Model discussion highlights

[Paul]

Welcome to the model discussion highlights thread. Posts from the main model discussion thread will be copied in here based on the number of 'insightful' reactions they receive. Once they hit the threshold, they'll automatically be copied over to make a community, crowdsourced thread filled with the most insightful posts. 

Then, those posts can stay out front a little longer than they may otherwise, in what is a very busy thread, and those wanting a more concise read of the model discussion thread can use this one. 

The threshold for copying a post in here will vary and will be tuned as we learn about how this will work. Hopefully, it'll be a great addition though. 

This will be locked for replies, with the only posts in here copied in from the main discussion. 

[IDO]

Much better in most regards, the 06z, and one step away from the ECM and GEM linkage of the Asian trough:

06z:  0z: 

It keeps the colder flow seeping into the UK trough, and the obvious knock on effect of blocking in the NW heights, and squeezing the Atlantic low, to disrupt and undercut.

Up to D6 a def bank! 

Original post: https://community.netweather.tv/topic/98064-model-output-discussion-3122022-how-cold-will-it-get/?do=findComment&comment=4756737

[Met4Cast]

GLOSEA: No/very weak westerly signal until beyond the Christmas period with easterlies/northerlies being the most likely out until that period albeit with a weakening signal. With that said, a clear trend from the model towards the New Year > January especially for a marked switch to westerly driven weather. 

No sign of an SSW within the model, rather similar to that of the ECM.

Original post: https://community.netweather.tv/topic/98064-model-output-discussion-3122022-how-cold-will-it-get/?do=findComment&comment=4756840

[Derecho]

Out of the GFS 06z ens, about 6 give us a battleground snow event in the middle of next week. The rest have the low further south.

A lot of the output suggesting we stay cold throughout next week with the Greenland high coming into play.

Models are likely to be overly keen in collapsing it into Europe later on in the outlook. It was only 3 days ago there wasn't that big a signal for a Greenland High later next week, it's a theme that has built in recent runs.

With this airmass being much colder on a larger scale to our north in such a scenario, it'd be interesting to see what it delivers if it comes into fruition. All we need is a bit of energy to our south or the Greenland High linking up further west rather then over Europe to get a mighty impressive northerly (or easterly if things allign differently).

Original post: https://community.netweather.tv/topic/98064-model-output-discussion-3122022-how-cold-will-it-get/?do=findComment&comment=4756849

[MattH]

If we just put the teleconnections and drivers (AAM, MJO et al) to one side for now and just focus on the long-term from an NWP perspective, what stands out is the persistence from the GFS and its ENS to lower heights over the central and western N Atlantic. As a general guide and rule of thumb, like a see-saw, if the atmosphere gets 'pushed' down (trough) in one place, then in another it is 'pushed' upwards (ridge) then knowing where these occur can determine medium and longer-term trends. This is why we are seeing the GFS Det (and Control) potentially bring in a very mild SW'ly airflow, because the trough dominates to the W and SW of the British Isles and the ridge builds over NW Europe but not near enough to the British Isles to stop the SW'ly flow.

However, not all the ENS show this, as exampled below. The CMC and the EPS both show generally higher heights, as a mean, through the 10-15 day period than compared with the GFS, so there is no certainty here that this pronounced upper trough will develop as the GFS is currently indicating.

Equally, mind, this is the British Isles and not Canada and to go a whole month with a blocked regime like we have at the moment is beyond realistic. Even through the likes of December 2010 the pattern did relent once, mid-month ish, but then clearly the blocking regimes returned for Christmas. From a Christmas perspective one could argue as well that the cold weather has arrived 'too soon' but, equally, Christmas itself, in terms of a specific day(s) is a very long way off, meteorologically speaking so hope for a cold, seasonal Christmas continues.

If the GFS is, however, correctly picking up on this pattern looking ahead then one of the primary ways to maintain some sort of cold block is what some of the GEFS members are showing, particularly P08, as exampled below. As I mentioned a few days ago WAA into the western flank of a surface and upper anticyclone helps to build it and blocking highs over Scandinavia and NW Europe often always develop when there is some sort of S or SW'ly flow over or to the W of the British Isles, at first.

