Model Output Discussion - moving into Winter

[Eagle Eye]

Mean at 168 vs operational (I think) at 168.

Ironically, the mean is showing a better angle of attack from the cold to defeat the low and a differently angled low, the mean much better for it to not block out the easterly so much.

Think the operational (or whatever it is at this point I don't know) will prove to be an outlier among it's own ensembles.
 

[Polar Maritime]

Just now, Bristle Si said:

Fair enough. Will it snow?

The models are certainly looking like it..

[bluearmy]

5 minutes ago, CreweCold said:

Uppers aren’t great to be fair. Mostly -6 or -7 at best. That’s sleet at low levels given the high sea temperatures and modified surface layer. DPs will be elevated. -8 uppers have to be the benchmark for less marginal conditions.

A cleaner ejection of CAA is needed from the NE.

If we end up beneath a slack deep  trough then you’ll be surprised - the control had uppers of -7 with thicknesses sub 520 

[Eagle Eye]

1 minute ago, Eagle Eye said:

Mean at 168 vs operational (I think) at 168.

Ironically, the mean is showing a better angle of attack from the cold to defeat the low and a differently angled low, the mean much better for it to not block out the easterly so much.

Think the operational (or whatever it is at this point I don't know) will prove to be an outlier among it's own ensembles.
 

Yay, my point seems to have been proved here.

[January Snowstorm]

The gfs issues seem to be related to the introduction of the new parallel that's now obviously live. We have seen over the last couple of weeks how the // has not been performing accurately. It has been standing out as an outlier in many runs..

[bluearmy]

2 minutes ago, January Snowstorm said:

The gfs issues seem to be related to the introduction of the new parallel that's now obviously live. We have seen over the last couple of weeks how the // has not been performing accurately. It has been standing out as an outlier in many runs..

It’s been no different to the now defunct gfs - swinging back and forth.  This is going to become the new Xmas day flight data ! 

 

[Allseasons-Si]

C'mon guys pull it together please

i mis-spell all the time but we all know what we are sayin

this is a great thread and we have an oppertunity to have a very good cold spell on our doorstep,that doorstep might disappear soon in snow

i like the trends,i like the input in here,we have the pros and the met on board for a possible December to remember and it's not winter yet,i do feel like there will be a repeat of a 2010 style winter coming up,maybe not on the severity type but you never know,we are at/on the infancy of that with the pattern forcast

i will stick my neck out and say that it will be on par for 2010,...the dynamics are there

so just reel in what the pros are sayin,we have @MattH in here with his insight on the situation,..all looking good

i am out for now as the clock has ticked by my bedtime

must dash and do it all again tomorrow

G'night.

[Polar Maritime]

12 minutes ago, Allseasons-si said:

C'mon guys pull it together please

i mis-spell all the time but we all know what we are sayin

this is a great thread and we have an oppertunity to have a very good cold spell on our doorstep,that doorstep might disappear soon in snow

i like the trends,i like the input in here,we have the pros and the met on board for a possible December to remember and it's not winter yet,i do feel like there will be a repeat of a 2010 style winter coming up,maybe not on the severity type but you never know,we are at/on the infancy of that with the pattern forcast

i will stick my neck out and say that it will be on par for 2010,...the dynamics are there

so just reel in what the pros are sayin,we have @MattH in here with his insight on the situation,..all looking good

i am out for now as the clock has ticked by my bedtime

must dash and do it all again tomorrow

G'night.

Reading many professional data-sets, The pattern we are about to enter certainly entertains the best early winter for the past decade at least. With that in mind and what the current models show even within the reliable timeframe it's the best winter prognosis for a long time..

Edited November 30, 2022 by Polar Maritime
More spelling mistakes..

[Allseasons-Si]

And the new gfs keeps on giving,...plenty of opertunities down the line...

C U.

 

 

[sheikhy]

Much improved gfs mean at 228 hours!!!looks a bullseye hit from that cold northeaster for us!!

Much improved gfs mean at 228 hours!!!looks a bullseye hit from that cold northeaster for us!!

[Eagle Eye]

Just for fun, perturbation 17 and 24.

The GEFS mean.

I'm not going to say it...

Nope...

Alright fine,

BOOM!!!

[Battleground Snow]

2 minutes ago, sheikhy said:

Much improved gfs mean at 228 hours!!!looks a bullseye hit from that cold northeaster for us!!

Nice little cold cluster appearing.

