There is definitely a theory based on snow cover correlating with high pressure. Although my understanding of it is poor, I thought it was more prevalent in deep winter months when large anticyclones are more likely over NE/ Northern Europe, as opposed to more mobile systems typically associated with Autumn. 

From memory it has something to do with sunlight reflected back into space (rather than being absorbed as solar energy into earth).

Bit of a jigsaw puzzle but I’ve read numerous iterations in this very forum over the years.

Isn't it basic physics? Landmasses which have a snowcover have dense cold air at/near the surface. Dense, cold air is heavy and exerts higher pressure at the surface. The Siberian high is an extreme example of this. 

It is fair to say that in years gone by Scandinavia used to see more extensive snowcover than nowadays - favouring the development of blocking highs across Finland and Sweden and increasing the chance of cold easterlies in the UK. However that’s a rarity nowadays. Even back in the day, there was many a winter when there was plenty of snow in Scandinavia and we didn’t have much cold. In short if the synoptics aren’t right, we wont drag in the cold air, even if its close by. 

Isn't it basic physics? Landmasses which have a snowcover have dense cold air at/near the surface. Dense, cold air is heavy and exerts higher pressure at the surface. The Siberian high is an extreme example of this. 

It is fair to say that in years gone by Scandinavia used to see more extensive snowcover than nowadays - favouring the development of blocking highs across Finland and Sweden and increasing the chance of cold easterlies in the UK. However that’s a rarity nowadays. Even back in the day, there was many a winter when there was plenty of snow in Scandinavia and we didn’t have much cold. In short if the synoptics aren’t right, we wont drag in the cold air, even if its close by. 

Spot on 

Wx summary as yesterday in respect of temp: temps across most of Europe i.e. mild Atlantic, colder weather establishing over NE Europe though the small corner of Siberia shown is now cooling in week 2. Rain for all UK and Baltic week 1 moving to UK and France week 2

Jet - too complex to summarise but never far from UK and notably strong Thu 28th/Sat 30th. Perhaps on average a bit further S than yesterday

GFS - current blast from the N soon replaced by a mostly W/Sw flow with controlling Lp somewhere to the NW of Britain (HP not as evident in the S as yesterday) until Mon 1st when shallow trough moves S to cover UK, sticks around and deepens 970mb Hebrides Fri 5th

GEFS - after current heavy rain and following cold snap, dry and recovering to temp norm by Sun 24th. Probably warm around Fri 29th otherwise temps scattered either side of norm, rain never far away after Mon 25th, a few big totals in some runs for Scotland

ECM - like GFS but has swapped positions since yesterday and now favours higher pressure over S of UK to end October

 

Isn't it basic physics? Landmasses which have a snowcover have dense cold air at/near the surface. Dense, cold air is heavy and exerts higher pressure at the surface. The Siberian high is an extreme example of this. 

It is fair to say that in years gone by Scandinavia used to see more extensive snowcover than nowadays - favouring the development of blocking highs across Finland and Sweden and increasing the chance of cold easterlies in the UK. However that’s a rarity nowadays. Even back in the day, there was many a winter when there was plenty of snow in Scandinavia and we didn’t have much cold. In short if the synoptics aren’t right, we wont drag in the cold air, even if its close by. 

Yes that's the explanation, thanks!

And this year the Scandinavian snow cover is far more extensive than in recent years, and next few weeks are showing a further build in the northern half of Scandinavia.

The next CPF update due very shortly will be interesting as it covers Nov/Dec/Jan. My guess is they'll be forecasting an increased probability of milder than average conditions aggregated through the 3 month period. 

The next CPF update due very shortly will be interesting as it covers Nov/Dec/Jan. My guess is they'll be forecasting an increased probability of milder than average conditions aggregated through the 3 month period. 

Isn't that generally what LRFs do almost every winter?

I'd love LRFs to be able to nail the general synoptics of any given winter, but they're not exactly reliable.

What I wish there was more of is a post-winter reviewing of global synoptics in the months running up to significant winters for the UK, looking for specific signs and triggers. I imagine there's people at the Met Office (and with some commercial forecasters to a much lesser extent) to try to help themselves improve their LRF'ing, but I don't see this research/reviewing published (or at least not in layman's language) 

 

 

Isn't that generally what LRFs do almost every winter?

I'd love LRFs to be able to nail the general synoptics of any given winter, but they're not exactly reliable.

What I wish there was more of is a post-winter reviewing of global synoptics in the months running up to significant winters for the UK, looking for specific signs and triggers. I imagine there's people at the Met Office (and with some commercial forecasters to a much lesser extent) to try to help themselves improve their LRF'ing, but I don't see this research/reviewing published (or at least not in layman's language) 

I think it has always been true that most winters are mild. This kind of analysis is certainly available in the literature but tends to focus on he role of various forcings eg ENSO, OBO etc rather than individual seasons

 

I think it has always been true that most winters are mild. This kind of analysis is certainly available in the literature but tends to focus on he role of various forcings eg ENSO, OBO etc rather than individual seasons

Be interesting to know how much weighting is given to those factors vs seasonal models when the CPF is produced.

