Model Output Discussion - Cold spell ending - what next?

[Community Team]

A fresh model thread as we enter into a new phase, with the cold spell drawing to a close, and a milder, wetter and potentially quite wild spell incoming in the nearer term.

You may have noticed that the model discussions now have their own area (a bit of a throwback to how things used to be laid out several years back), this is to allow more expansion of the discussion around the topic of the models. For instance, we have a new model emotions thread now up and running and will be introducing other threads which will hopefully be interesting to follow and take part in over time.

We also have an updated set of community guidelines, which I'd encourage everyone to read, just so you're aware of what's expected when taking part in this or other threads. On top of that, we also have a separate set of guidelines specifically for the model output threads to hopefully clarify what constitutes model discussion, along with other info about these discussions. As it's the first time we've had these in place, I'll copy them in here so as many as possible have a chance to see them:

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Happy Model Watching!

[IDO]

The 12z run is unlikely as the amplification is due to a wedge of heights in the polar region, well in FI, that bridges with the Euro high:

That is likely to be gone on the 18z. It wasn't on the 06z. Those Arctic highs are at that range are not worth the time of day.

The caveat is there is lots of uncertainty on the Pacific side with wave activity. So, we need another period of letting the models resolve the background issues and see if the general mean changes.

[Duane S.]

Following on from the last thread...

No doubt changes to the Hadley cell circulation through AGW has led to an expansion in the Azores High.

However if the atmosphere is predisposed to retrogression / southerly tracking Jet stream, then it is irrelevant.

[TillyS]

The 12z UKMMO still has quite a storm on Sunday, and another potent one on Tuesday:

The track is everything in terms of who gets it worse. Further north with the GFS.

It looks pretty fierce on the Fax chart:

[WYorksWeather]

The near-term mild signal is increasing again on tonight's GFS, looking at London. Focusing in on the 23rd, the mean now gets to above 12C. Median would be nearer 13C. And just to show how ridiculous things could get, the GFS P01 is the most extreme outlier I've yet seen. The temperature at midday on the 23rd reaches 16.8C in London. Not only would such an outcome absolutely destroy the daily record, it would even put the all time January record of 18.3C at risk if the model did under-estimate the temperature as it is known to do on occasion, or if somewhere outside London was fractionally warmer.

How's this for an Iberian high:

And here's the resulting temperature map:

I mean what can you say to that other than that it's just extraordinary. 12C up to Yorkshire, 14C almost everywhere Midlands south, and 16C in London.

Again, not likely to happen as it's still at the top of the ensemble and out on its own. I still think the more realistic scenario is we see a raw 12-13C, and probably fall just short of the daily record of 15.2C with something in the 14s. But it's still absolutely extraordinary to even see things like this being modelled as possibilities.

And once again, the most likely explanation is the warm sea surface temperatures near the Azores.

As we go on through the rest of winter and early Spring, worth watching out for any more of these kind of scenarios. The ingredients are there for something exceptionally mild with those kind of sea surface temperatures.

[MATTWOLVES 3]

Correct me if I'm wrong but those build of heights can migrate from the south and build over scandy..The gfs has hinted at this for half a dozen runs now..is it out of the question? Well check the met update to see greater chance if estly winds and there's your answer. For someone to come on here and start saying it's not scientifically possible is tripe..its not scientifically possible to say there a 20% chance of this then an hour later a 30% or back to 15% of this that and the other scenarios!

Like I said numerous runs toy with the idea of a build of heights through into scandy and that's a positive as we all know how savvy gfs is with detecting early signals.. let's see if ecm and gem towards backend of week or weekend start going down this route also.

[Purga]

Major SSW ongoing showing the split rather than the displacement type. If other parameters align favourably for us, things could getting much more interesting after the upcoming horrorfest dies down.

Squares with the extended UKMET view.

Edited January 17 by Purga

[That ECM]

16 minutes ago, MATTWOLVES 3 said:

Correct me if I'm wrong but those build of heights can migrate from the south and build over scandy..The gfs has hinted at this for half a dozen runs now..is it out of the question? Well check the met update to see greater chance if estly winds and there's your answer. For someone to come on here and start saying it's not scientifically possible is tripe..its not scientifically possible to say there a 20% chance of this then an hour later a 30% or back to 15% of this that and the other scenarios!