The GFS P08 compared with the GFS Det (below) highlights how yet further fine margins (whenever not!) could mean the difference between a tropical maritime SW'ly flow, or the potential for a building high over the UK that still has cold air in place with the main plume of warmth situated to the W of the British Isles which is aiding the build of pressure in the 'right' place for cold weather.

This is clearly far down the line and, again, as I mentioned the other day while snowfall is looking thin on the ground, lets just remember what can dominate at this time of year and enjoy a prolonged run of cold, crisp seasonal conditions that is here, right now, with us - As a side note, keep an eye on the backing flow if you live in NW England as some Irish Sea showers could well bring some 'unexpected' snowfall accumulations to NW England later on Friday and into Saturday morning, which HRES models are struggling with. 

Cheers, Matt.

Original post: https://community.netweather.tv/topic/98064-model-output-discussion-3122022-how-cold-will-it-get/?do=findComment&comment=4756875

[Eagle Eye]

The jet 'recovery' across East Asia is about to begin, reloading the Pacific jet wave and PNA back to more neutral territory which may reload the Atlantic long-term and wane the Greenland block. Although, it may just change the basing of the Greenland block into a more west based block it's hard to tell just from any composites I could find. Hence forth we still see a slightly -VE NAO on about half of the ensembles despite the recovery of the AO that seems fairly likely on most. I do think this will increase the zonal westerlies beyond Christmas but that doesn't mean we can't see long term cold up until then with the -VE EAMT interacting with the lag of the +VE AAM looking pattern with an amplified North African wave potentially forming a UK and/or Scandinavian blocking and helping the -VE AO pattern slightly mid-term. The recovery of the AO can be expected eventually though as the Troposphere transfers energy through regressing Eddy's.

We simply cannot keep up the -VE AO and eventually the pattern will collapse but most importantly right now, the pattern is expected to keep steady(ish) for the mid-term and we've seen a recent trend towards longer term cold on about half the runs. A lot relies on a lot of different things but there's decent support for a more substantial cold spell to keep going and importantly, the trend on most of the recent days has been an increasing number of support for the longer-term (ish) cold and fairly substantial cold. I would keep up the positivity for now because we've got a lot to be positive about.

Compared to recent Decembers this simply outweighs every other December (in my opinion) for snow and cold potential since 2010. Worrying about precipitation isn't worth it considering the time scale especially because in years before we were looking for anything that supported colder trends yet this year we're getting that cold and people are now over-anlaysing. I can understand why though. It's a real shame that for all of the year's this could have happened, it had to have happened in a year with a significant energy crisis as well.

Despite the timeframe of this it shows how good of a setup up we are within relative to recent years:

No one can guarantee you 3 foot snowdrifts in your back garden and if they could, they would be lying but they can say that there is chance of you seeing decent snowfall compared to anything really since around 2018 (especially away from Scotland) and to take this as it comes because looking into the distant FI won't solve anything (I know I used it there but that's on the GEFS ensembles and to demonstrate my point rather than analyse anything).

Original post: https://community.netweather.tv/topic/98064-model-output-discussion-3122022-how-cold-will-it-get/?do=findComment&comment=4756979

[Cambrian]

If we start from the slightly more reliable period up to day 8, the 6z GFS mean nicely shows the resilience of the Siberian trough extending southwestwards towards the UK and Ireland. Notice a second wave of low heights pushing down across Scandinavia by the middle of next week and the merging of the Atlantic low with the base of the trough to our south. 

 

The same with the T850s, the incursion of mild air is kept as a ripple to our south by the continued reinforcement of cold air from the northeast. 

Thereafter, if we put the day 9 to 16 mean anomaly side by side with those for day 1-8, it’s pretty much a repeat pattern, slightly more feint over time as ever due to the averaging out - day 1-8; day 9-16

 

Continued attempts from the Atlantic to slip low pressure around the south of the block, but only meeting deep cold air where they do. Though the second low might have a trajectory slightly further north than the first one,  the standout feature is the reinforcement of heights over Greenland from day 14 onwards and notice too no build of heights over Europe. For now, it’s a one-way ticket to Slideville. 

