Hunt For Cold: Model Discussion - Heading Into Christmas

[SMU]

A quick scan of the GFS ENS this morning reveals much more propensity for high lattitude blocking now post 180.

 

AO update later will be nice to see.

Still no zonal reset ...

[Weather-history]

Edited December 30, 2018 by Weather-history

[Weather-history]

[SMU]

One of those must be PTB 11

[feb1991blizzard]

5 minutes ago, Weather-history said:

That's what you call a perfectly mirrored trop response.

Edited December 30, 2018 by feb1991blizzard

[winterof79]

26 minutes ago, Steve Murr said:

A quick scan of the GFS ENS this morning reveals much more propensity for high lattitude blocking now post 180.

 

AO update later will be nice to see.

Still no zonal reset ...

https://www.meteociel.fr/cartes_obs/gens_panel.php?modele=0&mode=1&ech=192

There are some very exiting peturbs in there.

 

[Chesil View]

Nice ECM in the medium range this morning and even the GFS ensemblesgetting in on the act although the op still showing that models' allergic reaction to anything cold/snowy for the UK

[bluearmy]

1 hour ago, IDO said:

I see how the ECM avoids the UK flattening and it is rather precarious:

  T168

At T144 we can see the next wave of heights (SW corner) cut through the trough with a surface high and parcel of heights building above the current incumbent High. With the cut off upper low then reinforcing the UK high. This is quite fine mesoscale modelling at this range and has support within the GEFS, though they favour the wave not cutting the trough, thus giving the lower heights to the north more room to slowly sink the UK high. We can see from last night's ECM mean that the op option is probably not the main cluster:

We have to hope the ECM is simply better at that range for that fine detail!

As for the background strat developments. All seem to be going to plan for mid-Jan onwards. How the UK will be affected is the big question?

Yesterday’s clusters split ridgy/troughy across the e Atlantic 50/50 by day 15. There are six right through the extended which tells you plenty ...... the extended mean is again benign this morning with the high anomolys hanging on .... the control not far from the op at day 10 but sinks back across the uk with the undercutting lows too far south across Europe to affect us. 

I did note the Ukmo at day 6 find a surface high over the pole in a way that the other models didn’t .... ec was a day behind and this did help to bring the Atlantic ridge north day 8/9.  Whilst the vortex ends and flows between siberia and Canada we will not build a HLB but there is a sniff on this ec op that me Canada may be about to lose its lobe in a bad place for us - are we going to see an Aleutian lobe form to draw it west??? .  ln the absence of any defined guidance away from the meh, may as well stick with the block ..... it looks set...... just in the wrong place for us. 

[winterof79]

Quite a few outputs starting to show the PV being ragged about allowing for HLB to show it's head

[The PIT]

GFS back tracks and goes back to the Atlantic piling back in. Although it's delayed. ECM  sticks to it's guns and is no.1 chart for cold.

This must one of the longest spell with such a massive difference between the two models.

[nick sussex]

The ECM breathes some life into proceedings .

The GFS is on life support and the machines about to be switched off.

The UKMO is in a critical condition but the doctors still hold out some hope .

The Euros roughly agree on the key features but the ECM is more amplified , you have to look upstream over the USA to see the downstream effects of the handling of the phasing of the southern and northern arms of the jet.

This impacts the troughing to the west of the UK because that phasing develops a low which then effects the PV lobe over northern Canada .

Historically the GFS is poor at handling those set ups , the ECM might be a bit too amplified but it’s very unlikely to be wrong with the key features upstream at day 6.

I’d discount the GFS and save the trauma associated with following its upstream evolution , I would be shocked if it’s got the phasing and timing correct over the USA and Canada .

Edited December 30, 2018 by nick sussex

[Polar Maritime]

Temps still rising above the Pole..

Edited December 30, 2018 by Polar Maritime

[bluearmy]

1 hour ago, Steve Murr said:

A quick scan of the GFS ENS this morning reveals much more propensity for high lattitude blocking now post 180.

 

AO update later will be nice to see.

Still no zonal reset ...