Like I said numerous runs toy with the idea of a build of heights through into scandy and that's a positive as we all know how savvy gfs is with detecting early signals.. let's see if ecm and gem towards backend of week or weekend start going down this route also.

While gfs throws nhp like this I’ll remain very interested. Other than not the normal nhp it’s difficult to see a pattern yet. 
 

So the ones punting Bartlett let them, I’ll sit and wait and just scroll past, some enjoy having a contrarian style for the attention it affords them..

Edited January 17 by That ECM

[bluearmy]

Some very interesting NH profiles into week 3 on the gefs 

[UnderTheAnvil]

38 minutes ago, MATTWOLVES 3 said:

Correct me if I'm wrong but those build of heights can migrate from the south and build over scandy..The gfs has hinted at this for half a dozen runs now..is it out of the question? Well check the met update to see greater chance if estly winds and there's your answer. For someone to come on here and start saying it's not scientifically possible is tripe..its not scientifically possible to say there a 20% chance of this then an hour later a 30% or back to 15% of this that and the other scenarios!

Like I said numerous runs toy with the idea of a build of heights through into scandy and that's a positive as we all know how savvy gfs is with detecting early signals.. let's see if ecm and gem towards backend of week or weekend start going down this route also.

I was thinking this... has there been a pattern of two HPs linking up and splitting the PV? To my uneducated brain, that's what I've been seeing. Are the heights over Europe threatening to do this soon?

Model watching for me is like looking at a really slow Lava lamp and going "oooh" when the purple blob visits the UK from the N/NE

[bluearmy]

43 minutes ago, Purga said:

Major SSW ongoing showing the split rather than the displacement type. If other parameters align favourably for us, things could getting much more interesting after the upcoming horrorfest dies down.

Squares with the extended UKMET view.

This is discussed in the strat thread @purga 

Whilst there is a split of sorts just about to end (and when it does the Canadian segment rushes east to rejoin and we see the same  in the trop ) , the reversal is weak and looks to be more about the displacement of the Asian segment over scandi than due to the split. The current strat trop coupling is strong but there are some gfs ops recently that seem to show something of a disconnect again as we enter feb 
 

[WYorksWeather]

1 hour ago, TillyS said:

The 12z UKMMO still has quite a storm on Sunday, and another potent one on Tuesday:

The track is everything in terms of who gets it worse. Further north with the GFS.

It looks pretty fierce on the Fax chart:

The first storm is now into range on UKV as well.

101mph gust inland. I really hope this gets downgraded, as that's downright dangerous.

[Cold Winter Night]

7 minutes ago, bluearmy said:

Some very interesting NH profiles into week 3 on the gefs 

Indeed.

Many feature an Arctic High, detached from the Pacific High.
P7 even with a remarkable (and unrealistic) 584+ hPa Arctic High at 360h. A synoptic collector's item, you don't see such a fat beast at those latititudes very often, even within the ensembles.

[Stuie]

1 hour ago, TillyS said:

The 12z UKMMO still has quite a storm on Sunday, and another potent one on Tuesday:

The track is everything in terms of who gets it worse. Further north with the GFS.

It looks pretty fierce on the Fax chart:

couple of things, the gusts are measured in km/h and not mph thankfully. 

Like when chasing snow or X, there is still plenty of time for modification, normally in a negative manor but I would start to be concerned if Fridays output either agreed or intensified the status.

[WYorksWeather]

Just now, TillyS said:

Wow. That’s really wild.

Shouldn’t peeps be talking about this a bit more?

You can add the Arpege as well. Delivers a huge blow to Ireland:

Then perhaps slightly less severe for England than the UKV, but more widespread and not far off in intensity:

[MATTWOLVES 3]

Some absolute crackers from the 12z ens beyond week 2...we could be sensing a pattern change..

Who's up for it? I will get the ball rolling...let's see where this one takes us..im very optimistic for February folks.

Come onnnn...

[Augusta Snow]

22 minutes ago, bluearmy said:

This is discussed in the strat thread @purga 

Whilst there is a split of sorts just about to end (and when it does the Canadian segment rushes east to rejoin and we see the same  in the trop ) , the reversal is weak and looks to be more about the displacement of the Asian segment over scandi than due to the split. The current strat trop coupling is strong but there are some gfs ops recently that seem to show something of a disconnect again as we enter feb 
 

Hi Blue, long time lurker just wondering have we ever benefited from a displacement SSW? 

