Vic - Antarctic cold wave 7 - 16 Aug 2019

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JasmineStorm
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Fri Aug 02, 2019 7:19 am

Time to pull the trigger on this event, as I’m sure there is some model fun along with projection downgrades and upgrades to be had.

The stratospheric polar vortex disturbance which has been watched closely in the climate driver thread is commencing to propagate into lower atmosphere and mid latitudes. The SAM index is going negative with around 100 ensemble model members across EC, GEFS and GEPS believing a significant polar cold wave will propagate into SE Australia late next week. Details will change every model run but it’s becoming more likely that major polar cyclonic gyre will cut off near Tasmania next Friday August 9th.
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Didjman
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Fri Aug 02, 2019 8:55 am

All models at the following link are suggesting Batten down the hatches next Fri through to Sun!
https://www.weatherzone.com.au/models/

Even the LWT chart for Fri aggrees:
cpc.ncep.noaa.gov/products/intraseasonal/temp50anim.gif

As JS implied, still a long way off.
JasmineStorm
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Fri Aug 02, 2019 9:09 am

GFS is going quite feral :) GFS 0108 18Z run is going with a multi core lower tropospheric cyclonic vortex attack. Its an elongated King Rossby wave as seen by it's width across to NZ. The southerly fetch will put snow in places it doesn't normal fall if that verifies.
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chasersaddict76
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Fri Aug 02, 2019 2:17 pm

Very likely Antarctic bring freezing attitude right to SW/SE Queensland is massive from Southern Ocean Aug 11th.
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JasmineStorm
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Fri Aug 02, 2019 2:50 pm

This latest GFS 00Z run is truly remarkable. A dart board 968 hPa cold core destructive Bass strait cyclone. It can only downgrade from here :) BoM and Vic Emergency will need a war room if that comes off.
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chasersaddict76
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Fri Aug 02, 2019 3:08 pm

Next Wednesday best chart update for accurate
stevco123
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Fri Aug 02, 2019 6:48 pm

Surely that won't come off. But if it does... :o :o :o

:P :P
https://www.weatherlink.com/bulletin/53 ... 76dd68e8bc: for current weather updated every 2 minutes
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Didjman
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Fri Aug 02, 2019 8:19 pm

JasmineStorm wrote:
Fri Aug 02, 2019 2:50 pm
This latest GFS 00Z run is truly remarkable. A dart board 968 hPa cold core destructive Bass strait cyclone. It can only downgrade from here :) BoM and Vic Emergency will need a war room if that comes off.
I believe this is what JS was referring to:
https://www.weatherzone.com.au/models/? ... 2&focus=mh
Sean
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Fri Aug 02, 2019 10:06 pm

This has piqued my interest.

It's one of those, hmm, do I take the models seriously type thingos

*watching and waiting
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chasersaddict76
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Fri Aug 02, 2019 11:25 pm

I hate see the High Pressure tail jump over NW edge of any upper low that's how downgrade the upper low strength away..
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hillybilly
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Sat Aug 03, 2019 6:02 am

EC runs are all over the shop atm. Keeps cutting the big system off to our west. But big jumps between runs. GFS and CMC are more progressive and a classic big cold outbreak with a series of fronts. Somewhere is going to get some serious weather :o

Gonna take a few runs yet to settle down. First part on Tuesday looks like having a punch with gusty winds and a sharp showery band. Wednesday has a bit of a spike in uppers, so could see 20s pop up in the north ahead of the much colder air. Not too confident about the details of the sequence for Friday onwards, but would tend to back the CMC and GFs scenarios.
Macedonian
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Sat Aug 03, 2019 2:42 pm

My NSW low snow buddies are saying that the low snow chances for Vic have vanished according to the models.
Which is fairly amusing considering they were saying, only just last night, that we would be digging our way out by this time next week.
Sean
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Sat Aug 03, 2019 4:16 pm

Macedonian wrote:
Sat Aug 03, 2019 2:42 pm
My NSW low snow buddies are saying that the low snow chances for Vic have vanished according to the models.
Which is fairly amusing considering they were saying, only just last night, that we would be digging our way out by this time next week.
Generally the way it goes :D
JasmineStorm
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Sat Aug 03, 2019 5:23 pm

Another entertaining batch of runs with the cut off low scenario showing on virtually all models now. GFS keeps producing the bomb cyclone in Bass strait within 120 hours from now :) EC now onboard again with a similar bomb in western Bass strait but 2 days later. EC is a tad erratic from run to run you could say.... UK also bombing the low but further south.

Both GFS and EC given me around 5cm of snow. Haven't seen that since July 2015.... if it happens... but it needs to be a big southerly fetch to come off.

GFS also projecting an outbreak of thundersnow on Friday as off the scale TT's are produced as the 524 thickness line moves in with moisture.
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chasersaddict76
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Sat Aug 03, 2019 5:37 pm

The bomb low eye is likely south ocean of Adelaide and shift SE and bomb around Tasmania island by GFS
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chasersaddict76
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Sat Aug 03, 2019 6:45 pm

http://wxmaps.org charts seem right as others aswell
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hillybilly
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Sat Aug 03, 2019 7:27 pm

EC back on board for a big system. One of the deeper extratropical lows of recent years with pressure dropping to around 980 to 975 over northern Tas. Temperatures on Friday evening into Saturday are exceptionally cold. Freezing level drops to 700m, which would make it one of the coldest airmasses for a while. Probably similar to the August 2014 event which gave thundersnow here and a cm or two of cover.

Of course, next run could flip back to something different.

Will be a big storm surge on the coast, and heavy snowfalls in the alps. Would think at least 50-100cm of this model runsticks.
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hillybilly
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Sun Aug 04, 2019 7:18 am

EC looks very impressive this morning. Coldest airmass since August 2008 looking at the freezing levels. Only concern is the coldest air comes through between the best of the rain. Stays very cold for a long period from Friday arvo to Monday. Snow levels on Saturday morning are close to sea level (freezing level dips locally to about 500m). While inbetween they look to vary between about 500 and 800m.

Lots of activity in the sequence. Punchy fast moving front on Tuesday, warm frontal feature on Wednesday spreading rain from the north, strong front for Thursday with an intense low to our near south. Then a barrage of fronts Friday, late Saturday, Sunday and Monday. Rain totals will be substantial, winds a feature, and a significant storm surge on the coast. Of course, details will tweak, but currently looks like one of the more impressive system for a few years.

Btw looking back through our records. We got thunder snow here August last year (2018) and August 2014. Before that we had some in September 2003. Last year we had about 2cm accumulate. Last decent fall was August 2008 when we had about 10cm here so that the recent event to better :D This one is too far out to be too confident on the finer details.
JasmineStorm
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Sun Aug 04, 2019 10:39 am

Nice summary HB.

Thundersnow has never lined up for here locally but its definitely a chance on current projections.

We probably should get another couple of downgrades and upgrades in the next 48 hours :) It's certainly entertaining! EC putting flurries on Frankston and 0.5 to 1cm of sleet and snow on any Melbourne suburb over 50m ASL next Sunday morning was my favourite part of this mornings runs :)
Gordon
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Sun Aug 04, 2019 1:14 pm

Must be a challenge for BOM forecasting when the models pretty much line up a major event; but on the other hand, it's still several days out, and at the same time, what the computers are predicting is such a statistical outlier. Tricky!

Looking forward to seeing BOM's new 4 day chart.
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