Model Output Discussion - the cold has arrived

[johnholmes]

2 minutes ago, Anthony Burden said:

Evening all,Both UKMO and ICON at around 168 hrs /180 hrs showing Greenland high going nowhere possibly strengthens,Definitely a hint this less cold air from the southwest could be very short lived or possibly not at all.Charts will be struggling  for at least 24 hrs or more to resolve this,Greenland high the key to the door regarding a continued cold/very cold theme over Christmas and beyond.

Why the 'bold' print?

To the weather, the 500 mb anomaly charts are consistent with showing a westerly 500 flow from about Friday on so little chance of a return to the very cold weather most are in currently.

No charts as have had no internet until a few minutes ago but the chart last evening carried on from the last 3 or so.

To answer mushy and his comment about a fairly large + height anomaly Greenland. It is in fact between Greenland and NE Canada, just where the main trough usually is, currently displaced a bit west. My take anyway.

It will be interesting to watch way back west as to hoe the trough-ridge pattern plays out.

[weatherguy]

Hi all, taken a few days off to avoid model fatigue and to actually enjoy the coldspell that has taken hold - some lovely scenery around up here the last dew days!

Anywho, let's take a look at what the models are indicating in the medium term, using +72h as the starting point...

The GFS 72/96/120/144/168/192/216/240

The cold air established over the UK starts to see its influence wane as heights slowly build over the continent, and due to the angle of the incoming LP from the west (caused by the absence of a significant block) we establish a S/SW flow going into Sunday.  Interestingly, the warm uppers don't last long as, while we appear to enter a more zonal phase, the atlantic is very low-power for the time of year due to the core of the PV remaining on the Asian side and the emergence of an Aleutian HP system.  This means that we are subjected to a period of "cold zonality" with shots of PM air from the north-west as we move through the +144-+240 time period.  With a cut-off HP effectively acting as sticking a rod into a bike wheel, we can again see signs of more northerly blocking across the NH profile as we move into the more long-range period.  

I won't go into huge detail with the ECM as the 12z will be out soon, but we see a similar outcome here.

ECM +144/192/216/240

Again, S/SW flow established into Sunday, followed by the introduction of PM NW airflow (interspersed with TM SW airflows).  We also see the development of a combined Aleutian cutoff high and some renewed ridging towards Greenland.  

Something to keep an eye on is the state of the sPV, given the stress that the tPV is still under. 

 

This +168h chart shows the sPV is quite elongated after sustaining some mild wave 2 activity.  No signs of an SSW just yet, but this is not looking like the typical raging December PV, and this can only be good news for longer term cold prospects.

[Don]

10 minutes ago, bluearmy said:

Those of us who are of a certain vintage will recall winters way back when 

Clear the snow into a big enough pile and it won’t disappear before the next lot turns up ……

of course you need some snow to begin with 

gefs mean early into T200 finds a weak mid Atlantic wedge - those euro heights need to do one !

 

I can try clearing the frost into a big pile lol!!  People have mentioned 2022 having similarities with 1995, well so has the first cold spell delivering little snow for me! 

Edited December 12, 2022 by Don

[feb1991blizzard]

1 minute ago, weatherguy said:

Hi all, taken a few days off to avoid model fatigue and to actually enjoy the coldspell that has taken hold - some lovely scenery around up here the last dew days!

Anywho, let's take a look at what the models are indicating in the medium term, using +72h as the starting point...

The GFS 72/96/120/144/168/192/216/240

The cold air established over the UK starts to see its influence wane as heights slowly build over the continent, and due to the angle of the incoming LP from the west (caused by the absence of a significant block) we establish a S/SW flow going into Sunday.  Interestingly, the warm uppers don't last long as, while we appear to enter a more zonal phase, the atlantic is very low-power for the time of year due to the core of the PV remaining on the Asian side and the emergence of an Aleutian HP system.  This means that we are subjected to a period of "cold zonality" with shots of PM air from the north-west as we move through the +144-+240 time period.  With a cut-off HP effectively acting as sticking a rod into a bike wheel, we can again see signs of more northerly blocking across the NH profile as we move into the more long-range period.  

I won't go into huge detail with the ECM as the 12z will be out soon, but we see a similar outcome here.

