Model discussion highlights

[Midlands Ice Age]

Not an expert on the upper atmosphere and particularly the stratosphere but some points I have extracted by careful evaluation of the models - (I spent a career working with the early form of models!!😜 )

Note this note is possibly for the less experienced and I have deliberately tried to use simple terms, and analogies. 

1) MO with its seven day outlook run period,  tends to place an emphasis on the current data trend.  It is therefore fairly easy to follow the run and understand the changes.  

2) ECM with its 10day envelope seems to stick almost entirely with the current data as its main driver, but  introduces more of the 'unrecorded' and therefore 'unseen' data. By this I mean the tendency of the predicted worldwide changes in forcing, which are discussed at great length in here (by very capable people), to have more of an impact.

3) GFS goes out to 15 days,  and it also has less resolution.  It also seems to take on board the latest outlook changes suggested by  the world forecast systems   (by NOAA, stratospheric and other forcing changes), which over the longer model run produce much more scatter.

Fine so far?

The other thing I have noticed is that GFS is a bit like a dog with a bone.  Once it gets hold of an 'idea' or outcome , it will hang on to it as a final solution, despite the first part of the run (using the actual data) changing which can make it much more difficult to achieve.. Sometimes it is clear from its early modelling that its final desired outcome cannot be attained. But it still will persist with its 'desired' alternative.  This means that it can take quite a while for it to accurately resolve issues in the medium term.

An example of this is its current tendency to want to form a Scandy high in the longer range of its run.

It  currently seems to want to push WAA up through the B.I. to achieve its ultimate aim. It therefore uses its end solution to adjust its forecast for the medium term, perhaps more easily than the other models will want to achieve.  

I am not saying that it is always wrong, just that it can influence the medium term forecasts more than perhaps the other top models do. Sometimes it can see the changes in advance of the other models.

It therefore can explain its tendency to have to make changes in the medium term and why when it does so it can take a day or two.

It also leads one to believe that it can become over reactive.

MIA 

 

Original post: https://community.netweather.tv/topic/98087-model-output-discussion-the-cold-has-arrived/?do=findComment&comment=4758404

[nick sussex]

Large disagreements between the GFS and ECM .

The former trying to develop high pressure over and to the ne of the UK , the latter keeping any heights in the Greenland area.

The lack of amplitude on that low to the west of the UK means it’s a struggle for the GFS to get a decent high sufficiently north .

You really need a more elongated low with a more negative or at worst neutral tilt to help develop that high to its east and ne .

With these types of disagreements it’s hard to know what’s going to happen !

Original post: https://community.netweather.tv/topic/98087-model-output-discussion-the-cold-has-arrived/?do=findComment&comment=4758330

[mushymanrob]

This post will go down like a lead balloon .... but the latest EPS anomaly charts now support the GFS suggestion that we will return to a Westerly, milder, unsettled Atlantic pattern by next weekend...

This cold spell had all the ingredients of being something special, but all most of us are likely to get is a week of frost.

Of course, nothing is yet settled, but the NOAA 8-14 dayer is on the same page as @johnholmes pointed out earlier.

Original post: https://community.netweather.tv/topic/98087-model-output-discussion-the-cold-has-arrived/?do=findComment&comment=4758461

[Singularity]

Interesting that the 12z GFS has flattened the jet stream over the North Atlantic. This is one situation where flatter could mean cold weather continuing a bit longer, as low pressure becomes more zonally (west-east) elongated, making it more susceptible to disruption when coming up against a cold airmass.

On the other hand, UKM still looks quite amplified with the jet pattern and has the main Atlantic low hundreds of miles further was as of noon Friday, which complicates matters. I suppose it would unfold similarly to the past few ECM runs, unless the low was stalled further west than those predicted.

It's a shame GEM keeps being at the north-westernmost limits of the spread for the position of the low to our west Wed-Thu next week as that heavily influences how the runs unfold (merger of that low with the new one arriving off Canada, leading to much stronger push from the west).

On the longer-term, an update from Armando Salvadore today has restated that he sees "what appears a more coherent MJO wave into W. Pac" for the 2nd half of this month, which is put forward as the reasoning for the extended ECM ensemble mean featuring a HLB signal around 23rd Dec (for example).

That's given me pause for thought. MV's most recent version of his MJO analysis method does hint at something but emerging over the Maritime Continent and with a shortage of eastward propagation. This, though, could be down to GFS not resolving something sufficiently.

