Model discussion highlights

[Gowon]

Nice to see all the cold draining away from North America for once:

Original post: https://community.netweather.tv/topic/99584-model-output-discussion-into-winter/?do=findComment&comment=4964532

[Mike Poole]

9 minutes ago, That ECM said:

The “wall” again. Interesting.

It strikes me that there are 3 options with this Atlantic lows meet cold pool thing:

1. The lows disrupt to form a train of small lows that can slide and follow a southerly jet and track south.
2. A deeper low gets stalled on the approach to the cold air, and resulting WAA pumps up heights into Scandi (like ECM 12z).
3. A deeper low barges straight through and obliterates the cold pool (at least as far as it affects the UK).

The third is the only one that carries the risk of fully unleashing the Atlantic subsequently.

We’ve been watching this for a while now, where’s your money?  

Original post: https://community.netweather.tv/topic/99584-model-output-discussion-into-winter/?do=findComment&comment=4964749

[Cambrian]

12z GEFS gives a good idea of the extent of the adjustment, the disruption reaching right back to the other side of the Atlantic, and the time range at which it’s happening, bowling balls being dropped for potential sliders, which is good to see on a mean. 

12z yesterday at 132h - circular trough in the contours to the south of Greenland, echoed in the circle of low heights to its south…

 

…compared to 12z today at 108h - trough less deep in the contours, much elongated, mirrored by the heights to its south, also elongated and aligned NW-SE, troughing further south of the Azores, core heights a good deal lower.

The heights to the south do gain a little over North Africa, but with no effect on the European trough. However,the real action is where it’s been for weeks and weeks, with the northern block, substantially better heights once again between Greenland and Svalbard and better heights pushing down the gap between Greenland and Canada too, which is part of what is behind the squeezing of the trough. 

While we have this “local” trend for the lows to be modelled to track further south into Western Europe, the cold block intact with ever-building cold at the surface, the approaching warm air all the more easily undercut, it’s the repeated show of resilience over the Arctic that has our back for the long haul. 

And while the northern block keeps bucking the models only a matter of days out, the reliably modelled range will remain as concurrently short. Riveting stuff for (only) the last day of November. 

Original post: https://community.netweather.tv/topic/99584-model-output-discussion-into-winter/?do=findComment&comment=4964889

[bluearmy]

13 minutes ago, Severe Siberian icy blast said:

 

Can you explain this please I'd like to understand this fully ? Thanks

The northern annular mode is another term for the arctic oscillation 

the chart Dennis posted is looking at it through the whole atmosphere from the top of the strat to the surface 

Down in the trop you can see that we are forecast to have a neg AO and even high up at the top of the strat there is a short lived reversal near to the pole 

this is a gfs based forecast from the op run so whilst it’s likely to be fairly decent high up, down in the trop it could easily be wrong as the run heads through week 2 

Original post: https://community.netweather.tv/topic/99584-model-output-discussion-into-winter/?do=findComment&comment=4964895

[Dennis]

6 minutes ago, Severe Siberian icy blast said:

 

Can you explain this please I'd like to understand this fully ? Thanks

red colors are HP and blue are LP . Alot to tell on this : here is some good info to read , 

Annular Modes - Introduction (colostate.edu) : go to the search option and search for NAM

Hope you like 

Greetings from Norway

Original post: https://community.netweather.tv/topic/99584-model-output-discussion-into-winter/?do=findComment&comment=4964879

[January Snowstorm]

A couple of things worth commenting on at this stage:

1 - Almost all of the Long range forecasts are already bust. Early December is panning out very different to what was forecast. Are we in uncharted territory with GW etc and it's likely affects.

2 - Depth of cold over Europe. Have we ever seen that depth of cold so early in the season. I certainly don't recall it in the Internet age. With such warming going on across the world how in earth is it happening?!

