Model discussion highlights

[Tamara]

26 minutes ago, DJ Fart said:

Sorry, Tamara, you're wrong. 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

It's "Bom dia a todos".

Sorry, just an example of how a small detail can have a big knock on effect! (Relevant, eh?!)

But joking aside, that's a fantastic post, thank you for taking the time to write it and I hope you take my terrible joke as intended. 

 

Typo indeed. Thanks for pointing it out

In respect of the pattern, I am very interested in the stratospheric lead as the second half of the winter approaches and under the tropospheric considerations as laid out again in todays summary and which other GSDM analysis from @Met4Castand @Catacolare equally observing.

There is so much poleward tropospheric ammunition to hand, it does make one wonder how the polar field will respond in respect of persistent diminution bombardment. There is an argument for suggesting that too much forcing can actually alter usual pathway responses. But the GSDM diagnostic fully evidences the latest seasonal updates such as from Glosea.

The kayaks and shuffled polar roadblock are emphatically there to see.

Original post: https://community.netweather.tv/topic/99760-model-output-discussion-colder-but-how-cold-and-for-how-long/?do=findComment&comment=5005206

[MattH]

11 minutes ago, Catacol said:

I think it would be hard to find a better setup than that about to unravel. Only solar is out of ideal kilter but on its own, irrelevant.

-MJO amplified and back in the west pacific in the final third of this month 

- GLAAM has remained high, further surge expected. +EAMT?

- Vortex is weakened and possibly about to split

- Scandy has been cold since the autumn. There is cold nearby to tap into

- eQBO firmly embedded, ENSO Nino with +IOD now done and dusted

These are the keys for me. I’m not moving from what I said a few days ago. Cold for a long time..

All valid points here and just replying to this so I can post some GWO analogs as requested by @Met4Cast about this expected rise in the GWO once again during the second half of January. As per the MJO plots mind, don't take a face value, but as you can see the overall likely outcome is obvious and supports all other ideas and information...

No time at the moment for anything further, but yes, as per usual, be extremely cautious (everyone!) about individual model runs and variability, especially at longer lead times. The above quick set of bullet points is exactly what highlights the next 4 to 6 weeks and there is simply no reason to change all long-range thoughts, plus also the consistent signal from the Seasonal Models, for months, for the second half of the winter to be significant in terms of colder synoptics etc.

Cheers, Matt.

 

Original post: https://community.netweather.tv/topic/99760-model-output-discussion-colder-but-how-cold-and-for-how-long/?do=findComment&comment=5005845

[Met4Cast]

1 minute ago, Lampostwatcher said:

Most of them were Midlands south not south into france

The majority were south of the UK with some into southern England.

Red lines show the position of the warm front across the 00z EPS suite. It'll be interesting to see this chart from the 12z run.

Original post: https://community.netweather.tv/topic/99760-model-output-discussion-colder-but-how-cold-and-for-how-long/?do=findComment&comment=5005760

[Tamara]

5 minutes ago, MattH said:

All valid points here and just replying to this so I can post some GWO analogs as requested by @Met4Cast about this expected rise in the GWO once again during the second half of January. As per the MJO plots mind, don't take a face value, but as you can see the overall likely outcome is obvious and supports all other ideas and information...

No time at the moment for anything further, but yes, as per usual, be extremely cautious (everyone!) about individual model runs and variability, especially at longer lead times. The above quick set of bullet points is exactly what highlights the next 4 to 6 weeks and there is simply no reason to change all long-range thoughts, plus also the consistent signal from the Seasonal Models, for months, for the second half of the winter to be significant in terms of colder synoptics etc.

Cheers, Matt.

 

January/February 1978 comes to mind with a match to present GWO/GSDM expectations and also the bulleted points. The diagnostic as discussed in my own post earlier today in considerable details suggests a sustained Nino attractor phasing principally focused on Phases 5 & 6 (high amplitude) set against stratospheric diminution as we head to the late Jan & Feb period.

The GWO spent much of February 1978 in these phases and the Icelandic/Greenland roadblock and very active sub tropical jet are well known for their high impact conditions for those of you in the UK.

In this respect, take note of the disrupting jet stream of January 78 as arctic height rises forced the pattern. While each situation is taken on its own merits and never is exactly the same, especially in the changed climate background these days, it is still worthwhile taking present NWP into context on the basis of the forcing similarities

Boa noite. 