Much to ponder even as the current cold spell continues to unfold before our eyes.

Original post: https://community.netweather.tv/topic/98087-model-output-discussion-the-cold-has-arrived/?do=findComment&comment=4759084

[The Enforcer]

14 minutes ago, nick sussex said:

So far the models fall into the need a tweak to extend the cold to beyond help.

The GEM is utter crud and that needs a lot of creative license to save the cold.

The GFS is a tweak away from cold extension .

The UKMO at day 7 is on a knife edge but let’s put that in the tweak category as it needs a small nudge se.

The ICON at T180 hrs is okay but I think we’d need a small tweak there to be safe .

Under no circumstances do we want the ECM to go anywhere near the GEM !

I was thinking earlier that the models don't seem to 'like' a synoptic pattern where the UK is in this sort of no-mans land, where it is cold, but in a slack rather than direct feed, so not excessively cold or snowy compared with historical precedents.

They seem hellbent on breaking this pattern at the first available opportunity, usually with an extreme solution - hurricanes, spanish plumes at one extreme and chunks of polar vortex from the Arctic/Siberia at the other end of the spectrum. A model may run with variations of the same extreme for a few runs, so seemingly it starts to gather support within its ensembles and some credence. This appears to come to an abrupt halt when the proximity to current data eventually makes the model's extreme solution impossible at which point it shows the preservation of the existing pattern for a bit longer, with an alternative exterme change being introduced a couple of days later.

Original post: https://community.netweather.tv/topic/98087-model-output-discussion-the-cold-has-arrived/?do=findComment&comment=4759100

[Eagle Eye]

A-level taster day done so I've got time for a look at the weather finally now...

GWO continues to revert to a -VE AAM pattern so I think after we see the dynamical downstream effects of the East Asian jet retraction and its recovery and extension, we'll have an increasing chance of zonal Atlantic influence late December/early January. Based off MJO alone and we could see the cold pattern background signals lag correlations lasting right up until late December so the increasing zonal flow probably wouldn't take place till the new year despite the relatively quick dip into -VE AAM. The -VE EAMT and it's recovery have affected the East Asian jet if only for a couple days, significantly dipping the PNA. The surprising strength of the -VE PNA testament to the strength that the short timescale retractng East Asian Jet has upon amplification of the Pacific and North American pressure anomalies and furthering the Rossby wave thermal transfer amplifying waves downstream. I think that'll help slow down the progressivess of the atmosphere and hence the few days delay of the normal MJO cycle effects being felt 10-14 days later (I think). I think it'll also interact with the North African pressure systems and create a UK/Scandinavian blocking as the most likely solution off the back of any Eurasian feedback remnants depending on timing. However, the effects on us specifically will probably depend more on where the blocking is placed so watch this space, we could be in for some further cold if the Scandinavian blocking forms or we could end up with a milder pattern if the pattern takes too long to develop. For now though, the initial initial is starting to settle in with frosts and some snow already. Potential for more snow on the way and then next week, what's in store still is relatively unknown but we could see a few surprises as things don't actually look that bad as maybe a few runs have suggested and the overall pattern of runs is fairly good for coldies. There will more than likely be things that crop up closer to time that could deliver more widespread snow and we may get a good scenario through a proper shortwave/trough interaction. It's all very interesting weather wise going into the next few weeks and we'll see a lot of twists and turns along the way. The game has only just begun.

Original post: https://community.netweather.tv/topic/98087-model-output-discussion-the-cold-has-arrived/?do=findComment&comment=4759032

[Captain Shortwave]

Hmm seeing the words “The GFS looks consistent” was a bit of a head scratcher when you zoom out to the hemispheric charts.

   
 

The sharp ridge through Alaska on the 06z is gone, it explains the flatter pattern in the Atlantic too (Though even the 12z suggests that something isn’t normal in that we are getting warm air wrapping around that Atlantic low).

Again it would not surprise me if a quick escape from milder/more changeable weather was revealed in the week 2 range.

For balance I would say that the GEM would provide a poor prognosis, as you can see the low heights over Greenland/Canada are starting to gather with intent.

Original post: https://community.netweather.tv/topic/98087-model-output-discussion-the-cold-has-arrived/?do=findComment&comment=4759057

[Uncertainty]

 

10 members grouped with the op, arguably another 10 are similar. So it certainly has support.