 

Be interesting to know how much weighting is given to those factors vs seasonal models when the CPF is produced.

They are discussed in the acompanying narrative and are a part of the models used. I don't know what role they play quantitatively in the forecast

 

Isn't it basic physics? Landmasses which have a snowcover have dense cold air at/near the surface. Dense, cold air is heavy and exerts higher pressure at the surface. The Siberian high is an extreme example of this. 

It is fair to say that in years gone by Scandinavia used to see more extensive snowcover than nowadays - favouring the development of blocking highs across Finland and Sweden and increasing the chance of cold easterlies in the UK. However that’s a rarity nowadays. Even back in the day, there was many a winter when there was plenty of snow in Scandinavia and we didn’t have much cold. In short if the synoptics aren’t right, we wont drag in the cold air, even if its close by. 

Blocking highs generally extend high into the atmosphere disrupting the jet stream hence they are warm highs, cold highs over snow cover are usually very shallow. I think the Scandinavian nountains interacting the Rossby waves are the source of Scandinavian blocking

There is a definite colder cluster on the 06z GEFS between the 21 and 22 Oct. It's nothing major but it will be very interesting to see if we do have a mini cold snap around then. It would be notable simply because there has been hints over the last few days and it would be impressive that it was picked up so far out.

On the 8th I commented that the GEFS had picked up on a cool snap around the 21/22 October and it looks like it will verify. It is impressive as we have been in a relatively mild regime for some time, but it was still able to forecast it. The signal did wax and wane but it has always been there. It reminds me of some of the old school northerlies that it would forecast from a way out. However, I haven't looked at the actual synoptics and they may changed over the the last 2 weeks, but still Kudos to the GEFS.

 

Be interesting to know how much weighting is given to those factors vs seasonal models when the CPF is produced.

BBC quoting an LRF from somewhere as cold, calm and dry for the next three months starting Nov

Wx summary   temps across most of Europe i.e. mild Atlantic  cooler to N/NE but a difference in that the seriously colder weather is moving from Scandi to far NE Europe in week 2. Rain for W UK and Baltic week 1 moving to mist of UK and France week 2

Jet irregular; but particularly strong near Scotland Fri 29th and near Channel Wed 3rd

GFS - current cold N=ly dies quickly, then W or SW winds quite strong to Sun 31st between LP mostly near Iceland and HP near E France. Then LP 975 mb off SW Eire moves slowly across the UK, filling, to join up with LP over Sandi and NW-lies setting in Sat 6th

GEFS - temps soon back to norm, then a mild/warm spell around Fri 29th followed by wide variety in runs though mean near norm. In the S, a little rain until 29th, then rather more; In Scotland, rain from 25th onwards quite heavy in west

ECM - less windy than GFS, and LP reaches the western side of UK on Sat 30th, i.e. a couple of days earlier

 

To be honest the snow cover is late and every year there is a build up of snow cover. Not a good theory many more factors

Not as late as last year! The last couple of years there has been very little cold and snow in Southern Scandinavia. There has been none here. There is likely to be some correlation given the nearness of Southern Scandinavia to Eastern England and Scotland. Furthermore all of our really severe winters have been co-joined with cold in N.Europe. Although it is uncommon in recent years I'm sure a frozen Baltic also knocks a degree or so off of those NE winds on the rare occasions we get them.

The idea isn't new. I can remember in the early 80s the weather guru in the local rag said that he looked at developments across Siberia through November as an early indicator of the UK winter.

 

There really isn’t any clear linkage between the arrival of Scandinavian snow cover and our winter weather. It’s at best one tiny part of a complex jigsaw puzzle, and more likely a red herring.

Not clear maybe but as I've just said the remarkable run of snowless and mild winters in the S.E recently has been matched with record breaking winter mild and lack of snow in places like Stockholm, Helsinki and Moscow. Of course this is part of the Northern Hemisphere climate change but It doesn't help!

 

How on earth does what is on the ground affect atmospheric pressure????

The two are linked. The chaos in the atmosphere is generated by several factors. Do you think the ocean temperature has no affect on that?

Also see- http://www.aerodynamics4students.com/properties-of-the-atmosphere/variation-due-to-local-ground-conditions.php

I'm not saying snow cover causes high pressure in northern Europe- but it may be a reflection of it. 

 

BBC quoting an LRF from somewhere as cold, calm and dry for the next three months starting Nov

That'll be a different source to the one that was quoting mild , wet and windy then?

 

That'll be a different source to the one that was quoting mild , wet and windy then?

I personally wouldn't put money on any LRF. But the BBC forecasters are not noted for sticking their necks out unless reasonably certain.

 

That'll be a different source to the one that was quoting mild , wet and windy then?

If you want to see winter forecasts just look at the CFS on wetternezle.de all runs now go out to well into April 2022. Absolutly brilliant website None of the CFS runs are showing cold,dry,anticyclonic conditions that the bbc have mentioned.