 

Original post: https://community.netweather.tv/topic/99760-model-output-discussion-colder-but-how-cold-and-for-how-long/?do=findComment&comment=5005882

[Catacol]

2 hours ago, Scott Ingham said:

What do you think to the gwo looking like it’s hardly been touched? 
 

Me personally I’m excited for the next tropical wave and consequent rise in AAM off a good base state! 

I think it would be hard to find a better setup than that about to unravel. Only solar is out of ideal kilter but on its own, irrelevant.

-MJO amplified and back in the west pacific in the final third of this month 

- GLAAM has remained high, further surge expected. +EAMT?

- Vortex is weakened and possibly about to split

- Scandy has been cold since the autumn. There is cold nearby to tap into

- eQBO firmly embedded, ENSO Nino with +IOD now done and dusted

These are the keys for me. I’m not moving from what I said a few days ago. Cold for a long time..

Original post: https://community.netweather.tv/topic/99760-model-output-discussion-colder-but-how-cold-and-for-how-long/?do=findComment&comment=5005813

[The Northern Ramper]

Tamara has just casually thrown 1978 out there as the most likely set up, there has never been such a ramp.

Original post: https://community.netweather.tv/topic/99760-model-output-discussion-colder-but-how-cold-and-for-how-long/?do=findComment&comment=5005909

[Met4Cast]

EXETER KEEP THE FAITH! 

Extended update via app, they see the block & hold holding on into February! 

Original post: https://community.netweather.tv/topic/99760-model-output-discussion-colder-but-how-cold-and-for-how-long/?do=findComment&comment=5005025

[nick sussex]

5 minutes ago, The Northern Ramper said:

Tamara has just casually thrown 1978 out there as the most likely set up, there has never been such a ramp.

That’s funny because the end of 1978 31st December I was flying back from Cyprus with family into Heathrow and there was loads of snow and the North Circular was bedlam .

And I’m flying back next week from Cyprus around the time of the Atlantic low drama .

Is this a sign ! 

Original post: https://community.netweather.tv/topic/99760-model-output-discussion-colder-but-how-cold-and-for-how-long/?do=findComment&comment=5005919

[Eagle Eye]

Rebounding NAM reflection, initial Strat - VE NAM imprinting in the Trop w/the development of the Greenland high but due to it being forced from a weak - VE NAM, the wave reflection ended up being a weak imprint. However, it managed to drive back up and met an Arctic reversal so wavebreaking should force the - VE NAM down again, probably more delayed into late January/early February. This is response two of the tripole in response to a SSW and despite this not being a major SSW, it's acting like one due to the initial wave reflection. 

Original post: https://community.netweather.tv/topic/99760-model-output-discussion-colder-but-how-cold-and-for-how-long/?do=findComment&comment=5006005

[Cambrian]

It looks like the ECM is drawing up even more fierce battle lines for the middle of next week.

If we compare yesterday’s 12z ensemble mean for day 8,

  

with today’s for day 7, 

  

the low to the southwest is markedly deeper on today’s run, though clearly stressed and stretched west-east. The 0 degree isotherm is further north.

However, this is countered by the low heights associated with the Scandinavian trough being lower over the northeast of Scotland and the -8 degree T850 being further south over Scotland too. 

Milder to the south, colder to the north, a deeper low, steeper pressure and temperature gradients across the UK and Ireland - where gets the snow is just one part of the equation, nowhere near being resolved. The likelihood of it being highly disruptive is the other, and that has markedly increased today. 

Original post: https://community.netweather.tv/topic/99760-model-output-discussion-colder-but-how-cold-and-for-how-long/?do=findComment&comment=5005929

[Snowman.]

Wales burried, snow for many, snow to rain then back to snow for those further south. Red warning out 100% imagine the scenes.

Original post: https://community.netweather.tv/topic/99760-model-output-discussion-colder-but-how-cold-and-for-how-long/?do=findComment&comment=5006083

[Kasim Awan]

Merged polar low & Atlantic low snow maker moving South at 126 hours.

Original post: https://community.netweather.tv/topic/99760-model-output-discussion-colder-but-how-cold-and-for-how-long/?do=findComment&comment=5006022

[Nick F]

Morning.

Great EC det this morning, cold throughout and ends with a cold high.

