Model Discussion - A Sensible Scottish Perspective

[Ravelin]

Perfect illustration as to why you NEVER take the models as gospel, even at relatively close timescales... 

 

Still looking cold for Xmas Day and Boxing Day, but after that who knows.

That's a BIG flip in output but not the first time I've seen something similar happen. I don't have the knowledge to say why and I'm not inclined to venture into the MOD thread to try to find out, as the few sensible posters there will no doubt be drowned out by the wails of grief and wrist slitting theatrics. 

 

[Mair Snaw]

Its off its on its off its on... Icon and Aperge are the best models in the world today...just had a look at the mad house and its a fun read thats for sure... I've not seen anything like this model wise since January 2013 and the what the f**k moment from mr Brown... we all know what followed the rest of that winter and spring...

[edo]

Definitely still some legs in the chase. Certainly maybe now setting up a jam tomorrow scenario for some and still looking like a cold frstive weekend for us. I was going to say Mogreps trending colder again quite a big signal but then if signalling warm yesterday what's the point.... to sound like an MT poster

[Ravelin]

Still so much uncertainty heading forward, shown by the 15C spread in 850s across the ensembles for the GFS 12Z around the end of the year. 

I'll have a look tomorrow to see where it all stands, but the GFS mean has trended colder on the 3 runs so far today. Then there's the ECM trying to go for a Scandi high at day 10?

[Ravelin]

Well I don't think there is much doubt about Xmas day now, likely to be cool/cold across all of Scotland with the potential of some wintry showers moving in from the East. Breezy too, brozen sunshine. Not what most of us would crave for, but not too bad a forecast for Xmas day either. 

Looking forward, the next big day is New Years day so I'll focus on that since there doesn't appear to be anything more interesting on the horizon. 

GFS

 

GEM

 

ECM

 

All surprisingly similar looking at that range, and all looking on the milder side, especially in the south. Maybe one comfort to take from those, there is no real sign of a rampant and organised tropospheric PV in those, especially given the time of the year. That leaves things open for change. 

Edited December 23, 2021 by Ravelin

[Hawesy]

Thanks for doing these @Ravelin I don't follow the models closely these days (just a quick glance once a day!) but it's been a tricky period trying to pin down the festive weather. What in global terms is a minor change to the model output has big knock-on consequences when the battleground is right above our heads!

[Kirkcaldy Weather]

My forecast for Christmas and the official measure for a white Christmas is only for one snowflake

From around 2am showers mostly snow begin to reach Eastern coastal parts  one ingredient that won't quite come onto the east coast is the 528 dam, although the 850 temps of between -6 to -8 are OK possibly a bit of mixing graupel or hail with some showers. DPs actually look to improve into the early hours obviously those of us right at the coast closer to 0C but fine for lots of others 

An ice day on Christmas  

[Ravelin]

Blatent cherry picking from deepest FI... 

 

 Before then, New Year day still looking on the milder side. 

[Ravelin]

Even if its not what we might be looking for, the latest state for New Years Day.. 

GFS

 

GEM

 

UKMO

 

ECM

 

So all of the models showing a mild start to 2022 as they have been for a while. 

After that I a cool down of some sort is looking likely, but the scatter on the GFS is huge and ever changing. 

Meteociel - Diagrammes GEFS

WWW.METEOCIEL.FR

 

[Stormeh]

The models hinting at a possible cold snap from the north west around the middle of next week. Good chance it will deliver for the mountains and hopefully for low lying areas for a time even though it will probably be short lived. 

The way things are going this winter I would be delighted with a couple of cm of snow on the ground for a day so the kids and get out and enjoy it. 

[Kirkcaldy Weather]

Since i had the last decent check of the MJO its phases since have been 6 & 7 (there's still a question whether it can go into phase 8 so I'll not post those charts til we find out its next direction)  

• Pacific ridges have been persistent
• Using those composites we *SHOULD expect to see blocked charts (upcoming) + we see the pacific heights moving through the arctic

There are warming's in the stratosphere over the next couple weeks which I think are also having an affect on the models, maybe we will see those sorts of patterns ^ develop as we go through the first half of January, the feedback of MJO usually takes at least a couple of weeks sometimes it can be twice as long. 

[edinburgh_1992]

The models do seem to hint that we may be heading towards a prolonged period of cold zonality. 
 

So we could see some more seasonal temperatures and snow on low ground. Definitely not the worst outlook for Scotland, especially given the AO+ and NAO+ setup. 
 

 

[edinburgh_1992]

And just like that those signals have disappeared in todays models. 
 

