NSW/ACT Cold Front and ECL - August 23-25

Steve777

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Our lengthy spell of mild, sunny weather comes to an end tomorrow. Winter has a sting in its tail.

Tomorrow August 23 will be warm once again, but an unstable air mass will move across our region, resulting in widespread showers and thunderstorms across much of NSW/ACT. This will be followed by a strong cold front overnight August 23-24. Once the cold air hits the Tasman Sea an East Coast Low is spawned off the Central part of the NSW Coast.

This will be a short, sharp event. Once formed, the ECL moves quickly away to the E-SE. However, it will bring heavy falls to the coast South from the Hunter, up to 100 mm. It will be cold, if briefly. The air mass following the front will bring widespread snow to the Tablelands above 1000 metres, with lower falls possible.
 

Billy Bob

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There could be the odd severe storm with hail tomorrow, given the sharp temp gradient between the airmasses. It could be a good test of the new Hillston radar but the front will probably move through there too early. Anywhere from Canberra northwards could see strong storms tomorrow.

Won’t see much from the ECL here nor any snowfall, but good to see the coast will get a drink which will quell the fire danger a bit as we head into the bushfire season (in some places it has already begun). Hopefully you don’t get too much damage or flooding.
 

Winterwolf

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Models still offering a little hope for those wanting snow in strange places.
here in the Highlands we look a shot for some flakes, but it looks likely to be wet snow and on wet ground in marginal temps any settling would seem highly unlikely. I’ll take it though!
 

Billy Bob

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The SHs towns and Bungendore are always just that bit too low for snow. When SSTs were a degree cooler, we did get the odd snowfall from an ECL. Possibly some flakeage at the top of the Gib (for you) and a little bit on the ranges around here, very early Tuesday.

The pre-frontal stuff will deliver more here than the ECL as is usually the case. Anthony Cornelius is going for possibly severe storms with damaging winds/isolated hail across a broad area of inland NSW tomorrow afternoon. Canberra may see one or two of these cells I think. Surface temps will be around 20 again in the middle of the day, falling quickly to 10 and below behind the front under shower/storm activity.
 

Snowmaker7

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I am waiting on ACCESS-C to come out before I raise my own hopes of snow here in the SHs, but EC and GFS do look promising, as does ACCESS-G. ACCESS-G is showing freezing levels in western areas of the SHs down to ~950m at 10am Tues, very similar on EC and GFS, with plentiful moisture, and I mean very plentiful. ie. good enough for snow above 700m under heavy showers. VERY similar set up to the July 2016 event which brought awesome settled falls to the region. This is looking maybe slightly warmer, but moisture totals and fall rates far more intense, improving snow chances. Best chance for us in Bowral is between 6am and 10am Tues IMO.

1629626009464.png

1629626189665.png

1629626327610.png
 

Jac0b

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I'm really excited that spring is only 1 week away with storm season starting soon, possibly as early as tomorrow. September to Feb/Mar is definitely the more interesting time of year weather-wise east of the divide.

Does anyone think Sydney (more the Western suburbs) can pull off another sub-10 degree day on Tuesday? Two in the same winter would be extremely impressive.
 

Steve777

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I'm really excited that spring is only 1 week away with storm season starting soon, possibly as early as tomorrow. September to Feb/Mar is definitely the more interesting time of year weather-wise east of the divide.

Does anyone think Sydney (more the Western suburbs) can pull off another sub-10 degree day on Tuesday? Two in the same winter would be extremely impressive.
ACCU Weather and Weather.com are both forecasting a 12° max for Sydney on Tuesday. I normally add 2° to Weather.com forecast maxima for Sydney. My expectation is about 14-15°.

I think that sub-10 would be pretty unlikely. On June 10 all the ducks lined up for a cold maximum. I don’t think that it will happen Tuesday.
 

Wavey

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Some serious wind looks likely for tomorrow night here... EC is perfectly picking up the downsloping effect from the Knights Hill area with the SW winds. 67kn seems a bit extreme but 100+ km/h gusts on the surface at places like Albion Park seems like a good chance depending on where that low sits.

1629664483726.png

If GFS is right then southern Sydney around Cronulla and Kurnell will be the bullseye for wind IMO.

Snow wise, I think EC is probably the most realistic with 15-19cm on the southern OP and around 10-15cm on other high parts of the CT.

1629664790471.png

And GFS going for a whopping 40+cm, although GFS tends to be quite bullish with snow totals. With that said, I think depending on where that low sits, places on the eastern CTs but high enough such as Mt Trickett and Mt Werong could get 20-30cm or even more. Could also be a lot around Lithgow and Hartley similar to 14th Oct 2014. Anyway here is GFS just for posterity.

1629665057005.png
 
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davidg

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Very widespread. I like.