We've had a couple of near misses and very odd starts to Winter over the last 3 years. Massive potential that faded. Is it a case that we were unlucky and that luck is now coming good. Below ECM's musings at 240hrs. Bitter bitter cold out East!

Original post: https://community.netweather.tv/topic/99584-model-output-discussion-into-winter/?do=findComment&comment=4964900

[Kirkcaldy Weather]

 

 

 

On 27/11/2023 at 14:43, Kirkcaldy Weather said:

Starting with my post here

 

'Should see the shot of a snowstorm into the Northeast of America currently looks like 2 weeks from now as the +PNA really comes through'

With this I provided in the above post 

So moving + 2 weeks here's how we look

Super pleased how development has panned out with the parts I highlighted pretty much on point too

Now taking this chart also in the above post 

 372hrs

Syncing to where we go by Thursday ie 30th November 

Truly awesome and it highlights something I'd been looking to address for a long time, all too frequent we have opinions of charts equivalent in that time range being tarnished as 'fantasy island' which is unnecessary it just means seeking which 500hpa evolution fits most suitable given teleconnections feeding into said timeframe.

Shifting back to my post on 7th November which contains these from the CFS which are between 600 and 700hrs timeframes

 

Again link to the evolution we are witnessing 

 

Special and astonishing conditions present at both surface and UPPER atmospheric levels and yes i have noticed a negative mindset reference in the previous thread to using that terminology which is ludicrous.

Once the cyclonic developments during Thursday Friday and part of Saturday transfers eastward we will have further developments taking a track quite similar which have possibility of further wintry conditions particularly for Northern parts of the UK which keep supportive upper level ingredients and can benefit from north sea convection given suitable orientation of these lows

Into the late stages of Dec week one this transition will take us into a perfect representation of MJO phase 1 into December pairing into supportive teleconnections feeding into this timeframe which I have discussed prior in extensive detail  

 

 

Start of the trend to phase 2 evolution showing great too  

Given we still await the move to phase 3 probably within roughly 3-5 days I maintain my views here

 

'Given its just emerging there certainly isn't a rush for such evolutions but great the path being discovered already 🌨'

 

Super watching as the feedback of progress from the cycle which has gave our pattern currently into the ongoing IO phases ie 2&3 with models starting to develop various tasty features 

 

GFS op has been on the setup which is suggesting a negative PNA this has tendencies to pump high height developments over Scandi 

That GEFS mean from 18z is prime feedback 

 

Quite a few interest areas to watch VERY closely. Energy of most intense high heights transfers from Greenland and Canada to the Northeast and Scandinavia which links to a strong Pacific ridge - block. Trough over the Atlantic gradually becomes focused toward Canada parts of Greenland with negative tilt tendencies. Fairly significant outputs liking a severe and significantly intensifying cold pool with similar alignment with Feb 2018, PNA tendencies more into negative

Original post: https://community.netweather.tv/topic/99584-model-output-discussion-into-winter/?do=findComment&comment=4964339

[Mike Poole]

Tomorrow will be the first day of winter.  Here are the current temperature anomalies across the northern hemisphere, this is our starting point this year:

The state of play right now, as I see it, is as follows:

• The most immediate factor (other than will it snow on Sunday) is whether the current cold spell will come to an abrupt end with a resurgence of the Atlantic in a week’s time.  
• On here, many have made convincing arguments based on the model output that mild will quickly prevail.  Some of us (including me) have looked for evidence that the cold will prevail, if not in totality, to sufficient extent that it can readily be reloaded when background signals become more favourable again around mid-December.  
• The models clearly struggle in terms of how easy the cold pool to our east and northeast will be to dislodge, and are taking this down to the wire.  But today sees that swing of the pendulum away from an Atlantic zonal reset, towards one of two other options, trough disruption and a sliding train of lows on a southerly tracking jet, or a stalling, deeper low pumping up a Scandi high.
• Both of these options carry some risk, the first that the jet does not track far enough south, the second that the pattern happens too far east. 
• But they could be the start of an epic winter.  We just don’t know yet.  This is where the current temperature anomalies come in.  They are extraordinary - look at the heat over Greenland, the cold pool to our east and northeast, warmth in the USA.  
• If the Atlantic is indeed to be held at bay with what is actually quite a meagre block, it is because there really is no polar vortex driving it.  That is banished to the other side of the hemisphere.
• Enter the stratosphere, where for the first time in 30 years we have an early winter Canadian warming, ensuring a weak strat vortex for the foreseeable, and possibility of a SSW down the line.
• The MJO is predicted to return to Phase 7 about mid month, and AAM is forecast to rise on that timescale, this will promote blocking once more.  I am much more comfortable if this happens with an imprint of the current pattern (particularly the cold pool) remaining, it will reload the blocking in favour of UK cold, giving our second major bite at the cherry.  [If we have to endure a period of strongly Atlantic dominated weather (and let’s not forget the GFS 6z FI) in the meantime, I’m less confident.  The MJO has form for failing to deliver in that scenario, the Atlantic is difficult to stop in full flow.]
• Then there is the possibility of a SSW in January, outcome of course uncertain, but it would likely (in combination with El Niño) produce a cold end to or extension of winter.  This is our third bite at the cherry.
• But most of all, in my mind, is the nature of the weather patterns this year - extreme weather all around the world caused by stuck patterns.  We could be seeing the start of one now.

Of course, it could all vanish on the 0z runs.   But could it, really?  We will see…

All the best

Mike

Original post: https://community.netweather.tv/topic/99584-model-output-discussion-into-winter/?do=findComment&comment=4965001

[Dennis]

a special event soon for the strato first week december23

the normal westerlies turns to easterlies 

 

Original post: https://community.netweather.tv/topic/99584-model-output-discussion-into-winter/?do=findComment&comment=4964965

[Catacol]

Popping back in - to post this ENS chart for Sat 9th.

Russian/Kara ridge, Aleutian Low, southerly jet, Scandinavia colder still, no Euro High - and the next Pacific Wave in the wings, forecast today to be entering phase 7 at this point.

Yummy.

Original post: https://community.netweather.tv/topic/99584-model-output-discussion-into-winter/?do=findComment&comment=4965081

[snowking]

Well despite the memories of December 2012 still being scarred into my hippocampus, I always prefer the chase for scandi-based heights than Greenland ones.

Why? Well you’re probably all sick of me banging on about NWP’s tendency to overestimate height rises to our NW in the medium range. What we’ve found, however, many times down the years is that modelling at longer ranges tends to underestimate the potential strength of blocking to our north-east, mostly it would seem due to the distribution of split flow energy coming out of the jet stream across the Atlantic always tending to err more towards putting greater-than-reality strength into the northern arm. Then as modelling counts down closer to T+0 we tend to see lows taking a more southerly track with the chain reaction of subsequent events conspiring to leave us with an even stronger high than modelled at longer distances.

Now as ever with one of my posts (where’s the fun in getting off the fence) there is a caveat - one of the big spoiling factors which seems to have increased in frequency in recent years is the reluctance of the Azores high to just bloody well sling it’s hook and leave us some space for lovely Genoa-ish low heights to help draw in the coldest air from our east (presumably due to climate change-linked expansion of the Hadley cell). This has, many times, left the UK frustratingly on the periphery of some really severe winter outbreaks across the North Sea.

That, at this stage, would be my major watch factor.

I am far more enthused at the prospect of this potential chase than I have been with the recent spell - impressive and nice to see as it is/has been so early in the season, it never inspired much confidence in anything too impressive snowfall wise.