[Dancerwithwings]

GEFS is being naughty…but nice candy

[ICE COLD]

There’s loads of good ens on the GEFS 18z . Some transferring high pressure towards the NE after the initial GL high or some just keeping pressure high over GL . These all around the T288 mark . Just hoping to long out this cold spell for as long as possible ( hopefully until March ) 

[feb1991blizzard]

In the past i've sent many a thread off topic by arguing about unrelated stuff so to make amends and take the moral high ground, for once i am going to actually try and get a thread back on topic.

a very slight upgrade on the 850mb temps on 18z GEFS with - 4c isotherm about 100 miles further south.

Edited December 1, 2022 by feb1991blizzard

[ICE COLD]

4 minutes ago, Dancerwithwings said:

GEFS is being naughty…but nice candy

The control is nuts . Looks like the Siberian monster about to gobble up the UK with -20 850s (if only ) 

[Connor Bailey Degnan]

Happy Meteorological Winter everyone! All set for a December to remember! 

[Geordiesnow]

Just caught up with the output and yes the GFS is frustrating and there is always a chance it could be right but its still got the main feature that I want too see which is Arctic air dropping down from the North. 

All models showing a Greenland high aswell, I'll still remain some caution on this but its a pretty strong signal for it and we are getting closer to the medium range. 

As for uppers, yes they might not be as cold as 2010 but I would not be worrying too much about the details you don't want a weak northerly though as getting significant cold air could well be a struggle.

[Catacol]

3 hours ago, chionomaniac said:

I’ve not been concentrating on slight inter run differences today, but it still looks like the best  block is building for over 10 years, and that this won’t be some transitory event. Obviously there is no guarantee of snow falling over a particular place at a particular time, but there is a strong likelihood that the vast majority of us will see snow at some point. 
 

I have seen some suggestion on here that pacific tropical activity will wain, and that the Greenland block will retrograde west opening the door for milder SWesterlies to materialise soon after the initial polar surge. Yes this is always a possibility but unlikely probability. In fact the tropical forecasts are somewhat suggesting the opposite of this, and the latest 12z Gefs and Eps mjo ensembles show a lot of members heading into phase 7 with some strong high amplitude members amongst them.

What does this mean, well any blocking is likely to repeat, meaning a longer lasting cold spell.  The tropospheric weakening of the lower Strat will continue and maybe long enough lasting that when the inevitable upper Strat attack comes it will have a lower Strat ripe for submission  

There are signs both tropospherically ( look up tripathi paper precursors) and hints at the 10hPa long range too that wave 1 is increasing and could be fully fledged towards the end of December  

I know this may differ from other thoughts, but I see strong signs to be optimistic if a prolonged cold spell floats your boat  

 

I’m glad @MattH  posted that torque chart earlier cos I’ve lost my GSDM plots for now…and it does setup a very interesting mini experiment. With such a sharp decrease in torque happening now, given likely sharp decrease in relative AAM tendency to follow, we are going to see an existing very strong (record breaking?) block squeezed south with one hand while with the other pacific momentum gives it a boost. And meanwhile, as you say, we have a resultant significant wave 1 event ongoing and the obliteration for now of any sense of downward westerly propagation.

This first push of cold has caught me out - I didn’t expect such a significant shunt of cold air quite so fast, and I’m still not 100% convinced that things will line up quite so clean and direct next week. Messy interactions of warm and cold pockets as SE Euro heights interfere a bit longer seems entirely possible and the low to our SW will certainly also have warm sectors. But maybe we get that ECM or GEM fast solution. After so many failed opportunities over many years snow hunters deserve some luck.

But going back to the medium term scenario - what next? Watching this play out will be fascinating. Agree with reignition of the MJO into favourable phases around 12-15 Dec I think and lag impacts of falling AAM will impact same time. Block will be grinning merrily at the layers above - utterly dominant according to this prediction while flux turns the screw still

 

so - what about the block? A degree of guesswork required - but I’m going to suggest the lack of downwards westerly propagation and the sheer size and strength of that block will indeed promote longevity. It is likely to decline in strength at least initially but by the time that happens we appear to have a cold trough embedded over the U.K. and in the days after Dec 15 I think we will be seeing a reload of that block as pacific momentum restarts. Cold phase 2 in the last third of the month.

All good. Fingers crossed by that final third we may also be seeing an SSW as a possibility…

 

 

[Eagle Eye]

Trying to be a bit more serious here...

My attempt to make sense of everything at midnight, what could possibly go wrong?

