Model output discussion - Closing in on Christmas

[bluearmy]

ok everyone ..... upstream is the issue with the trough in the eastern states ....if that digs then the WAA it generates drives the n Atlantic ridge ala gfs. If it doesn’t dig south with the trough then the flow off the eastern seaboard has a positive tilt and that gives you the flatter solutions ......the more amplified the solution upstream, the more amplified  the solution downstream - the old waves on a rope .....  day 6 isn’t too far away ...hopefully by this evening we have better agreement from the better verifying models as to where we start this. 
 

a concern for coldies would be that the initial Xmas northerly looked like being of note ......that ridge failed and then we looked for the next retrogression (via a second bout of WAA) and ridge to bring the following trough south (perhaps too aggressively) like gfs does. If that fails then are we then possibly looking at a third attempt upstream ...? This is where the good news arrives .....by that stage, the arctic high dropping into n Russia enforces the block to our east which drives the trough s into e Europe ....it can’t head east or northeast ...... I have bookmarked the new year period for a good few days now with signs of a drop south of lower heights into an already cold environment ...... with a trough to our east we run the risk of warm sectors spoiling the fun but we certainly have a ticket from the winning book of tickets here and with developments high up, that book may contain quite a few winning tickets for the next 4/6 weeks ......

so our potential wintry outlook depends on quite a few variables so as ever, take nothing for granted ! 

[Guest]

Great agreement from GFS and ECM this morning, however the lack any cold pool anywhere near to our north means despite pretty decent Synoptics it takes ages to get a truly cold weather in and you see that on both GFS and ECM with 850s struggling. 

[That ECM]

3 minutes ago, Alderc said:

Great agreement from GFS and ECM this morning, however the lack any cold pool anywhere near to our north means despite pretty decent Synoptics it takes ages to get a truly cold weather in and you see that on both GFS and ECM with 850s struggling. 

Great agreement? 

[Mucka]

18 minutes ago, bluearmy said:

ok everyone ..... upstream is the issue with the trough in the eastern states ....if that digs then the WAA it generates drives the n Atlantic ridge ala gfs. If it doesn’t dig south with the trough then the flow off the eastern seaboard has a positive tilt and that gives you the flatter solutions ......the more amplified the solution upstream, the more amplified  the solution downstream - the old waves on a rope .....  day 6 isn’t too far away ...hopefully by this evening we have better agreement from the better verifying models as to where we start this. 
 

a concern for coldies would be that the initial Xmas northerly looked like being of note ......that ridge failed and then we looked for the next retrogression (via a second bout of WAA) and ridge to bring the following trough south (perhaps too aggressively) like gfs does. If that fails then are we then possibly looking at a third attempt upstream ...? This is where the good news arrives .....by that stage, the arctic high dropping into n Russia enforces the block to our east which drives the trough s into e Europe ....it can’t head east or northeast ...... I have bookmarked the new year period for a good few days now with signs of a drop south of lower heights into an already cold environment ...... with a trough to our east we run the risk of warm sectors spoiling the fun but we certainly have a ticket from the winning book of tickets here and with developments high up, that book may contain quite a few winning tickets for the next 4/6 weeks ......

so our potential wintry outlook depends on quite a few variables so as ever, take nothing for granted ! 

You are missing the reality that the reverse is also true.

The ridge being thrown up ahead of the low is obviously driving the pattern.

If that low digs more S than E then you get a more vertical ridge on its W flank which means the upstream will always be more amplified than it otherwise would if the low doesn't dig south and that is less vertical.

Think of it this way.

Tilt your hand back 45 degrees and imagine that is the Atlantic ridge with the low to its E not digging South.

Now push the bottom of your hand and you will see it acts like a pivot and your hand tilts more vertical and thus your hand reaches a higher point than when at a shallower angle.

This is the basic physics principle at work here.

None of that excludes the possibility upstream could be flatter and overrun it anyway or be more amplified on its own but it means that whatever the upstream it will always be more amplified the further N (more vertical) the ridge is ahead and that is dependent on the downstream pattern.

 

Edited December 19, 2020 by Mucka

[NewEra21]

I want the cold and snow as much as anyone on here, but I'm far from convinced with the current output.

The GFS still looks the best, but once again as good as it looks the 850s really are nothing special.

ECM seems to have pushed things back to day 10+ once again, and once again nothing too special 850s wise.

UKMO is the worst of the bunch in terms of prospects, it's not horrendous but just the worst of the big 3 models.

You look at some of the amazing charts and would expect them to be freezing, but they really don't seem to have much bite to them. I know 850s etc are not everything, but to me I just can't get excited as nothing actually looks that cold!

[mountain shadow]

Manyana manyana. Same every Winter.

The ECM clusters yesterday pointed it to the unlikely Greenland high and there we are.

Maybe we can get a little more amplification to bring some colder air, then its into 2021 still chasing.

[bluearmy]

37 minutes ago, Mucka said:

You are missing the reality that the reverse is also true.

The ridge being thrown up ahead of the low is obviously driving the pattern.