Original post: https://community.netweather.tv/topic/98064-model-output-discussion-3122022-how-cold-will-it-get/?do=findComment&comment=4756995

[bluearmy]

Small area of vorticity picked up on Sunday on the ec 06z op and control over England 

they handle it’s track differently so for now, a waiting game for the next couple runs. 

the Thames estuary and Kent/se Essex could well see something form in the s North Sea on Sunday pm too - this has been a recurring feature so probably more to it 

the eps control 06z makes less of the Norwegian shortwave at day 5/6 so introduces what would be a cleaner northeaster flow 

Original post: https://community.netweather.tv/topic/98064-model-output-discussion-3122022-how-cold-will-it-get/?do=findComment&comment=4756997

[johnholmes]

Looking the last anomaly charts 6-10 and 8-14, see below, it suggests remaining cold or very cold from 6 to about 10 days but becoming less cold in the early 8-14 period. heights over southern UK rise from around 540 DM to 546 DM.

 

Mind you the flow is still from a fair way north over the states, a westerly flow should make it less bitterly cold at least, maybe mild for a time as surface low pressure systems run east across the Atlantic?

Climate Prediction Center - 8-14 Day 500mb Outlook

WWW.CPC.NCEP.NOAA.GOV

 

 

 

Original post: https://community.netweather.tv/topic/98064-model-output-discussion-3122022-how-cold-will-it-get/?do=findComment&comment=4756685

[Eagle Eye]

The dynamical recovery of the AO probably has a lot to do with the unstable inertia that has propped up the -VE AO state losing it's support with a loss of AAM and therefore the Eddy's 'retreating' across the Northern Hemisphere battlefield as the Rossby energy transfer retreats to being mostly across the tropics with a flatter Atlantic to probably come into place by early next year. Signs that we could get an increase again in January but for now I'd treat it as signs.

The GWO supporting my view of the jet coming into line with the thermal wave northward transfer (of the jet momentum so the jet reverts back to normal) and eventual pattern flip into circumglobal ridges and it's been a general trend recently. Circumglobal ridges linked with Atlantic influence and mild and wet.

So beyond Christmas things may return back to normal with the occasional colder chance but I keep saying it...

Take this chance on the face of it and it is the best early Winter chance since 2010, as simple as that, we've still got till Christmas before any chance of severe cold setting in goes and even beyond then we don't know for sure that we won't get helpful background influences.

Original post: https://community.netweather.tv/topic/98087-model-output-discussion-the-cold-has-arrived/?do=findComment&comment=4757081

[BlueHedgehog074]

In summary, the models show further cold weather to come for the rest of this week into next week (and perhaps beyond, but far out to be sure). The pressure charts from the ECMWF below, while liable to some changes in some the later frames, shows an idea of the outlook for our part of the Northern Hemisphere for the next 6 days. 

Essentially High Pressure combined with high upper heights over the Greenland area, and a string of Low Pressure systems running along to our South and South-West. There is also a Scandinavian trough of Low Pressure extending some of its low heights and slack surface Low Pressure South-West over the UK further into this week and during the weekend.

Although the source of the cold is originating from the North and North-East for the UK, you can see the flow is slack (isobars well spaced out) and the flow will become variable over the weekend. Lack of winds should mean frosts continuing to form at night, especially inland with clearer skies at times. Could be some cold mist and fog too. Air cold and still enough for frosts to linger throughout the day, particularly in the shade. So will continue to feel like a Winter wonderland in many parts, especially for places that have seen fallen snow so far (latter mostly for some Northern areas and towards Eastern and Western coasts).

In fact, looks to be quite dry away from the coasts and Northern areas, bar one or 2 possible wintry surprises - these always have the possibility to catch people out unexpectedly. That is until sometime next week where you’ll see on the later frames of the ECMWF above that an angry, deep, Western Atlantic Low tries to slowly shift further East towards South-Western parts of the UK. This giving a strengthening chilly South-Easterly flow over South-Western parts heading into Tuesday and Wednesday next week as shown in the last 2 charts above.

