board. In this particular case I understand the Texas storm was quite severe and caused some damage, although I can't find the ABC News link anymore. I never heard anything about the Goondiwindi/Boggabilla storm. These were isolated cells with very high RADAR reflectivity.

Regards,
  Dave

[TroyVR]

This thing hit like a freight train. Calm 1 second, pouring rain and ferocious winds the next. Absolutely Brilliant stuff In my opinion.

http://www.youtube.com/watch?v=a6Uach7lFK8