Snow event for central Scotland on Tuesday as that secondary low that develops in the polar flow near Iceland drops southeast. Then another potential snow event across the far south mid-week, as an Atlantic low tracks east, but still uncertainty over its track for now.

UKMO looks really good too up to Thursday, looks like a cold NE flow developing after then.

GFS looks rather too bullish to turn it mobile, unsettled and milder off the Atlantic.

GEM looks like it goes down a similar turning mobile / milder route to GFS

Stick with the Euros IMO.

 

Original post: https://community.netweather.tv/topic/99760-model-output-discussion-colder-but-how-cold-and-for-how-long/?do=findComment&comment=5006453

[snowking]

21 minutes ago, Kasim Awan said:

For 8 days of very cold weather that is very poor snow coverage.

Kasim come on, I appreciate you’re commenting at face value on the exact precipitation output shown in this single deterministic run, but you’ve been here long enough to know how poor modelling of precipitation is at such range under such conditions.

———

This next part is not aimed at you because I appreciate you try to provide a face value overview direct from modelling. But I do think in general these forums in the morning might provide psychologists with the best possible data source they could have for the effects of sleep deprivation.

Nothing has changed from where we were yesterday. Deterministic runs are still just picking scenarios at random from the range offered in the ensemble suites over the last few days. Usually at the sort of ranges we’re talking you would start to err towards the view that deterministic runs, with their superior resolution, should be getting a handle on things. But this is such a difficult setup to compute, far from the usual west - east flow one would expect locally (never mind globally) that I don’t think the deterministic runs are any more use to us right now than the rest of their respective suites.

And whilst it’s a fun exercise in imagination, there is absolutely no use in looking at any form of precipitation chart beyond (if I’m being really generous) 90 hours other than for a brief fanciful glance if you really want to torture yourself.

Original post: https://community.netweather.tv/topic/99760-model-output-discussion-colder-but-how-cold-and-for-how-long/?do=findComment&comment=5006518

[Nick F]

00z UKMO 'current laying snow' chart animated through next week until Thursday suggests northern areas look to see greatest chance of laying snow, probably from that low that forms near Iceland and drops SE and also from showers, but also a chance in the southeast as one or two lows track east close to the south.

Although it's too far off to forecast snow for now, seems a reasonable assumption, for now, to think Scotland, N England and N Ireland stand to see greatest chance of snow, lower chances further south, unless the Atlantic lows track further north, but the low from the southwest more likely ending up further south into France.

Original post: https://community.netweather.tv/topic/99760-model-output-discussion-colder-but-how-cold-and-for-how-long/?do=findComment&comment=5006567

[Catacol]

21 minutes ago, Tamara said:

Bom dia e todos

I make no apologies for yet again re-pasting this sequence originally posted just prior to New Year, because it has become an even more focused roadmap. Not just for the upcoming 10 day period, but indeed confidence increasing as a blue-print for well into the second half of the winter:

....................................................................................................................................................................................

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

......................................................................................

To update the template of this analysis:

A very starkly high octane angular momentum budget is emerging and prolific within the global-wind-flow budgets. This translates to stockpile ammunition supply levels for deeply sustained poleward amplification eddies taking on veritable tanker sized reserves.

Based on how much tropospheric led influence there has been on the NH pattern in recent weeks since the starting pistol was fired to destabilise the polar profile, these further poleward swathes of +ve momentum transport take on especially egregiously gargantuan proportions for future wholesale instability and implosion across the polar field. In this respect it is not hard to comprehend the latest sentiments of Amy Butler and how she sees the synoptic pattern imprinted

The copied post referred to a baseline phase landing place for the Global Wind Oscillation. This baseline, ahead of the strongest wind-additions yet c/o eastward progressing high amplitude MJO wave back to the Pacific has remained higher than intermediate phase 4 (as discussed in the copied post)

The latest GWO phasing, even under present lull stopgap at very low amplitude 5/6, reflects the remaining considerably high levels of +AAM anomalies within the atmospheric circulation as aggregate total AAM. (Phase 4 GWO would be more suggestive of flatter return of the jet and greater attrition from the Atlantic against blocking. (Though even this sharpens somewhat against late Jan/early Feb wavelengths)

This GSDM wind flow budget situation is significant. More on this shortly.

