Model Output Discussion - Into Winter

[AO-]

36 minutes ago, Penrith Snow said:

A SSW could have screwed up a favourable trop set up, remember the SSW on 1st January 2019, it was followed by forecasts of 0f (-18c) temperatures in February, we got 18c alright but it was plus 18c not minus!

Good Morning,

If I remember correctly 2019 was a minor warming with a displaced vortex over Europe. It looked promising at the moment, but nothing seriously wintry came out of it. 

 

Weeks of Easterlies without a cold Europe led to cloudy and foggy weather.

Edited December 31, 2023 by AO-

[Eagle Eye]

21 minutes ago, Mike Poole said:

Don’t want to reopen yesterday’s argument, but the mechanisms that were modelled to lead to the SSW were tending to split the vortex at all levels not just the top, so they (the mechanisms, not the SSW) would have impacted more directly (well, I think so anyway), as well as the later downwelling from the SSW.

The same mechanisms that created the SSW are still happening just w/less amplitude, the vortex isn't split but it's still going to be significantly 'hurt'. The teleconnections are still favourable just a more transient signal maybe.

[Gowon]

5 minutes ago, bluearmy said:

The Ukmo and icon both have a favourable polar profile with the vortex segments more separated and the polar high inserting itself into the gap. That should allow better WAA upstream and a more stable block at a higher latitude.  

I think there are a few twists and turns on this yet. The trend is unmistakably for the first amplification to bring a slowly se sinking surface high and a nor’easter of sorts which gets cut off (maybe not so in the se of England depending on the euro trough) 

then the second amplification to follow currently looks like it might be better - I think that will depend on the polar profile at the time and whether the split is sufficient to allow the polar high to assist.  It could easily end up a rerun of the first attempt. 

The latest ICON doesn't separate the vortex at 120h

[nick sussex]

Those in the more favoured areas hoping to see some snow need to hope the ECM op is correct because less cold uppers simply won’t cut it to produce snow showers off the North Sea .

Even then the window is relative narrow , though of course a window is better than no window !

[winterof79]

40 minutes ago, Lukesluckybunch said:

It was a cold outlier..doesn't mean it's wrong though

Bottom end of its suite but not a cold outlier.

Im not getting this despondency today over a cold spell that really never was forecast to start until high pressure moves in.

Writing off Jan on 31st Dec is brave.

[AO-]

EC doesn't seem favourable this morning, but for my location it hasn't downgraded (a lot). Still on schedule for the 8th wrt cold and maybe even sooner as more members show cold(ish) from the 6th. Beyond the 10th is FI, even though the trend is not very promising. There is not enough CAA before the block appears, because the Scandinavian block is still present and merges with the Atlantic ridge. In the West there is not enough CAA to keep a proper angle and get a HLB. In my opinion these are details at the moment.

 

Edited December 31, 2023 by AO-

[Alexis]

23 minutes ago, TSNWK said:

Incorrect.  Because of the Canada warming stressing the trop the impact would have been pretty instant 

How come we didn't see any instant effect in the model outputs then?

[bluearmy]

9 minutes ago, Gowon said:

The latest ICON doesn't separate the vortex at 120h

Yep it is slightly worse at day 5 but the 00z began to move apart between days 5 and 6. The 06z does look less likely to follow the 00z run. 

16 minutes ago, northwestsnow said:

I have  been ruminating about a possible second bite of the cherry this morning..

EC 46 collapsed the pattern last night so that is nagging away ,hopefully a better ec46 this evening ..

 

Didn’t like that run yesterday - too many euro heights showing.  could be becoming a trend aswell second half jan as recent runs have shown. 

[Harsh Climate]

5 minutes ago, winterof79 said:

Bottom end of its suite but not a cold outlier.

Im not getting this despondency today over a cold spell that really never was forecast to start until high pressure moves in.

Writing off Jan on 31st Dec is brave.

I think It's going to be a slow burner

Have many of us got the patience and stamina though? 

[Met4Cast]

19 hours ago, Tamara said:

The westerly wind anomalies which developed over the Equator early December onwards that have been fluxed poleward over the last three weeks c/o zonal mean transports cater for the upward spike in angular momentum. (This also paves the way for a cold pattern to return to N Europe later January into February - see further down). 