Lets hope this next one is worth waiting for

Original post: https://community.netweather.tv/topic/99584-model-output-discussion-into-winter/?do=findComment&comment=4965037

[bluearmy]

Note that the ec op and control between days 5 and 7 are in different clusters (seen this once in the past month or so and I think it was about the time that the verification stats nosedived around mid nov) 

subtly different but an indication that next week is v difficult for the nwp 

Original post: https://community.netweather.tv/topic/99584-model-output-discussion-into-winter/?do=findComment&comment=4965329

[johnholmes]

59 minutes ago, Kasim Awan said:

The issue is it's a misunderstood concept, it doesn't mean models may be wildly out or the cold will be so strong that the synoptics may change to a cold setup once the mild arrives, it merely means that temperatures may be a little lower than modelled and fronts slightly slower upon arrival however even this is rare now due to the power of high resolution models.

The difficulty of milder air pushing dense cold air away is not myth it is meteorological fact. Was pre model days and still is. No one has found a way of solving this so far. How many days for deep cold to affect the milder air coming in, how dense the cold air both at the surface and the bottom 3-5,ooo ft. The direction in which a low approaches, some seem less likely to advance than from slightly different directions. It makes trying to forecast the arrival of genuinely mild air still almost as difficult as it was pre computer models.

 

Original post: https://community.netweather.tv/topic/99584-model-output-discussion-into-winter/?do=findComment&comment=4965369

[Mike Poole]

ECM clusters this morning from T120 onwards:

Much messier than yesterday’s 12z, that’s for sure. In the first timeframe there are 3 clusters (2,4,5) which aim to build heights into Scandi, so the signal persists (whether the UK remains cold on them is another matter).  Thereafter, just look at the borders, there are all sorts of options in there, and the model doesn’t know.

However, I think I can see a pattern of sorts.  If you look at the T120 plots, you can see the train of lows heading our way.  Already some of the ‘carriages’ of that train look bigger than others, see for example the representative member of cluster 3:

If, through trough disruption, these ‘carriages’ end up all pretty much the same size, one might expect them all to slide (one of the GFS runs showed this nicely yesterday, think it was the 12z).  If, however, the ‘carriages’ are not the same size, then two other things might happen, if one low becomes a bowling ball it might just push the cold away, or if there is a bit of a gap between them then a ridge might push up between them.  I think what we are seeing on the clusters is the models finding an opportunity to push up a ridge into Scandi between unevenly sized ‘carriages’ on the train of lows, but in each run that might be between different ‘carriages’ at different times, hence the red-border patterns occurring at quite different times.  So the evolution might be more consistent as to what may happen, but it might happen at very different times on individual runs.  

Whether such a push up towards a Scandi high actually gains a proper foothold and delivers an easterly for the UK, is quite another matter!

Original post: https://community.netweather.tv/topic/99584-model-output-discussion-into-winter/?do=findComment&comment=4965361

[knocker]

Put simply the ecm next week has intense trough development in the Atlantic driven by a strong jet which at the same time amplifies the Euro ridge which  effectively mixes out the colder air in the west, including the UK and isolates the colder air to the east.

 

Original post: https://community.netweather.tv/topic/99584-model-output-discussion-into-winter/?do=findComment&comment=4965504

[MattH]

1 hour ago, Met4Cast said:

It’s good to finally see the ECM & GFS picking up on this current amplified MJO pulse. The BOM model has done rather well with this. 

A slow (and weakening) transition through phase 8 seems likely which is an early indication for a more sustained period of high latitude blocking. 

An amplified phase 4/5/6 will increase +FT & +MT rising the AAM quite sharply, not to mention put increasing pressure on an already weak stratosphere vortex, I’d not be surprised to see an increasing signal for an SSW sometime in early January. 

In terms of the background forcing this winter is showing more promise than any winter since 2009/2010 for me. 

Hi.

This, essentially, still sums up the outlook period. The current and upcoming evolution, despite run-to-run differences, hasn't changed. There remains strong evidence for the more westerly push through next week, the regime change eventually coming through, but clearly with the cold block in place to the NE, won't be a straightforward transition, but despite what some may think, cold air can get displaced.

