The hunt for cold - Model discussion (late November)

[Mapantz]

.... and back to the models ...

Thanks.

[Frosty.]

7 minutes ago, snowray said:

Indeed Frosty, something exciting seems to be in the air for coldies coming up, 12z could be a mega run, fingers very crossed!

It's been a case of early Christmas drinks here too, last night and again today, an early Merry WHITE Christmas to every one, only 2 weeks to go. hic....

Indeed snowray, I'm using my instinct here..the models just don't look like delivering the usual default mild cr*p we are so used to..I wouldn't even be posting if I didn't think coldies are in the game for something before crimbo!

[A.J]

2 minutes ago, MattStoke said:

You can't discount one model but the GFS is normally the least accurate of the main models in such setups.It almost always blows up low pressure systems too much and blows away blocking high pressure too quickly. Doesn't necessarily mean it is wrong this time but one would have more faith in the other models in this setup.

Steve's post didn't to me read like he was completely discounting the GFS output anyway.

....but it all depends what it's showing.....over the past week or two, we've gone through the whole model ensemble of 'crapness'.......yes, each model has had it's turn of being 'unflavour of the month'.....according to material posted in this thread, the GF,S, ECM, UKMO, ICON, et al are all utter failures at various stages and their designers should've been on the 'virtual pill' to stop these model monstrosities from ever have been conceived.....Ok, a little OTT but then again OTT is the bedrock of a good chunk of stuff posted here to be fair......A jolly good ramp is good from time to time as long as it's infused with a dose of realism.............I'm in a grumpy mood, so I'm going to open the gin bottle to lift my spirits (the runs for next week sadly don't inspire much confidence of the white stuff for my locale, I really need to move....lol)

[Mike Poole]

9 minutes ago, Frosty. said:

Indeed snowray, I'm using my instinct here..the models just don't look like delivering the usual default mild cr*p we are so used to..I wouldn't even be posting if I didn't think coldies are in the game for something before crimbo!

I'm right with you there, Karl - it's the very fact that the models are not showing what they usually show - on average over a considerable period of time - at this time of year, that is reinforcing my expectations as well as the more scientific drivers.  Was the same in the late spring, my view was - something different here, so, what haven't we had for a while, oh yes a hot summer, maybe that's what the signal was - and it was as it turned out.

Whether it will happen before Christmas, less sure, but from the model output at the moment, it's certainly on the table.  

Edited December 9, 2018 by Mike Poole

[snowray]

20 minutes ago, lassie23 said:

That should give us two days of sleet darn sarf 

I'm still waiting for my first slett here, happy days. Going to build in igloo for my pets for Christmas, you can bring your goats and donkeys too if you like.

 

This is all snow for us.

Edited December 9, 2018 by snowray

[Frosty.]

12 minutes ago, Mike Poole said:

I'm right with you there, Karl - it's the very fact that the models are not showing what they usually show - on average over a considerable period of time - at this time of year, that is reinforcing my expectations as well as the more scientific drivers.  Was the same in the late spring, my view was - something different here, so, what haven't we had for a while, oh yes a hot summer, maybe that's what the signal was - and it was as it turned out.

Whether it will happen before Christmas, less sure, but from the model output at the moment, it's certainly on the table.  

Cheers mike, you have been brilliant this year, hats off to you..yes, the models thankfully look interesting for us coldies in the run up to crimbo..and beyond hopefully.

[Leo97t]

Just now, Frosty. said:

Cheers mike, you have been brilliant this year, hats off to you..yes, the models thankfully look interesting for us coldies in the run up to crimbo..and beyond hopefully.

Agreed. Mike has definitely been the standout commenter for me this year! 

[Banbury]

2 hours ago, northwestsnow said:

Steve,

Where do get the info on mogreps?

Darren is only talking short term ( this week ) - long term " not much excitement "

[Catacol]

2 hours ago, jules216 said:

Then in  around  2 weeks time we see another pulse of stratospheric warming around eastern Siberia moving the core of polar vortex at 10hPa to Greenland/Iceland area(picture.2).  In the same time we see on the hemispheric view of 500mb height anomalies that the core of tropospheric polar vortex is moving in the same direction - towards Greenland(picture.3)

Am I making a false assumption of atmosphere in thinking that these stratospheric warmings are doing us no favors at all on short to medium term?

