Model Discussion - A Sensible Scottish Perspective

[Ravelin]

Since the main model thread has become its usual winter madhouse, and dominated by an overwhelming southern bias, I'd thought we could do better. We might not have the expertise of some in the main thread, but certainly more than other prolific posters. 

We can of course, also legitimately take a Scottish perspective without it getting buried in dross. I'll start with posting some charts for Xmas day as they currently stand, since its the focus for most interest in the coming week. 

GFS 12z

  

UKMO 12Z

 

GEM 12Z

  

I'll add the ECM when it updates in a bit. 

From these you can see why the UKMO is favoured by our southerly cousins, as the 850s are colder across much of the UK, however for us the other two ain't too bad. Probably snow mostly confined to higher ground but I'd expect a lot of us would see falling snow on Xmas day, even if it didn't settle. 

Edited December 19, 2021 by Ravelin

[Sceptical]

Excellent idea!

[Stormeh]

This is a great idea @Ravelin

The 12z GFS still looking decent for Christmas Day for many of us, hopefully the ECM shows the same later.

[Kasim Awan]

Guys, feel free to join the alternative one too. Lots of northerners in that thread including myself and others in Northern England, weather wise we are closer to Scotland than the south.

 

Edited December 19, 2021 by Kasim Awan

[Ravelin]

The GFS is getting pelters in the main thread, after being the hero for a bit. When you see the 850 plots going from something like this... 

To this, in the space of 12hrs... 

Then you know something is awry. Not only has the mean increased quite noticeably, but the spread has increased too, and therefore the uncertainty. Normally you'd expect the spread to decrease as the actual weather got closer, but look how on the 23rd its increased massively. In the end there can only be one correct solution, just which one it is though is anyone's guess. 

[Ravelin]

The ECM 12z... 

 

More similar to GFS/Gem than UKMO? Certainly is in terms of 850 temps, but unusual for UKMO to be wrong at t144? 

By the way, feel free to have a go at posting, this isn't intended to be my personal thread, and it won't be of much use if it becomes that. 

[Sceptical]

@Ravelin

You're doing a fine job!

Nice calm vibe in here, I'm liking it  

[ghoneym]

GFS wind chill for the bid day  

Plenty snow in that cool air flow, ground temps will be good for it settling also.  Even eastern coasts will see snaw from the 12z GFS run. Great stuff!

JMA not too shabby either

ECMWF upper temps more than good enough for snaw all over as well. All trending in the right direction for us North of the border.  

Edited December 19, 2021 by ghoneym

[Stormeh]

Yes ECM is fine for Christmas Day

It’s great to see the chance of a white Christmas is there. At least the models are not showing the usual south westerlies. Exciting few days of model watching for us over the next few days

Hopefully the UKMO is wrong and the GFS, GEM and ECM are correct.

[CameronWS]

Do you think snowfall would likely be to sea level, say based upon the latest ECM?

[Ravelin]

12 minutes ago, CameronWS said:

Do you think snowfall would likely be to sea level, say based upon the latest ECM?

To sea level, with 850 temps of - 7/8C then probably, if we are lucky enough to have some decent precipitation. Coastal falling or lying snow however can be much more of a problem due to the local modifying effect of the sea. 

25th looks touch and go for many away from the N & E... 

The 28th looks more promising 850s wise... 

But 850s aren't the only thing needed. 

Edited December 19, 2021 by Ravelin

[Penicuikblizzard]

I’m liking the new Scottish model discussion

[edinburgh_1992]

Looking ahead, the long-term outlook is quite bleak. Models are now consistently showing high pressure pushing in from Spain, apart from the odd member here and there. So the potential cold and snow over Christmas could be very short-lived. 

For the Christmas period, there is still a chance for many of us to see snow here in Scotland. As often happens, it is looking quite marginal at the moment: I’m still hopeful that we might see a slight south shift in the next model updates. It really wouldn’t take a lot to get all us all back in the game here in Scotland (eastern coastal areas included). 

[Penicuikblizzard]

1 minute ago, edinburgh_1992 said:

Looking ahead, the long-term outlook is quite bleak. Models are now consistently showing high pressure pushing in from Spain, apart from the odd member here and there. So the potential cold and snow over Christmas could be very short-lived. 

For the Christmas period, there is still a chance for many of us to see snow here in Scotland. As often happens, it is looking quite marginal at the moment: I’m still hopeful that we might see a slight south shift in the next model updates. It really wouldn’t take a lot to get all us all back in the game here in Scotland (eastern coastal areas included). 

