Scotland/Alba weather discussion - Autumn 2020 onwards

[Quinach]

Lovely winter's day.

Light winds, clear blue skies and a max of 5c after a cold frosty night.

What's not to like.

Castle Fraser bustling with people taking advantage of the weather so had to wait a bit to get a reasonably deserted view of the castle...

Bennachie seemed to attract the only bit of cloud around (until some high cloud drifted in from the west in the late afternoon).

Plenty of grass frost out of the sun, and the ponds in the fields were still frozen...

Already down to -1.5c and a well defined winter halo around the moon...

[Polar Gael]

Just dipped into the TOORPing palace of varieties to catch up on the latest model output and chat.

A fair bit of 'stella', 'screaming potential', etc on the go. Of course, it's never 'nailded on' whilst it's still in 'F1', but to these ageing eyes, this winter is looking different from the last several (BFTE in 2018 excepted). PV remains in flip-flops and t-shirt (ie a wintry shambles), the immediate pre and post-Crimbo synoptics are not without interest into the New Year and GloSea is apparently predicting a SSW, which could, perhaps, possibly, maybe...

[LomondSnowstorm]

So - the next 48 hours:

Not too much of note for the central belt (other than some lovely frost tomorrow night into Christmas Eve) but, quietly, I do wonder if there's some significant snowfall potential for Inverness, Aberdeen and a lot of places in between (the precipitation for the Borders looks generally to be through the day tomorrow when it's a bit on the mild side for snow aside from maybe some of the higher hills):

The key time looks to be between midnight and 6am, when the freezing level looks pretty good for everywhere affected by the showers:

Although some suggestion that this will be sleet around the Aberdeenshire coast initially with slightly higher dewpoints.

The GFS has this arriving a bit later and extending a bit further south, with some potential more widely:

Again there's hints of slightly higher dewpoints near the coast but I think you wouldn't need to be very far inland for snowfall:

Totals? Well I could see a couple of inches quite widely, and up to 4 inches where the streamers hit. A possibility of a dusting further south (maybe Midlothian+Renfrewshire and East Ayrshire with a shot of seeing something). It isn't really a full on cold front, otherwise I would suggest the risk would extend to more of us, but it seems like a classic disappearing trough which reappears once it runs into higher ground just south of the central belt, albeit weakly.

Beyond that, the 27th is where the risk reappears, as the crucial Greenland High builds to the west of the next low, which sinks over us:

 

There's a reasonable degree of certainty that this will happen (despite my worries), but the real question is where exactly is this trough going to end up, because with the centre being so close to Scotland even small changes will make a huge difference to what happens.

The generally agreement really ends around 6am on the 27th (although I suspect that's overegging the certainty a bit), as the rainfall from the initally westerly turns to snow on the back edge, with higher precipitation totals towards the centre of the low:

 

While these charts may look relatively similar between the NMM (12Z) and the ECMWF, the low was positioned significantly further south and weaker on the 00Z runs, so the timing and positioning is very unclear. In addition, we could easily see secondary troughs forming and convective precipitation, particularly around the west and south west. I'd also say that, as per the UKV, the UKMO shows the low holding further north through the day, bringing a significantly snowfall risk from the west through the central belt:

By Sunday evening, we have three very different scenarios based on tiny tweaks to the synoptic pattern - the ECMWF with the low pretty well in situ, some precipitation associated with it but quite dry and very cold at the surface away from any features or convective precipitation (although bear in mind the caveat that secondary features will likely show up somewhere with such low pressure nearby):

An UKMO pattern which would seem to bring a continued snow risk across a large chunk of western and central Scotland into the evening, maybe tailing off or shifting temporarily as the low sinks south more gradually and a bit further east:

And a GFS which sinks the low quickly and bring in a very premature easterly:

Now, as we saw earlier this month, these upper air temperatures don't completely prohibit snowfall even near the east coast, but what they do mean is that any snowfall from this setup would be transient as the winds shift round to a snow killing direct easterly and the initial snowfall turns to rain:

 

Now this detail is relatively unique to the GFS 'pub run' so far - the earlier GFS had a similar feature but with the low staying a bit closer meaning we didn't see a snow to rain event quite so quickly. But this does illustrate a possible pitfall of this setup - you really don't want to be to the north or northeast of this trough because things will very quickly turn to mush. I should note, though, that even in this relative worst case scenario, the easterly comes good in the end because the Greenland high is very likely to win out, and the cold upper air temperatures eventually arrive from the east to save the day:

And as KW says, the second half of that output is really quite something, could still be a very special spell of cold and snow longer term (which tells you that there are quite a few paths to the 'holy grail' here).