The GWO is a phase plot depiction of aggregate wind-flow within both the tropics (MJO related) and the extra tropics as a measure of how efficiently propagation of wind-flow is proceeding between the tropics & extra tropics. This matters, because it is a barometer for synoptic pattern (poleward) amplification potential and provides a diagnostic towards directional flux of wind-flow eddies.

Poleward flux has now become quite supercharged

What of the significance of this?

As the intraseasonally driven MJO crosses the Maritimes at high amplitude, then very strong +ve torque mechanisms will be re-engaged to over top a system already awash with +AAM anomalies. The GWO likely to drill upwards into very high amplitude Phase 5/6. Taking into account maximum winter wavelengths, then this teleconnects ever more strongly to entrenched -ve NAO (under chaotic stratospheric diminution to spotweld a deeply -ve Annular Mode).

How can this be visualised?

The upcoming next cascade of westerly wind burst propagation into the extra tropics creates white water rafting within the sub tropical jet from the Equatorial Pacific downstream to the Atlantic -at the same time as the polar profile becomes riven with -ve mean zonal -ve wind anomalies. Defining solid roadblocks for southward directive of a deeply unstable thermal boundary.

How can this in turn be visualised?

With deeper upper cold air ensconced north of the polar boundary, this leads to feedbacks of entrenched surface cold with time to feed an ever starker thermal boundary, This encourages and emboldens larger progressions of numbers of kayaks slipstreaming below it. This translates to trains of low pressure undercuts - and it is not difficult to envisage the potential for high impact weather events to unfold in such a scenario. 

The kayak posse delivers an "atmospheric river" of saturated sub tropical air and a large jump of temperature into the upper teens for my part of the world well below the thermal boundary at the same time as in contrast...

.... that is better left to the mercurial imaginations of any members who might be looking in from NW Europe.

Putting all this diagnostic analysis together, it is hard to see anything other than a tanked -ve Annular Mode relationship dominating much of the rest of the winter. However, and as ever, further analysis is wholly prudent to document how proceedings unfold.

Muito obrigada. Feliz quarta-feira

 

 

 

Quite excellent. I was going to post something later of a similar but much less well explained and detailed nature. I won't bother now. 

The drivers that have lined up to produce this first amplification phase and are lined up to produce the second surge of amplification next week are going nowhere anytime soon. As I posted before, MJO progression is clear and well timed. I think week 22-29 January will be the least cold section of the next month or so but GLAAM has remained high with little damage caused by the ping back of relative AAM progression. We are shortly going to see another surge that will set us up beautifully, given lag, for the end of the month and on into February.

But this is a poor summary compared to the post above. Read that and wrestle with its contents.

As to next week - no change. Snow will be in the mix whether those who enjoy posting the least favourable interpretation of current signals and output like it or not. 

Original post: https://community.netweather.tv/topic/99760-model-output-discussion-colder-but-how-cold-and-for-how-long/?do=findComment&comment=5005117

[Nick F]

Looking at the extended EPS spread, the 00z det was on the cold side later on but by no means without support, the TWO and meteociel graph makes it look like an outlier, but it's not really on the wetterzentrale spread.

The mean does rise though towards day 10 and after, so we have to assume, for now, that it will turn milder after next week for a time, as the Canadian and north European TPV lobes merge to cover the far N Atlantic in low heights driving a more westerly flow. This ties in with background larger scale teleconnections e.g. MJO motoring through 'warmer' phases at decent amplitude.

Still a decent spike in precipitation for Weds 17th on London EPS, so still suggest a good chance of precip and likely snow with the T850 mean below 0C, in 1st chart posted above.

Original post: https://community.netweather.tv/topic/99760-model-output-discussion-colder-but-how-cold-and-for-how-long/?do=findComment&comment=5006604

[Catacol]

1 hour ago, TillyS said:

The models are all miles better than they looked 2 weeks ago. Just nowhere near as good as they looked 2 days ago. And with a week to go, that’s a worrying trend.

Neither worrying, nor a trend. The up/down movement of NWP does not constitute a trend. It is mere noise. The ensemble data for the next 7 days or so has been near rock solid for a long time now - the problems come when people jump on the micro scale movements each morning and consistently emphasise any slight sense of a "downgrade" (whatever that means.) As a reminder - ensemble data for the middle of next week today:

and the same day from nearly a week ago

For the week after next it has been flagged by all those with knowledge of how the pattern is moving that some degree of relaxation is inevitable. Is this worrying? No. It is the direction of travel we have laid out. The exciting prospect is that NWP is likely to overestimate the speed of cold breakdown and we have potential battleground scenarios a plenty in the mix for much of that week. Personally, I think the south will miss the snow at that point but the north could do very well indeed.