As I mentioned in a previous post, with some attachments and slides, the outlook is focused on this next MJO passage. There was some caution here as to whether the signal was being over-amplified by tropical cyclone activity and that may still be the case, but the overall trend in model data, as exampled in the two images here, is for the MJO to quickly progress towards the Maritimes and then the W Pacific. Any sort of amplitude through phases 6-7-8, along with a rise in the GWO to higher Nino phases continues to point towards very interesting synoptics further down the line.

It should also be noted that for months seasonal forecasts have often signaled key areas of tropical forcing (-VP200 anoms) to be over MJO phases 6-7-8 this winter, which links in with the El Nino.

December, as a month, was always meant to be the most +ve NAO of the winter, often unsettled, often mild and wet. This current cold spell is aided by the entrenched cold air that has been in place over Scandinavia in recent weeks as well and, without question, has been a major bonus to start winter. What we aren't likely to see is a pattern that becomes 'locked in' - This isn't a La Nina/wQBO December, nor is the sPV well organised and strongly connected to the tPV.

If we can manage to see these synoptic changes through the final third of the month (approx 20-30th) with colder synoptics and especially if these influence the Christmas period then this December will end up far more noteworthy, in terms of cold synoptics, than was originally expected. Without question too, the CW and the weakening of the sPV is just waiting for a follow-up "punch" and a phase 7-8 MJO, with amplitude in December, has a well-known link to 'down the line' SSW's. I still fully expect an SSW to take place at some point in January.

Enjoy the cold and winter synoptics that are here, now, let the medium term come and go and then keep firm eyes on the second half of December...

Regards, Matt.

Original post: https://community.netweather.tv/topic/99584-model-output-discussion-into-winter/?do=findComment&comment=4965581

[johnholmes]

On Tuesday ( 28/11) NOAA 8-14 is much the same as the previous one so a broad westerly is to be expected within that time frame; meridional still on the 6-10

Friday 1 December - Another look at NOAA and ECMWF

NOAA 6-10 has no signal for blocking over the last 3 days or so and its 8-14 chart continues this. However the contour values arriving over the UK  are about/a bit below average so although less cold than now, not mild by any means. A similar temperature level from the ECMWF output for a similar period to NOAA 6-10 day. The overall 500 mb pattern on both outputs is broadly westerly, a touch north of west at times. On the NOAA 6-10 and 8-14 you can see that the usual major trough around ne Canada is nothing like as deep as we usually see around the start of winter. The trough off western USA/Canada shows on the 6-10 but not really on the 8-14. So we see a generally westerly 500 MB flow over much of the chart extending into Europe with no signal for any marked European trough.

This all suggests to me that whilst deep cold is unlikely in the 6-14 day period, neither is any really mild air, other than perhaps now and then for the far south of the UK. Snow probably confined to high ground from the Peak District north but on lower ground at times further north. Beyond 14 days then that is not for these charts.

Climate Prediction Center - 6-10 Day 500mb Outlook

WWW.CPC.NCEP.NOAA.GOV

Original post: https://community.netweather.tv/topic/99584-model-output-discussion-into-winter/?do=findComment&comment=4965535

[Met4Cast]

It’s good to finally see the ECM & GFS picking up on this current amplified MJO pulse. The BOM model has done rather well with this. 

A slow (and weakening) transition through phase 8 seems likely which is an early indication for a more sustained period of high latitude blocking. 

An amplified phase 4/5/6 will increase +FT & +MT rising the AAM quite sharply, not to mention put increasing pressure on an already weak stratosphere vortex, I’d not be surprised to see an increasing signal for an SSW sometime in early January. 

In terms of the background forcing this winter is showing more promise than any winter since 2009/2010 for me. 

Original post: https://community.netweather.tv/topic/99584-model-output-discussion-into-winter/?do=findComment&comment=4965542

[nick sussex]

The ICON 12 hrs run certainly trending towards the ECM 06 hrs control run .