The ECMWF keeps the low closer by throughout, initially drifting south then back into the North Sea near the east coast, with occasional hints at this sort of mushy easterly (this chart for the 29th) but with perhaps a better angle of attack, with surface winds more northerly and temperatures closer to 0C( the palest yellow is 0-4):

 

The UKMO is probably the best shot longer term too - with the low sitting out ,there's the potential for some really significant snowfall as surface winds would be either relatively light or northerly, but with the trough close enough to aid instability:

In short, the 27th onwards is a period of very significant potential. At this stage it's difficult to pin details down, but what I would say is to look out for the bullseye - if it settles anywhere in the vicinity of Fair Isle to Dogger Bank I would be getting the sledges out. Also a note on why we should be ok if any 'shallow' easterly is short lived - take a look at the soundings for Edinburgh Airport for the approach of the 18Z mushy easterly:

Still pretty good! it takes until midday on the 28th in Edinburgh and 6pm in Glasgow to see temperatures rise enough to clearly see precipitation turning to rain.

It's good to be back!

 

Edited December 22, 2020 by LomondSnowstorm

[edo]

@LomondSnowstormhow we have missed you, I have read 10s of pages in the model thread this week and got more from that post along with @Ravelin and @Mr Frost and @Kirkcaldy Weather than the other 100 Many thanks to you guys for taking the time to construct your posts. 

Also a big welcome back to snowy owl let's hope for some snow chat over the next few weeks.

Edited December 22, 2020 by edo

[Mr Frost]

26 minutes ago, LomondSnowstorm said:

So - the next 48 hours:

Not too much of note for the central belt (other than some lovely frost tomorrow night into Christmas Eve) but, quietly, I do wonder if there's some significant snowfall potential for Inverness, Aberdeen and a lot of places in between (the precipitation for the Borders looks generally to be through the day tomorrow when it's a bit on the mild side for snow aside from maybe some of the higher hills):

The key time looks to be between midnight and 6am, when the freezing level looks pretty good for everywhere affected by the showers:

Although some suggestion that this will be sleet around the Aberdeenshire coast initially with slightly higher dewpoints.

The GFS has this arriving a bit later and extending a bit further south, with some potential more widely:

Again there's hints of slightly higher dewpoints near the coast but I think you wouldn't need to be very far inland for snowfall:

Totals? Well I could see a couple of inches quite widely, and up to 4 inches where the streamers hit. A possibility of a dusting further south (maybe Midlothian+Renfrewshire and East Ayrshire with a shot of seeing something). It isn't really a full on cold front, otherwise I would suggest the risk would extend to more of us, but it seems like a classic disappearing trough which reappears once it runs into higher ground just south of the central belt, albeit weakly.

Beyond that, the 27th is where the risk reappears, as the crucial Greenland High builds to the west of the next low, which sinks over us:

 

There's a reasonable degree of certainty that this will happen (despite my worries), but the real question is where exactly is this trough going to end up, because with the centre being so close to Scotland even small changes will make a huge difference to what happens.

The generally agreement really ends around 6am on the 27th (although I suspect that's overegging the certainty a bit), as the rainfall from the initally westerly turns to snow on the back edge, with higher precipitation totals towards the centre of the low:

 

While these charts may look relatively similar between the NMM (12Z) and the ECMWF, the low was positioned significantly further south and weaker on the 00Z runs, so the timing and positioning is very unclear. In addition, we could easily see secondary troughs forming and convective precipitation, particularly around the west and south west. I'd also say that, as per the UKV, the UKMO shows the low holding further north through the day, bringing a significantly snowfall risk from the west through the central belt:

By Sunday evening, we have three very different scenarios based on tiny tweaks to the synoptic pattern - the ECMWF with the low pretty well in situ, some precipitation associated with it but quite dry and very cold at the surface away from any features or convective precipitation (although bear in mind the caveat that secondary features will likely show up somewhere with such low pressure nearby):

An UKMO pattern which would seem to bring a continued snow risk across a large chunk of western and central Scotland into the evening, maybe tailing off or shifting temporarily as the low sinks south more gradually and a bit further east:

And a GFS which sinks the low quickly and bring in a very premature easterly:

Now, as we saw earlier this month, these upper air temperatures don't completely prohibit snowfall even near the east coast, but what they do mean is that any snowfall from this setup would be transient as the winds shift round to a snow killing direct easterly and the initial snowfall turns to rain:

 

Now this detail is relatively unique to the GFS 'pub run' so far - the earlier GFS had a similar feature but with the low staying a bit closer meaning we didn't see a snow to rain event quite so quickly. But this does illustrate a possible pitfall of this setup - you really don't want to be to the north or northeast of this trough because things will very quickly turn to mush. I should note, though, that even in this relative worst case scenario, the easterly comes good in the end because the Greenland high is very likely to win out, and the cold upper air temperatures eventually arrive from the east to save the day:

And as KW says, the second half of that output is really quite something, could still be a very special spell of cold and snow longer term (which tells you that there are quite a few paths to the 'holy grail' here).

The ECMWF keeps the low closer by throughout, initially drifting south then back into the North Sea near the east coast, with occasional hints at this sort of mushy easterly (this chart for the 29th) but with perhaps a better angle of attack, with surface winds more northerly and temperatures closer to 0C( the palest yellow is 0-4):

 

The UKMO is probably the best shot longer term too - with the low sitting out ,there's the potential for some really significant snowfall as surface winds would be either relatively light or northerly, but with the trough close enough to aid instability:

In short, the 27th onwards is a period of very significant potential. At this stage it's difficult to pin details down, but what I would say is to look out for the bullseye - if it settles anywhere in the vicinity of Fair Isle to Dogger Bank I would be getting the sledges out. Also a note on why we should be ok if any 'shallow' easterly is short lived - take a look at the soundings for Edinburgh Airport for the approach of the 18Z mushy easterly:

Still pretty good! it takes until midday on the 28th in Edinburgh and 6pm in Glasgow to see temperatures rise enough to clearly see precipitation turning to rain.

It's good to be back!

 

Incredible detailed post - what a joyous read that was from start to finish!

Absolutely brilliant to have you back posting again.

Edit: Cheers @edo 

Edited December 22, 2020 by Mr Frost

[LomondSnowstorm]

Not too much to add based on the overnight runs, with the details still somewhat up in the air, but the ECMWF seems to me to be the pick of the bunch - the later stages in particular bring back the spectre of the vaunted 'polar low':

Is it a true polar low? DIfficult to say but it's as close as you'll see to one at that (albeit speculative) range, with 500hPa temperatures below -40C:

The centre is tantalisingly close by the end of the run, with significant precipitation alongside it:

 

In terms of the bigger picture, the Met Office modelling seems to point towards a Sudden Stratospheric Warming, seemingly led by/in tandem with the exceptional polar vortex destruction you can see on the chart above at the lower levels.

The basic pattern above is also seen with the GFS, which while again a bit less pretty in the early reaches comes out with more secondary troughs coming through from the northwest before an eventual full blow easterly/'reverse zonality' under the high (this is shameless ramping by the way, not worth taking seriously at this range but illustrative of some of the possibilities if the early part pans out):

All in all, some encouraging output again. We have some issues with warm sectors on the low from the 27th which may cause difficulties but I wouldn't worry quite yet given the placement is very far from nailed down, and I've seen more runs that create secondary lows or even just split the main low anyway, which would certainly lower that risk.

 

[mistyqueen]

Morning all from a crisp and very fresh feeling Skye! Temp currently 1.7c, a few clouds and very calm and clear. Out for a walk later today, but will have to light stove in the kitchen first! Enjoying those charts but I refuse ( as usual! ) to build up my hopes for any white stuff falling here. There is, however, a light dusting on the Cuillin and also over on the mainland hills, so you never know! 

[101_North]

I'm in dire need of some seasonal weather! This endless grey pish is wearing me down! Bit colder this morning but still grey and damp

[Sceptical]

Feeling chilly at 3C, cloudy with light rain. 

Colder tomoroow with snow.

[Polar Gael]

Who said 2010...?

 

 

#rampityramp

 

[JamesM]

Travelling to find the best snow is essential isn’t it?

Part of me will be disappointed if there is an epic spell but I can’t really go anywhere!

 

[Sceptical]

Met office have issued a yellow warning for snow and ice today and tomorrow. The warning covers the northern half of Scotland.