[Summer Sun]

The ECM 850s mean peaks with a low of around -2 on Wednesday it then rises up to around +5 on Saturday and then drops away again to around -1 circa 8th/9th

Edited December 30, 2018 by Summer Sun

[northwestsnow]

32 minutes ago, bluearmy said:

Yesterday’s clusters split ridgy/troughy across the e Atlantic 50/50 by day 15. There are six right through the extended which tells you plenty ...... the extended mean is again benign this morning with the high anomolys hanging on .... the control not far from the op at day 10 but sinks back across the uk with the undercutting lows too far south across Europe to affect us. 

I did note the Ukmo at day 6 find a surface high over the pole in a way that the other models didn’t .... ec was a day behind and this did help to bring the Atlantic ridge north day 8/9.  Whilst the vortex ends and flows between siberia and Canada we will not build a HLB but there is a sniff on this ec op that me Canada may be about to lose its lobe in a bad place for us - are we going to see an Aleutian lobe form to draw it west??? .  ln the absence of any defined guidance away from the meh, may as well stick with the block ..... it looks set...... just in the wrong place for us. 

Rather than fog clearing it sounds like its getting thicker!!

 

[Guest]

Things are looking very much better than many on here seem to realise "including" the GFS 0z run! 

Although this model thread is intended for scrutinising and commenting on model output, I feel that many of the golden rules of model watching are being ignored by some of you. When we are looking for signs of broad scale pattern changes, we should be focusing on the wider picture and not the micro detail.  We are hoping to see signs of the wind reversal from the SSW in the high Arctic and close to the pole - so this means studying the northern hemisphere profile and not the UK/Euro charts (they will come into play once the pattern reset evolves). We know (or at least should know) that the models struggle with pattern changes, especially when we have 2 major upcoming changes in the background signals which are well underway - the SSW which has been well broadcast and the tropical forcing/influences which have been been referred to by only a small number of us and yet they are key (and this is not just the MJO which is only a part of the processes involved in the GSDM - Global Synoptic Dynamic Model including GLAAM - Global Atmospheric Angular Momentum and the torques). I will not comment on these in this post other than to say, that what we expected is falling into place and I believe (as I've said in a number of recent posts) that the tropospheric surface layers are much more conducive to downward propagation of the wind reversal than some think.  The expected surge in EAMT (East Asian Mountain Torque) is nicely underway and this will play an important role during the next few days and into early January.  The SSW is happening right now and a split looks likely around Jan 1st to Jan 3rd.  We should know very soon whether and to what extent that happens and then it'll be a question of how long it lasts.  The SPV (stratospheric polar vortex) will be undergoing further attacks but these may well not be necessary with the damage already likely to have been done.

To keep this simple, I shall now only focus on the models and what I feel we should all be looking out for.  The models have been tending to show slightly more amplification in recent runs anyway and this is not due to HLB (yet) but to how primed the lower atmosphere is with a generally weaker jet stream.  It is possible that we might see several days of greater Atlantic influence during the broad scale pattern transition. The models have (correctly IMHO) been narrowing that gap and extending the longevity of the current MLB and only modest amplification.  All this is happening in the 7 to 10 day time frame.  I will focus on day 10 to see how things are progressing in terms of what the models are showing but remember, I feel that they are not even half way there to factoring in all the background signals right now.  Several of you have already posted the ECM chart and as GFS has been coming in for a lot of stick (including by me) I shall look at their 0z output.

Day 10 - T+240

The GFS op run is very much an outlier but even this shows some amplification.  The key thing is that it is building HP near the pole - in this case on the far side.  A key sign of SSW surface impacts will be HP building strongly around that region - ideally centred nearer to or right over the pole.  This will be strong signs of the wind reversal and surface polar easterlies. 

The GEFS control run is more amplified with some ridging through Scandinavia and starting to build HP right over the pole. Even this is an outlier!  

This is the mean chart which shows an average from all 24 ensembles + the control run.  This should always be viewed carefully as "averaged out" pressure will not be the best way of of interpreting the actual flow. What it does clearly show is that HP is building around the pole.  