But the big news is the extended eps…

Big shift away from +NAO!

Will have to see the mean later on, but yet again we swing towards extended cold!

Original post: https://community.netweather.tv/topic/98087-model-output-discussion-the-cold-has-arrived/?do=findComment&comment=4759338

[Mike Poole]

ECM clusters, annoyingly there is only one cluster for T120-T168, but the op run is well represented in the T192-T240 timescale:

Op in cluster 4, the one with the new Greenland high, but cluster 2 also has this.  T264+

Cluster 2 has ongoing monster Greenland high, cluster 1 has a declining Greenland high.  

Good support for the op overall, and quite a shift for the ensemble suite to continued cold.

Edit: @Uncertainty beat me to it, but with very much the same take on it!

Original post: https://community.netweather.tv/topic/98087-model-output-discussion-the-cold-has-arrived/?do=findComment&comment=4759340

[Uncertainty]

5 minutes ago, Mike Poole said:

ECM clusters, annoyingly there is only one cluster for T120-T168, but the op run is well represented in the T192-T240 timescale:

Op in cluster 4, the one with the new Greenland high, but cluster 2 also has this.  T264+

Cluster 2 has ongoing monster Greenland high, cluster 1 has a declining Greenland high.  

Good support for the op overall, and quite a shift for the ensemble suite to continued cold.

Edit: @Uncertainty beat me to it, but with very much the same take on it!

The early signs were already there from the 12z GEFS, the tilt of the low looking so much more negative. 
 

The cfs has been subtly trending towards renewed Greenland heights in w2 and 3. It did surprisingly well (if a little hasty) with the scandi - Greenland retrogression signal we’ve just had but was quick to break it down. Now this (note this is an average of the past 8 runs - @blizzard81has noted the most recent of these…)

Many of us on here have been plugging this spell since the late summer, and in general the seasonals caught it pretty well. Given they have shifted towards a more blocked January, there’s every reason to think this East based Nina / Wqbo-inc solar combo could deliver the coldest winter since 12/13 or even 09/10. All eyes on the progression of that mjo in to the WP. If we get that, then it’s game on.

Original post: https://community.netweather.tv/topic/98087-model-output-discussion-the-cold-has-arrived/?do=findComment&comment=4759361

[SqueakheartLW]

Now that Christmas Day is in range of both GFS and GEM it is a good time to see what the early signals are for the big day itself.

Christmas Day GFS 12z                                          Christmas Day GEM 12z

Cold and Dry/Inversion Cold                                   Cold and Dry/Inversion Cold
Ct,P03,P04,P07,P08,P11,P12,P19,P24,P27            Ct,P06,P07,P08,P12,P13,P14,P17,P18

Cold and Zonal/Cold and Wet (Snow Risk?)          Cold and Zonal/Cold and Wet (Snow Risk?)
P01,P02,P13,P14,P20,P21,P26                                P02,P03,P05,P11,P15

Cold and Snowy                                                        Cold and Snowy
P18,P25,P30                                                              P01,P10,P19

Battleground UK Snow Risk                                    Battleground UK Snow Risk
P06                                                                              None

Non Descript/Average                                              Non Descript/Average
Op,P09                                                                        P16

Mild and Zonal/Mild and Wet                                 Mild and Zonal/Mild and Wet
P05,P10,P15,P16,P17,P22,P23,P28,P29                P04,P09,P20

Mild and Dry                                                              Mild and Dry
None                                                                           None

 

Summary of above ensemble members

Below I have a summary of both 12z GFS and 12z GEM for Christmas Day into several broad categories

Temperature

Cold                                   Average                          Mild
37 of 52 members          3 of 52 members          12 of 52 members

Precipitation

Dry                                    Average                           Mild Wet
19 of 52 members          3 of 52 members          12 of 52 members

Cold Wet/Snow Risk       Snowy
12 of 52 members          6 of 52 members

Looking at the above it seems a colder Christmas is favoured over a milder or average one for the temperatures at least. Box 1 ticked if you want something colder for the big day itself.