[Kirkcaldy Weather]

06z is on the edge of being a big snow event just another outcome to add to the cool / cold theme and the low pressure to the WSW no chance the pattern falls apart easily, all fascinating to watch and I’m going to say it I find it rather sexy Christmas Eve ice day likely for many and overnight into Christmas Day temps could be a few degrees colder before that slightly warmer section moves in through the day, then we await the low pressure and whatever fun and games it has in store. 

[Ravelin]

Well I'd to run to Inverurie and back for a Specsavers appointment (got to be sure I can spot snowflakes) this morning. It was 2C most of the way, slightly warmer at 3C on the way back. Showers were encountered in both directions but definitely of the liquid variety, no real even semi-solud element to them. Otherwise it's not awful as there's glimpses of blue sky and no real wind. 

I'm quite hopeful of waking up to a covering of snow tomorrow morning, after that, well its still in the lap of the weather gods. Maybe looking just slightly too warm, but with my extra height you never know, and I can gain always another 200m or so by jumping in the car for 5mins to the top of the hill. 

[Sceptical]

The Met Office take on the next 10 days.

Looks okay for Scotland at least.

 

[Hawesy]

44 minutes ago, Sceptical said:

The Met Office take on the next 10 days.

Looks okay for Scotland at least.

 

Thanks @Sceptical - a pretty level headed forecast. As usual location will be key: the chances of me in a mild coastal location seeing anything significant are low, chance of someone inland and with modest elevation, pretty high. Should make for a lively thread in the next week or so and looking forward to it!

[Sceptical]

5 minutes ago, Hawesy said:

Thanks @Sceptical - a pretty level headed forecast. As usual location will be key: the chances of me in a mild coastal location seeing anything significant are low, chance of someone inland and with modest elevation, pretty high. Should make for a lively thread in the next week or so and looking forward to it!

No worries .

I remain fairly optimistic for this winter, hopefully Scotland sees the goods soon.

[Kirkcaldy Weather]

Latest gfs =   

 

[Cheggers]

Red sky at night kilties delight

Caught earlier in Kinghorn. 

[Penicuikblizzard]

7 hours ago, Kirkcaldy Weather said:

06z is on the edge of being a big snow event just another outcome to add to the cool / cold theme and the low pressure to the WSW no chance the pattern falls apart easily, all fascinating to watch and I’m going to say it I find it rather sexy Christmas Eve ice day likely for many and overnight into Christmas Day temps could be a few degrees colder before that slightly warmer section moves in through the day, then we await the low pressure and whatever fun and games it has in store. 

Is the big event in Scotland as the model thread is concentrating on down south ??

[Kayemill]

Similar in Darvel. 
 

 

edit I need to get a newer phone. 

Edited December 23, 2020 by Kayemill

[Puffy MacCloud]

This morning started with a light grey hue, then a bright grey and then, after lunch, some sunshine. Cold again though.

Temperature 1.9deg.C, down from a max of 4.3deg.C at 13:29, humidity 89%, wind 0 to 2mph northerly with a max gust of 10mph, pressure 1020.0hPa rising quickly, there's been 0.2mm of rain today and cloud cover has dropped throughout the day to 1/8 now and the dew point is 1deg.C.

Got a good sighting of Jupiter and Saturn earlier this evening.

[Puffy MacCloud]

5 minutes ago, Penicuikblizzard said:

Is the big event in Scotland as the model thread is concentrating on down south ??

Usually...

[Kirkcaldy Weather]

1 minute ago, Penicuikblizzard said:

Is the big event in Scotland as the model thread is concentrating on down south ??

As ever with colder conditions its rarely straightforward to progress right away into a cold spell but the way the progression is going at the min that's the growing trend from my perspective, mod thread rarely will focus on / mention Scotland (not saying that's a right or wrong just the way it is more often than not) 

 

 

[Northernlights]

A bit overcast today with some light showers coming in off the Firth from the NE a few degrees colder and it would have been snow. Currently partly cloudy and 3c.          Ben More in  Sutherland completely covered in snow this afternoon

New oil tank connected and filled last Monday so should be warm for Christmas.Family breathed a sigh of relief and so did I .All perfectly planned!!!! not

A bit of fun today was using  my phone and the calving cameras microphone to speak to the cows in the steading from the furthest field. Heads and ears went up as they tried to find me in the steading.  Really bad of me to confuse them.

Just want to wish everyone on the Scottish thread a Merry Christmas

 

Edited December 23, 2020 by Northernlights