Model Output Discussion - Colder but how cold and for how long?

[Weathizard]

Once you get cross model agreement on this kind of hemispheric set up it’s goodnight Vienna on any significant blocking or proper cold spell for at least a few weeks, unfortunate given some of the charts we chased this time last week.

[KTtom]

2 minutes ago, Harveyslugger said:

The northerly has not disappeared completely?many snow showers for the favoured spots as it always is with northerlies 

For our location we could do with a bit of a more robust northerly to set up a good old Pembrokeshire Dangler, then a slight westerly tilt of north from the flow and bingo! The second part looks odds on, just as case if the northerly is sustained enough to get the dangler formed...

[Anthony Burden]

Evening all,looking at all model’s uncertainty remains the form horse regarding the track of this Atlantic low and the possibility of wide spread snow to England.Will it or won’t it any body’s guess at the moment safe to keep eyes peeled to the Fax chart’s although even they can alternate,so sit back and just enjoy won hell of a week of weather.

[MATTWOLVES 3]

While some of you get ready with the obituaries I will point out next week is just the beginning of what's to come! Some places will see snow..some places will see snow when there's nothing showing right now! Those who are located in the worse areas will be the ones who lose there cool,say they've had enough..will emigrate abroad or tell us next year they're definitely going to Norway for a break...hang on a sec we've already had that saga this winter

What comes next weekend and beyond is not finalised..those who think it is are kidding themselves. Blocking wil be back.

Mogreps 12z early look still some support to keep it colder out to day 8...

Don't be having nightmares folks..get ready for some little suprises in the days ahead.

[Harveyslugger]

1 minute ago, KTtom said:

For our location we could do with a bit of a more robust northerly to set up a good old Pembrokeshire Dangler, then a slight westerly tilt of north from the flow and bingo! The second part looks odds on, just as case if the northerly is sustained enough to get the dangler formed..

Monday is the Pembrokeshire dangler?you can see it on ukv

[WolfeEire]

3 minutes ago, Penguin16 said:

Does the warm sector on Tuesday look a cert or still up in the air?

It will be literally up in the air for sure!

Right now, all models show a mild sector in some shape or form. It shouldn't translate into a corresponding warmup at surface level due to a combination of factors. It would make conditions less conducive for snowfall wherever precipitation occurs. Looks like a second half of Tuesday episode. Turns much colder again Wednesday. 

[Liam J]

Can’t believe the mood & comments of some in here?! Is that because there’s not feet of snow IMBY being modelled….. There is absolutely no way the models can pick out features & troughs developing in the low heights and unstable airmass from this range! (this gets repeated multiple times)

Finally we can look forward to some proper winter weather starting on Sunday and lasting through next week….. severe frosts, ice days & snowfall chances  

Some absolutely cracking charts for our part of the world!

[Paul]

Once again, if you just want to moan, please head to the moans thread:

https://community.netweather.tv/topic/99729-moans-and-ramps/?do=getNewComment

Most will probably have noticed the big green bar in the editor, just acting as a reminder to keep the models in here. Fortunately, the majority in stick to that (thank you!), but for those who continue to post frequent very off topic and disruptive stuff, please understand you do face being blocked from posting in here. Many other threads are available, so please use them when you don't want to discuss the model output.

Finally, if you do see obviously very off topic posts, moans and the like, even if it's very tempting to reply, please don't. Please just hit the report button!

[Bricriu]

11 minutes ago, Weathizard said:

Once you get cross model agreement on this kind of hemispheric set up it’s goodnight Vienna on any significant blocking or proper cold spell for at least a few weeks, unfortunate given some of the charts we chased this time last week.

You'd be surprised, as I mentioned earlier, how dire output can change to something  more favourable,  especially given the chaos in the strat.  Look up the charts for some noteworthy  cold spells over the years,  you'll see that in the days prior to  some of them you'd never  think  a cold spell was on the way given the  state  of  the NH profile. 

Edited January 12 by Bricriu

[danm]

10 minutes ago, mountain shadow said:

Apologies,  the Northerly is still there for Scotland and parts of NE England. 

Northern Ireland is usually quite prone to showers in a northerly.

[LRD]

17 minutes ago, mountain shadow said:

My perspectives only a short 48 hours ago was that we would see a proper Northerly with widespread snow showers followed with a high probability of a major snow storm for Central and Southern England,  this was to be followed by renewed Greenie blocking.

Instead, we've seen the Northerly disappear completely along with the snow storm with mild and wet now more favoured for next weekend.

Maybe I've misunderstood the posts by the teleconnections gurus, but it doesn't feel the cold spell offered.

Just a few points on this

1) I agree with the general gist of your post. Looks like this is in danger of being another underwhelming spell after looking like it had potential to be pretty eventful (still might but I reckon those chances are diminishing now). I wouldn't say 'high probability of a major snowstorm' but it looked promising. Got to say model-watching/snow-chasing in winter is becoming a bit of a boring, fruitless hobby despite how interesting the countdown to this forthcoming cool/cold interlude has been. If this winter doesn't deliver something significant, I really would start to wonder and lose even more interest 

2) The teleconnections have got it right. Detail, they won't predict. And, alas, it's the devil in the detail that looks like making this an uneventful cold spell for MOST of the UK. That still might change of course

3) The mild weather from next Saturday/Sunday was always on the cards. There have been nods to this in the models and within this thread but they were quite often shouted down as 'looking for the breakdown before the cold is even here' by some. It's a mild spell that might not last that long, though

Edited January 12 by LRD

[Rocheydub]

I'm not so sure why there is so much weeping and gnashing of teeth here, models with egg on face etc. These are super computers who do not compute embarrassment or emotions. The computers picked up the long wave signals a good few weeks back and stuck with it generally speaking. That's all we can expect from those distances and I think they did superbly well at that. The micro and macro scale of 2 such tiny islands in the grand scheme of things is nigh on impossible to get 100% correct at these big time differences. If you're not aware of the phrase "if a butterfly flaps its wings" then I suggest you google it. Chill pill. It's only weather after all. Worldwide life in our recent months and years shows us we all actually have vey little to moan about if a lack of snow is your biggest worry.

Back to the models. I'm not going to post the ECM 240 chart as it's on several pics up above, but I'm greatly encouraged to see the clear signal for the draining of low heights over Svalbard and Scandy. The would give us a quick enough route into another cold spell. I'll be keeping a keen eye on that area next after this week is over.

I'll enjoy this week, whatever it brings, I wish you all well in your chase. Whatever your weather desires are. But remember, posters here and the NWP super computers don't decide the weather, mammy nature does.  

Much love.

[Bricriu]

3 minutes ago, WolfeEire said:

It will be literally up in the air for sure!

Right now, all models show a mild sector in some shape or form. It shouldn't translate into a corresponding warmup at surface level due to a combination of factors. It would make conditions less conducive for snowfall wherever precipitation occurs. Looks like a second half of Tuesday episode. Turns much colder again Wednesday. 

[Weather vane]

15 minutes ago, danm said:

With northerlies we’re almost always more reliant on troughs or disturbances cropping up or a battleground snow event, away from the most prone spots. Northerlies are rarely good for convective snow showers away from northern Scotland and some coastal areas. 

Easterlies are much better in this regard. 

However, it’s way too soon to write off snow chances next week. Things often pop up at short notice so no point writing off snow chances 

100%. With the straight northerly set up, we know precip is much tougher to achieve. Once a northerly is on the cards,  expectations need to be tempered, no matter how enticing some day 7+ charts look. Combined with the demise of blocking, which has been clear for several days now, we can't be surprised at what looks like the likely outcome of 4-5 days of dry cold, and then back to Atlantic driven. I for one am very happy we have cold or even very cold temps next week. For me, that's a win as it's proper seasonal January weather.

[Weather-history]

ECM 12z does have a snowy breakdown for the SE

[phil nw.]

Come on folks try and stay on topic.Too many one liners which are adding nothing to model discussion and are having to be hidden.

Maybe a bit of perspective we are not even in the Northerly cold air yet and when it comes it's probably going to be the coldest spell so far this Winter.Uppers of between -8c to -10c quite widely,even lower in Scotland.
As for snow then i am not going to repeat what others have said but bear in mind that forecasts from the Met have already changed from a day or so ago and likely will be revised again if new features pop up.

If you are still wanting to moan about this then please use the moans thread and let's keep this thread tidy and on topic.

Thanks all.   

[DOdo]

Even If the ECM was bang on We would still have 8 days of decent  cold weather whatever about snow . I dont go past 144,

[Bricriu]

3 minutes ago, Rocheydub said:

I'm not so sure why there is so much weeping and gnashing of teeth here, models with egg on face etc. These are super computers who do not compute embarrassment or emotions. The computers picked up the long wave signals a good few weeks back and stuck with it generally speaking. That's all we can expect from those distances and I think they did superbly well at that. The micro and macro scale of 2 such tiny islands in the grand scheme of things is nigh on impossible to get 100% correct at these big time differences. If you're not aware of the phrase "if a butterfly flaps its wings" then I suggest you google it. Chill pill. It's only weather after all. Worldwide life in our recent months and years shows us we all actually have vey little to moan about if a lack of snow is your biggest worry.

Back to the models. I'm not going to post the ECM 240 chart as it's on several pics up above, but I'm greatly encouraged to see the clear signal for the draining of low heights over Svalbard and Scandy. The would give us a quick enough route into another cold spell. I'll be keeping a keen eye on that area next after this week is over.

I'll enjoy this week, whatever it brings, I wish you all well in your chase. Whatever your weather desires are. But remember, posters here and the NWP super computers don't decide the weather, mammy nature does.  

Much love.

Well spotted. The GFS op in some recent runs has hinted at height  rises in this area. As we know the GFS can sniff out  a signal then drop it only to show it again later. Let's see does it pick up again  in the days ahead 

Perhaps  this will be the next direction  of travel after the milder turn. 

[Sherry]

Looking at the models snow chances are pretty bleak for the majority but a decent dry spell coming up albeit it chilly, but sunshine for majority then looks like a return to Atlantic driven weather after that! So enjoy the sunshine and crisp weather perhaps a chance of snow in February but looks like a bust for now 

[Kreftysoton]

Down here on the riviera it has been the coldest 7 days recorded for many years so i cant grumble!  Sunny days!  Frosty days an hour of snow monday evening that left a nice covering. First since 2018.. looks cold again tomoz here 3c then 4c or 5c so not all bad! I know weirdly the north has been warmer the past week which is probably why this spell seems so short after the models and signals promised so much!  

[joggs]

28 minutes ago, Weathizard said:

Once you get cross model agreement on this kind of hemispheric set up it’s goodnight Vienna on any significant blocking or proper cold spell for at least a few weeks, unfortunate given some of the charts we chased this time last week.

At least a few weeks?.

Can you back that up with evidence please?.

Edited January 12 by joggs

[WYorksWeather]

Been a while since I've got chance to post, so I'm going to divide my thoughts into three bits. Firstly, we have an analysis of any snow risk, then a look at the medium range modelling, then my general thoughts on where we go from here.

Short range

Arpege

Of course, forecasting snow is never easy, but what we can do is see what some of the higher resolution models are showing for the next few days.

The 12z Arpege reaches to Tuesday evening, and shows relatively little activity until Monday, and on Tuesday temperatures are higher, and conditions are likely less conducive to snowfall.

The period of interest is shown here.

 

Looks like some chances of snow for Scotland, but there is also some just grazing eastern coasts. It wouldn't take much to get a bit of a covering into some English coastal areas. The band of snow is moving slightly east of south, maybe SSE, so any slight variation in the track could bring more eastern areas into play, and of course a shift the other way could see all of the snow just remain in the North Sea. The right chart shows temperatures, and conditions are highly conducive to snow accumulations.

UKV

For Monday's time of interest, the 15z UKV shows the following.

   

Possibly more widespread snow in Scotland. However, the bands of snow seem to have slightly more of a south-eastern track, and therefore there seems to be a lower risk of much in the way of snow showers for England. The difference in track does, however, bring Wales and parts of the SW into play for a slight covering. Worth pointing out that conditions if anything even more conducive to snow than the UKV, it looks seriously cold on Monday morning. Surface temperatures sub-zero for most of the UK, 850s near -10C, dew points around -5C.

I would also note that as a slight warm sector (in relative terms!) moves in from the west, UKV is suggesting another chance for some of us on Tuesday, possibly down into northern or even central England.

In short, I don't think the evidence supports that this will be an entirely dry high. Widespread snow is probably a no, especially in the south, but I do think some areas will get some snow out of this. Forecasting exactly where is almost impossible even at only three or four days out, so treat this as just showing the possibilities.

Medium range

So, now on to the ensembles. Again, the advantage of being away from the models for a couple of days is that I have charts saved from a while ago, so I can compare and see how things have changed over the past couple of days. Here is what the GFS was showing for York and London on the 12z on Wednesday.

 

And here is what it is showing today.

So, here is my thoughts. Firstly, we can see that modelling is firming up on pretty deep cold for early next week. Probably some exceptionally cold temperatures in exposed locations. Sub-zero daily means will be expected in most areas, and possibly ice days further north. The mean projects that 850hPa temperatures will drop away to around -10C, briefly rise to around -5C on Monday and Tuesday, then drop back to around -7C. In short, looking out to around Friday, it constitutes a significant upgrade of the cold.

However, looking further ahead, it has to be said that there is a stronger signal for a breakdown of the cold spell beginning around the 20th, with a return to average or above average temperatures by the 24th. It must be said that we're still too far from the time in question to be confident in the exact timescale, but the trend is much clearer than it was a couple of days ago, when there were more model runs staying cold.

General thoughts

I'm going to be extremely boring and take the middle ground on this. It has to be said that the initial spell of cold we've had this week has been a bit of a damp squib away from the south, where some areas have seen rare snowfalls and colder temperatures, so it probably feels more notable. At my location only a couple of nights have even seen overnight frosts.

That will change next week, and it does look cold until next weekend, likely very cold. After that, though, there is a stronger signal for a return to average, or above average conditions.

I'm still expecting my prediction that the CET for the first half of January will finish below average on 1961-1990 is favoured on the balance of probabilities, but I'll admit I'm feeling a bit nervous about it, and it won't be anything spectacular, most likely in the 3s or 4s. It is very early to say this, but a mild last third of the month is favoured at this stage, though by no means guaranteed. This would naturally be a disappointment to many on here.

All I would say if this does play out in an unwanted fashion from a cold fans' point of view, let's not disrespect the knowledge that is imparted by many of the posters on here who discuss the teleconnections - it is a matter of probability. Background signals currently indicate a strongly increased chance of cold, but that does not guarantee cold for the UK, and does not guarantee snow if we get cold. It's important to remember that.

To illustrate, getting a good winter cold spell with some snow in the UK is probably like rolling a die and getting a six. Getting something really memorable, with very large accumulations that stick around for weeks, is probably like rolling double six. Good background conditions are like being allowed a couple of additional attempts at those rolls. They don't guarantee you anything.

I may drop back in for the 12z ECM ensembles later.

[Paul]

This is genuinely one of the more bizarre evenings I can remember in here. You have the models showing things like this:

And it's not good enough? I mean seriously! I get that there's not too much in the way of widespread snow shown at the moment, but a lot of the details aren't even close to being sorted out for next week yet. Yes, there's some discrepancy between runs and the ecm has gone a bit milder for a while tonight, but again that should highlight the difficulty of nailing down what's happening, rather than being seen as a definitive outcome. 

Perspective needed. 

[MATTWOLVES 3]

Hey folks just gone through 50 members of ecm snow charts and some do actually go with a snowy breakdown..long way off but it remains a possibility for sure.

Edited January 12 by MATTWOLVES 3

[Cheshire Freeze]

There really is no easy way out of this pattern shown on GFS FI