Relative angular momentum is up c/o fluxing of westerlies from the tropics into the sub-tropic. This, as we know, can be seen as a +ve angular momentum anomaly on the calculated aggregate tendency plot (shaded red) from 30N

.

Uniform extra tropical +ve mountain torque has driven tendency in relative angular momentum and the GWO well into phases 5/6

With the Nino attractor phases fully engaged, the amount of westerlies propagated into the atmospheric circulation between tropics & extra tropics do, as you suggest, indicate a higher floor to the angular momentum budget in the 'lull' ahead of the next upswing as the MJO traverses the tropics during January. GWO Phase 4 is a good medium base floor level I would think.

If we were to take a diagnostic template of GWO Phase 4 (and account for a likely return shallow orbit through phases 0,8 & back to 4) during an intermediate 'lull', then that very intermediate lull phase you describe will likely feature the return of a flat upper flow extending towards Europe.

The difference to recently though with the Atlantic forcing will be the jet suppressed further south - and with a cold pool established then attritional forcing of lows against the blocking likely to be a feature. (This accounts for some of the thinking as expressed within my previous posts in respect of the sub tropical jet)

With a cold pool established, any erosion from the south/west into NW Europe is likely to be attritional and not likely to displace cold pooling totally.

Taking into account we are still now in the lag period for the effect of +ve momentum from FT/MT mechanisms c/o the recent tropical>extra tropical cycle, we are seeing the new convective signal come into the Indian Ocean. Sea temp anomalies are supportive of deep thunderstorm convection. This, allied to convection in the western Pacific, will generate further mean zonal west wind anomalies to propagate across the tropics into the sub-tropics. With the westerly wind additions generated in December still in the atmospheric circulation, total and relative angular momentum will increase sending the GWO back into a (potential high amplitude) phase 5 orbit.

This progression & evolution suggests a strong -ve NAO with positive height anomalies shuffling between Greenland > Iceland and Scandinavia. Meantime southern Europe wet & mild under the sub tropical jetstream.

Muito obrigada. Melhores Cumprimentos

Some a little disheartened in here today so just want to bring this post from Tamara yesterday back to attention. 

The outlook going forward continues to be one supportive of a -NAO, the first attempt at high latitude blocking may end with a UK high but plenty of opportunity still exists beyond that & it seems likely we’ll see further attempts with cold never too far away. 

I’m not convinced any of this is resolved yet. 

[Bricriu]

1 hour ago, Met4Cast said:

This is a trend we really don’t want to see but does seem to be gaining traction. High pressure becoming UK based rather than higher amplitude. 

Cold yes, but snow risk would be rather non existent. Hopefully we start to see a trend back towards something more amplified. 

It would fit in with the UKMO  outlook. Cold and dry at first, with the chance of snow increasing going into the second week of January 

[markw2680]

When MOST of the models are showing similar to this for around the 7th I think if we get here we will all be happy to take it, why are we obsessing over what will happen after the 7th? Even that’s a week away and fi so will be subject to changes, there’s no way on earth any models have the correct outcome for 7,8,9 and yes 10 days away. It’s trends we want that’s all. It’s all looking good at this stage and at least we have a chance 

[AO-]

2 minutes ago, Met4Cast said:

Some a little disheartened in here today so just want to bring this post from Tamara yesterday back to attention. 

The outlook going forward continues to be one supportive of a -NAO, the first attempt at high latitude blocking may end with a UK high but plenty of opportunity still exists beyond that & it seems likely we’ll see further attempts with cold never too far away. 

I’m not convinced any of this is resolved yet. 

To add a chart to your argument. Second attempt coming. Eventually I guess that the WAA will connect to the Polar hp. 

Edited December 31, 2023 by AO-

[weathercold]

Not seeing the enthusiasm shared by some- we can’t seem to maintain a high lat block across most model suites, we can’t seem to tap into the brutal cold east of us. There is no longevity to this currently, at best a high bang over us.