Now I "cherry pick" perturbation 11 to show what we are looking for - a full and strong reversal at the pole and already extending its influence with a proper Greenie high developing.  That's a split SPV and a nicely coupled strat/trop with the main vortex into central Europe. This evolution would start us off with a northerly but as the HLB really gets going, pressure should rise strongly around the top of the LP and then through Scandinavia with an easterly becoming established..... 

...just like this on the day 16 - T+384 chart.  Returning to day 10 - here's the ensemble panel.

All bar a couple have HP building over the pole and it's just the timing and stage of development that varies.  If you want a closer look - here's the link:

http://www.meteociel.fr/cartes_obs/gens_panel.php?modele=0&mode=6&ech=240

Click on the first chart and use the double white arrow (pointing right) at the bottom of the close up chart to run through all of them. 

I'm running out of time again.  For those that might accuse me of "ramping"  I am trying to show what we should be looking out for.  I am also saying that GFS is starting to embrace the changes.  If their 6z run was to be more like perturbation 11 then this place would be in meltdown. Then the following run might revert back to something much less exciting for coldies. The main thing is to watch things evolve over several days.  Much will be decided by around Jan 2nd/3rd in terms of the split.  Yes, there could be a delay but I actually feel that things will be brought forward when we factor in the +ve GLAAM and the +ve torques as well as the MJO.  It can go pear shaped but I believe that there are so many background signals more or less in sync and playing ball this time that we'll be treated to something very special.  David   
 

Edited December 30, 2018 by Guest
check charts, links and correct typos

[northwestsnow]

ICON moving towards Euro models?

Looks more HP influenced than the 00z run @120..

[nick sussex]

The MJO mystery continues .

The current location using the VP200 measure matches very well with the expected OLR .

The former forecasts continued progression east with movement into the more favourable phases over the next few weeks .

The MacRitchie MJO is almost into phase 6 . Whereas the normal modelling is slower.

Those continue to show large disagreements though as to what happens when the signal speeds up. 

 

Edited December 30, 2018 by nick sussex

[karlos1983]

 

@Mucka I bet you wished you waited for the ECM to roll out lol 

[Pinhead27]

44 minutes ago, winterof79 said:

Quite a few outputs starting to show the PV being ragged about allowing for HLB to show it's head

Thanks for the 'moving pictures'. To my untrained eye they give a much better idea of how things 'work'!

[SMU]

27 minutes ago, bluearmy said:

My winter forecast loves off the scale...

[nick sussex]

7 minutes ago, northwestsnow said:

ICON moving towards Euro models?

Looks more HP influenced than the 00z run @120..

It also has a similar phasing of both jets over the ne USA to the ECM .We ideally want phasing and as much amplitude as possible as that develops into a deeper low . As that runs east it will engage the PV lobe over ne Canada . 

Edited December 30, 2018 by nick sussex

[northwestsnow]

Cant help but feel the next few days(NWP) will be crucial for the Jan pattern..(or at least the 1st half)..

[Mike Poole]

Fascinating output at the moment, I'm minded of the period watching the modelling around the time of the last SSW in February.  There was much angst until the event had actually happened and the real signal gradually became clearer.  I expect much the same this time, we're not guaranteed the cold solution again, these events are all different, just pointing out the uncertainty has still to be resolved.  

One thing that is possibly worth noting that it does look now like a prolonged wind reversal in the strat i.e. this isn't going to be one of those technical reversal - just -occasions, which surely must account for some of the times an SSW doesn't lead to cold for the UK. 

The GEFS zonal wind chart shows the reversal on Jan 1, and all but 1 member still reversed at the end of the run some 2 weeks later,  with the mean about -10m/s throughout:

As this is the 0z suite, as others have posted there were some good members for trop evolution in that suite - all looking very promising.

 

Edited December 30, 2018 by Mike Poole

[Methuselah]

Well let's see how the 06Z pans out, as overnight doom and gloom often seems to evaporate as the daytime runs develop...?