Model Output Discussion - Colder spell ending, what's to follow?

[West is Best]

6 minutes ago, CreweCold said:

Why would you use the European view when upstream is so critical to developments further along? The upstream pattern will eventually dictate what happens downstream, to a decent degree.

Undoubtedly true & something I've mentioned on many occasions in my very amateur way down the years. Because of the prevailing westerly flow over the UK and the upstream drivers to our west of the weather patterns coming off the US eastern seaboard, we are heavily dependent on upstream blocking, or at the very least significant amplification of the jet stream.

Searching to our east for UK cold is like fool's gold. It often promises but rarely (almost never) delivers. Only when there is a sufficient buckle in the jet with concomitant upstream blocking does it become significant for sustained cold.

Nothing much doing at the moment anyway. The ensembles yo-yo in FI, sometimes mild, sometimes cold but in the short to mid term it's pretty zonal fayre.

[blizzard81]

3 minutes ago, CreweCold said:

Its overall movement will be ESE, even if it spins around a bit on itself as it approaches the UK. That's because heights to the N of it will eventually increase

Time will tell. Or more like it won't look like that anyway come days 9 and 10. Lets hope it looks much better. 

[Chesil View]

So the ECM isnt showing snowmageddon in 10 days time .

 

The attached chart is so very  familiar isnt it? Stalled low to our west driving mild southwesterlies towards the UK, pesky  scrussian block to the east in the wrong place , and worst of all Azores high ridging into  Iberia.  Oh I forgot to mention big chunk of PV  North East Canada/South Greenland.

Absolutely the very last thing you want a week before Christmas eh?

Except of course that the attached chart is for the 19th December 1962.

 

Edited December 9, 2020 by Broadmayne blizzard

[JBMWeatherForever]

As ever it only takes very small changes in the near term synoptics for a major change further out. But that is particularly apparant at the moment.  If the trend continues for blocking in the artic to strengthen, then we will soon be seeing a significant number of cold synoptic runs from the models, foretelling the commencement of a significant cold spell from the north east. The model output is looking very interesting and a cold and wintry christmas period is now more than a distinct possibility.

[stodge]

Evening all

With a disappointing (for cold fans) 06Z GFS OP prompting toys to be thrown out of prams aplenty, let's see if sanity or even hope can be restored by the 12Z output.

12Z GEM - the initial journey little changed with the Atlantic LP originating at lower latitudes swinging NE and invigorating the main LP to the south of Iceland by T+120 and triggering a positive alignment but this isn't a normal zonal winter so far and while part of the energy forms a secondary feature to the south which heads SE into Europe, the main LP withdraws west into the Atlantic as heights continue to build through Greenland in the absence of any significant vortex. The complex LP begins to move east toward and across the British Isles as a new area of LP exits North America. It remains on the mild side but the heights continue to build over Greenland. I also note the strong ridging from the Pole but it's looking like a west-based negative NAO which won't end well for cold fans in western Europe. Potential but in all the wrong places.

12Z GFS OP - a poor 06Z for cold fans but let's see. by T+120, the LP is a bit deeper than GEM but otherwise not too different as you'd expect. From there, the parent LP extends the trough over the British Isles but fills in situ maintaining a slight positive alignment as heights build to the north and north west. Heights also rising to the SW as the Azores HP tries to ridge in at T+180. By T+240, the jet is clearly moving south in response to heights buildinf to the north west and the next LP has filled but moved in over or close to the British Isles maintaining a mild but unsettled theme as we enter Christmas week. By T+312, the Atlantic LP has become and elongated feature aligned SW-NE across northern Britain and into Scandinavia. Heights have built over Europe but the focus of heights is south from Greenland. As we reach Christmas, the low finally sinks south as pressure rises from the NW and an anticyclone develops from the cold Greenland HP first to the north of the British Isles and then to Scandinavia with an ESE'ly flow to finish the run on Christmas Day with -8 850s for most so we'd be looking at snow IF we et any precipitation but the HP is building into Scandinavia. The 10 HPA hints at a warming from Europe at the very end of FI.

12Z ECM - well, a Christmas gift of sorts from GFS OP and cold it would be if perhaps not white. Will ECM be the thorn in our side or the slap on our back? I'm not expecting much to be honest - more hints at what might unfold beyond T+240. At T+120 no surprise at all but it then gets quite messy by T+192 with shortwaves aplenty and perhaps an attempt to build heights over the British Isles. However, by T+240 it all comes to naught as a new LP takes over and heads NE and I'm left wondering about the Azores HP ridging NE into Scandinavia as the next step. Not much hint of anything cold from that chart. Strong heights over the Pole and perhaps the PV starting to move west into Canada,

Looking elsewhere, 12Z GFS Control would be a very snowy Christmas for many but not from the 00Z Parallel which shows how even a strong Scandinavian HP AND a strong Greenland HP can leave the British Isles mild.

Conclusion - this is a time to hold nerve and be patient. We know there's going to be a milder interlude which could well last 7-10 days at least but there are plenty of positives beyond that. The strong polar heights help and it looks increasingly as though ridging from the Pole into Greenland will keep the PV far enough into Canada to allow amplification and slow the jet. The Greenland heights push the jet south which is another help. Cold fans are still very much in the game tonight but the next few days will try everyone's nerves I suspect.

[SnowSalah]

Hi everyone, I’m very much new to this with just being a fly on the wall for the past 2/3 winter seasons. I’m learning slowly and surely though as the time goes on. One thought of mine re: the models. They do seem to be changing almost everyday now, we just have to hope that ridge gets linked with the artic high and pray for a bit of luck after that

[That ECM]

@Steve Murr or anyone else. Do you have the link to the T168 Ukmo please?