Wintry nirvana this ain’t, sustainable cold neither. All v sobering this morning compared to where we could have been a week or so ago pre the SSW projected collapse.

Still not seen even one deep freeze run - says it all.

Currently in Estonia, fresh fall over night -8 max daytime here today. Proper winter!

Edited December 31, 2023 by weathercold

[Guest]

I don't want to say I told you all so but.....

The ECM lacked the detail and as such has moved towards the GFS.

[Harsh Climate]

5 minutes ago, weathercold said:

Not seeing the enthusiasm shared by some- we can’t seem to maintain a high lat block across most model suites, we can’t seem to tap into the brutal cold east of us. There is no longevity to this currently, at best a high bang over us.

Wintry nirvana this ain’t, sustainable cold neither. All v sobering this morning compared to where we could have been a week or so ago pre the SSW projected collapse.

Still not seen even one deep freeze run - says it all.

 

Just look at the GFS assembles over the last day or so, there are lots of deep cold/snowy nirvana clusters! Every cluster is certainly a possibility to one degree or another.

[AO-]

1 minute ago, DCee said:

I don't want to say I told you all so but.....

The ECM lacked the detail and as such has moved towards the GFS.

The details you mention are far from what GFS had in mind. I don't agree that EC moved to GFS. There are too many details in this evolution to come to where we are. 

[Gowon]

6 minutes ago, weathercold said:

Not seeing the enthusiasm shared by some- we can’t seem to maintain a high lat block across most model suites, we can’t seem to tap into the brutal cold east of us. There is no longevity to this currently, at best a high bang over us.

Wintry nirvana this ain’t, sustainable cold neither. All v sobering this morning compared to where we could have been a week or so ago pre the SSW projected collapse.

Still not seen even one deep freeze run - says it all.

 

The ECM yesterday morning was near enough a deep freeze?

[Bricriu]

27 minutes ago, Eagle Eye said:

The same mechanisms that created the SSW are still happening just w/less amplitude, the vortex isn't split but it's still going to be significantly 'hurt'. The teleconnections are still favourable just a more transient signal maybe.

So if we had got the major split the chances of a cold spell lasting longer would have been greater. It seems  Mike Poole  and you are in agreement  on that. No cold spell will hang around forever anyway. If we manage to get two or three snowy  days out of this I'll be happy.

[TomB]

1 minute ago, DCee said:

I don't want to say I told you all so but.....

The ECM lacked the detail and as such has moved towards the GFS.

Please don’t.  Posters have been conscientiously looking at the models and giving an appraisal of what they show.

 

 

[weathercold]

1 minute ago, Gowon said:

The ECM yesterday morning was near enough a deep freeze?

Close to yes but not majorly supported and nothing sustained, flattened at day 10.

[bluearmy]

3 minutes ago, DCee said:

I don't want to say I told you all so but.....

The ECM lacked the detail and as such has moved towards the GFS.

Which gfs ?  4 runs a day and hardly consistent beyond day 7 

That’s why the gfs gets so much faith from people - because whatever verifies, the gfs will have shown it at some point in the preceding 44 runs from day 16 down to day 5. 

[weathercold]

3 minutes ago, Harsh Climate said:

Just look at the GFS assembles over the last day or so, there are lots of deep cold/snowy nirvana clusters! Every cluster is certainly a possibility to one degree or another.

ECM ensembles big step back today - Mike posted 

[BLAST FROM THE PAST]

I can’t see the despondency, pretty decent set of 00z runs.  SE for a change certainly looking in a good place.  This first bite for me is just that, as mentioned I anticipate there to be a second hit and of a stronger block….with surface cold not really disappearing before it arrives.  ECM at t240 looks primed for the retrograde.

 

from Spaceweather the talk is NASA says a SSW is occurring.  But it’s warming and hitting a stratosphere that was incredibly cold and the warming isn’t anticipated to be as strong as 2018 but is much earlier in the season.  I mentioned a while back if the starting supercold point would have an effect.  
For me half glass full beginning to get re-filled

 

BFTP

Edited December 31, 2023 by BLAST FROM THE PAST

[Ali1977]

People are talking as if we’re loosing the signal for cold - when it’s actually increasing with every run