With pressure from the Greenland blocking, it’s not yet clear whether this Low will party over the UK at all. Very very possible for the Low to just fully avoid the UK to the South and become squished and disrupted. May just find the blocking over Northern/North-Western UK could be too powerful and win the fight that Azores/Atlantic Low wants to start.

The Low does however have the chance of bringing a more organised area of rain, sleet and snow, with Southern areas of the UK probably seeing the best shot at this. Without that Low having any influence, cold and mostly dry conditions will probably continue to be the theme, nonetheless.  In spite of that, a more cyclonic flow between the North and East could easily be picked up next week sometime. It’s still at a range for that to be possible, particularly later next week. Plus some disturbances could easily pop about in the flow. This of which could drag more organised areas of sleet or snow further inland.

With how things could continue to go, an increased number of wellies and sledges could very well end up getting some attention at some point during the next week or so. 

Original post: https://community.netweather.tv/topic/98087-model-output-discussion-the-cold-has-arrived/?do=findComment&comment=4757158

[Dangerous55019]

Hello everyone. 

being as its been a week (or there abouts) since I last posted in here, I thought I'd take a look at the CFS v2 four weekly anomalies, to either help clear the waters for other members or help muddy them? Lol 

Week 1 - 8th to the 14th December: We have a large trough of low pressure centered right over the Midlands and southern UK and stretching out over north eastern Europe, and towards Scandinavia. We also have what looks to be a large blocking area of high pressure over Greenland and north eastern Canada. To my eyes that is going to leave us in an easterly airflow! Cold? Yes! Snow? I'll leave that to our more experienced members! Lol 

Week 2 - 15th December to the 21st December (The Winter Solstice): Pretty much a very similar setup to week 1! But with the trough of low pressure over us here in the UK weakening.

Week 3 - 22nd of December to the 28th December (So covering Christmas): The large area of high pressure over Greenland and north eastern Canada is now starting to extend outwards towards Scandinavia! The trough of low pressure over us here in the UK appears to have vanished... But has it? There's definitely something over us here in the UK, and the rest of main land Europe. But what it will do (as this is three weeks out) I have no idea. 

Week 4 - 29th December to the 4th January (Into the New Year): The large blocking area of high pressure that has been sat over Greenland, appears to be weakening. But there is a trough of low pressure now showing to the north west of Scotland... To my eyes this would leave us in a cold(ish) and unsettled northwesterly airflow. First winter storms? Time will tell.

So there you have it folks! Hopefully this will help some of our more experienced members of this forum. 

Original post: https://community.netweather.tv/topic/98087-model-output-discussion-the-cold-has-arrived/?do=findComment&comment=4757169

[Neilsouth]

13MINS in, big discussion about the charts/models and the low pressure system in the atlantic

Original post: https://community.netweather.tv/topic/98087-model-output-discussion-the-cold-has-arrived/?do=findComment&comment=4757173

[Catacol]

AAM rebound underway - will begin to neutralise the retrograde signal that has helped ease the Greenland High towards the west

We are not yet in a low momentum base state with the GWO holding a pretty neutral orbit

and so there is not currently a signal for a flat atlantic. If the MJO can get its act together and recover some amplitude then renewed amplification is still on the table. Timescale? Well - all rather tricky. AAM is pinging back already, MJO has yet to engage. I would say that we get our next 10 days of cold and then we hit a crossroads moment - as signalled in ensembles and on John's 8-14 day charts and as flagged by a few more experienced folk - that will set the tone for the rest of the month. By that time some might not care because they may have had their fill of cold and some snow after 10 action packed days....but others may still be chomping to get in on the action!

My thoughts have been anchored on the belief that the last third of the month would see the peak of cold for December. This was based on observations of early December cold usually not delivering, of the timing of the next phase of the MJO and on the belief that, by this point in the month, the column of westerlies better known as the vortex would be sufficiently distressed that, instead of gathering pace and cohesion, the opposite would occur. Now....one of these assumptions are already up in smoke. It is properly cold outside right now - the arctic air that has landed is the coldest I can remember in early December since 2010 and that was the coldest since....well - 1981? I couldnt be happier to be proved pessimistic. So the early phase of winter is delivering as we speak. The MJO heading back towards 7/8 I await patiently - and what about the strat?

