Model Output Discussion - Colder but how cold and for how long?

[jright35]

27 minutes ago, Cuban Zebra said:

Ooh GFS!!!

This shows an upgrade in cold but the low going south. Dry and frosty in most parts if this comes off.

Edited January 11 by jright35

[SussexSnow]

3 minutes ago, jright35 said:

 

Not completely dry on the ensemble, admittedly for mid Sussex.  This is New Snow 

P23 is the light blue line  

[feb1991blizzard]

This is what we need to be seeing in the coming days, an intense upper trough in -16c air.

[SouthwestChaser]

I don't trust the GFS. It's too indecisive. One day it's saying Atlantic returns, the next, too cold for snow. That said, I'd take a (practically) snowless cold spell over a return to the endless mild Sothwesterly depressions . I'm still hoping that low may just flirt with the south though, that'd be perfect for us in the SW.

[mountain shadow]

22 minutes ago, Met4Cast said:

If the models aren't getting blocking right at days 3/4, why do people expect them to be right at days 9/10? 

There is no blocking at days 9/10 though.

Pretty much all input I've seen shows the cold being swept away next weekend. 

It will take a marked change in output to change that now.

[Mcconnor8]

Just now, mountain shadow said:

There is no blocking at days 9/10 though.

Pretty much all input I've seen shows the cold being swept away next weekend. 

It will take a marked change in output to change that now.

And that marked change is always possible when it is 9 or 10 days away.

[weirpig]

1 minute ago, SouthwestChaser said:

I don't trust the GFS. It's too indecisive. One day it's saying Atlantic returns, the next, too cold for snow. That said, I'd take a (practically) snowless cold spell over a return to the endless mild Sothwesterly depressions . I'm still hoping that low may just flirt with the south though, that'd be perfect for us in the SW.

The gfs is cannon fodder. 4th performing model  and yet people still look at it.   Rather look at the Hiram. To be honest. For me I’d stick to the ecm and ukmo.  You won’t be far off 

[seabreeze86]

GFS ensembles are interesting at 96hrs for the first time they are many that go below -12hpa some as low as -16hpa. These were not there earlier and at such a early timescale This is for Redcar at 96hrs

Edited January 11 by seabreeze86

[SouthwestChaser]

2 minutes ago, mountain shadow said:

There is no blocking at days 9/10 though.

Pretty much all input I've seen shows the cold being swept away next weekend. 

It will take a marked change in output to change that now.

Too early to speculate on the end of the cold spell yet I think. Let's just argue about how much snow and where

[Met4Cast]

4 minutes ago, mountain shadow said:

There is no blocking at days 9/10 though.

Pretty much all input I've seen shows the cold being swept away next weekend. 

It will take a marked change in output to change that now.

There was no blocking at day 5 either on a few recent GFS runs.. that's sortof my point. We've just seen a huge shift in the broadscale pattern from the 18z, there's no saying that wont happen again as we approach the current day 10. Wedges are extremely difficult for models to resolve and get a handle on. 

[SussexSnow]

Just now, seabreeze86 said:

GFS ensembles are interesting at 96hrs for the first time they are many that go below -12hpa some as low as -16hpa. These were not there earlier and at such a early timescale 

Agreed.  As said above, on the locations I'm monitoring, the average has never been so low (-8.9c) as it is now 

[Djdazzle]

56 minutes ago, Nick123 said:

The pros also gave 2 other options, they said unlikely, but all the same was on table. And it now looks like the southerly track has become a lot more likely. Expect updates 

I’m surprised that the pros said the southerly track was unlikely, since most LP systems tend to track further south than initially modelled. Presumably they would know this?

[PsychedelicTony]

For me with the PV split as shown in the GFS 18z the question is more when not if. The longer this plays out the better for everyone. North, South irrelevant to some extent. 

It won't be dry for everyone. 

And the longer it stays cold the more chance you have where YOU are of being exposed to a trough or feature that will deliver. 

The Atlantic encroachment is only ever any good if it gets beaten back by the cold and retreats South. 

The drier it looks the better it is longterm. 

 

[Purga]

At least there are some cold ENS still after next week/ I wouldn't kick P17 out of bed ! Blizzardy Snowmagedon anyone?

[Snowman.]

Some absolute filth in the ensembles. Personal favourite is below.

  

That is an exceptionally rare chart, Westerly flow in Sub -10c 850s, PV sat on the UK . Beats 2010 in my opinion just for the sheer lack of real heights. Absolutely insane.

Edited January 11 by Snowman.

[Cold Winter Night]

3 hours ago, Troubleatmill said:

Would you not expect some or even one ensemble to go cold going off what the knowledagble are saying? If not what's the point of models??

I'm playing devil's advocate obviously as ive been around long enough to know what you say is true. But when NO ensemble is cold and humans says everything AAM, MJO ect...is pointing cold (models WILL take these into account)....something gives surely

Anyhow, thanks for responding, much appreciated mate

That discrepancy between the extended ensemble and the expectation based upon a retention and renewed increase in AAM is basically what I was wondering about in my response to Tamara's post in the afternoon. Have you read her input in this thread today? Very informative.