I did notice it’s a bit more marginal looking south of the central belt on the latest charts on the big day. It is always quite common for a southward shift in the models as we get nearer the timeframe   

[Ravelin]

Looking at the GFS 12Z 850 ensembles for my location, which will be much more favourable than most, is still interesting... 

Slightly less scatter than there was on the earlier runs but still a lot more than yesterday, and still starting relatively early. What I often find more useful though is the box plot version... 

The first obvious observation is that the OP is an outlier, in the true sense rather than how 'outlier' is often used on the MOD thread, from around the 30th onwards. Secondly, look closely at the lower 10-50% quantiles and out to the end of the 31st they are much more tightly grouped than the upper 10-50% quantile. That's indicative that there's much more grouping going on in the colder ensembles than for the warmer ones. Hopefully that means a greater chance of the cold options winning, but then again the 'outlier' OP could be the winner, such are the vagaries of the weather. 

[Coopsy]

Sod the models, I’ve got a more accurate way of working out if it’ll be a white Christmas.

I’ve had four white christmases whenever I’ve visited family in Scotland and the year has been an odd number.

I’m coming up this year...just saying

[Sanserit]

Trying to get my head around all these charts, I’ll get there eventually.

To be honest, in my 50+ years, I’ve experienced many more damp Christmases than white ones but white New Years? Now that’s a different story and one I’ll be keenly following once we get through this week.

[Ravelin]

5 minutes ago, Sanserit said:

Trying to get my head around all these charts, I’ll get there eventually.

To be honest, in my 50+ years, I’ve experienced many more damp Christmases than white ones but white New Years? Now that’s a different story and one I’ll be keenly following once we get through this week.

50+ too and anecdotally I'd say the same. The extra week seems to make quite a difference. I'd be quite happy if the @Coopsyeffect is works again this year. 

[Ravelin]

GFS 18z rolling out and here's Xmas day... 

  

Overall profile a bit different from its 12Z, cold is further south at the same time, but snow accumulation not as extensive or deep for us. 

[ghoneym]

4 minutes ago, Ravelin said:

GFS 18z rolling out and here's Xmas day... 

  

Overall profile a bit different from its 12Z, cold is further south at the same time, but snow accumulation not as extensive or deep for us. 

A run for the bin Rav it's ok tho because it's the 'pub run' and there's no 'balloon data' and it's not showing what I want so I'm going to dismiss it like a Mod thread maniac

[Ravelin]

It appears like mist in the MOD thread have given up on Xmas day snow as all of the models are suggesting the cold air from the E will struggle to get here. Still possible for parts of Scotland but certainly looking more uncertain. The 850s for NE Scotland illustrate this... 

Although the OP for 24-26th is still good, the spread has increased again, with only 27-29th really looking to have any consistency. Heading in to the new Year the spread would suggest just about any outcome is on the table. 

Still time for things to swing back? 

Edit:

GFS snow depths charts, always to be taken with a pinch of salts... 

Looking better by 28th...

Edited December 20, 2021 by Ravelin

[Ravelin]

State of play for Xmas day as per the main models, I'll use early hours charts since the UKMO & ECM are 24hr intervals so I can't use afternoon charts for all 4 models.

GFS

 

GEM

 

UKMO

 

ECM

 

That looks promising for Scotland at least as all 4 models have the colder air over us and in a very similar position. The gnashing of teeth for the southerners is a result of the split in the models after that point, with the GFS & GEM pushing the cold air further south, with the UKMO & ECM having it retreat northwards again.

   

The ECM is apparently on the warmer side of it's ensemble suite, so maybe the GFS/GEM solution is going to be closer to the mark than the UKMO/ECM? As usual we'll just have to wait and see.

 

Edited December 20, 2021 by Ravelin

[Mair Snaw]

Brilliant idea to have this thread.. i will still pop into the wrist slashing thread just for a bit of fun and just to check what the rest of the uk is getting weather wise.. and maybe when we have snaw i might be tempted to post a picture or 2..

[jellybaby1969]

9 minutes ago, Mair Snaw said:

Brilliant idea to have this thread.. i will still pop into the wrist slashing thread just for a bit of fun and just to check what the rest of the uk is getting weather wise.. and maybe when we have snaw i might be tempted to post a picture or 2..

Dont go into the madhouse now..the bickering has all kicked off

[Ravelin]

Well the GFS 6Z hasn't clarified anything, sticking to a cooler Xmas outlook than the earlier UKMO/ECM runs. 

The 850s for Aberdeenshire have taken a tick down on Xmas day, pity the main precipitation comes 2 days earlier when it'll more likely be cold rain.