[Anthony Burden]

Gefs still showing interest from around 19th/20th with more members showing some 

colder outlooks.One thing to keep an eye on along with ever changing charts,all waiting 

patiently for pressure rise in the right place and orientation not long to wait in my opinion.

[heath]

23 minutes ago, Broadmayne blizzard said:

So the ECM isnt showing snowmageddon in 10 days time .

 

The attached chart is so very  familiar isnt it? Stalled low to our west driving mild southwesterlies towards the UK, pesky  scrussian block to the east in the wrong place , and worst of all Azores high ridging into  Iberia.  Oh I forgot to mention big chunk of PV  North East Canada/South Greenland.

Absolutely the very last thing you want a week before Christmas eh?

Except of course that the attached chart is for the 19th December 1962.

 

Not to mention 26 December 1978

[Mike Poole]

I think the ECM ensemble mean has more going for it than than the op run to be honest, includes possibility of JMA evolution, I would say, but also suggests possibility of link with Arctic high with heights over Greenland, and the trough into Spain is notable, but not extending into E Europe at the moment, happy with this mean overall:

[Radiating Dendrite]

10 minutes ago, heath said:

Not to mention 26 December 1978

Both those charts are completely different to what we have showing now and also both years had a very different set of background signals. Personally find pattern matching completely futile, the atmosphere is completely dynamic and never the same.

[northwestsnow]

Thats a better mean Mike...

[mulzy]

8 minutes ago, Mike Poole said:

I think the ECM ensemble mean has more going for it than than the op run to be honest, includes possibility of JMA evolution, I would say, but also suggests possibility of link with Arctic high with heights over Greenland, and the trough into Spain is notable, but not extending into E Europe at the moment, happy with this mean overall:

Yes very decent.  The extended EPS extends the mean trough eastwards to cover northwest Europe and the area of higher heights over Europe pushed further south east.  Height heights remain to our north especially over the Greenland locale.  A colder set than this morning’s suite.

[Griff]

Team GEM trailing a blaze and showing the way yesterday... 

Today's output... 

And my new conspiracy theorist the GFSP... 

 

Not heard anything about invisible blocks or the correct temperatures for 850s for a little while... 

...I am however increasingly interested in the role of WAA, definitely learning something new everyday (sometimes opaquely sometimes transparently ). 

Denis (twitter @PvForecast) is as enthusiastic as a man can be about strat warming and currently a big drop in AO... 

The only accurate forecast to be made is the inevitable mood changes around here, almost run to run at the moment.

[Daniel*]

2 minutes ago, mulzy said:

Yes very decent.  The extended EPS extends the mean trough eastwards to cover northwest Europe and the area of higher heights over Europe pushed further south east.  Height heights remain to our north especially over the Greenland locale.  A colder set than this morning’s suite.

I was just going to share. Yep very good.... lower pressure in Europe.... 

[swfc]

5 minutes ago, Daniel* said:

I was just going to share. Yep very good.... lower pressure in Europe.... 

Where or how do you access that Daniel, tia

[Daniel*]

2 minutes ago, swfc said:

Where or how do you access that Daniel, tia

Beyond a paywall sadly. Weathermodels.com

[clark3r]

Seen a lot of people getting excited about models for Xmas, still way to far  ahead in models to be able to predict, if Xmas was showing snowy charts and only 5 days- 7 days ahead then I would be getting excited, fingers crossed we get a blast from the north, north east, east between Christmas and new year with snow would be a dream

[northwestsnow]

19 minutes ago, mulzy said:

Yes very decent.  The extended EPS extends the mean trough eastwards to cover northwest Europe and the area of higher heights over Europe pushed further south east.  Height heights remain to our north especially over the Greenland locale.  A colder set than this morning’s suite.

Mate...

I've no idea whether to be downbeat or upbeat but thats good news you have provided.

Let's collectively all blow hard towards that high pressure across SE Europe ,every little helps !!

[pureasthedriven]

35 minutes ago, heath said:

Not to mention 26 December 1978

Blimey, give me a proper GH building, emerging Scandi heights and an Azores low any day of the week! 

[MATTWOLVES 3]

Deleted. 

 

Edited December 9, 2020 by MATT☀️

[Mike Poole]

1 hour ago, West is Best said:

Nothing much doing at the moment anyway. The ensembles yo-yo in FI, sometimes mild, sometimes cold but in the short to mid term it's pretty zonal fayre.

Are you really saying this (now at the present moment) is zonal, over Atlantic sector or upstream?  GFS T6:

[Nick F]

Given we ideally want the upper flow over the Atlantic to buckle to take advantage of the high latitude blocking available, ive been looking for signs of amplification upstream and I think I found it ...

Both extended 12z GEFS and EPS mean retrograde the Canadian TPV which in turn aids carving out an amplifying Aleutian trough. This leads to amplification downstream over N America - this coould lead on to Atlantic ridging as a result, this would stop the Atlantic low conveyor and help advect deep cold south out the arctic. Long way off this becoming reality, but tentative signs there...

[TSNWK]

Agreed! thats a lovely mean profile from ECM there for Week2 with lowering heights over Europe and heights to our north - my view is that with we have the best northern hemisphere profile for winter during winter  for 10 years - we are so very very near - if we all blow together at 9:55PM towards Europe we might just get this over line

[Mapantz]

25 minutes ago, swfc said:

Where or how do you access that Daniel, tia

You can get them for free now, just not quite in as fancy colours.

https://apps.ecmwf.int/webapps/opencharts

Edited December 9, 2020 by Mapantz
gremlins