ECM +144/192/216/240

Again, S/SW flow established into Sunday, followed by the introduction of PM NW airflow (interspersed with TM SW airflows).  We also see the development of a combined Aleutian cutoff high and some renewed ridging towards Greenland.  

Something to keep an eye on is the state of the sPV, given the stress that the tPV is still under. 

 

This +168h chart shows the sPV is quite elongated after sustaining some mild wave 2 activity.  No signs of an SSW just yet, but this is not looking like the typical raging December PV, and this can only be good news for longer term cold prospects.

I am afraid i think we'll be waiting a while yet for an SSW if we do get one unfortunately.

2 minutes ago, Don said:

I can try clearing the frost into a big pile lol!!  People have mentioned 2022 having similarities with1995, well so has the first cold spell for me delivering little snow! 

or try clearing the rain into a big pile.

[Don]

1 minute ago, feb1991blizzard said:

I am afraid i think we'll be waiting a while yet for an SSW if we do get one unfortunately.

Who knows, things seem to be changing on a daily basis regarding prospects?!

[Djdazzle]

3 minutes ago, feb1991blizzard said:

I am afraid i think we'll be waiting a while yet for an SSW if we do get one unfortunately.

And it doesn’t even guarantee us cold weather if we do get one.

[Don]

12 minutes ago, bluearmy said:

Those of us who are of a certain vintage will recall winters way back when 

Clear the snow into a big enough pile and it won’t disappear before the next lot turns up ……

of course you need some snow to begin with 

gefs mean early into T200 finds a weak mid Atlantic wedge - those euro heights need to do one !

 

These days the best chance you have for snow not disappearing before the next lot turns up is by sticking a sample of it in the freezer!!

[I remember Atlantic 252]

looks good for temporary snow, would expect this though to be northern areas, Kasim could see a dumping here

[Don]

1 minute ago, Djdazzle said:

And it doesn’t even guarantee us cold weather if we do get one.

Although the prospects are constantly changing, it does seem to have changed for the worst during the last couple of days, just as the Metoffice mentioned the potential for the cold continuing in the extended!!  Hopefully things will improve in the coming days!

[RhHh]

21 minutes ago, bluearmy said:

Those of us who are of a certain vintage will recall winters way back when 

Clear the snow into a big enough pile and it won’t disappear before the next lot turns up ……

of course you need some snow to begin with 

gefs mean early into T200 finds a weak mid Atlantic wedge - those euro heights need to do one !

 

My late father always used to say that if piles of snow remained then more snow was likely to follow. 

[Hotspur62]

Wasn’t it Crewe Cold mentioning a scandi high as a possibility around Xmas or shortly after about 7 days ago ?He has been fairly accurate so far and rightly advises us to always look at the NH in the bigger picture.Well I tend to agree there is quite a good chance of a Scandi High as GFS hints at on the 12z.

Certainly been a fascinating period of model watching this last 2 weeks and will be equally entertaining to see how the next 10 days pan out as if this time tomorrow todays trends continue I would suggest the mild weather forecast for a few days will be short lived and may not even occur for Northern Britain.Let’s hope these trends continue for coldies(95% of this forum I would suggest)

Edited December 12, 2022 by Hotspur62

[Dacyfo]

Very rarely post on here but imho UKMO is excellent.

[weatherguy]

20 minutes ago, feb1991blizzard said:

I am afraid i think we'll be waiting a while yet for an SSW if we do get one unfortunately.

Yes agreed, nothing in the forecast to suggest we'll see one any time soon.  More pointing out that the sPV is looking a bit unsure of itself and this combined with the tPV state is quite unusual for December - should encourage further high latitude block development in the medium term.

[bluearmy]

25 minutes ago, Don said:

These days the best chance you have for snow not disappearing before the next lot turns up is by sticking a sample of it in the freezer!!

Guilty of this as a youngster !

anyway, noting that it seems likely in the extended period that the tpv will remain split but the main segment likely to end up over e Canada.  With HLB still looking likely across the NH, that probably means our next opportunity for amplification in our sector will be via a scandi ridge of some kind - if the euro anom stays high that could be sceuro - let’s hope not. 
 