 

Currently there is indeed a Siberian warming forecast at the outer edges of modelling - and in "normal" times transferring the vortex back over to the Canadian side would potentially whip up a +NAO pattern if there was a clear strat/trop connect. But the question is - just how much of a vortex is going to be left standing by this stage and is it possible that the Siberian punch does more damage than simply shift it? By the time that punch comes it may be ripe for take down....And even if it doesn't disintegrate that Siberian punch might send it a long way over to the west in its weakened state, allowing blocking to continue as per pacific forcing and an enhanced southerly jet and undercut. 

To be honest - this is all just speculation. We are still too far out. 

[Methuselah]

I just hope that this month's (should it happen) SSW has a similar outcome to that of December 1984: a winter to remember!!

Edited December 9, 2018 by Ed Stone

[shaky]

Icon12z!!90 hours and looks more like ecm with trough disrupting!!!slowly but surely maybe!

That scandi high is further west at 102 hours and stronger!!!

Edited December 9, 2018 by shaky

[snowray]

46 minutes ago, Frosty. said:

Indeed snowray, I'm using my instinct here..the models just don't look like delivering the usual default mild cr*p we are so used to..I wouldn't even be posting if I didn't think coldies are in the game for something before crimbo!

Well its a good omen Frosy that you are posing again, I was wondering where you had gone. I must say, I do often think that I need a new hobby for the winter months, something, erm, a bit more constructive, like pottery, or model train sets. But here I am back every year for more torture.

[Chesil View]

1 minute ago, Ed Stone said:

I just hope that this month's (should it happen) SSW has a similar effect to that of December 1984: a winter to remember!!

Indeed so Ed  I had something like seven seperate  worthwhile snowfalls that winter even here in lowland Dorset.

[jules216]

25 minutes ago, Catacol said:

Currently there is indeed a Siberian warming forecast at the outer edges of modelling - and in "normal" times transferring the vortex back over to the Canadian side would potentially whip up a +NAO pattern if there was a clear strat/trop connect. But the question is - just how much of a vortex is going to be left standing by this stage and is it possible that the Siberian punch does more damage than simply shift it? By the time that punch comes it may be ripe for take down....And even if it doesn't disintegrate that Siberian punch might send it a long way over to the west in its weakened state, allowing blocking to continue as per pacific forcing and an enhanced southerly jet and undercut. 

To be honest - this is all just speculation. We are still too far out. 

@Catacol maybe we can say that it is high risk high reward situation? If warming is strong enough and we get SSW then vortex is dead and it doesnt matter that it relocated towards Greenland. But if vortex proves more durable we may get a -EPO pattern with cold eastern USA and not sufficient undercut which will then advect more euro high situation as residual vortex around Greenland will not allow retrograding pattern and instead of highs around GIN corridor we end up with Sceuro high? 

Edited December 9, 2018 by jules216

[Mike Poole]

ICON already with stronger high and shift west at T102, with 6z same time for comparison, could be an interesting few hours of model watching upcoming!

Actually that is quite an astonishing difference at such a timescale.

Edited December 9, 2018 by Mike Poole

[northwestsnow]

5 minutes ago, shaky said:

Icon12z!!90 hours and looks more like ecm with trough disrupting!!!slowly but surely maybe!

That scandi high is further west at 102 hours and stronger!!!

Looks like EC to me too mate.

[Rocheydub]

It looks like it’s about to open a pathway for those Atlantic systems to slide on a NW/SE run, that would really bring this place alive. Most probably won’t though, as I’ve seen similar set ups over last few days and none have done it.... Yet!

[Catacol]

Awww hell - let's take a guess. A lot of questions spinning around about what may or may not happen in terms of strat forcing around Xmas alongside rejuvenated pacific wave. I wasn't going to take a punt until we had a bit more data....but all this snow hunting gets under the skin so let's take a stab.