If that low digs more S than E then you get a more vertical ridge on its W flank which means the upstream will always be more amplified than it otherwise would if the low doesn't dig south and that is less vertical.

Think of it this way.

Tilt your hand back 45 degrees and imagine that is the Atlantic ridge with the low to its E not digging South.

Now push the bottom of your hand and you will see it acts like a pivot and your hand tilts more vertical and thus your hand reaches a higher point than when at a shallower angle.

This is the basic physics principle at work here.

None of that excludes the possibility upstream could be flatter and overrun it anyway or be more amplified on its own but it means that whatever the upstream it will always be more amplified the further N (more vertical) the ridge is ahead and that is dependent on the downstream pattern.

 

So you’re agreeing with me then mucka .....although I think you mean more ridge on its eastern flank ??

Yes of course less amplified upstream mean less amplified downstream but then hopefully the upstream block then deflects the jet se if the upstream is flattish and won’t do the job for us 

[northwestsnow]

GFS continues with its promises of murr and frankincense but be wary of sheperds bearing false gifts !!

Euro less amplified at 144 so let's see if GFS can get one over on the big 2.

Scottish mountains and hills in the North should do well with some snow around between Christmas and NY...

Edited December 19, 2020 by northwestsnow

[Tim Bland]

Solid set of ensembles, probably best yet with most runs heading between -5 & -10. Look at the snow row for London for 31st (33.3%) which backs up the above post from Blue re the 3rd attempt most likely to succeed around new year ️

[northwestsnow]

3 minutes ago, Tim Bland said:

Solid set of ensembles, probably best yet with most runs heading between -5 & -10. Look at the snow row for London for 31st (33.3%) which backs up the above post from Blue re the 3rd attempt most likely to succeed around new year ️

Very good.

EC mean looks flatter again this morning though for balance...

We need GEFS to be right !

[syed2878]

3 hours ago, Mucka said:

Lots of lovely snow moving down from the N by 192. Is it too much to ask?

sadly mucker living next to the Atlantic it is a big ask and yet we can all dream for such Synoptics to verify rather concerning though that the UKMO is not on board and the 120 H doesn’t look promising let’s see where we go from here.

[pureasthedriven]

1 hour ago, swfc said:

Yes true, I find it so frustrating tho. Tbh early doors is the key so onwards and upwards

ECM and it’s likely day 10+ evolution chiming very much with MetO overnight update. 

[nick sussex]

USA forecasters highlight this morning that rather than yesterday’s convergence of solutions the outlook is now less certain because of the latest shortwave drama .

The shortwave which runs east from the Pacific side into the mid west  is now the main troublemaker .

You can see by this mornings ECM that it models that differently and you lose that WAA into western Greenland .

Ideally you want the deepest system and also not any secondary lows.

The UKMO is by far the worst upstream at day 6 as its handling of the shortwave would leave little hope of developing any kind of post Christmas northerly .

Both the UKMO and GEM this morning were singled out by NCEP as throwing out real curveballs . Doesn’t mean of course they’re wrong but are real changes to what’s been the expected evolution .

 

[sheikhy]

Is that it then!!expect gfs to backtrack and maybe not look as easy on the eye?if gfs is right i expect 12zs ukmo and ecm to look better!!

[clark3r]

What we have seen in the last few days is fantastic potential on the gfs which keeps getting downgraded into reliable time frame, I’m not convinced at all that snow is on its way, it will get colder but nothing extraordinary, hope I’m wrong 

[Radiating Dendrite]

Just now, clark3r said:

What we have seen in the last few days is fantastic potential on the gfs which keeps getting downgraded into reliable time frame, I’m not convinced at all that snow is on its way, it will get colder but nothing extraordinary, hope I’m wrong 

The cold has not made it to the reliable yet though, so it has not downgraded as it has only existed in fantasy land. 

When models disagree we usually see a blended solution. Mid Atlantic High and a North westerly is what I am expecting for the first course. Snow for prone areas of Scotland and North Western England, not not overly cold.....4-5c maxes during the day and some frost at night (depending on wind strength).

[TSNWK]

8 minutes ago, nick sussex said:

USA forecasters highlight this morning that rather than yesterday’s convergence of solutions the outlook is now less certain because of the latest shortwave drama .

The shortwave which runs east from the Pacific side into the mid west  is now the main troublemaker .

You can see by this mornings ECM that it models that differently and you lose that WAA into western Greenland .

Ideally you want the deepest system and also not any secondary lows.

The UKMO is by far the worst upstream at day 6 as its handling of the shortwave would leave little hope of developing any kind of post Christmas northerly .

Both the UKMO and GEM this morning were singled out by NCEP as throwing out real curveballs . Doesn’t mean of course they’re wrong but are real changes to what’s been the expected evolution .

 

Ok. Positive thoughts from me for considering.. if the latest issue is modelling a shortwave upstream of the USA leading to poorer outcome for coldies from the Euros but still looking ok from GFS can we on this occasion place more trust in GFS a US model that logic would dictate might be focused and accurate for that beck of the woods.   

Big 06z coming . 

