Model thread discussion - cold spell looming

[ICE COLD]

6 minutes ago, Quicksilver1989 said:

Coldies may want to look at P15 from the 06z GFS ens, what a treat. 

Yer nice

[Battleground Snow]

3 minutes ago, CentralSouthernSnow said:

So why is everyone getting so hyped saying It’s another beast... 

Because the evolution at 192 isn't certain and the orientation of the high will probably look different by then, e.g the gem and allow lower heights to undercut, and bring snow. It's still impressive  synoptically even without the snow.

Edited February 6, 2021 by Battleground Snow

[Mike Poole]

40 minutes ago, Weather-history said:

That's if the snow doesn't sublimate, could very well do if you get a really dry airmass 

That was a feature of the 2018 BFTE.  It was quite surreal to observe snow literally vanishing into thin air.  

I said last night that I was sceptical about the return to mild end of next week, I wasn’t expecting so much change in the model output as early as this morning’s runs, with the GEM and GCM excellent, and now the GFS 6z.  

[CameronWS]

1 hour ago, GSP said:

The Beast from the East 3 years ago was all well and good. But this spell is going to catch a lot of people out.

What would be the difference? Looks less disruptive to me - but I’m pretty clueless so just wondering 

[Snowman.]

9 minutes ago, CentralSouthernSnow said:

Can I just ask.. with this monster scandi high, where would the low pressure come from... 

When you build a Scandi high they can be persistant and usually dry at the start. 

Cold air starts wrapping around the SE of the high along with low pressure and instability, that travels west underneath the high, the UK is the last stop but much of Europe begin to slowly go into the freezer.

Below is the 2018 Beast and you can see how it evolves.

 

You can see the same thing happening on the GEM. There will be a relaxation of snow but it would likely remain very cold with any snow cover persisting.

[nick sussex]

Interesting overnight trends !

After the progressive GFS 00hrs run , the 06 hrs makes a westwards correction which is encouraging.

I don’t think we should see this as a done deal yet in terms of a nailed on Scandi high orientated favourably  to advect the coldest air westwards .

A continental feed though looks at least like keeping most of the UK with cold air at the surface into next weekend .

The biggest hurdle in these set ups is to get the right jet cut back sw wards into the Low Countries .

It’s not just about the Scandi high but its orientation so more nw to se with the PV chunk sat underneath it ready to get that deep cold into the UK.

Overall though a great period of model watching coming up , so we’ve just finished one drama and could be embarking on another !

Edited February 6, 2021 by nick sussex

[Cold Winter Night]

This forum is for enthusiasts and there are no consequences attached to making bold predictions that fail to verify, other than loss of reputation. Nevertheless, it feels a bit risky to claim that the models are wrong, that the Atlantic will not push through, and that a Scandi High will form.

Yesterday, I said i was very confident of those developments appearing more and more in the output.

Well, I did not expect to see that happening this fast!
Still, it does not surprise me at all. With more and more output showing this, confidence gets solidified.
Mind, the Westernmost parts of the UK, and Ireland, are still at risk of the milder air getting in too close, and of the Scandi High cold not reaching that far West. That is the reality of those locations.

The other day, I included a chart of the onset of the January 1947 cold spell. With a reason.
The past few winters, when there was nothing exciting happening in the output, I have looked at many great cold spells and how they developed. As a geographer, I love studying spatial patterns. When I saw the output last week, especially EC at the later stages, I recognised it from many of those legendary cold spells.

The cold in Europe, the incoming Atlantic and some lingering heights near Greenland/Iceland. It happened before, although no two weather events are exactly alike, but the basics are the same:

The deep cold holds its ground, the Atlantic comes in, fails and instead pushes WAA North. WAA + CAA in Eastern Europe = Scandi High formation. Usually followed by retrogression to Greenland, and often a repeat.

1947 may still be one of the most extreme, and for coldies ideal evolutions, but as an example of how this stuff works it is great.
Below the progression from January 20-28, 1947

[MattStoke]

A chart from the Euro4 for those writing this off as completely dry away from the south east based on most models and apps showing nothing.

I think a lot of people will be surprised when the radar springs into life with showers and streamers crossing the country.

[Purga]

GEFS trending colder and a significant number of members going for an extension of the cold and no 'warm-up' as such.

00z                                                                  06z

    

Note the surface cold trends the same way

00z                                                                  06z

    

 

Edited February 6, 2021 by Purga

[matty40s]

 

[Kreftysoton]

I really hope the models keep pushing back the atlantic progression. Would be nice down here to have a proper cold week rather than the original 3-4 days. How nailed is the scandi high? Guessing it can still go wrong.

[SqueakheartLW]

After limited progress with the 00z models this morning in delaying the end of the cold spell I shall have a look at what the 06z GFS is showing in terms of this.

The end of the colder spell on the latest 06z is at 156 hours away, identical to the 00z so yet another 6 hour extension to the colder spell so another tick to the GFS for this one

For the first time since I started looking at the possible end of the colder spell apart from the low pressure out to our west there is the first signs here of a Scandi high showing in the average pressure chart. Perhaps the cold will put up more of a fight after all so a tick for GFS for heading in the right direction on the 06z. The anomaly chart also shows some quite deep cold to our east which the mild air has to try and shift but will it do it?

The peak of the milder spell on the 06z comes at 228 hours away, a little more than on the 00z which was 216 hours away. Allowing for adjustments for run times this has pushed the milder peak back 18 hours which is a big tick for the GFS

Another high pressure dominated milder spell which is a big tick for GFS 06z. What makes this one better is the positioning of the high pressure. It is further north now so meaning more of a continental feed rather than Atlantic and the result is much less mild air as a result and when I compared the 850hpa temperatures between 00z and 06z the average had dropped quite a bit from 1.9 to -1.8 at the peak, a decent -3.7 drop. At last the milder spell looks to be getting watered down so a big tick here for the GFS 06z

Mildest earliest run of the 06z GFS

Member 28     +120 hours     850hpa temp -3.3

Coldest for longest run of the 06z GFS

Member 19     +306 hours     850hpa temp -5.2

This run actually stays below -5 at 850hpa for its entirety once it dips below this value so overall a decent run for cold

[Tim Bland]

UKMO has been showing a lot of showery activity for a while now. Below are the latest, remember each frame is 12hr precip amounts 

[Ben Sainsbury]

ICON-EU 09z a touch further NW than its 06z run, only up to T30 though.

 

[Man With Beard]

2 hours ago, Alderc said:

Its very unusual to see such a correction northwards, however I'm already getting nervous that if it gets much further north it'll bring the warm sector into play and it'll be rain or freezing rain on the south coast. We ended up under freezing rain with the BFTE in March 18 after snow as uppers ended being on -1/-2C. 

Infact the ICON lifts the uppers on the south coast to just -2C so already getting squeaky bum time, although the surface flow looks to remain east or just north of east so screams at the moment to be a snow to freezing rain event.  

Ahhh, the problems of getting snow on the south coast. You're never far from disaster on both sides! My gut feeling is it will be S Devon/Cornwall only, but I'm getting close to giving up predicting what will happen

[MJB]

27 minutes ago, Kreftysoton said:

I really hope the models keep pushing back the atlantic progression. Would be nice down here to have a proper cold week rather than the original 3-4 days. How nailed is the scandi high? Guessing it can still go wrong.

From an IMBY POV , I am happy with what this mornings 6z showed , just getting far enough in to give a snow event

[Grumpy Yorkshireman]

Good afternoon

This is possibly the most in depth forum with so many differing options, time frames and opinions. With that in mind I don't think anyone should be reluctant to post in this rather unique year. AER even started their weekly blog suggesting he would be "spit balling" this week as he didn't know!!!!

With specific regards to this coming week, could somebody please give an informative description of "convective, sublimated and "nailed on" snow. I for one am a little confused as to how storm Nancy is nailed on while I read snow showers could form in the North Sea and drop varying amounts on the east coast and may not show up before they arrive.

I feel like I am doing a watching masters in weather prediction this winter and the excitement is massive. somebody mention rehab after all this has happened, but I guess we then look at when it gets warm and will the summer be warm hot or unbearable if climate change is believed.

I wish everyone a great week, snow or not and, it certainly looks a great ride into what may be a non existent warming period before more ice age stuff. 

[CentralSouthernSnow]

2 hours ago, Alderc said:

Its very unusual to see such a correction northwards, however I'm already getting nervous that if it gets much further north it'll bring the warm sector into play and it'll be rain or freezing rain on the south coast. We ended up under freezing rain with the BFTE in March 18 after snow as uppers ended being on -1/-2C. 

Infact the ICON lifts the uppers on the south coast to just -2C so already getting squeaky bum time, although the surface flow looks to remain east or just north of east so screams at the moment to be a snow to freezing rain event.  

It would be all snow conductive.... uppers change closer to the time. If it came off it would deliver 3-7cm. Personally I think it won’t go too north, it will be middle ground. South coastal areas only. 

[Jayces]

30 minutes ago, Grumpy Yorkshireman said:

With specific regards to this coming week, could somebody please give an informative description of "convective, sublimated and "nailed on" snow. 

I'm no expert but will give it a bash -

Convective I believe happens when there is a big temperature difference over sea (and maybe land) compared to upper air temp, the steeper it is the more it creates clouds that produce snow.

Sublimated I had to Google earlier and it's where I think it's so cold that the snow turns into vapour so basically evaporates.

Nailed on, well I don't think that's a thing unless you are standing outside and it's actually snowing?

[Man With Beard]

39 minutes ago, Grumpy Yorkshireman said:

Good afternoon

This is possibly the most in depth forum with so many differing options, time frames and opinions. With that in mind I don't think anyone should be reluctant to post in this rather unique year. AER even started their weekly blog suggesting he would be "spit balling" this week as he didn't know!!!!

With specific regards to this coming week, could somebody please give an informative description of "convective, sublimated and "nailed on" snow. I for one am a little confused as to how storm Nancy is nailed on while I read snow showers could form in the North Sea and drop varying amounts on the east coast and may not show up before they arrive.

I feel like I am doing a watching masters in weather prediction this winter and the excitement is massive. somebody mention rehab after all this has happened, but I guess we then look at when it gets warm and will the summer be warm hot or unbearable if climate change is believed.

I wish everyone a great week, snow or not and, it certainly looks a great ride into what may be a non existent warming period before more ice age stuff. 

Hi Grumps! I confess I've followed all the models religiously for 20 years and I really can't work out everything that's going on. It's clear the SE corner will get something more substantial in the next three days, elsewhere though, well, perhaps a dry spot close to the east Midlands but that's likely to vary ... my sense is anywhere Pennines east can't miss - there's too many opportunities, too many variations in the east wind, too much of a temperature gradient between the sea and the sky, too much instability in the air. Midlands, Wales and west country is my head scratcher. I'm sure the north sea showers will make it all the way to the Welsh mountains but models don't seem so keen. 

I'm not sure if that answered your question but anyway, that's my twopenneth this afternoon. I might give a totally different answer tomorrow

Edit: thanks @Jayces, I think you've given the answer

Edited February 6, 2021 by Man Without Beard

[Lukesluckybunch]

4 minutes ago, Man Without Beard said:

Hi Grumps! I confess I've followed all the models religiously for 20 years and I really can't work out everything that's going on. It's clear the SE corner will get something more substantial in the next three days, elsewhere though, well, perhaps a dry spot close to the east Midlands but that's likely to vary ... my sense is anywhere Pennines east can't miss - there's too many opportunities, too many variations in the east wind, too much of a temperature gradient between the sea and the sky, too much instability in the air. Midlands, Wales and west country is my head scratcher. I'm sure the north sea showers will make it all the way to the Welsh mountains but models don't seem so keen. 

I'm not sure if that answered your question but anyway, that's my twopenneth this afternoon. I might give a totally different answer tomorrow

Edit: thanks @Jayces, I think you've given the answer

4 minutes ago, Man Without Beard said:

Hi Grumps! I confess I've followed all the models religiously for 20 years and I really can't work out everything that's going on. It's clear the SE corner will get something more substantial in the next three days, elsewhere though, well, perhaps a dry spot close to the east Midlands but that's likely to vary ... my sense is anywhere Pennines east can't miss - there's too many opportunities, too many variations in the east wind, too much of a temperature gradient between the sea and the sky, too much instability in the air. Midlands, Wales and west country is my head scratcher. I'm sure the north sea showers will make it all the way to the Welsh mountains but models don't seem so keen. 

I'm not sure if that answered your question but anyway, that's my twopenneth this afternoon. I might give a totally different answer tomorrow

Edit: thanks @Jayces, I think you've given the answer

Hi there how would you rate my chances living in bicester?

[Man With Beard]

2 minutes ago, Lukesluckybunch said:

Hi there how would you rate my chances living in bicester?

Seriously, I've tried doing a forecast for your sort of area the past three days, but if I did another forecast today, I think I'd write "Sorry, I don't have a clue, and noone else does!"

[Lukesluckybunch]

2 minutes ago, Man Without Beard said:

Seriously, I've tried doing a forecast for your sort of area the past three days, but if I did another forecast today, I think I'd write "Sorry, I don't have a clue, and noone else does!"

Hah I see what your saying snow is difficult to forecast.I'm betting i am too far West though

[Grumpy Yorkshireman]

Hi again

fortune favours the brave so Man Without Beard ..... thanks for yours and Jayces answers and lets see if you can guess the snowfall. As you say, the East is favoured but knowing the Pennines and the peak district, it seems a lottery as to who gets it over on the dark side

more charts and experienced guessing then!!!!

[MattStoke]

21 minutes ago, Man Without Beard said:

Hi Grumps! I confess I've followed all the models religiously for 20 years and I really can't work out everything that's going on. It's clear the SE corner will get something more substantial in the next three days, elsewhere though, well, perhaps a dry spot close to the east Midlands but that's likely to vary ... my sense is anywhere Pennines east can't miss - there's too many opportunities, too many variations in the east wind, too much of a temperature gradient between the sea and the sky, too much instability in the air. Midlands, Wales and west country is my head scratcher. I'm sure the north sea showers will make it all the way to the Welsh mountains but models don't seem so keen. 

I'm not sure if that answered your question but anyway, that's my twopenneth this afternoon. I might give a totally different answer tomorrow

Edit: thanks @Jayces, I think you've given the answer

GEM and Euro4 show snow showers getting all the way across to Wales, even over the Peak District.

Edited February 6, 2021 by MattStoke