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Jellybeans

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A real interesting note on the GFS AAO projections tonight:
182C21BB-AC3D-41F2-9B91-1E3B91025A9F.png


A mass weakening of the AAO in the stratosphere (weakening of the SPV).
You’d expect a -AAO to start propagating down in the first days of September, if it holds.
 

rocketboy

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I’d say something positive and optimistic but wow, it might be better to just let this one keep brewing later next week. But yer ‘Storm Wow’ come on down and fill the bucket.
 
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download (9).png Don't look too good this plot heading the wrong way if it verifies.
the system may just scrap in.
download (9).png
 
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rocketboy

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Heading for a resurface.
aao.sprd2.gif

How does this tie in with Jelly's recent observations on the behaviour of AAO disrupters.

It was pretty amazing how on the money Jelly was with those early observations. It was a "season wrapper" on the hard positive AAO forecast - only for it to collapse away and give us season starter number 3.
 
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Jellybeans

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How does this tie in with Jelly's recent observations on the behaviour of AAO disrupters.

It was pretty amazing how on the money Jelly was with those early observations. It was a "season wrapper" on the hard positive AAO forecast - only for it to collapse away and give us season starter number 3.
gfs_sh-samindex_20190812.png


It fits the timeline for the AAO. We see a peak in a +AAO in the latter stages of this month. And then in the first days of September we see a dip in the -AAO.
ecmwfa1ec---shem_full_au-354-C-10hgt_2019081312_whitecounty.png


EPS Control shows a more intense stratospheric disturbance in the last days of the month.
gefs_basic-hgt--shem_full_au-354-C-10hgtanom_2019081318_whitecounty.png

Same story on GEFS.

Expect a -AAO dip in the first days of September for a week or so at least IMO.
Expect a decent stratospheric event, we need a few more days to assess whether it is strong from a SSW level.
 

POW_hungry

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How does this tie in with Jelly's recent observations on the behaviour of AAO disrupters.

It was pretty amazing how on the money Jelly was with those early observations. It was a "season wrapper" on the hard positive AAO forecast - only for it to collapse away and give us season starter number 3.
EDIT: Argh yea, just saw @Jellybeans reply ^^, yep there you go...
Significant Strat/PV disturbances initiated it. Ensembles nailed it.
It's been in flux since the start of July.
August appears nil different. Strat thread in general weather is a good start in understanding it.
 

POW_hungry

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Vibe for another decent to big early spring event you reckon given jelly’s suggestion of another anom in early September?
If I am to be honest, I worry about the system next week as it’s going against the AAO tide, so to speak. If downgrades are on the cards they’ll come in the next day or two as ensembles prog the +’ve territory of SAM. @Jwintermix put it well; it may just scrape through in time.

That said, yep I am inclined to agree with @Jellybeans for the start of SEP, as the strat disturbances have been on a prominent cycle and has been progged on ensembles for a while now.

RE: Spring… A –‘ve SAM scenario in SEP may run into issues if we have any onset of Monsoonal influence as that’ll put rain in the mix. +'ve IOD will also be less relevant as the Monsoon kicks into gear.
 

Jellybeans

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If I am to be honest, I worry about the system next week as it’s going against the AAO tide, so to speak. If downgrades are on the cards they’ll come in the next day or two as ensembles prog the +’ve territory of SAM. @Jwintermix put it well; it may just scrape through in time.

That said, yep I am inclined to agree with @Jellybeans for the start of SEP, as the strat disturbances have been on a prominent cycle and has been progged on ensembles for a while now.

RE: Spring… A –‘ve SAM scenario in SEP may run into issues if we have any onset of Monsoonal influence as that’ll put rain in the mix. +'ve IOD will also be less relevant as the Monsoon kicks into gear.
Yeah I think the 26-30th longwave looks like it's weakening as it passed our region. Sign of the +AAO times. By then, we will have 200-250cm SC depth and we will have heaps to play with.

Given the cold SSTs around North Australia (like a Nino, but not exactly like a canonical type), I don't think the monsoon onset will affect a -AAO event in the first two weeks into Seprember. Bureau is forecasting a late monsoon onset.

First (and maybe second) week of September looks like the last possible period for a "big" snow-bearing system IMO.
 
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POW_hungry

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Given the cold SSTs around North Australia (like a Nino, but not exactly like a canonical type), I don't think the monsoon onset will affect a -AAO event in the first two weeks into Seprember. Bureau is forecasting a late monsoon onset.
One hint of the Westerly trade wind component in the IO will flick the switch on our season, IMO.
I am with you, I hope it's late Sep at the earliest.
 