A lot - at least for the way I see things - rests on the strat. This current cold hit has arrived because of a trop led dagger pushed straight through the layers over Greenland. This itself was a product of the Nino-esque setsup of the atmosphere in November which intially brought us a very strong Ural ridge stopping atlantic systems dead in their tracks over the UK, hence a mild and wet month, but then pulled west over Greenland as the amplification signal fell away. If we are to prevent a Nina grip on winter, and further falling momentum which is the trademark of a Nina winter, from sucking the amplification out of the system entirely we need something else to boss the pattern. EITHER we get a major bump up in the momentum profile again as we head into late December and on into January (and while we can't rule this out I can't quite believe we will roll a double 6 again, having rolled it in November, and see a trop led amplification signal big enough to maintain ongoing high lat blocking) OR we get significant assistance from the strat. Late November was full of good precursors - we had that very strong Ural ridge and we had low pressure over the Aleutians. This is your ideal strat stress precursor pattern and it was clearly visible. So - can we see the strat wobble, tilt and fall apart?

Too early to tell. If it happens then this winter could become a big one. If it doesnt then we may look back at a winter that started in great style but then gradually fell away. I am musing and not offering much of a forecast here, other than to suggest that we enjoy the next 10 days, expect at that point to arrive at a crossroads, and then peer with purpose into the mists of stratospheric forecasts as we hope to get the added boost to turn this winter into a properly long term cold one. We can still get the cold Xmas period from current pieces in play enhanced by the MJO and current bounce back of AAM. But to get more than that then a strat meltdown would be very very welcome.

On this note I'll close with this vertical profile. I bow, nose on the floor, to Chio's expertise in this area, but I get a sense of things when I put my head at the top of the vortex column and look down from on high - just what this tool gives us.

I see a vortex that looks to be very misshapen and showing signs of tilting. Notice the clear pressure on the upper vortex from the Asian side as demonstrated in Chio's recent warming charts - squeezing that upper vortex into the atlantic sector and threatening to setup a damaging wobble. Get a bit more tilt - take the centre of the upper vortex far enough away from the centre of the lower vortex and it might just be game on for a December SSW event, maybe early January. We can hope.

Original post: https://community.netweather.tv/topic/98087-model-output-discussion-the-cold-has-arrived/?do=findComment&comment=4757278

[Singularity]

I've been refraining from looking past however the middle stages of next week unfold, but will drop this note: Judging by the MJO & Kelvin Wave analysis on Mike Ventrice's site, it seems to me that the cold surge out of East Asia is being predicted to kickstart more of a fast-moving Kelvin Wave than a traditional MJO event.

Those tend to have shorter-lived impacts on AAM etc, but it can be a pretty sharp kick, which might be just what's needed to set up a high near or over Scandinavia (a possibility that several others have rightly been noting for a while now). No telling at this stage what orientation it would have though or where cold pooling would have occurred prior to its establishment, which makes all the difference in terms of how cold received airmasses are, especially aloft (850 hPa level).

Modelling, mainly GFS/GEFS, is having a hard time picking out that signal against the near-term lagged effects of the recent AAM drop.

Incidentally, the GEM 12z might not actually be in the same camp as GFS - looks to me that a happenstance merger of two lows in the North Atlantic had much to do with the sudden, strong push from the west. Without that, it might well have looked more of  a 'Scandinavia high precursor' come day 10.

Original post: https://community.netweather.tv/topic/98087-model-output-discussion-the-cold-has-arrived/?do=findComment&comment=4757322

[geordiekev]

Just a gentle reminder every cold spell had mild incursions, the jet stream is like a skipping rope producing a wave. Personally can't see the jet stream moving to position where the peak waves reach meridian where we have blowtorch SWs anytime soon, just a waning & waxing of deep cold.