And then - once again flagged and evidenced and therefore not a worry - we have the shift back to a more amplified pattern. Currently NWP products are not picking this up or it is out of range, though monthly products that came out yesterday have screamed blocking through February loudly. This is going to be very interesting to watch unravel.

Perhaps a routine that doesn't involve jumping into a negative interpretation of imprecise data modelling each morning might be worth considering.

 

Original post: https://community.netweather.tv/topic/99760-model-output-discussion-colder-but-how-cold-and-for-how-long/?do=findComment&comment=5006594

[Nick F]

No point squabbling over how dry it will be, too far away to pin down where troughs, convergence zones or lows will track next week that may bring snow

I think the key to the longevity of next weeks cold spell will be how long the TPVs over Canada and N/NE Europe are kept apart by ridging mid-N Atlantic and Greenland. 

GFS/GEM ops are more bullish to merge to 2 TPVs over the Atlantic later next week, turning the flow more zonal / milder / unsettled. While EC det keeps the two upper vortices apart. However, as already posted, the mean of both GEFS and EPS do join the two together by day 10, with the more zonal look taking over.

But the smoothed out mean may not be the best guidance at handling upstream developments and how the upper flow and surface lows over the Atlantic interacts with the cold air entrenched over northern Europe

Original post: https://community.netweather.tv/topic/99760-model-output-discussion-colder-but-how-cold-and-for-how-long/?do=findComment&comment=5006538

[johnholmes]

Thursday same charts

The NOAA chart now shows all contours into UK are from a westerly point but also still from a cold source, (NW Canada/Alaska) and about 528 DM maybe just above.The upper trough has moved west, from between Iceland and nw Scotland to be nearer Iceland. There is little indication of any troughing into Europe for the third chart in succession.

ECMWF  just looking at the -5 C 850 MB line, (period 17-21 Jan) starts S Wales to the Thames and ends up over the northern tip of Scotland, with a general WNW 500 MB flow from the initial N’ly

Finally the T+144 to 168h Met O upper air and surface charts, (15-17 Jan)  show  the upper ttrough  extending to some extent into southern Europe but not as sharp as the issue I showed on Tuesday a N’ly on the first day changing to a deepish surface feature with a SW;ly flow for all but the far north of Scotland by the end (17 th=Wednesday)

So what can we suggest for the surface weather in the 6-10 day and then the 8-14 period some of these charts cover? Deepish cold to start by the end of this weekend over pretty much all of the UK. Dry for most but mini troughs are quite possible in the N’ly (they do often feature in these flows), a few snow showers around coasts early next week, enhanced over any area affected by a trough. There is a probability of the low shown on the Met O T+144 of spreading some snow into areas, say Midlands south possibly turning to rain in the SW. How far north this gets is difficult to suggest and best to wait to see how the synoptic models deal with it, by Sunday this should be getting clearer! The fact that NOAA charts show a westerly by the end of the 6-10 day period coupled with this being shown on the 8-14 (this is the third consecutive such chart,) does suggest to me a more unsettled and rather cold westerly with lows eventually succeeding in moving less cold air, perhaps only temporarily in the 10-14 day period.

Beyond that, not for these charts

Climate Prediction Center - 6-10 Day 500mb Outlook

WWW.CPC.NCEP.NOAA.GOV

Original post: https://community.netweather.tv/topic/99760-model-output-discussion-colder-but-how-cold-and-for-how-long/?do=findComment&comment=5006868

[Ice Day]

Another improvement in the GEFS out to day 8 (0z / 6z) - this is for my area

A fairly significant improvement I'd say.  It's going to be pointless looking any further at the moment IMO, but upgrades in the short/medium term is what we want to see.