I’ll keep quiet next time not to jinx it 

[Ravelin]

7I mentioned the other day in the weather thread that the GFS was showing some interesting outcomes mid month. Well the very end of today's GFS 12Z takes that to the extreme... 

 

The kind of synoptics that lead up to this, 'amplification' around the 17th/18th, have been turning up on a lot of the GFS runs recently. Way too far out to take seriously, and outwith the range of the other main models too. GFS has a habit of picking these things up at range, often then dropping them for a bit only for it to reappear closer to reliable timescales, even if the timing and exact outcome has changed somewhat. Just something to keep half an eye on. 

[edinburgh_1992]

Definitely worth keeping an eye on, although I’m not keeping my hopes up given that ECMWF is showing a completely different evolution. 
 

First we need the high pressure to push further north (as predicted by GFS). That gives us both better chances for cold and snow or sunny and dry weather. 
 

If the high pressure stays to the south, then we can forget about seeing any sun for days. Unseasonably mild, wet and windy being the key words. 

[Ravelin]

19 minutes ago, edinburgh_1992 said:

Definitely worth keeping an eye on, although I’m not keeping my hopes up given that ECMWF is showing a completely different evolution. 
 

First we need the high pressure to push further north (as predicted by GFS). That gives us both better chances for cold and snow or sunny and dry weather. 
 

If the high pressure stays to the south, then we can forget about seeing any sun for days. Unseasonably mild, wet and windy being the key words. 

I'd agree, a small change earlier in the evolution will make a big difference. GFS sticking with it though on the 18Z run... 

[Ravelin]

Still there thus morning, but probably getting watered down a bit.... 

Still good, but no split PV or cross polar flow this time. 

[Glaswegianblizzard]

Might we be seeing the first sightings of a 2010 or 2018 scenario? Would love to go back and see the initial posts that spotted those trends.

[Ravelin]

Just to keep it up for now 6Z and 12Z GFS for around the 21st. I've picked representative charts for the period and not exactly the same date or time as frankly at that range it'll change, if it even happens. 

 

[Ravelin]

Bit of a difference this morning... 

But looking at the ensemble 850s it's pretty much a mild outlier (black line) ... 

From this you can see that IF the GFS is correct then after a milder period we're looking towards the 17th onwards to be back in the 'fun zone' as they say on The Chase. 

 

[Ravelin]

As expected the GFS dropped anything that interesting for a few runs, at least in the OP run, which is all I usually have time to look at (likely some extreme ensembles from looking at the 850s graphs). The 6Z run this morning is worth posting though, around the previously mentioned period of 17th/18th,

 

ECM just coming into this range and yesterday's 12Z wasn't too dissimilar, although this mornings 0Z is quite different. 

 

End of the GFS run is also of note, although different. 

[Kirkcaldy Weather]

On 29/12/2021 at 14:29, Kirkcaldy Weather said:

Pacific ridges have been persistent

 

[Ravelin]

Not posted here for a while as frankly even cherry picking the best charts for cold would have been virtually impossible for most model runs. 

GFS today showing possible cold option around the 17th for a day or two. 

 

This has only started really showing up again today and even then there's a split in the GFS ensembles. You can see this in the 850s graph where from 17th some go cold, some stay milder but there's a gap in the middle. 

ECM was dead against anything cold but the 0Z run today starting to show similarities to the GFS, but shorter lived. 

It'll be interesting to see the 12Z ECM in a bit. GEM sits the high over us and doesn't really move it... 

Possibilities, but straws are being grasped. 

[Kirkcaldy Weather]

On 29/12/2021 at 14:29, Kirkcaldy Weather said:

Since i had the last decent check of the MJO its phases since have been 6 & 7 (there's still a question whether it can go into phase 8 so I'll not post those charts til we find out its next direction)  

• Pacific ridges have been persistent
• Using those composites we *SHOULD expect to see blocked charts (upcoming) + we see the pacific heights moving through the arctic

There are warming's in the stratosphere over the next couple weeks which I think are also having an affect on the models, maybe we will see those sorts of patterns ^ develop as we go through the first half of January, the feedback of MJO usually takes at least a couple of weeks sometimes it can be twice as long. 

Looking at the above and comparing to where we are now, some adjustments the low pressure shown more focused over canada is in reality further south with big snow making systems moving through and into North Eastern areas of USA this can screw us out of a good setup of a colder pattern as was the case with the failed easterly that scarred Mr Frost  I believe that's what is the problem for us getting our high going north, however the MJO has continued in phase 7 and now phase 8 which looks like  given that we will hopefully look to Greenland a few weeks from now maybe a flow in from the north east or east 

[Kirkcaldy Weather]

 

 not so much a crazy thought potentially as the ensembles see it as a possible scenario