Even 62/63 had its less cold sectors & propagated further blocks  (notice the lack of deep blues throughout Dec, Jan) Enjoy the ride

Original post: https://community.netweather.tv/topic/98087-model-output-discussion-the-cold-has-arrived/?do=findComment&comment=4757069

[Cold Winter Night]

29 minutes ago, claret047 said:

Can someone explain to me how the actual charts are arrived at. Is the data collected for each run used on to coin a better phrase "a blank canvas" or is it inputted into the previous run and the results spewed out therefrom. On the other hand is the data from say today's 12Z inputted into yesterday's 12Z for todays 12Z model. Alternatively is it a combination of 2 of these with perhaps some human input thrown in for good measure. Sorry for the ramble, but I would be intrigued to know.

New data are gathered (weather stations, satellites, airplanes, etc) every time at 0z, 12z etc. though some data are older or not available every run.
Then from all those data, the 0h starting state of the atmosphere (and oceans) is calculated. So the starting point is not a blank canvas.

From there, the equations representing the physical process of the atmosphere, oceans, and ice produce every next step.

If you would like to learn more about the ECMWF IFS model (EC/EPS), this is recommended reading:

1 Introduction - Forecast User Guide - ECMWF Confluence Wiki

CONFLUENCE.ECMWF.INT

 

Original post: https://community.netweather.tv/topic/98087-model-output-discussion-the-cold-has-arrived/?do=findComment&comment=4757332

[Eagle Eye]

I realised that I didn't really specificy timescales on my last post except my Christmas end which based off the progression of the zonal pattern might be a bit too progressive.

Signs that we're moving towards the phase 2/3 pattern of the MJO but those affects probably won't be felt until at least the new year considering that's around the time the AO finally comes out of negative. So I'm going to extend my cold deadline to the new year. Its a genuine possibility that there will be cold opportunities for all of this month. The main affects towards the middle to the end of the month might not be driven by the MJO (yes it will be helped of course) but by the East Asian reaction to the jet retraction amplifying wave centres hence increasing Rossby Wave transfer via the synoptic wave train. That would henceforth create that Scandinavian block or somewhere near there through downstream interactions. The recovery of the jet retraction is interesting to me as well but I discussed that earlier as well.

Original post: https://community.netweather.tv/topic/98087-model-output-discussion-the-cold-has-arrived/?do=findComment&comment=4757365

[The Enforcer]

As of 22:20 there is the first significant incursion of precipitation into mainland England (Yorkshire/Nottinghamshire/Derbyshire):

What did the hi-res short-range models predict?

NMM T+10 - underplayed:

UKMO T+10 - non-existent:

Arpege T+10 - skirts the coast:

ICON T+4 - underplayed:

Conclusion: it doesn't matter if the models suggest it is going to remain dry.

Original post: https://community.netweather.tv/topic/98087-model-output-discussion-the-cold-has-arrived/?do=findComment&comment=4757829

[damianslaw]

GFS continues to hint at my earlier predications for how the rest of the month pans out, at some point we will see a temporary easing of the cold thanks to warm air advection through the UK, atlantic trough to the west, but at the same time heights will be lurking to the east and a battle of sorts will take place between the atlantic and continental heights, possibly bringing something milder for all, snow to rain transition, but once the frontal activity moves through there is nothing behind it with the atlantic quiet and heights are then able to quickly build to the east, scandi high eventual outcome. Expect this messy transitional period to arrive before christmas, but not sure exactly when.

We shall see...

In the meantime, more of the same, could be a snowy surprise for the NW England tomorrow night into early Saturday morning, a very cold weekend ahead, freezing fog could be the biggest hazard. Much of next week remaining cold, northerly flow, chance of snow anywhere again, this quite possibly lingering through into the following weekend. 

Original post: https://community.netweather.tv/topic/98087-model-output-discussion-the-cold-has-arrived/?do=findComment&comment=4757915

[tight isobar]

Detached micro energy looks interesting Sunday/ Monday snow showers could crop up almost anywhere!!. Something else to keep note of!

Original post: https://community.netweather.tv/topic/98087-model-output-discussion-the-cold-has-arrived/?do=findComment&comment=4757769

[bluearmy]

Look out for an eastern USA  trough which drives a downstream mid Atlantic ridge in the 9/12 day period. 
 