Original post: https://community.netweather.tv/topic/99760-model-output-discussion-colder-but-how-cold-and-for-how-long/?do=findComment&comment=5006829

[bluearmy]

Sadly I don’t get much of a chance to put this into practice but the ens mean 24 hour snowfall charts are a good way of judging the trends on where the snow line is 

once within day 5, you’d expect the ops to be more reliable as a broad brush risk indicator 

The geps having only 20 members are a little more crude than gefs and eps and given the operationals propensity to lay every flake and sleet drop as cover perhaps taken with a pinch of salt 

most recent run first 

eps

  
 

Gefs

  

GEPS

 

 

 

Original post: https://community.netweather.tv/topic/99760-model-output-discussion-colder-but-how-cold-and-for-how-long/?do=findComment&comment=5006860

[Lord Grogon]

So my non-technical take on what will happen. Based on nothing more than my direct experiences, plus reading this site.

1) It will get much colder over the weekend. There will be much talk in the media of "stiff northerlys" and "arctic blasts"

2) A few places in the north will get snow showers. But on the whole most places will remain dry. Some will grumble at this, but others will maintain that we should keep the faith.

3) There will be much talk of a big midweek snow event. But ultimately it will trend southwards and miss the UK.

4) There will be louder grumbles,  but others will say "at least it is still cold".

5) A much bigger low will approach from the west. There will be talk of "battleground scenarios" and "midlands north event"

6) The low will pile through. There will be snow on the leading edge that will produce dramatic pictures on the news. But overall it will soon become a rainy/slushy mess. It will mark the end of the cold spell and people will be sad.

7) Others will say "Doesn't matter. Background signals are supporting an even better cold spell opportunity next month." There is much rejoicing and the chase is resumed" 

Original post: https://community.netweather.tv/topic/99760-model-output-discussion-colder-but-how-cold-and-for-how-long/?do=findComment&comment=5006917

[Tamara]

References, as ever, crop up to x+y= responses to MJO phases in isolation. Again, to keep reiterating, tropical AND extra tropical wind-flow has to be assessed in respect of synoptic responses. There is no linear single interaction/response between the tropics and extra tropics without looking at directional flux of propagation of wind-flow as well, at this time of year, considering the interactions between the troposphere as a whole and the polar field.

Eastward moving tropical convection waves (MJO) at high amplitude and set against very high +ve inertia within the aggregate global wind-flow budget is going to retain greater amplification tendency than a situation where angular momentum and angular momentum tendency are both suppressed. In this sense, and taking the present scenario where the MJO is moving through the so called "La Nina response phases" of the Maritime continent, it is not as simple as equating this to increased polar jet+ Atlantic westerly forcing = mobile +NAO pattern and breakdown of blocking patterns.

The more extended period is fraught with so many pitfalls for NWP that I would genuinely stop trying to second guess the outlook for the last third of January. It makes sense that the Canadian lobe of the polar vortex will send energy towards the Atlantic but based on both the modelling within the polar field, which is highly unstable, and so much latent +AAM inertia within the aggregate wind-flow budget and then in addition to all that  - another very sizeable push of inertia and momentum between the tropics and extra tropics during the period under consideration;  there are so many hurdles for NWP to handle that extended ensemble data is next to rudderless at this time.

This assessment is intended to be neutral in respect of the overall diagnostic - but it happens to be one that continues to keep cold blocked patterns in the ascendancy for N/NW Europe and tendency for the white water rafting within the sub tropical jet stream to be adjusted upwards within modelling suites day on dy. That doesn't inextricably mean another 1947 redux, but probabilities do suggest that attempted Atlantic breakdowns will be attritional and prone to be shorter lived, if they occur, rather than any wholesale mobile pattern change.

Increased westerly mobility has higher probability for more southern parts of Europe - overall.

Original post: https://community.netweather.tv/topic/99760-model-output-discussion-colder-but-how-cold-and-for-how-long/?do=findComment&comment=5006946

[Tamara]

6 minutes ago, RainAllNight said:

It sounds as though you don't think we need to be worried about these ensemble means. I'd be thrilled if you were right!

No. In a nutshell. There is such a wide envelope within those means, and, as outlined the overwhelming suspicion that the jet stream will keep tending to align to send too much polar jet energy on a flat eastward path, that the best that can be said is that assessment of these means should sensibly be incremental day on day. This, much rather than the folly of instant face value extrapolations. Extended means are especially volatile, over smoothed, and subject to considerable further much more detailed evolution than they are within much more traditional zonal winter patterns.

Original post: https://community.netweather.tv/topic/99760-model-output-discussion-colder-but-how-cold-and-for-how-long/?do=findComment&comment=5006967