When looking at precipitation risk and type a dry Christmas looks favoured initially but when you add both wet categories as well as the snowy one together the total is 30 of 52 members which means overall a wetter Christmas is favoured

Current favoured combination is COLD and WET

This means there's definitely a good chance of something wintry showing up on the big day itself. Whether this is icy cold rain, sleet or snow remains to be seen. Perhaps an increase in ensembles getting into the cold and snowy category may help.

Original post: https://community.netweather.tv/topic/98087-model-output-discussion-the-cold-has-arrived/?do=findComment&comment=4759359

[Daniel*]

Big shift to prolonged -AO blocking by ECMWF ensemble mean 

The operational as we know was even more assertive  

 

The positive NAO options have also all but collapsed

All signs that hemispherically things are remaining more primed to colder weather patterns further into December.

Original post: https://community.netweather.tv/topic/98087-model-output-discussion-the-cold-has-arrived/?do=findComment&comment=4759402

[Singularity]

25 minutes ago, Captain Shortwave said:

Atlantic/Alaskan ridge double team to bring a return to colder weather

This is something Armando Salvadore mentioned earlier as a response to renewed MJO activity. Looks to be a +EAMT event.l involved too via very cold air crossing eastern China and the spilling over the West Pacific.

Anyone know whether he infiltrated ECMWF this morning? 🤪

Original post: https://community.netweather.tv/topic/98087-model-output-discussion-the-cold-has-arrived/?do=findComment&comment=4759315

[bluearmy]

Some excellent commentary this morning

aaron - I feel much the same but won’t stop watching each run! 

who would have guessed that an ec op would be over amplified!  Maybe it’s just Friday 12z ec ops that need to be banned !  the background pattern isn’t much altered - the mean extended eps jet a little higher across the Atlantic below a ridge but not unexpected given the way that the op tends to skew the rest of the suite towards it.  What is becoming apparent across the three model suites is that there Is no appetite to raise temps away from cold this side of Xmas. We are very cold currently. We look like we are going to become chilly to cold. Thereafter, just how cold again is uncertain. 

someone mentioned cold and wet - that’s certainly on the table. Some neatly placed wedges given the cold background pattern and near continent could easily deliver, especially high up. 
 

At the moment, you’d punt that the Scots are in a decent place to see snow on the ground for the big day ! 

 

Original post: https://community.netweather.tv/topic/98087-model-output-discussion-the-cold-has-arrived/?do=findComment&comment=4760089

[mushymanrob]

a long way off, but the strong greeland block is still there on christmas day...

 

Original post: https://community.netweather.tv/topic/98087-model-output-discussion-the-cold-has-arrived/?do=findComment&comment=4760368

[IDO]

As for well into FI, upstream is difficult to call, and we see from the GFS op versus control, two different scenarios:

  

The op throwing up an Alaskan standing wave, and the control injecting wedges into that region. A negative EPO will please the US cold fans.

In the reliable, the warning for Sunday/Monday for the SE is likely to be south coast at low risk according to latest GFS op, though 30-40% chance according to GEFS.  ARPEGE and ICON high-res both go through the channel and miss. The second chance of snow, around D3-5:

...is too early to pinpoint risk, but most models keep it south of the channel, though ICON impacts south/SE, but that model has not impressed me of late:

Accumulated precipitation before the milder air moves in, is as expected, the usual suspects (GFS op):

Acc precipitation:  London 2m: 

London 2m temps ens are cold, so around 2c maxes for the next week IMBY. A very cold 10-day spell is unusual so very noteworthy of late.

Original post: https://community.netweather.tv/topic/98087-model-output-discussion-the-cold-has-arrived/?do=findComment&comment=4759964

[Jordan S]

A proper update this time, So the focus on snow has largely been for coastal areas of western, northern and eastern areas along with the southwest and parts of the north further inland, but potentially the south of England/southeast and especially south Wales/western England more in focus for potential snow developing tomorrow/Monday in association with a low skirting southeast then east through west, south Wales then along the far south of England tomorrow into Monday.

GFS..

Given the rather moist light southeasterly wind that looks to develop in the channel and possibly into southeast England this could enhance snowfall that potentially develops here, perhaps showers at first then the possibility of turning more persistent in southeast England tomorrow evening/night and possibly into Monday morning with western England potentially seeing this more significant snow through daytime, more confidence with this.

Arome precipitation..

Development of heavier snow and location is highly uncertain for the southeast but this common knowledge right now.