The shortwave formation near Iberia stops a ridge from pushing ne . 

This looks to be the bellwether for increased chances of hanging onto the cold.

Original post: https://community.netweather.tv/topic/99584-model-output-discussion-into-winter/?do=findComment&comment=4965697

[Catacol]

10 minutes ago, Mike Poole said:

Yes, agreed, but the bit in bold will be crucial if, as looks likely, the Atlantic does start to make inroads.  If the cold does not hang on over Scandi (putting the UK to one side for a minute), then my optimism for the late December cold spell will massively diminish.  If everything has gone back to normal zonal fayre by that point, then how many of us would trust supposedly favourable phases of the MJO to actually deliver from scratch?  

This puts the onus back on the current model uncertainty resolving itself in a way that, even if the UK warms for a while, doesn’t produce a completer zonal reset.  Damage limitation will become the watchword of the next couple of weeks modelling, unless, of course the Scandi high and easterly option (which is still in the mix) verifies.  

Momentum elastic ping-back has already peaked and settling. We have the jet firing up in response as MJO is in 2/3/4 but I think here the brakes will be applied because that momentum surge is not record breaking and the cold will hold to our E and NE. CPC charts to me say the same. So.... cold pushed away from the UK mid week - which at the very start of this spell was the form call - but the trough to stall. That might mean some wet days for us and general damp grimness - especially as the residual heights over Greenland that I have mentioned before should ensure the trough stays chilly with plenty of arctic rather than tropical air being fed into it. But Scandy to stay cold and lack of Euro High to allow central Europe also to stay pretty cold.

Watch then for 7/8/1 MJO phases and renewed momentum surge mid month. Phase 7 around Dec 9....allow for lag - one week? - so signs of heights rebuilding as we approach the final third.

One of the best tweeters still tweeting since Masiello disappeared is Eric Webb. Some very detailed discussion from him yesterday. He sees -NAO digging in for the long term and a hemispheric wave patttern conducive to strat disruption. It is good to read real pros coming up with the same arguments at this point.

Most exciting winter in years continues. Snow chances this weekend. MJO playing ball. Strat pressure well forecast. I can see a cold Xmas week followed by a Jan SSW and given Aleutian Low activity I'm willing to gamble on a split. This winter has a chance of being a cracker.

Original post: https://community.netweather.tv/topic/99584-model-output-discussion-into-winter/?do=findComment&comment=4965863

[Catacol]

1 hour ago, Kasim Awan said:

I disagree, I can't see full model backtracking of such a powerful jet stream. Though it is possible, if it happens it will be due to models overestimating the jet stream and not underestimating the influence of surface cold.

I'm no physicist....but there are plenty of known model issues.

Model Biases and Verification

WWW.WPC.NCEP.NOAA.GOV

Note this line on UKMET - "Has problems with shallow cold air."

I suspect this problem is more complex than you are making out, and there is always a role for observation. Observationally, as John has much experience of, cold blocks give ground slower than modelled. Many have noted this over many years without any clear sense that a slider slides, or a system rebounds, because the jet itself is overmodelled each time. As with everything - a complex relationship.

Original post: https://community.netweather.tv/topic/99584-model-output-discussion-into-winter/?do=findComment&comment=4965573

[Catacol]

25 minutes ago, Ali1977 said:

I like the last line of the METO long range , a chance of a longer cold spell later into Dec!! Guessing that’s MJO related!!

anyway, cmon ECM

Most significant development of the day, especially for those of us that have championed a cold but not spectacular spell at the start of the month leading to a IO driven relaxation for 10 days or so followed by shift back to deeper and more impactive cold. The MetO have all the computer power hidden up their sleeve. Yesterday there wasn't a hint of a colder shift in the text - and today that cryptic little dangler at the end. That suggests to me they are seeing cold holding on over Scandy as many have predicted and then a renewed surge of heights backing that cold W and SW at Xmas time. I don't pay a huge amount of attention to MetO updates because they can swing around....but they rarely risk a cold statement especially at range. The fact they have come out and risked it today I think is huge.

