Focussed Model Discussion

[Paul]

This is a sister thread to the looser Cold hunt - models and banter thread, and is a stricter, more focused and generally more in depth model discussion. 

Thread Moderation
The team will moderate this thread to keep it on topic and focused on the models. Please only post model related discussion in here.

You are welcome and encouraged to cross-post on this thread and the models/banter thread. 

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Model Comparison
Global Jet Stream
Stratosphere

[Rocheydub]

I'm afraid the pub run shows little difference in the Gin corridor. However, it shows enough to make me watch the next few frames. I was hoping the ICON was going to lead the way. It's very early in the run, but I'm not hopeful of it following the ICON at this stage, we'd have needed earlier pressure changes.

[Frosty.]

Looking at the Gfs 18z focussing on the early stages it gets rather interesting  with snow for various parts of the uk..and not just on hills!❄️

[Empire Of Snow]

18z, the Icelandic LP at 138h forces the Azores to ridge eastwards underneath Scandinavia, similar scenario to the ECM if I'm not mistaken. 

[Empire Of Snow]

180h another LP at 980mb West of Ireland will mess things more. Possible Easterly set up after it slides? Nope, it's moving NE. 

[Rocheydub]

2 minutes ago, Empire Of Snow said:

180h another LP at 980mb West of Ireland will mess things more. Possible Easterly set up after it slides? 

It's not very clean, you could be right though. The NWP are all over the place at 72-96. I mean more than the usual subtle changes. Usually happens during SSW's but they normally converge at 96-120. This is the worst I've ever seen for our locality on the planet...

[frosty ground]

7 minutes ago, Empire Of Snow said:

180h another LP at 980mb West of Ireland will mess things more. Possible Easterly set up after it slides? Nope, it's moving NE. 

Massive ridge is about to be thrown up at 228 hours

[Rocheydub]

Looks like a link up is about to happen in FI between Atlantic and Arctic high.

 

[matty40s]

The USA weather bloggers and forecasters seem very miffed that the storm seems to be moving more to the NW than forecast. .....this is playing directly into our hands, the ECM wasn't expecting this.

[Banbury]

6 minutes ago, Rocheydub said:

Looks like a link up is about to happen in FI between Atlantic and Arctic high.

 

Squeezed out on this run

[CSC]

1 minute ago, matty40s said:

The USA weather bloggers and forecasters seem very miffed that the storm seems to be moving more to the NW than forecast. .....this is playing directly into our hands, the ECM wasn't expecting this.

Do you have any links you can provide?

[Midlander]

3 minutes ago, matty40s said:

The USA weather bloggers and forecasters seem very miffed that the storm seems to be moving more to the NW than forecast. .....this is playing directly into our hands, the ECM wasn't expecting this.

‘‘Tis interesting but what does that mean for us please, for those who still hope for colder conditions would we want the storm further NW?

[Banbury]

240 + is excellent but ALL FI 

[Empire Of Snow]

FI is dreamland in this run. 

[Man With Beard]

I've had an evening of reflection (as you do! ), checking the end again, checking the ensembles, and, to my surprise and maybe anyone who has read my posts this week... I don't think the ECM ensembles have been massively wrong at all this week. Yes really. They've made a error with the placement of the low over Europe. But there will be a very short easterly, and the whole sinking trough, followed by minor ridge, followed by another sinking trough - well that was always the pattern. I think two things have happened. First, the fact that uppers were programmed to be minus 5C or below was misinterpreted (I'm including myself here). Uppers of this level on a mean chart do not represent extended cold. You need minus 7 or 8 on a consistent basis for that. Minus 5C generally results in periods of cold interspersed with less cold periods. Second, the Scandi High was a red herring. It never showed as a strong option on the ensembles (1030mb mean is my usual benchmark). Alas, I think I got caught up with the prospect of having some cold at all, and perhaps lost a bit of balance in my assessments. I hope I learn. Will I ever

[John Cox]

2 minutes ago, Man With Beard said:

I Alas, I think I hit caught up with the prospect of having some cold at all, and perhaps lost a bit of balance in my assessments. I hope I learn. Will I ever

Looking at GFS 276+ i suspect you + all of us never will.