The AO has already started to decrease and with the reinforced Greenland blocking helping split the tropospheric vortex as shown by the 3D vortex at 180 hours, we should see the associated -NAO and an increased chance of cold coming our way as shown by the recent model outputs in the mid term that are starting to get towards a reliable(Ish)time frame. This split vortex from the Greenland blocking should help to decrease (and reverse) the zonal wind and therefore...easterlies. Once again, that is shown in the recent model output. So we're getting into a timeframe where it's not about these individual teleconnection patterns but instead about surface to troposphere localised conditions. I'm not going to discuss them for now but the significant negative AO and -VE NAO likely stems from the +VE AAM which was helped by the MJO values in the Western Pacific with the lag correlations of phases 6 and 7. The La Nina state of the ocean seems to not be affecting us too much as of yet, perhaps the ocean and the atmosphere not well coupled which I think has been said before. I think it's the best setup for cold since I joined (except maybe the SSW but they are more delicate evolutions for them even to occur, increasing recent energy trains across Asia roughly and wave-1 amplitude increasing in the lower Stratosphere may help and/or be the products of increase trop-strat coupling and may lead to a SSW but for now I'm not going to stick my neck out) because the easterly stems from actual teleconnection backgrounds and the possibly significant -VE NAO state suggest that, for now, this may take quite a long time to recover. Alternatively, we could see a quick return to a +VE NAO due to the sped of which the -VE NAO happened and the thermal recovery process theoretically occurring quicker due to that speed.

The AAM is being forced into a more neutral state but I'm not sure of the dynamical processes involved with that so for now I'll say that I simply don't know. At a total guess, I think localised dynamics more associated with shortwaves may be what ends up at play here. The zonal wind shouldn't really recover amazingly quickly as the strength of the weakening looks to be fairly strong and stretched out so we may end up seeing a lengthening of the -NAO state but it just depends on what happens with the Greenland high movement and whether the La Nina oceanic state has more of an effect and for now I don't think it's worth mentioning that much. Long-range forecasts are quite difficult to interpret from this but purely based off the oceanic La Nina base state I think a flatter and therefore more Atlantic influenced theme going into late December and January but we cannot rule a SSW off the cards just yet so that's interesting to add to this increasingly complicated equation. A possible bottom up split evolution if a SSW does occur with large deviations around the Greenland area away from the zonal mean and so the Stratosphere is in asymmetry and there is a large deviation away from the local thermodynamic equilibrium (LTE) and to be in LTE the zonal wind weakening is transferred back down to the theoretically already split Troposphere. So it's not really a typical SSW evolution but you essentially get the same results. Anyway, went off on a tangent there. The GWO doesn't really help with matters amazingly here but along with recent trends of the GWO, it looks like we should eventually move towards phases 2 and/or 3 associated with northwards momentum transport with the loss of AAM and so an increasing southwards drag and possibly eventually a more circumglobal ridging pattern with a stronger westerly flow and so Atlantic dominance is the main variable here I would suggest. Decreasing amounts of meanders in the jet stream with the increasing westerly flow meaning a flatter sypnotic pattern. It's still quite far out but you'll see what it seems to be associated within your read further down. 

If we look at the MJO forecasts, eventually we should move our angle of attack towards phases 2 and 3 but then a re-entry towards phases 4 to 7 is quite a quickly moving weak MJO setup. The weakening of the AAM over the next couple days seems to be associated with the dip into -VE RMM values and the West Hem and Africa areas as the roughly 14 day general lag correlation makes sense here. So I would suggest getting close to phases 2 and 3 here help prop up the weakening of the AAM but the general stability comes from the fact that the RMM values aren't really that amplified in either direction so the weather synoptics are probably going to be on a knife edge throughout December. That re-entry into the increasing RMM2 values should get us back into a (fairly weak) +VE AAM so that's a positive from mid to late December but how strong that +VE AAM could be will probably fluctuate a lot run by run. I think the next month or so will be balanced between the +VE and -VE AAM so dynamical recovery processes of a -VE NAO state and significantly negative AO state will matter quite a lot here beyond this cold we're being forecasted at the moment.

So, what about the closer timescale?

ECM

Vs GFS

Vs  CMC (GEM)

Significant differences deriving from whether the NAO is west based or not but for now I'm going to be boring and say...

More runs needed.

 

[geordiekev]

How's GEM for accumulation predictions, any good or overblown?

To think the main course is possibly yet to come.

[Ghost of winters past]

3 hours ago, Vikos said:

Winter still far away for us....

  FAIL....As per.

Ghost.

 

[Row w]

I'm no expert when it comes to reading charts, most of my knowledge has come from you bunch of geniuses on here but that definitely looks like a battleground between cold and mild on the 18z gfs run there, hoping for the cold to win out and we get to see some seasonal weather in the run up to and hopefully Christmas

[Battleground Snow]

GFS v ukmo v Gem at 144,

Bit different to last night, but gem and ukmo deliver the cold faster still.

[Lukesluckybunch]

Gfs continues to make a complete drama out of this..very messy UKMO nice run!