Any highest accumulations look to be either for western England such as Swindon as an example, or for parts of the far south/southeast such as places close by Basingstoke or a little further east. But that is an educated guess atm with all the different options on show. Given the models tendencies to underestimate precipitation totals from small scale features in this set up, what looks most likely "if this develops as expected" is 1-2cm in any patchy showery zones ( such as north Berkshire ) but for the favoured spots I've mentioned above where snow looks to become quite heavy at times including to lower levels and very slow moving, then in the most effected area, the highest totals could be upto 5-10 cm (2-4 inches) to lower levels and upto 15cm (6 inches) on high ground very locally, with far southeast England although much less certain, potentially seeing similar totals but these will almost certainly be isolated totals, not widespread and for many in the main zone, roughly upto 3-8cm will be the main maximum totals in the worst effected places if the precip develops as expected. Snow in the southeast possibly aided by a convergence zone (wind blowing towards each other in a very localised location creating more instability) this would keep the intensity going aswell for the southeast.

Arome wind direction..

Ukmo..

Don't take this as gospel but it is plausible. Less likely but most of the precip for southeast England could remain away over the English channel with only spacial light dusting/accumulations from isolated showers. Could also be further brief snow moving northwest over central, southern the western England into Wales just ahead of a low pressure system to our south on Monday evening, taking heavy snow into France.

Then by the end of next weekend we see a cyclonic and less cold interlude as said was the more realistic outcome couple weeks ago and has been said recently by others, although ofcourse this change as expected taking place not exactly when I hinted in my post, so this taking place from 18th December as opposed to 14th-15th, but that tends to happen with cold spells. This brings snow/ freezing rain potential briefly to parts of Wales and Northern England the snow then quite likely for Scotland and probably remaining as snow with everywhere else eventually likely getting into air high enough for rain although perhaps hills over north Wales northern England remaining cold enough for it to fall as snow, briefly mild in South. In a very similar evolution to the GFS.

But the cold will not be far away (well it's unlikely to leave Scotland) and there's a higher chance than not that we will see colder and more wintery conditions returning southwards once again as shown also by recent model output, likely atm just in time for Christmas, though perhaps emphasis on a Scandinavian high as hinted by a couple other posters and modelling. 🙂 But this isn't certain ofcourse and other milder unsettled options even though unlikely, remain possible.

Original post: https://community.netweather.tv/topic/98087-model-output-discussion-the-cold-has-arrived/?do=findComment&comment=4760547

[nick sussex]

The GFS fails to start blocking off the high at day 6 .

This means heights seep west nw and there’s little forcing on the Atlantic low .

The UKMO is finely balanced but does start to  block off the high at day 6 and has more forcing  on that Atlantic low .

In black low heights start blocking off the high which is shown in red. 

By day 7 the high can’t escape as that troughing edges east on day 8 this will add even more forcing into the Atlantic as it will also nudge those heights further east .

 

By the time the GFS starts to try and block off the high the ship has sailed and phasing has already started with the Atlantic low and low heights to the ne of the UK. And that happens so far west it’s game over .

Its really all about whether phasing takes place between low heights heading sw and that Atlantic low , and also where in relation to the UK.

Original post: https://community.netweather.tv/topic/98087-model-output-discussion-the-cold-has-arrived/?do=findComment&comment=4760947

[Eagle Eye]

Signs on the ECM extended that we may be moving towards a repeating pattern with a fairly mobile MJO trying it's best to keep moving towards phases 5-8 and hence the increases 6 and/or 7 chance as well. So a potential repeating pattern on the cards as we go into the early/mid January period after a short zonal dip. For now, Im going to leave that alone though and let it be FI but let's hope it becomes a repeating trend. If it does then this Winter COULD end up being like 'the old Winters' but I'm not going to ramp yet, instead, all I'm going to say is that it doesn't guarantee a -VE NAO, just increases the chances and its still too far out that we can't be sure of anything yet.

The downstream effects of the East Asian jet retraction interest me. We're into the time where we can see the clear amplification of Rossby thermal transfer cropping up on the models in a fairly reliable time although exact handling will be very off at this point. The effects on how Eddy's are handled may be negative but the generalised conception of increasing Eddy Heat Flux especially in the upper Troposphere may be slightly better handled than usual. Usually , this would probably increase the -VE AO but we're in such a -VE AO dip that it may just delay the recovery of the AO through the formation of that UK and/or Scandinavian blocking signal that's starting to persist on the models. It's still too far out to worry about localised dynamics of the high but the signal is showing for the blocking to form and of course how it forms will affect the short term gain at that time but as long as the wandered blocking pattern keeps up the relative pattern flip cold throat should exist. I think up until very late December potentially later than that, this pattern may be able to keep itself going synoptically hence the cold chance probably persists till around early January. Then we've got the potential MJO influence and that may happily coincide with another energy scattering PNA cycle.