 

[Roger J Smith]

With regard to that U.S. low, it has been tracking a bit further north each day relative to model runs and now in reality is pushing its snow envelope about 200 miles further north(west) than many of the models had shown as recently as yesterday. It may not necessarily be a good thing as the track is now going to take it in more of a straight line to where it was going to go in an arc, and that arc was going to be pointing more northerly than the straight line so, by 48h it's a net loss to overall westward shift of pattern features. However, this shift over the past 2-3 days illustrates that the models are only approximately catching the full reality of the here and now part of the run, which means the medium term and longer term portions are almost certain to bust badly. In what direction is the operative question. I don't know but have the hunch that the slowly dying Atlantic is the real story and nature abhors a vacuum so something else (a northerly or easterly) will arise to take its place. Would lay a bet that either the 00z or 12z model suite swings back to the cold end of the spectrum and the cold will then be closer to reliable time frame. We'll see about that one. 

[Jason M]

Very few easterlies in the GEFS rolling out (now at 150 hours). The GFSP is bringing in a westerly by 114 hours. I think the good ship 'easterly' is about to sink below the waves. The band is still playing on the bridge (NAVGEM, JMA the odd GEFS) but they are expected to rush to the lifeboats very soon. 

Still, not to worry we can do it all again in...yes you guessed it...….10 days time!! 

[Singularity]

Key difference beteeen the potential by late next weekend onward and that for the week ahead?

This coming weeks’ requires a precise coming together of events to bring more than transient notably cold weather to the UK, but the week after’s requires that to prevent such a thing.

 

This being as the SSW impacts become dominant hemisphere-wide instead of regionally.

 

That being said - given the positioning of the lower stratospheric ridge, I feel it’s unlucky not to get at least a brief shot of deep level cold from the east this coming week. So I’m hesitant to draw a line under that chapter just yet.

I see Fergie is of similar mind .

He and MetO are right to keep emphasising the cold and snow theme toward end of Jan and on into Feb; the HLB signals for that dwarf anything we’ve seen for the week ahead.

[Purga]

2 minutes ago, Singularity said:

Key difference beteeen the potential by late next weekend onward and that for the week ahead?

This coming weeks’ requires a precise coming together of events to bring more than transient notably cold weather to the UK, but the week after’s requires that to prevent such a thing.

 

This being as the SSW impacts become dominant hemisphere-wide instead of regionally.

 

That being said - given the positioning of the lower stratospheric ridge, I feel it’s unlucky not to get at least a brief shot of deep level cold from the east this coming week. So I’m hesitant to draw a line under that chapter just yet.

I see Fergie is of similar mind .

He and MetO are right to keep emphasising the cold and snow theme toward end of Jan and on into Feb; the HLB signals for that dwarf anything we’ve seen for the week ahead.

[WhiteFox]

15 minutes ago, Roger J Smith said:

However, this shift over the past 2-3 days illustrates that the models are only approximately catching the full reality of the here and now part of the run, which means the medium term and longer term portions are almost certain to bust badly.

 Would lay a bet that either the 00z or 12z model suite swings back to the cold end of the spectrum and the cold will then be closer to reliable time frame. We'll see about that one. 

I think you may be right. Looking at previous MJO forecasts, we were originally looking at an emergence into late phase 4 then quickly through to phase 6. One of the things that has happened over recent days is that it is now forecast to emerge towards the start of phase 4. This then delays the extra kick towards blocking that may have provided what we needed to land the blocking required. 

With the SSW the signal is there for blocking in northern latitudes, but the key for us is getting it in the right place. The (probable) failed easterly required threading through the eye of a needle and, as so often, this didn't work out.

But, background drivers are moving more in our favour, so it may be that we are looking at threading the eye of the needle to not get a colder outcome going forward. This may not be picked up on the models quite so clearly well in advance as there are clearly struggles with a pattern of background signals which have rarely been modelled before.

Plenty of interest, and I definitely feel that we won't have to wait too long. In the meantime there is still plenty of interest in the pattern over the next few days.

[Man With Beard]

D13 clusters (well one cluster) . Pretty black and white (well red and purple). That should be cold for the UK all day long! (and much longer!) 

We will see! 

[kold weather]

Ok so my general analysis looking at all the ensemble data from the 12z suite is this:

1: Easterly is done for in all probability, stil a chance the blocing high holds for longer than planned, but actually not sure its really going to benefit us and a clean break will probsably allow phase 2 onwards a chance.