[Stuie]

Following on regarding the potential winds and my comment yesterday? about the ECM not buying into it, you can look here at it`s forecast.

https://charts.ecmwf.int/products/medium-10ws-mean-spread?base_time=202401170000&projection=opencharts_europe&valid_time=202401291200

[damianslaw]

Out to 10 days, ECM and GFS show a predominantly westerly airflow from Friday onwards, with a strong ridge to our south attempting to build north but thwarted by a very strong jet. We exchange a cold, in the north very cold week, for a nationwide very mild week, chalk and cheese conditions.

No clear signal how things may develop as enter February, but interesting to see GFS continues to show heights building into the UK which could herald a pattern change to blocked again.

[Stuie]

7 minutes ago, MATTWOLVES 3 said:

Some absolute crackers from the 12z ens beyond week 2...we could be sensing a pattern change..

Who's up for it? I will get the ball rolling...let's see where this one takes us..im very optimistic for February folks.

Come onnnn...

Tough one, Matt. Your end frame has a near complete vortex parking itself in it`s happy Winter home. Yeah I`m game to keep watching or I wouldn`t be typing but we do need something special to stop that last frame!

[WYorksWeather]

Since others are talking about the extended range cold prospects, I may as well chuck in the CFSv2 weeklies for weeks 3 and 4. We know they're usually barely worth the pixels they're displayed on, but why not.

CFSv2 has a slightly milder than average week 3 (31st Jan - 6th Feb), then a possible transition to something colder, with no signal in week 4 (7th -13th Feb). Usually CFSv2 defaults to mild in the extended, so seeing a near-normal signal suggests there's at least a raised possibility of something by the second week of February.

 

[Mike Poole]

ECM clusters tonight T192-T240:

Almost a 50/50 split between cluster 1 that builds heights towards Scandi, and cluster 2 which does not.

T264+:

Cluster 1 remains +NAO, while cluster 2 is the Scandi block regime - but I would imagine this representative member hides a rather motley crew of options as far as they affect the UK.  

The carrot remains dangled, but no more than that at this stage.

[Stephen W]

21 minutes ago, damianslaw said:

Out to 10 days, ECM and GFS show a predominantly westerly airflow from Friday onwards, with a strong ridge to our south attempting to build north but thwarted by a very strong jet. We exchange a cold, in the north very cold week, for a nationwide very mild week, chalk and cheese conditions.

No clear signal how things may develop as enter February, but interesting to see GFS continues to show heights building into the UK which could herald a pattern change to blocked again.

Agreed. I was thinking the same. Attempts for the high to ridge north and also height rises towards Scandinavia but with the PV set up over Greenland and a strong jet, it’s difficult to see how any ridge won’t be flattened. North potentially unsettled and cooler with the south drier and relatively mild or perhaps very mild depending on wind direction.  If heights to the North East can establish perhaps things may become favourable but it looks tough against that strong jet.

[Don]

25 minutes ago, WYorksWeather said:

CFSv2 has a slightly milder than average week 3 (31st Jan - 6th Feb), then a possible transition to something colder, with no signal in week 4 (7th -13th Feb). Usually CFSv2 defaults to mild in the extended, so seeing a near-normal signal suggests there's at least a raised possibility of something by the second week of February.

Also note the cold back over Scandinavia in week 4.  

[Kirkcaldy Weather]

A brief update areas to keep a close watch on tonight - tomorrow 

As multiple areas of increased instability form we'll have increasing streamer development of which I'm particularly interested over toward the Humber and expect there will be increased possibilities for thundersnow certainly good CAPE just offshore but some of this pushes towards the coast bringing the streamers, looking likely for a shot to see at least a covering from the Humber down into the wash and toward East Anglia especially northern East Anglia.

Across to the west and the Irish Sea also sees an increase in CAPE creating a nice looking streamer heading into Wales especially Northwest and West Wales

The above being a general idea. Some modelling keeps the Humber event offshore however my thoughts above are just as much of a probability/possibility.