 

[JBMWeatherForever]

Looks increasingly likely that the cold will not be budged from northern parts this weekend.  A complicated set up this weekend with only small adjustments needed for the cold to be just continuous. Will be interesting to see the ECM 12z shortly. Hopefully will start to follow the trend of the UKMO and others. Think it might,  and also with the potential for a severely cold outbreak from the east before the new year also growing ! 

[sheikhy]

Ecm goes on its merry way and no change at 120 hours it seems!!!

[booferking]

Ecm having none of it next chase begins.

[Johnp]

1 minute ago, sheikhy said:

Ecm goes on its merry way and no change at 120 hours it seems!!!

The 96 chart looks wrong to me. Don’t know why, it just seems ‘weird’

[Portlander]

On 11/12/2022 at 15:12, Cold Winter Night said:

With FI still at 96h, max 120h if you're stretching it, we can be sure of cold until the end of the reliable, because the cold is here now.
Maybe not as cold as you hoped, maybe not with snow for everyone, but it can't be denied that it's here.

Perhaps comparisons to 2010 or the like are always a bit unfair. Many Decembers of the past have seen cold episodes like the one we're in right now and for some they end up being more special or memorable than the Big Ones.

A face value evaluation of the ensemble output suggests we're going milder, especially the further South and East you are, without a return to real cold before Christmas.
The De Bilt 2m plume is ugly in that regard. The KNMI (Dutch Met Office) speak of a 70-80% chance of milder and unsettled later on.

A return of the cold would take a big swing in the ensemble.

However, in the 96h+ timeframes much depends on the handling of the Atlantic. Many posters have discussed this in great detail, but whether the block is stronger, or better placed than models show, makes all the difference both in that mid term and in what follows longer term.

To many observers it may seem like many in here who expect a better setup than the models show are being silly, or even in denial, but tendencies to underestimate blocking and cold are not without precedent.

Even comparing the EC 0z T+144h of 6 days ago to what it actually looks like today at T+0h reveals a lot:

- The Greenland block is stronger, in better shape and more East-based than EC Op 'thought.'
- That infamous tropical storm low is much smaller and less deep (location is spot on though).
- There is an Alaskan ridge and associated trough along the US/Canadian Pacific coast, which ECM did not foresee 6 days back.
- The Russia/Kazakhstan High has been pushed slightly more SE than foreseen.

For De Bilt that results in the next few days being colder than forecasted based on the 5 December 0z EC/EPS.

So, my point is, there's still a lot of interest in the models, because of the NH pattern, we may see surprising shifts in the output.
Maybe already in the next few hours of 12z's, maybe over the upcoming week, or maybe not! Isn't that the fun of model watching?

As a total new guy, I love this kind of post. Seeing what the models thought would happen compared to reality is really important

[snowice]

 

ECm 144not agree with ukmo

[Mike Poole]

ECM T144, well it has left a bit of the southern low there still, so not a total phase, so definitely a move away from its prior position, and could be east of us on the same timescale as UKMO.  

[Stuie]

ECM has changed it`s tune a tad not phasing the secondary low completely with the Icelandic LP, for now...

@Mike Poole snap.

[tight isobar]

Thee Oishi blows, @ jet sequences ( on the favoured 250 level) is not modelling as it’s leveling at lower heights should be as now we have a controlled spherical jet! With favourable blocking formation running at circular freedom.      Looking at the trop - it’s either eyeing the response- or has already bagged out!??   The stagnation of the Pacific lowers layers are becoming a Freind to perhaps foe!! almost consistently sting- JS on the ovel pac side seems now energising a mobile pattern! But in doing so, is gaining broken jet prognosis- into the maritime parts?!.. the 10hpa are even falling into the sequence- as lower west warming’!!! Atm you can call a milder blip (almost certainly)- but no man- nor model will punt the 10/15 day prog!! I’m intrigued!!.. and round 2 of mid latitude dripping.. could have our name scetched in!!! .. if it has... it’s only the most wonderous of thought .. that may imagine where we are going!!!.. increadible start to winter “ for sure “

[That ECM]

[Tim Bland]

Some snow Sunday, will turn to rain before dying out though