This is what she responded:

9 hours ago, Tamara said:

Based on the modelling of the huge gyre of vortex across NE Europe and that part of the arctic to retrograde in tandem with the Greenland amplification it makes sense that height anomalies will respond accordingly to a more cyclonic regime. But is is within that regime with embedded upper and increasing surface cold across N/NW Europe and remaining pockets of -ve zonal mean -ve zonal winds at high latitudes that considerable resistance must surely make it difficult for flat westerly inertia to cleanly navigate the road blocks. Additionally, it will not be long before a further push comes from momentum transport from the tropics into the extra tropics to replenish the sub tropical jet stream and equally further poleward amplification. Putting that together, disruption of vorticity is more intuitive to expect than positively tilted wholesale displacement of -ve higher latitude inertia & its associated dense cold air.

NWP is not ignoring the tropospheric diagnostic and not battling it. NWP doesn't lead the diagnostic. It is rather led by it, but trying to decode a lot of complex factors that do not align with the traditional westerly gyre of a +ve AO and NAO. 

Lastly and finally on this, the term "rudderless" refers much more to collective smoothed ensemble means. It is of course possible to look at individual clusters of ensemble solutions to see which are maybe in the ascendancy or vice versa. But even here, if the overall modelling is blindsided by a false signal or jet stream bias calculation at a given distance, then members within the clusters will also reflect that inaccuracy. They are best looked at as a snapshot in time of progress (or otherwise!), and not any definitive prediction at that given distance.

In fact, the "wedges" that we see appearing in GFS 18z are evidence of the resistance there might be in the atmosphere against the onset of a powerful Westerly flow. Models notoriously have trouble getting that right.

The extended EPS tonight also contained a hint of amplification through Iberia and the UK towards Scandinavia again.

So yes, ideally you would hope to see the eventual verifying outcome in the ensemble as early and as clearly as possible. If the ensembles were always wrong, they would indeed be pointless, but that is not usually the case. This however is a quite exceptional situation we appear to be in this phase of winter, so it's not strange to see the models struggle.

[*Stormforce~beka*]

7 minutes ago, Snowman. said:

Some absolute filth in the ensembles. Personal favourite is below.

  

That is an exceptionally rare chart, Westerly flow in Sub -10c 850s, PV sat on the UK . Beats 2010 in my opinion just for the sheer lack of real heights. Absolutely insane.

Ruddy 'ell! What would that purple blob bring??

[Liam J]

What has GFS been on tonight?! Upgrades at very short time frames with some incredible cold now being modelled by many GEFS members from the northerly….

 

[Scott Ingham]

50 minutes ago, seabreeze86 said:

GFS ensembles are interesting at 96hrs for the first time they are many that go below -12hpa some as low as -16hpa. These were not there earlier and at such a early timescale This is for Redcar at 96hrs

Yeah I spotted this it’s what I’ve taken away. It shows there are possible upgrades to come!

[Continental Climate]

2 minutes ago, Liam J said:

What has GFS been on tonight?! Upgrades at very short time frames with some incredible cold now being modelled by many GEFS members from the northerly….

 

That's quite a few getting down to -16 850's on Monday and Tuesday. You would have to think that there would be some disturbances in that flow. Today has been an incredible day of upgrades. Currently a 5/6 day freezing cold spell guaranteed maybe 7/8 days of cold with further upgrades. If we can all get a few inches of snow on the ground this could be quite memorable. 

[Mcconnor8]

4 minutes ago, Liam J said:

What has GFS been on tonight?! Upgrades at very short time frames with some incredible cold now being modelled by many GEFS members from the northerly….

 

Thinking there's a good chance we wake up to a stonking set of 0z runs if the trend of the 18z is continued, clearly everything is very volatile right now given how early the changes were on the 18z runs.

[Wivenswold]

1 hour ago, jright35 said:

This shows an upgrade in cold but the low going south. Dry and frosty in most parts if this comes off.

Pressure isn't that high and there will some very strong troughs forming bringing regular snow shows, admittedly not for everyone but I think it would blanket a fair amount of the North and Eastern sides of Britain.

[Liam J]

2 minutes ago, Continental Climate said:

That's quite a few getting down to -16 850's on Monday and Tuesday. You would have to think that there would be some disturbances in that flow. Today has been an incredible day of upgrades. Currently a 5/6 day freezing cold spell guaranteed maybe 7/8 days of cold with further upgrades. If we can all get a few inches of snow on the ground this could be quite memorable. 

Been a mental day of model watching! 18z gone off the scale lol I don’t think the overnight runs can get any better?! Some people need to realise that what’s being shown are low heights, a very unstable & very cold airmass = plenty of troughs/disturbances and snow chances & not all of these are going to show up on modelling at this range…. 

2 minutes ago, Mcconnor8 said:

Thinking there's a good chance we wake up to a stonking set of 0z runs if the trend of the 18z is continued, clearly everything is very volatile right now given how early the changes were on the 18z runs.

Let’s hope for a good set of overnight runs! A little over 3 days until the cold sets in  

[Ben Sainsbury]

Watching the model output today, I'm getting the impression that the low approaching from the south-west will almost definitely head across France and actually more of us may benefit from a series of shortwaves that develop NW of the UK, then moving SE across the country. I imagine these shortwaves will primarily consist of snow given they're embedded within the colder airmass. 

Interestingly however, for Bristol the GEFS 18z has a max snow risk of 28% vs the 12z at 25% and for London 34% rather than 31%. So there's still much to be decided with regards to that low approaching from the south-west. An exciting time for model watching regardless!

Edited January 12 by Ben Sainsbury

[Mcconnor8]

ECM 18z to +90 looks slightly improved on the 12z similar to GFS/ICON improvements. Slightly colder Northerly with slightly better Greenland heights.