Me thinks the scattering of energy interacting with the more southerly based jet will drift up hot air from North Africa which may cause some areas of Europe to see ridiculously mild air for this time of year and probably not something you associate so close to a quite significant -VE AO pattern. Just using 1 model run to show what I mean is probably not a good idea at the time range that I'm talking about and it goes against my principals but I'm just using it to show the mild air that could possibly be drawn up.

It's very unlikely to look anything like that but it does show what could be drawn up by the energy and amplification scattering interacting with the high just off the coast of North Africa. A very interesting thing as we go closer to time I think but we still can't be sure that the North African (ish) High will be interacted with nor the direction that its drawn up so we could end up seeing one extreme or the other.

Looking more into the short term future...

Initial pulses of colder air in a cold pattern and maybe the formation of a shortwave or something similar that could still end up dumping a decent amount of snow somewhere, then...

Cold air that would normally look blocked in fairly well seems to get thwarted to the south and a pulse of amplification correlated with the  downstream effects of the PNA pattern (correlated with the East Asian jet retraction fairly well, funny how everything links together) but how long it stays for is hard to tell for now. There is a chance it could just be a mild blip and that it goes on to prop up the -VE AO pattern as discussed earlier. Or it could hold itself in for longer and set itself in for a longer time, for now I just don't know and its fairly evenly balanced.

Original post: https://community.netweather.tv/topic/98087-model-output-discussion-the-cold-has-arrived/?do=findComment&comment=4761080

[TEITS]

1 minute ago, DiagonalRedLine said:

As I’m sure has probably been mentioned by a lot people in the past, changes to a milder/less colder outlook still feels fairly comfortably far away to get too alarmed about yet (but to be fair some of the possible trends being picked up towards a less cold/milder period is getting apparent). 

With this not being too certain at the moment, then how long any less cold/milder period lasts won’t seem certain either.

For the sake of it though, I hope any break to less colder or milder conditions goes off with a snowy bang.

Unlikely to be a snowy breakdown.

Quick summary from me is the less cold spell next weekend looks like being very shortlived. The ridge of high pressure bringing the S,lys will be shunted E and be replaced by low pressure. However because of the pressure remaining relatively high across Iceland/Greenland, the position of the jet stream and the passing of the low pressure will see the UK returning back to colder N/NE,lys. The likes of Scotland will hardly notice any warming up.

Original post: https://community.netweather.tv/topic/98087-model-output-discussion-the-cold-has-arrived/?do=findComment&comment=4760170

[Cambrian]

It’s going to take a lot to shift this cold air now, nothing mild on its way, that’s for sure. 0z ECM control looks to have it right to my eye for Christmas Eve and Christmas Day! 

   

Siberian lobe of the PV still in control. Weak Canada lobe offering up the occasional low pressure system to get wrapped in to the Siberia - Scandinavia trough, to swing in spells of snow from the north. -8 uppers in place, jet stream still running well to the south and the UK and Ireland have even installed their very own jet stream deflector.

After the hot, dry summer, it’s a genuine relief to me to see some proper winter weather pack in so early in the season. -6 degrees the night before last, snow showers since yesterday afternoon and evening, every flake settled on the hard frozen ground. It’s only light to moderate snow showers but with hard cold, -5.3 degrees last night, looking like subzero all day today, a continental feel to it. 

Here’s a pretty snow pic from this morning.

The pattern is nowhere near as extreme as 2010, the comparisons with other years just do my head in, but it’s great to have proper winter weather and beautiful in the here and now. I’m loving the freezing mists too, that crop up at any time of day!

The whole hemispheric setup is so much better than recent years, completely enthralling, enormous potential for wintry weather pretty much anywhere in our islands from small crop-up systems through to large scale battleground events. 

Like Prince / Artist formerly known as / Symbol chappie would have said if he was still knocking about (bless him) - Let’s party like it’s 2022. 