Let's just start with this - not a lot to say about this except an ongoing forecast for another strong pacific wave about to kick off

Effect of this will be to enhance poleward wave activity with concurrent torque increases that will power up AAM at 30N and reduce it further north. This chart is annoyingly 4 days old - but you can see the trend. Look carefully right over on the right hand side at the yellow colours appearing at 30N while it goes decidedly purple at 60N. AAM balancing going on - cant be strong at both 30 and 60 at the same time!

So - given lag times of this torque spike and MJO wave heading into the Indian Ocean we have a clear signal for height rises in the second half of the month....and i'll stick to my previous 18th Dec guesstimate for this taking hold.

Simultaneously up top we have the vortex in an unhappy state due to ongoing wave 2 and then wave 1 warming. I'm not going to post the same charts as last night - but that warming is clear and most certainly now coming. What will it do?

For me the first signs (and bear in mind I'd rather wait a few more days before having any real confidence....) are on this chart. The Attard site is really good for getting a picture at 10, 50 and 100hpa

Notice how the warming at this midlevel of the strat has started to focus on the Canadian sector with the bulk of the vortex moved to Siberia and a smaller filament spiralling off into the atlantic. Lower down that picture is even more clear, showing that from 50 to 100 hpa we have a fairly clear connect and a likely downward forcing applied to our pattern

Note also the warming signal to our south connecting to a slight warming to the NE as well as that Canadian signal.

Attard then runs out of steam - doesn't go beyond 180 hours - but within a few days we then see this on the GFS 2 days later:

Another wave 2 warming signal on a vortex already distressed that then becomes a very vigorous wave 1 hit as advertised by a few others

I would really like to see what the impact of these hits is going to be around 50hpa - but I don't have access to that data out beyond 180 hours. But here is a guesstimate.

Resurgence of height rises to our north around 18 Dec and now I'm swinging towards these being initiated from the atlantic sector. Scandy high not gone - but shunted east by this stage. Trough to drop over the UK in the run up to Xmas bringing cold northerlies. Warming then hits a distressed vortex sitting over Siberia and effectively knocks it down - what energy remains spills to the west allowing the greeny high to link up to the scandy high and a southerly jet initiating an undercut scenario in the week between Xmas and New Year. Once that link up has occurred we have a pattern set to entrench because the vortex will be struggling and the pacific signal will be controlling things for the medium term. Pressure over Europe will have to fall given the strength of that northern block.

There. First guess done. Plenty that can go wrong with that view - and I will not be holding to it if I see adjustments - I'll simply change my interpretation and say I got it wrong - but for now this is my view. Pacific forcing in charge... and stratospheric impacts to reinforce that pattern. Any vortex energy that can spill around the edges of the block will be what gives us some added special potential. If the vortex isn't taken down by that Siberian punch then things change a bit....delays probably...but let's hope that punch is a knock out.

EDIT - just checked the GFS 00z run. Not too far away in the extended I think. Pattern from 228 to 324 about right for me, but the trough will dig further south and those heights to the NW will be more pronounced.

 

Edited December 9, 2018 by Catacol

[snowray]

Quiet on here considering the massive 12z runs that are about to come out that are going to exterminate the mild dross to smithereens! ICON already has shown us how quickly things are changing with cold upgrading and a decent undercut. 

FI once again is at +T96! 

[Midlander]

A pleasant surprise too see an upgrade from the ICON, but the precip charts still forecast only rain.

[Rollo]

How I would love to understand all your post but what little I do I thank you for, Keep on doing it please.

 

[Skullzrulerz]

10 minutes ago, snowray said:

Quiet on here considering the massive 12z runs that are about to come out that are going to exterminate the mild dross to smithereens! ICON already has shown us how quickly things are changing with cold upgrading and a decent undercut. 

FI once again is at +T96! 

I believe they should start shortly?

[IDO]

We can see from the jet, the problem we have in keeping the Atlantic at bay, and why the ICON blows the block away on the 12z from Friday:

Unless the jet is currently being overemphasized it will tough to expect the block pushing west.

[snowray]

Atlantic fronts being pushed back again as early at T48 on the gfs 12z, nice.

12z V 06z.

[Spah1]

Block looks more robust next Thursday from UKMO 96hrs