POW_hungry

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Yeah I think the 26-30th longwave looks like it's weakening as it passed our region. Sign of the +AAO times. By then, we will have 200-250cm SC depth and we will have heaps to play with.
Just on this, I am still resigned to a later influence of this LWT to the SE IMO.
Still 8-days off the SE in the below prog. So 30AUG-3SEP is the sweet spot IMO.
imageserver.png
 

Jellybeans

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Just on this, I am still resigned to a later influence of this LWT to the SE IMO.
Still 8-days off the SE in the below prog. So 30AUG-3SEP is the sweet spot IMO.
imageserver.png
Perhaps. Regardless it’s weakening (and hence probably the reason why it’s slowing). I’d prefer it to be 5 days later from the 29th-30th.

It all depends on the AAO timing, and the strength of the long wave.
 

POW_hungry

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gfs_sh-samindex_20190812.png


It fits the timeline for the AAO. We see a peak in a +AAO in the latter stages of this month. And then in the first days of September we see a dip in the -AAO.
ecmwfa1ec---shem_full_au-354-C-10hgt_2019081312_whitecounty.png


EPS Control shows a more intense stratospheric disturbance in the last days of the month.
gefs_basic-hgt--shem_full_au-354-C-10hgtanom_2019081318_whitecounty.png

Same story on GEFS.

Expect a -AAO dip in the first days of September for a week or so at least IMO.
Expect a decent stratospheric event, we need a few more days to assess whether it is strong from a SSW level.
EC Ensembles goes even harder on the strat warming and PV shift, on the 00z run.
I haven't paid a lot of attention in the last few days, but this prog (alone) is the strongest this season.
Screen Shot 2019-08-14 at 9.34.37 pm.png
 

Jellybeans

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EC Ensembles goes even harder on the strat warming and PV shift, on the 00z run.
I haven't paid a lot of attention in the last few days, but this prog (alone) is one of the strongest this season.
Screen Shot 2019-08-14 at 9.34.37 pm.png
Now we are talking 2002. We are talking a real SSW there, that's some real serious imagery, and catching up to GFS that has been following this for a few days now.

This could have really big implications for our weather IMO.
 
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Jellybeans

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My apologies that was the last polar Vortex split. There’s been various degrees of SSW events over the years but i’d have to check if the split was SSW induced.
@Jellybeans May know.
Yes the split is part of the SSW event itself, rather than a seperate event.
More specifically a split is a type of SSW.
The other type is a PV displacement event which is what both EPS and GEFS model for this period. Instead of it driving the vortex to split, it pushes it out and weakens it.

No major snow from that event?
It depends really, I can check SC depth tomorrow, but depending on the timing within September, it may or may not have had a larger effect. The earlier, the better, as the SH circulation moves south. This event is reasonably well timed within the season.
When was the last SSW? Seen something saying June 2013, does that sound right?
It depends what you call a SSW. I had an argument with someone about it a month back. You could call this August's events a (minor) SSW per a research paper. The last major one as stated by @POW_hungry, was in 2002.
What magnitude would be enough to stir thing up do you think ?
Put it this way, the previous disturbance (late July/early Aug) was not even half of what that prog is.
This will be massive if it comes off. Stirring things up would be putting it lightly.

It could be the best thing that has ever happened to the Australian Alps
OR
It could become complex and become weird from a tropospheric perspective.
OR
They could fade or weaken.

Early signs are pointing closer to the first option.
We live in hope.
 

AussieWhite

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Yes the split is part of the SSW event itself, rather than a seperate event.
More specifically a split is a type of SSW.
The other type is a PV displacement event which is what both EPS and GEFS model for this period. Instead of it driving the vortex to split, it pushes it out and weakens it.


It depends really, I can check SC depth tomorrow, but depending on the timing within September, it may or may not have had a larger effect. The earlier, the better, as the SH circulation moves south. This event is reasonably well timed within the season.

It depends what you call a SSW. I had an argument with someone about it a month back. You could call this August's events a (minor) SSW per a research paper. The last major one as stated by @POW_hungry, was in 2002.


This will be massive if it comes off. Stirring things up would be putting it lightly.

It could be the best thing that has ever happened to the Australian Alps
OR
It could become complex and become weird from a tropospheric perspective.
OR
They could fade or weaken.

Early signs are pointing closer to the first option.
We live in hope.
Cheers mate
 
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September usually see's 1-2 cutoff lows traverse the tasman way. If your lucky one gets over SA/VIC or pass's close too tassie.
 
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