Original post: https://community.netweather.tv/topic/98087-model-output-discussion-the-cold-has-arrived/?do=findComment&comment=4758163

[Singularity]

We have a pretty strong signal now for the main high-latitude blocking to drain away into the mid-latitudes late next week.

Ordinarily, that's the signal for a return to a typical Atlantic westerly regime for the UK, unless a residual wedge of high pressure positions just-so to slow and disrupt incoming troughs.

However, on this occasion we have not seen a big drop in AAM and there are signs it will climb again just as the main HLB subsides. That complicates matters as we have a relatively weak zonal push followed by re-amplification propagating up from the tropics.

The big question and main uncertainty here is whether an amplifying ridge sets up at the subtropical to mid-latitudes, or high latitudes. With no particularly dominant signal to drive the outcome, this will be tough for the models to resolve and for forecasters to navigate. 

A tendency for the AO to stay negative suggests that even if a subtropical to mid-latitude high initially results, it could find its way north before long. The window might be rather small though, as there's no clear sign of further tropical wave / MJO action to stop AAM from falling more substantially by the late stages of the month.

If a high has found its way north to Scandinavia or thereabouts, then the retrograde stage as AAM begins to fall could hold much interest for cold/snow seekers depending on how that high has orientated itself. Regardless, SSW probability for Jan would be notably increased.

Otherwise, we'll probably be watching high pressure oscillate between Europe and the Azores as a typical La Niña-like pattern manifests.

Original post: https://community.netweather.tv/topic/98087-model-output-discussion-the-cold-has-arrived/?do=findComment&comment=4758237

[johnholmes]

Update using NOAA 500 mb anomnaly charts and the latest ECMWF 10 day output.

Sorry but I am unable to get a basic link re EC, just the piccs which I know, even when you enlarge them are not very good. If someone knows how to improve this please pm me so I can alter things.

Main centre of +ve heights is where major trough usually is, flow into uk still n of w, and main atlantic flow is around 40n then joining Greenland flow into uk over w’ern Europe, s’ern uk contour=540DM so higher than 2-3 days ago but still originates from top of Hudson bay (unusual) and thence from sw Alaska/kamchatca peninsula

8-14 shows only major +ve heights s of Alaska and major trough pole-hudson bay and south uk is in w’ly atlantic flow 546 DM still from sw Alaska area

But to me they suggest intense cold leaving say 8-12 days from now, more mobile taking over still below average temps

ECMWF shows   536DM over uk on first frame from nw with -5C 850 and a rather slack n’ly surface flow with lows west and south of the uk.By Sat 16 then signs of a more w’ly 500 flow, the 850 -5 edging north clippinf sw England with the surface flow shown as light and variable. During the 18-19 the w’ly 500 flow becomes established with the 552DM contour into the s’ern half of England. The surface flow has backed s of west for most areas.

So a slow decrease in the cold for all areas is shown. You will note though how this is being put back each day over the last 3 days.

Trying to get milder air into the UK after a fairly cold spell of several days is and always has been slower than any forecaster or model predicts. So will the next ECMWF output do it again. Tomorrow will show us.

Climate Prediction Center - 8-14 Day 500mb Outlook

WWW.CPC.NCEP.NOAA.GOV

Original post: https://community.netweather.tv/topic/98087-model-output-discussion-the-cold-has-arrived/?do=findComment&comment=4758326

[Mike Poole]

ECM ensembles T168 (or some of them anyway!):

And here’s the way out!  As @bluearmy rather cryptically noted above, there’s a sizeable number of these that put up a ridge in front of the low that would otherwise bring the downfall of the UK cold spell were it to cross the Atlantic and impinge on the UK bringing air from the south.

Here’s perturbation 12 to illustrate what I mean:

It will be really interesting to see if this option gathers traction - it would gain traction if the models are currently underplaying the potential to maintain or re-build heights in the Greenland area, and it is entirely plausible that they may be.  One to watch.  

Original post: https://community.netweather.tv/topic/98087-model-output-discussion-the-cold-has-arrived/?do=findComment&comment=4758196