Model Output Discussion - Colder but how cold and for how long?

[nick sussex]

ICON increases the margin for error . And we then see a slow sinking se of the Scandi trough .

With low heights and a good cold pool but let’s not forget the 500 hpa .

The earlier GEFS had a decent cluster towards the -40 level . This is true Arctic air .

Should be some major convection and also very heavy snow showers with that rarity thunder snow for those in the highest risk areas , or for coldies most fun areas ! Because of the instability and strong flow that could throw up more surprises and not just be limited to windward areas .

That’s post day 6 , the earlier northerly is brief but should still be okay for windward coastal areas .

In terms of frontal snow from the sw , ironically the bigger the margin for error in terms of cold extension the less likely that is to make much inroads at least in the earlier stages .

Edited January 10 by nick sussex

[Mcconnor8]

Just to highlight how much the GFS has changed since yesterday, here is the 72 Hour chart from this GFS12z and 96 Hour chart from the 12z yesterday, quite a significant difference bringing the cold in sooner with much better blocking, Euro heights MUCH weaker as a result of the Azores low being shifted West quite a bit.

Deep cold heading South rapidly at T+96! 850s look at a tad colder than previous runs.

Edited January 10 by Mcconnor8

[TSNWK]

Just now, Continental Climate said:

That's a considerable difference at only 114. Just goes to show more time for upgrades yet. Also worryingly more time for downgrades as well. APERGE is loads better a very sturdy block. 

Aprege new one for me.. where does it rank on credibility?

[Mcconnor8]

Just now, TSNWK said:

Aprege new one for me.. where does it rank on credibility?

It's the French high res model, only runs to +114 but think it is pretty good for our area.

[Continental Climate]

2 minutes ago, Mcconnor8 said:

It's the French high res model, only runs to +114 but think it is pretty good for our area.

That sounds promising doesn't it? A euro model probably focused on our part of the world. 

BTW what was BFTP's outburst earlier about? Did he fall out of his window in shock at seeing how great the models are? Does he have early access I wonder? 

[Scott Ingham]

4 hours ago, bradymk said:

Quite noteworthy imo that GFS is persisting with the increase in heights again to either our west, north / north east day 10 +

Especially given it's tendency to revert to 'normal' at that stage and given that only a few days ago, it was showing a return to flat unsettled pattern at the end of GFS runs.

Yea this next build of heights suggested by gdsm products is gaining a little traction. Only hints though atm but fun to watch 

[Rocheydub]

6 minutes ago, TSNWK said:

Aprege new one for me.. where does it rank on credibility?

It's around years, best use (IMO) for it is short time frame predictions of 850's, thickness, precipitation etc.

[winterof79]

For anyone interested this was GFS output 6th Jan for the 15th

Vs todays 12z for the same date.

Trends are your friends in between wobbles

 

[Rain All Night]

13 minutes ago, TSNWK said:

Aprege new one for me.. where does it rank on credibility?

See "Météo-France" on the graph below:

https://charts.ecmwf.int/products/plwww_w_other_ts_upperair?area=Europe&day=3&score=Anomaly correlation

It's the same core model as the ECMWF model but it's run with a variable resolution - highest (and higher than the other global models) over France, lowest (and lower than the other global models) over the Antipodes.

Météo-France use it to feed their AROME hi-res limited area model (France's equivalent of our UKV).

Edited January 10 by RainAllNight

[Rocheydub]

Just now, winterof79 said:

For anyone interested this was GFS output 6th Jan for the 15th

Vs todays 12z for the same date.

Trends are your friends in between wobbles

 

Today's run is for the 14th, but I see your point.

[Nick123]

My local forecast just said snow from the middle of next week is a certainty. I fully expect a monumental backtrack from all models now 

[Climate Man]

Just now, Nick123 said:

My local forecast just said snow from the middle of next week is a certainty. I fully expect a monumental backtrack from all models now 

Stav on BBC, risk of disruption 

[Mcconnor8]

GFS 12z looks freezing!!! -10c isotherm well through the country by Monday morning.

[Harsh Climate]

Cold air really digging south across the UK as early as Sunday evening

Showers turning readily to snow in the north, Blizzards in Scotland. Obviously, eastern coastal regions favored.

 

Edited January 10 by Harsh Climate

[Scott Ingham]

Fantastic post by Tamara highlighting the fact the angular momentum and the gwo phases never really bottomed out which is something we looked for in terms of longevity. If we can stay in a cold pool then the height rises to the east and back west forecast as the next stage to look for look bang on the money.

lets see it play out like next week has done from musings 3 weeks ago 

[on the coast]

UKMO at 96 is a thing of beauty. 

[Severe Siberian icy blast]

2 hours 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

 

 

 

Well a difficult read particularly when im learning alot again now and understanding things so much better but with that comes an obsession to read carefully every word because its part of my learning process but when i haven't  got loads of time it really come up at wrong time for me but everything has been put on hold!!!

I need to understand the abbreviations used, gwo, glam, aam, annular mode. I understand the geography and science behind it but i need a better understanding on it all if im taking my journey seriously.

Any references greatly appreciated 

Cheers

Shaun

[Harsh Climate]

2 minutes ago, Mcconnor8 said:

GFS 12z looks freezing!!! -10c isotherm well through the country by Monday morning.

Let's see if  we get that little runner from the NW

[Scott Ingham]

6 minutes ago, winterof79 said:

For anyone interested this was GFS output 6th Jan for the 15th

Vs todays 12z for the same date.

Trends are your friends in between wobbles

 

Scott Ingham day still looking good! Although could be a day or 2 out in regards to largest impacts!

[Hathers]

Guys so many dedicated posters in here. Thank you for all of your input from someone who is passionate about the weather but just reads many posts with interest. You all deserve a snowy winter. 
Been on this forum for nearly 20 years and this is one of busiests periods I’ve ever seen. Wonderful stuff. 

[Metwatch]

40 minutes ago, Big Gally said:

It’s all happening folks.

This would do nicely for those in central areas but plenty of time for adjustments and possibly trends southward / northward. Anyone really is in for a chance of significant snow currently into next week.

Edited January 10 by Metwatch

[Met4Cast]

2 minutes ago, Severe Siberian icy blast said:

Well a difficult read particularly when im learning alot again now and understanding things so much better but with that comes an obsession to read carefully every word because its part of my learning process but when i haven't  got loads of time it really come up at wrong time for me but everything has been put on hold!!!

I need to understand the abbreviations used, gwo, glam, aam, annular mode. I understand the geography and science behind it but i need a better understanding on it all if im taking my journey seriously.

Any references greatly appreciated 

Cheers

Shaun

GWO - Global Wind Oscillation 

GLAAM - Global Atmospheric Angular Momentum

AAM - Atmospheric Angular Momentum

Annular mode - Essentially the Arctic Oscillation

[Jacob]

GFS 12z so far looks more at the mercy of the Atlantic and the shortwave south west of us is further north east and is more developed 

[Rocheydub]

At T-96 and the cold air really digging south. Beautiful.

[IDO]

On this run, the Azores low is further north, and its initial front looks like it will be rain for much of the south: