Model output discussion - Winter has arrived

[MATTWOLVES 3]

1 hour ago, West is Best said:

Good consensus now in the GFS ensembles out to T144 (roughly Dec 13th). As the header on NW homepage states, a chilly start then gradually rising temperature profile.

Into FI and cold lovers will be hoping that the yellow line is the one that comes off  

 

I'm afraid the return to zonality was inevitable. Despite being told that the synoptics were amazing and wonderful and quite the best thing for years, they really weren't. Look to upstream blocking for UK cold. Concretely that means a proper Greenland High. Otherwise no amount of high pressure out to our east will be able to resist the Atlantic onslaught. Sorry if that's unpopular. It just happens to be true.

I'm not so sure that rings true!! Having Greenland Heights is most definitely a good thing, but is certainly not the be all and end all.. To much blocking to the NW can also bring an halt to Atlantic weather systems... Yes it will be fidgid but not necessary snowy! Put in place a big Scandinavian High with an Estly feed, then we have the perfect scenario for Atlantic systems to push in against this air bringing the potential for significant snow! And when those Scandy Heights are big and robust they can take some shifting! All to play for still...

[Methuselah]

1 minute ago, MATT said:

I'm not so sure that rings true!! Having Greenland Heights is most definitely a good thing, but is certainly not the be all and end all.. To much blocking to the NW can also bring an halt to Atlantic weather systems... Yes it will be fidgid but not necessary snowy! Put in place a big Scandinavian High with an Estly feed, then we have the perfect scenario for Atlantic systems to push in against this air bringing the potential for significant snow! And when those Scandy Heights are big and robust they can take some shifting! All to play for still...

Aye, Matt, but it's Tesco's finest... Every little helps?

[SLEETY]

The Greenland was the reason for the record cold spell in parts of Ireland in 2010 the Scandinavian high pressure systems seem more prone to sudden collapse, think most on here would take any of the two scenarios cinsideting the crud winters of recent years 

[stodge]

Afternoon all

I'll comment more specifically on the 12Z output this evening but just a couple of thoughts from me as we await the next offerings:

1) The route to very cold often starts from very mild and those who look at the Azores HP ridging through as a bad sign miss the point that some of our most noticeable cold spells have occurred because the Azores HP (or a lobe of it) has pushed NE into Scandinavia and we've advected the chill air from the east. What normally happens when you have a strong PV is the northern arm of the jet is so powerful it keeps the HP at mid-latitude so we get the block over Europe (hello, Mr Bartlett). It's perfectly possible for the HP to transit NE and become a higher latitude block.

2) HP over the UK is a mixed blessing - if you want cold it can be great as long as there isn't too much cloud trapped in the circulation (and that can be a problem given we are surrounded by water). Inversion is king in mid-winter and an ice day is perfectly possible if fog and frost persist. Ideally, you want the HP over Scotland to advect the chillier continental air in but the easier path is not a straight E'ly but an ESE'ly or SE'ly. HP doesn't last forever and normally it either sinks south or withdraws east (the latter keeps the cold for longer). Just occasionally and again a disrupted or weak PV is a big help, we can get the holy grail of retrogression. Now, that's what the cold and snow fans really want as that opens the door to the N'ly or (and this is the real gold star) the NE'ly from Scandinavia. It's an evolution we see more in spring oddly enough and coincides with the final warming.

3) The Greenland HP is cited as the "Holy Grail" and of course it's a big help but it needs to ridge either directly south into the mid-Atlantic (the N'ly) or SE through Iceland (the NE'ly). If it ridges SW toward Canada, it triggers a west-based negative NAO and Mr Mild comes knocking at our door - that's essentially what happened in both January 2011 and March 2018 to break down the severe spells so I don't and wouldn't rely on a Greenland HP - a Scandinavian HP is much more durable and helpful.

4) As long as the PV is weak or disorganised or over Siberia or central Canada we have a chance at cold - it's NOT a guarantee of cold by any stretch but it's a shot we don't have with a strong PV over NE Canada/Greenland in most instances. An SSW may help but again it's no guarantee - the 2018 SSW was a thing of rare beauty and power and the way it shredded the PV and opened the door for the cold air was remarkable and well forecast throughout late February. I'm not a fan of Siberian warmings as they often displace the PV back over the Canadian side and we then have to hope the PV doesn't re-strengthen in situ which can happen. We almost never see a warming from the Canadian side and it's been interesting to note warmings from both Siberia AND Europe being forecast in GFS FI. The combination of such warmings may well have an impact but I'm sceptical of an SSW because even if it happens it's no guarantee we'll end up on the right side. 

[Scott Ingham]

1 hour ago, West is Best said:

Good consensus now in the GFS ensembles out to T144 (roughly Dec 13th). As the header on NW homepage states, a chilly start then gradually rising temperature profile.

Into FI and cold lovers will be hoping that the yellow line is the one that comes off  

 

I'm afraid the return to zonality was inevitable. Despite being told that the synoptics were amazing and wonderful and quite the best thing for years, they really weren't. Look to upstream blocking for UK cold. Concretely that means a proper Greenland High. Otherwise no amount of high pressure out to our east will be able to resist the Atlantic onslaught. Sorry if that's unpopular. It just happens to be true.

Its a 4 day warm up as the patter pushes east for a few days. Its perfectly normal in any winter to have these periods and is essential. Its this warm up thats driving more hot air into the northern latitudes to encourage strat disruption down the line. Stop being pessimistic dude...

[Bristawl Si]

1 hour ago, Rollo said:

Steve looking at mid European temperatures this morning I despair of anything remotely cold enough to produce lowland snow for some time to come unless we get a brutal northerly.

My Geography A level grade of an A, all those years ago, tells me that a continent, big land mass, like Europe can cool down very quickly in Winter, so Day zero can be nowt like Day 5 in terms of temps.

[Methuselah]

13 minutes ago, Bristle boy said:

My Geography A level grade of an A, all those years ago, tells me that a continent, big land mass, like Europe can cool down very quickly in Winter, so Day zero can be nowt like Day 5 in terms of temps.

Oh, what a 'clever clogs' you are, Bris... I failed Geography at CSE!

[SLEETY]

Need that scandi high to build further NW then you would see brutal uppers invade from the NE of Europe. 

[Eskimo]

14 minutes ago, Scott Ingham said:

Its a 4 day warm up as the patter pushes east for a few days. Its perfectly normal in any winter to have these periods and is essential. Its this warm up thats driving more hot air into the northern latitudes to encourage strat disruption down the line. Stop being pessimistic dude...

I don't think its pessimism to see an alernative view, 'dude'. You could be right, Scott. However, so could West is Best. What makes this thread tolerable at the best of times is the tolerance to alternative views. 

[Duane S.]

 It isn’t going to take much of a tweak to send things much colder later in the month.

Is the MJO wave about to break into the Pacific in a few days? This might help create more Mid Atlantic amplification and trough disruption to start appearing the charts soon, maybe to eventually combine with ridging eastwards towards Iceland from scandi (which is being fed by the block going nowhere any time soon). Low solar, no real signs of the main vortex settling back over Greenland and a continued tendency of a southerly tracking jet to boot. All in all, fascinating model viewing at the moment
 

[MAF]

1 minute ago, Eskimo said:

I don't think it's pessimism to see an alternative view, 'dude'. You could be right, Scott. However, so could West is Best. What makes this thread tolerable at the best of times is the tolerance to alternative views. 

+100 on that reply. each to their own, and hence why i never normally post in this topic. 

[Snipper]

18 minutes ago, Bristle boy said:

My Geography A level grade of an A, all those years ago, tells me that a continent, big land mass, like Europe can cool down very quickly in Winter, so Day zero can be nowt like Day 5 in terms of temps.

I’m in your club. “Os” and “A” levels back in the day seemed far more sensible in dealing with the real world. 

[SLEETY]

Always best to ignore the gfs model when their is so much uncertainty in the output expecially when the Russian high is the big player. 

 

The model is crud in these situations, and will always push the Atlantic through. 

Watch the backtracking begin in just over one hour 

[BlueHedgehog074]

I think to be honest, wouldn’t be terribly surprised if the Atlantic takes over (even partly) for at least a little while. It could be easy to become concerned that once any possible Atlantic influence dominates, it could last for ages. Not all Winters are (and have to be) like that, mind. A number of the colder Winters even, had a few Atlantic periods. Considering there is still a fair amount of uncertainty in the close range of the models, then not too certain what could happen at the moment. 

Just a look, however, at what a number of operational models are showing at 144 hours. Note: have used the 00Z ICON instead of the 06Z one despite it being the latest run due to it only going up to 120 hours.

06Z GFS

00Z ECMWF

00Z UKMO

GEM

00Z NAVGEM

00Z ICON

Broadly, the GFS does seem to be on its own regarding how it handles the Low Pressure to our West in the mid-Atlantic. The Scandinavian/Russian blocking does try to put a bit of pressure on it. But the Low is bigger, more organised and refuses to slide under the block. Most of the other models have it disrupting, becoming squashed and sliding East or South-East directly through the UK or through the Southern part of the UK. The ICON and GEM are generally the models that have some of the Low Pressure going through the South of the UK. Except from clearly the GFS, the NAVGEM has the Low Pressure to our West a bit more rounder than on the GEM, ICON, UKMO, and ECMWF. It does still show signs of getting squashed with the pointy area of the Low extending East through the UK. Though later frames do reveal as the pointy area of the Low slithers South-East through the UK, it fills out. And while it does so, the Low Pressure further West upstream moves towards it and starts to merge with the filling Low/Shortwave over the UK:

Perhaps worth adding is that the models that show the Low Pressure becoming more squashed and disrupted also tend to be models that extend some of the heights from the Russian High further West towards Southern and Central Greenland to our North. Something that would be important to have to make Low Pressure undercut and/or disrupt. 

Does seem like the GFS is on its own at the moment. Could very well be over-doing that Atlantic Low. Would be tempted to throw it into one of these

 

But no matter how small the chance could be, the GFS may not necessarily be wrong. Just unlikely at the moment. Considering that the other models who disrupt and slide the Low under the blocking, it is a fine line between whether the UK picks up a surface flow from the East or one from the West, depending how far North or South these Lows slide through the UK (if they do). So no doubt there is some unreliability at the moment regarding this. And even at the earlier 120 hour time frame, the operational models did show some differences to the handling of the Low Pressure(s) to our West upstream. An example from both the GFS and UKMO below:

GFS

 

UKMO

 

UKMO already shows signs of the Low getting a bit squashed. More of a negative tilt to it, and it has higher heights extending from the Russian/Scandinavian ridge Westwards to our North. Plus, it has some amplification via the Newfoundland/Western Atlantic ridge upstream. These things of which forces the Low on a more North-West to South-East track towards and through the UK - the squashed trough settling over the UK at 144 hours, as shown in the UKMO chart higher up in this post. Quite a few things things to be sorted it seems. As such, until things earlier in the model runs are resolved, then there’s not a guarantee as to what will happen after. Some of the possibilities being that the big fight between the Atlantic and the Russian block continues. Or like on some models, once they slide Low Pressure through the UK later in this coming week, some increasingly menacing Atlantic Lows could try to take over from the West, which could either invade the UK or stall in the Atlantic. Equally, like on the ECMWF, these Lows becomes a friend for the cold weather fans (especially those who like dry, chilly weather) and the Atlantic Lows throw up some Azores ridging ahead of them bringing a mid-latitude block over the UK and strengthen ridging to our East/North-East.

The models like the ECMWF above and and also the GEM, who both tend to blow up Low Pressure in the Western Atlantic later in there runs, is outside of the 144 hours range. And even that Low could show more signs of becoming disrupted or getting squashed as it tries to head closer to the UK. 

Again, as illustrated earlier, including what other people have shown in their posts, models still ain’t got a complete clue as how to handle events earlier on in their runs. 

Though it can’t be ruled out, models still aren’t really showing the cold weather fans’s favourite monster, the Greenland Vortex , to become fully invasive to our North-West and North. And depending how you look at it, the combat between both the North-Eastern UK blocking and the Lows to our West could be made up of a hero and some evil boss. Personally would be fine with a UK high if that’s where we end up, so ironically for me, the Atlantic Lows could become the hero if they dig down far enough South in the mid-Atlantic drawing up a UK High towards us.

[bluearmy]

4 minutes ago, SLEETY said:

Always best to ignore the gfs model when their is so much uncertainty in the output expecially when the Russian high is the big player. 

 

The model is crud in these situations, and will always push the Atlantic through. 

Watch the backtracking begin in just over one hour 

Point is that the gfs was the model which picked up on the potentially more mobile period now being supported by all the models at days 7/10 .....you can’t jut say it always does as prior to the change it was showing consistent blocked runs .... you could argue that it reacts to a hint of mobility by running with it rather than working out it could just be a disruption  

 

[Matt H]

8 minutes ago, SLEETY said:

Always best to ignore the gfs model when their is so much uncertainty in the output expecially when the Russian high is the big player. 

 

The model is crud in these situations, and will always push the Atlantic through. 

Watch the backtracking begin in just over one hour 

I’d love to ignore the GFS but we’ve been burnt so many times in recent winters that it’s always best to be cautious now. Hoping for a change this afternoon though.

[Matt H]

No significant Atlantic breakthrough out to t150 on the ICON 12z. Better than the 00z as well.

[SMU]

ICON 12z

Look how far west the WAA has corrected -

UK looking east not west

trough dropping into Svalbard 

Edited December 6, 2020 by Steve Murr

[SLEETY]

12 minutes ago, bluearmy said:

Point is that the gfs was the model which picked up on the potentially more mobile period now being supported by all the models at days 7/10 .....you can’t jut say it always does as prior to the change it was showing consistent blocked runs .... you could argue that it reacts to a hint of mobility by running with it rather than working out it could just be a disruption  

 

We haven't had any mobility yet and ecm was showing a blocked outlook in its later output from its midnight run and no sign of mobility returning. You appear to think the gfs is correct when mobility has not even happened yet then come to conclusion that every other model will follow  the might gfs FAIL model, rofl

[Skullzrulerz]

56 minutes ago, Scott Ingham said:

Its a 4 day warm up as the patter pushes east for a few days. Its perfectly normal in any winter to have these periods and is essential. Its this warm up thats driving more hot air into the northern latitudes to encourage strat disruption down the line. Stop being pessimistic dude...

And unfortunately these are the type of comments (nothing against you @Scott Ingham that discourages some users not to use the thread anymore 

I don't see nothing wrong with looking for a warm and dry outlook then there is to a cold and snowy outlook ? I'm not sure why people can't respect people's others liking of the weather and each to their own 

Before the 12z outputs start at current there seems to be a general trend of turning milder for a time and then perhaps a dry period which could be quite frosty sure it's not a winter wonderland but to the last few winters we had it's a lot better then staying indoors while someone does a rain dance 

 

 

Edited December 6, 2020 by Skullzrulerz
Spelling

[Ali1977]

4 minutes ago, Steve Murr said:

ICON 12z

Look how far west the WAA has corrected -

UK looking east not west

trough dropping into Svalbard 

Yes a big swing there for the better, let’s hope the others follow 

[Beanz]

2 hours ago, West is Best said:

Good consensus now in the GFS ensembles out to T144 (roughly Dec 13th). As the header on NW homepage states, a chilly start then gradually rising temperature profile.

Into FI and cold lovers will be hoping that the yellow line is the one that comes off  

 

I'm afraid the return to zonality was inevitable. Despite being told that the synoptics were amazing and wonderful and quite the best thing for years, they really weren't. Look to upstream blocking for UK cold. Concretely that means a proper Greenland High. Otherwise no amount of high pressure out to our east will be able to resist the Atlantic onslaught. Sorry if that's unpopular. It just happens to be true.

It’s rising, then tailing back off.  The mean never rises above 3c so hardly mild zonality 

[Scott Ingham]

7 minutes ago, Skullzrulerz said:

And unfortunately these are the type of comments (nothing against you @Scott Ingham that discourages some users not to use the thread anymore 

I don't see nothing with looking for a warm and dry outlook then there is to a cold and snowy outlook ? I'm not sure why people can't respect people's others liking of the weather and each to their own 

Before the 12z outputs start at current there seems to be a general trend of turning milder for a time and then perhaps a dry period which could be quite frosty sure it's not a winter wonderland but to the last few winters we had it's a lot better then staying indoors while someone does a rain dance 

 

 

Everyone is entitled to their opinion your right but everyone is entitled to have their opinion challenged as well. I would have no issue the other way around

[Scott Ingham]

41 minutes ago, Eskimo said:

I don't think its pessimism to see an alernative view, 'dude'. You could be right, Scott. However, so could West is Best. What makes this thread tolerable at the best of times is the tolerance to alternative views. 

I don't see an issue to challenge another view though. We're all grown men.

[Eskimo]

25 minutes ago, Scott Ingham said:

I don't see an issue to challenge another view though. We're all grown men.

Your absolutely correct, that's why I've frequented this place for the better part of 10 years - the difference of opinion is what drives interesting conversation. However, an alternative view, especially as we are predicting the future with no certainty isn't pessimistic, just different, and both views should be respected. 

Edited December 6, 2020 by Eskimo