Best keep this relevant before Mods stab me. Note again this chart, same sort of period as yesterday. That high anomaly over Kara is beginning to back west....

Original post: https://community.netweather.tv/topic/99584-model-output-discussion-into-winter/?do=findComment&comment=4965844

[Blessed Weather]

3 minutes ago, MattStoke said:

I don’t know why people pay any attention to the BBC forecasts when they can just look at the second to last ECM operational run.

MeteoGroup provide the BBC with their forecasts that we see on the TV. They use input from 3 different models and then 'add value' by allowing their meteorologists to make human input/tweaks before issuing a forecast. Here's some snippets about how they arrive at the forecasts:

The making of : a weather forecast
MeteoGroup uses a combination of three weather prediction models to arrive at the best result. These are the European model (operated by ECMWF), the American model (operated by US NCEP), and the British model (produced by UKMO). Our long-standing use of each of these models has taught us how well each scores on the various elements, which allows us to give a certain weighting in relation to each weather element to be calculated.
The most important step in our production of the specific forecasts we offer customers involves adding value to the data we buy. Our innovative, cross-functional Weather Systems Team is responsible for a bulk of (machine learning) post-processing algorithms we run on all of the data obtained from the models. Post-processing is used to correct the quite coarse-scale nature of model output; these corrections are necessary to ensure that local effects are taken into consideration. The process outlined above is at the heart of our high-quality forecasts and results in the MOS (Model Output Statistics). The meteorologists on duty are responsible for putting the finishing touch to the ultimate weather forecasts to be issued; of course, they have the full width of MOS data at their disposal. Senior forecasters are allowed to make changes to the MOS via the MeteoBase system.

Full article: https://medium.com/@meteogroup/the-making-of-a-weather-forecast-4ee5bfcc942e

Original post: https://community.netweather.tv/topic/99584-model-output-discussion-into-winter/?do=findComment&comment=4966567

[nick sussex]

An interesting start to the day with some  changes to the upstream set up.

The models are trying to send some energy se rather than spilling everything over the top to the ne .

The change is more dramatic when you compare yesterday’s 00 hrs runs with today’s .

The question is whether this trend can accelerate. If it does then the outlook can change quite markedly in the medium term .

The ECM out shortly so hopefully that follows the new trend .

Yesterdays UKMO 00hrs run to T144 hrs 

 

Today’s to T120 hrs .

Note the upstream low aligning more nw se . The wedge of heights developing over southern Greenland towards Iceland .

 

Original post: https://community.netweather.tv/topic/99584-model-output-discussion-into-winter/?do=findComment&comment=4966425

[sebastiaan1973]

And while a technical SSW is difficult to forecast with precision at extended leads, the expectation based on the composite analogs remains that one will indeed take place between approximately Christmas and January 8, along with a major winter storm in the vicinity of the holiday week. This impending disruption of the polar vortex is not only significant due to the sensible implications for later December and into January, but also the balance of the winter season given the unexpected prevalence of the negative NAO through the early portion of December. Having the NAO average negative prior to the vortex even weakening makes it extremely likely that December will end up featuring a negative NAO in the monthly mean. This represents a significant deviation from warm ENSO climatology and offers invaluable as to how the rest of the season may evolve. Research conducted by meteorologist Eric Webber confirmed that El Niño events that feature a greater incidence of negative NAO in December are more likely to exhibit additional episodes of high latitude blocking, leading to a colder and snowier outcome for January through March over the Eastern US.

 A nice read -> https://easternmassweather.blogspot.com/2023/11/december-preseason-impressions-appear.html

 

And the Tweet where he writes about:

https://twitter.com/webberweather/status/1728115422648562170?s=20

Original post: https://community.netweather.tv/topic/99584-model-output-discussion-into-winter/?do=findComment&comment=4966707