2: A portion of the PV lobe over Canada starts to get elongated and relocates SE towards NW Europe (roughly) ariund 216hrs. Possible cold WNW/NW flow, though how cold is still somewhat dependant on just how much cold air comes withthe PV.as it stretches out. I'd suggest marginal snow events quite likely and watch out for possible higher levels of storminess as well, especially from any secondary lows that come in on the southern flank, could fire up quite fast.

3: Upper high forms over Greenland some point between 180-240hrs and helps to shove the upper low set-up to the SE. Should develop into quite a good set-up aloft, may not be ultra robust but it will do the job and the Azores High should help to keep propping up the pattern and keep it pretty stable. I would think for now northerly to maybe NE most favoured. If we are lucky that could lock into quite a significant pattern that holds for a time.

[bluearmy]

45 minutes ago, Man With Beard said:

I've had an evening of reflection (as you do! ), checking the end again, checking the ensembles, and, to my surprise and maybe anyone who has read my posts this week... I don't think the ECM ensembles have been massively wrong at all this week. Yes really. They've made a error with the placement of the low over Europe. But there will be a very short easterly, and the whole sinking trough, followed by minor ridge, followed by another sinking trough - well that was always the pattern. I think two things have happened. First, the fact that uppers were programmed to be minus 5C or below was misinterpreted (I'm including myself here). Uppers of this level on a mean chart do not represent extended cold. You need minus 7 or 8 on a consistent basis for that. Minus 5C generally results in periods of cold interspersed with less cold periods. Second, the Scandi High was a red herring. It never showed as a strong option on the ensembles (1030mb mean is my usual benchmark). Alas, I think I got caught up with the prospect of having some cold at all, and perhaps lost a bit of balance in my assessments. I hope I learn. Will I ever

The ridge pushing in by the flattening of the flow in the mid term was not forecast by the ens mean and anomolys  ......it shoud have stayed more amplified to to the nw and is flattened would have toppled more into scandi .... we are certainly missing some amplification from the ec model on verification ...............

[Catacol]

Cross posting this from the cold thread, in case it is worth placing here too...

I don’t think the old model thread covered itself in glory today. Disappointing runs for sure - but if you remove the op run hype of the previous day solid predictions from technical posters of the pattern for the end of the week were conspicuous by their absence, and the reason was simple: nothing from Wednesday onwards ever looked nailed on. I’m not sure why people hang on individual runs so much and lose sight of forcings and hemispheric pattern....but it has been the case all along that the forcings of the SSW and Pacific have been clear to see, but equally clearly timings have been an issue. Can interested amateurs hope to get timings right when even the Met, with their supercomputer and dedicated professional staff, have also struggled this season....with the approach of colder conditions consistently put back? I think not. 

The droppng of the trough into Europe midweek was the only feature of the pattern change that was “easy” (comparatively) to spot at around the 192 range but the specific direction of travel after that has been hazy.

However let’s be clear. Firstly, as I tried to show last night, models all have their frailties and ECM is not king all of the time. On that basis take the full suite we have available and never right any off entirely. Taking next week as the focus there remains a huge amount of uncertainty as to what happens once heights over Europe have lowered, and while a raging easterly now looks unlikely for Thurs/Friday this doesn’t mean an easterly is out the question soon after. Secondly - and related to this - ensembles are still good, and if you cycle back to the wise words of John H earlier today the prognosis remains good. Thirdly the drivers that a few people today have tried to knock (and if we’d think we can’t improve our weather understanding then why are we here....hence such posts seem extremely odd to me) are still here and approaching peak impact. If an easterly is lost for Thurs/Fri then we move on to the next opportunity, somewhat disappointed but still optimistic given those drivers. And lastly - some people may get a good snow event on Tues/Weds....an event we were able to signpost at around a week and should have people pleased!!! Sitting in the SW I’m a bit envious of those in the midlands and north who may cash in....good luck to you all.

Finally - good points have been made today about probability. Has to be true. We are never dealing in certainties when looking at forecasting beyond 72 hours ( and often at considerably less....) and it is worth reflecting on this. Probability means that outside chances can happen. And huge favourites don’t always come out on top. Reflect on that. As one fellow Scottish Rugby fan said earlier - bloody good job too. If the outlier and the underdog was automatically doomed the world would be an extremely dull place. So as we are all weather enthusiasts in here, perhaps we should cling to the understanding that hunting snow is a long odds game in the UK and be comfortable with that, or go find another hobby.