[Hotspur62]

Amazing how everything is always so complicated in terms of getting cold for the UK!!Nothing is EVER simple.Just wish for once that if it was not a short wave here or a trough digging south there instead of east etc etc.You get my point.But I suppose it makes it all the worthwhile if the pot of gold turns up for the UK in the long run.I thought we wouldn’t have a clearer picture we wouldnt know much more until Sunday evening and I stand by that.Just going by the last 10-12 years in these situations it seems we might need 2 or 3 attempts to hit the jackpot and this is another example for this.Literally last couple days of this year into new year is my bet for decent Northerly and a GH.Wish it was earlier for the many on here that put in so much hard work on this forum,that effort alone deserves more !!Keep the faith and as Delboy said he who dares wins
 

[MKN]

14 minutes ago, sheikhy said:

Is that it then!!expect gfs to backtrack and maybe not look as easy on the eye?if gfs is right i expect 12zs ukmo and ecm to look better!!

Either can be right or wrong at this stage the crucial time period currently stretches from 144 to 192. Which as we all know is not the most reliable. When that becomes 96 - 144 then we can't start to look at what follows. 

[Beanz]

22 minutes ago, sheikhy said:

Is that it then!!expect gfs to backtrack and maybe not look as easy on the eye?if gfs is right i expect 12zs ukmo and ecm to look better!!

You can’t ‘backtrack’ from what’s going on in FI...

[chris55]

Lots going on again this morning.

This little feature caught my eye for 23/24th

Icon and ECM have it as a more developed low over souther England. GFS doesn’t develop it so much.
Airmass may be slightly to mild, but one to watch for some snowfall on the northern edge of the low...

 

ECM

 

ICON

[terrier]

Well it all seems to have gone the way of the pear this morning the ukmo at t120 doesn’t look great the gfs & ecm we are looking at far reaches of fi again. Even out at day 10 the 850s are rubbish we just have nothing cold wise to the east to tap into. I do feel we are going to be relying on a ssw to help us out here but we all know that doesn’t guarantee anything for the U.K. So apart from a few frosts over Xmas it looks decidedly dodgy this morning on the output. But as we all know if it can go wrong for a cold spell in the British isles it normally will do. 

[BlueHedgehog074]

Looking at the 3 longer range models at 192 hours, and is fair to say that the 00Z GFS is the most amplified at that time:

00Z GFS

00Z ECMWF

00Z GEM

Even though both the ECMWF and GEM are flatter (but not completely), it’s a bit too early to say whether they’ve picked up a less amplified signal, although the GFS does seem a little on its own this morning. Just to add as well that the GEM and ECMWF aren’t totally without interest as things do amplify a little more to our West upstream towards the end of both runs with a chilly flow developing from the North-West. In fact, on the ECNWF the flow does turn more to the North as it drops the deep upper trough to the North of the UK to our East

 

Though I imagine other have already posted this chart earlier on in the thread. 

A lot of us would I’m sure love the GFS to be right. It’s very possible it may just be being a little bit too quick with the pattern, but I guess we’ll see how things continue to develop. One thing that seems evident on all three of these models is that they do remove some of the high heights over Europe and replace it with Lower heights, which could at least help assistant the Jetstream to take a more North-West to South-East path. So an advantage regarding that. 

Being let down loads of times before, then for once would be cool to see something like the GFS come off. Even a somewhat of a less amplified version would suffice. 

In the closer time frame, Christmas Day, in particular, is still currently looking like a generally cool and mostly fine day with the Atlantic ridge toppling over the UK. Highest of pressure to our South-West. An example from the GFS:

 

 Very cold early on Christmas morning and while it may not be white in terms of what falls from the sky, could be frosty at least. Perhaps a few odd showers towards the North-West of the UK, especially later in the day. Maybe wintry over the mountains. Otherwise mostly dry  

 

[Day 10]

In a word MIXED! 

Interesting how the GFS Op & it's ensembles continue their continuity, it does have it's day in the sun sometimes and this could be one of them. Intriguing 6z coming up. 

[BLAST FROM THE PAST]

Are folk looking at the same models as me?  I can only think that they aren’t seeing the fabled GHP from ECM and UKMO?  Guess what, I doubt they’ll revert to it either as I don’t think a true GHP is on the cards at all and GFS is just ‘pleasing’ our hopes.  The ECM is a peach, the trough has no where to go but almost N to S over us or just to our east.  There is a huge HP over Russian arctic that isn’t getting shunted away ....and there also isn’t a stack of LPs on a strong jetstream waiting to barrel eastward.  

Look at the 2 frames and the movement of the HP and LP systems.....(look at North America) there’s no SW’ly fest happening anytime soon.  Sorry we don’t have -40c piling over us ...Christmas week and I’ll take this run anytime for the UK.

The UKMO would lead to the same route of ECM imo too...and don’t worry too much about the projected 850s, they’ll adjust as we get nearer.  It’s going to get cold and those saying snow just for Scottish and northern hills .

 

BFTP

Edited December 19, 2020 by BLAST FROM THE PAST