ACCESS-C looking like snow to 1000m on the CT's. Southern parts should be lower though according to GFS. Broad agreement on all the models, higher parts of the Oberon Plateau could see heavy falls in this setup but will depend on the timing between the cold air arriving and the precip. departing.

That cold air certainly hangs around as well, snap back to winter to round out August.
 
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Snowmaker7

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Some serious wind looks likely for tomorrow night here... EC is perfectly picking up the downsloping effect from the Knights Hill area with the SW winds. 67kn seems a bit extreme but 100+ km/h gusts on the surface at places like Albion Park seems like a good chance depending on where that low sits.

1629664483726.png

If GFS is right then southern Sydney around Cronulla and Kurnell will be the bullseye for wind IMO.

Snow wise, I think EC is probably the most realistic with 15-19cm on the southern OP and around 10-15cm on other high parts of the CT.

1629664790471.png

And GFS going for a whopping 40+cm, although GFS tends to be quite bullish with snow totals. With that said, I think depending on where that low sits, places on the eastern CTs but high enough such as Mt Trickett and Mt Werong could get 20-30cm or even more. Could also be a lot around Lithgow and Hartley similar to 14th Oct 2014. Anyway here is GFS just for posterity.

1629665057005.png
This system as the potential to produce some pretty incredible snow fall rates and accumulations over the CTs, ie localised 7-10cm/hr. GFS 06z run was showing upwards of 70cm across the OP. Will be very interesting if this pans out the way its looking, and with bit of luck with the trajectory of that low level cold pool those of us in the SHs could see a good snowfall
 

POW Hungry

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ACCU Weather and Weather.com are both forecasting a 12° max for Sydney on Tuesday. I normally add 2° to Weather.com forecast maxima for Sydney. My expectation is about 14-15°.

I think that sub-10 would be pretty unlikely. On June 10 all the ducks lined up for a cold maximum. I don’t think that it will happen Tuesday.
AXS-C has 10m temps for Sydney sitting on ~8°C at 7pm tomorrow night.
Diurnal maximums of 16/17°C are at 1-2am.

It'll be hovering around 11°C for Sydney during daylight hours tomorrow IMO.
 

Snowmaker7

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Crookwell good for some sleety/Wintery mix stuff 9am-12pm tomorrow.
But looking at AXS-C a fair chance of settlement after 8pm as the low level airmas is drawn North.
AXS-C the outlier when it comes to the low level cold pool tomorrow morning. Having it both warmer and further west than the others. Snapshots for comparison 7/10am tomorrow. Albeit 1°C 900hpa temps cold enough for settled snow above ~900m IMO
1629683425794.png

1629683470418.png

1629683501868.png
 

POW Hungry

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AXS-C the outlier when it comes to the low level cold pool tomorrow morning. Having it both warmer and further west than the others. Snapshots for comparison 7/10am tomorrow. Albeit 1°C 900hpa temps cold enough for settled snow above ~900m IMO
1629683425794.png

1629683470418.png

1629683501868.png
GFS looks like the outlier to me - especially considering it's spatial res ~28km, to Access-C 4km....
Comparisons are night and day when you put GFS & AXS next to each other.


EDIT: GFS 13km inside 10 days
 
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Winterwolf

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Edit: Last cell packed some ooomph - very strong winds, heavy rain, bit of pea size hail. All over fairly quickly. Highlands in the storm sweet spot! Hopefully tomorrow in the snow sweet spot....

A bit of small hail with that last cell that brushed us. Hoping the next cells are more on target and if so i will post some pictures. Border Collie still driving me crazy.
 

Wavey

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That southerly is really stirring up the atmosphere down south, some quite decent storms down around Narooma riding that change.

BoM has also slightly downgraded tomorrow's rainfall here from 60-100mm to 45-90mm (ie. 50% chance of 45mm or more and 25% chance of 90mm or more). I still think totals will very much be on the lower side of that forecast as winds are looking pretty SWly. Whoops I meant 50-90mm for Wollongong, didn't realise I was still looking at Sydney.
 

POW Hungry

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The BOM has also upgraded Sydney’s expected rainfall total to 45-90 mm and downgraded the maximum to 14°.
Penrith 35-60 mm, 14°.
Newcastle 25-50 mm
Wollongong 50-90 mm.
I know we're all across it, but the BOM rainfall 'aint totals. They're 'chances of'.
I.e. "45-90 mm" translates to 50% chance of 45mm, 25% chance of 90mm

Just flagging so they're not hung, strung, quartered for being a fizzer...
 

Homer

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Josh, please post any further observation posts in this thread......

 

Joshua Randazzo

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Josh, please post any further observation posts in this thread......

sorry i typed in wrong tab
 
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