Original post: https://community.netweather.tv/topic/98087-model-output-discussion-the-cold-has-arrived/?do=findComment&comment=4760356

[phil nw.]

We are indeed seeing some signs of the cold relaxing in a few days but will it only be for a short time?

I have been looking through a bit of data to try and see where we are and where we might go.

A view of some combined graphs from the different model runs and some of the ensembles show the spread of possibilities rising sharply towards next weekend.

Just at the point where the northern blocking signal fades and we see the push from the Azores with a small ridge.Nothing dramatic but enough to send a bit of a warmer air into the south at least.

Later eps/gefs guidance still favour +ve arctic ht anomalies and our temperatures still generally below normal.

It looks like overall we remain generally on the colder side of the jet ,allowing for the odd push close to the south.It's a case of whether the blocking re-asserts whilst we remain in this unusual pattern.

As ever the often used observation of much uncertainy beyond the next 5/6 days seems the right phrase.At least there is no strong signal for a return to our usual zonality.

Original post: https://community.netweather.tv/topic/98087-model-output-discussion-the-cold-has-arrived/?do=findComment&comment=4760655

[Blessed Weather]

40 minutes ago, Eagle Eye said:

Signs on the ECM extended that we may be moving towards a repeating pattern with a fairly mobile MJO trying it's best to keep moving towards phases 5-8 and hence the increases 6 and/or 7 chance as well. So a potential repeating pattern on the cards as we go into the early/mid January period after a short zonal dip. For now, Im going to leave that alone though and let it be FI but let's hope it becomes a repeating trend. If it does then this Winter COULD end up being like 'the old Winters' but I'm not going to ramp yet, instead, all I'm going to say is that it doesn't guarantee a -VE NAO, just increases the chances and its still too far out that we can't be sure of anything yet.

(SNIPPED)

Really enjoy your informative and upbeat posts EE. 👍 
Unfortunately - and assuming current forecasts are correct - I'm not optimistic about the MJO helping with a pattern repeat in the short-term. The GMON (GEFS extended) forecast, the BOMM (Australian Met ensemble bias corrected) forecast and the EMOM (ECMWF ensemble bias corrected) forecasts to 6th - 8th Jan has the MJO in the COD (Circle of Death). Which means the MJO is largely indiscernible from background noise and will have neglible impact on global weather patterns.

And even if the MJO emerges from the COD in early January, add the typical 10 to 12 day lag and it's likely to be well into Jan before we would see an impact in this part of the world. Current forecasts:

GMON BOMM EMOM

Original post: https://community.netweather.tv/topic/98087-model-output-discussion-the-cold-has-arrived/?do=findComment&comment=4761169

[Day 10]

Good morning,

I have put all 6 main outputs together at day 6 to compare where they sit with the incoming low out in the Atlantic, I still feel this is far from a done deal with milder air blasting through. A lot can still change in 6 days.

At the minute we have the ICON, UKMO & GEM the best options with a more negative tilt and a continuation of the colder pattern, followed by JMA, GFS & ECM eventually bringing in milder conditions with maybe a short snowy breakdown in the north.

Continuation of the colder pattern?

Milder breakdown?

I want to add, I still think FI is shorter than this. Really wouldn't surprise me if the first option is more likely and the whole pattern at day 6 is further south. Lots to play for, somewhere could end up with a lot of snow out of this.

Original post: https://community.netweather.tv/topic/98087-model-output-discussion-the-cold-has-arrived/?do=findComment&comment=4761678

[Mike Poole]

Well, the saga continues this morning.  I have never fully bought into this mild breakdown malarkey, believing that the blocking, and the propensity to rebuild blocking, are greater than the models are giving credit for.  That’s not to say the milder interlude won’t happen, going by the models alone, it still looks likely, but I think there are 2 solutions this morning, with GEM and UKMO maintaining the cold status quo, here T168 with the high southern Greenland and a push on the pacific side:

Leading to GEM going on to resemble last night’s JMA at T240:

GFS and ECM are different, the Greenand ridge is further west, and the lows phase (marked yellow), leaving us in the mild flow, T168.

Pacific ridge not as well directed either.  

So plenty to be resolved on the timescale of a week.  

Original post: https://community.netweather.tv/topic/98087-model-output-discussion-the-cold-has-arrived/?do=findComment&comment=4761671