Model Output Discussion 29th December - Into mid-Winter.

[chionomaniac]

The GFS 6Z ends up with the mother of all Scandi highs that extends right into Siberia delivering the most frigid cold pool right into the heart of Europe. If that did happen........

[The Northern Ramper]

Everything including its parents against the  ukmo this morning. I cannot see how the other models have it wrong at such a short timeframe. 

Somebody turn it off and on.

[Methuselah]

Can't say that I'm entirely convinced by that run; in particular regarding the uppers (entrained within the circulation of the Orthodox Xmas Day LP) of around -5C: not only have most other runs indicated uppers of a couple of degrees lower, at least, but I cannot abide rain & sleet.

Like the end though - that'll do nicely!

[Scandinavian High.]

Some very cold air moving in from the east.

[damianslaw]

Significant differences within the reliable timeframe between UKMO and GFS/ECM, normally UKMO follows either the GFS or ECM closely, but we continue to see it showing something quite different, which is quite unusual especially at the 96 hr timeframe. With GFS sticking to the colder evolution theme, if it maintains this through next 12z run and ECM does the same, then I'd be inclined to believe the current UKMO is a major outlier, but we shall see, it may have it right..

There are a number of developments shown on both latest ECM output and GFS 6z run which build the foundations for a polar continental flow from between north and east as we approach the second week of Jan as follows:

1. PV lobe over N Canada strengthening - this is the game changer as it is forced down into N Amercia, allowing warm air advection on its eastern side, and cold air advection on its western side, enabling greater amplification to take shape, and crucially locking the lobe into situ, with the aleutian ridge building in towards the Pole

2. Knock on effect, trough disruption over NE USA seaboard, sharpened negatively titled trough, mid atlantic heights are thus able to hold towards s greenland rather than sinking away to the SE.

Thanks to the above developments, we then have the foundations for the following:

3. Maintenance of lowering of heights over SE Europe, as forcing on the ridge isn't wishing to send it that way

4. A buckled split jet flow, energy transferred into the southern arm

5. A deeper trough feature moving down from the north and into Europe

6. Ridge is then able to build behind over scandi - end result:

7. Iceland / Mid atlantic high / scandi high link up..

I'm not saying this is what will happen, simply what the ECM and GFS are showing will happen.

As we know things do change from run to run, but the growing trend from both these models has been for a colder theme to emerge as we enter Jan.

[feb1991blizzard]

14 minutes ago, chionomaniac said:

The GFS 6Z ends up with the mother of all Scandi highs that extends right into Siberia delivering the most frigid cold pool right into the heart of Europe. If that did happen........

DO you not think though that the inability to get the blocking further to our North to enable the really frigid air into the UK is because of the stratospheric PV being sat over the pole, if it was already displaced further over the other side of the pole then......

[booferking]

We could get a Greenland high out of this yet 7 i count at the same time frame..

[Rocheydub]

As others have stated, the real differences start as early as T96 on the UK run, leading to a totally different outcome T120 onwards, I guess we'll know more by 1830hrs this evening when ECM hits 120, but I'm not digging out the snow boots yet. FI at 96 for me!

But bloody fantastic eye candy being served up this morning in ECM and GFS, hard to believe they'd both be wrong at this range, but we've seen it before. As ever, more runs needed... And maybe a little Prozac!

[bluearmy]

10 minutes ago, feb1991blizzard said:

DO you not think though that the inability to get the blocking further to our North to enable the really frigid air into the UK is because of the stratospheric PV being sat over the pole, if it was already displaced further over the other side of the pole then......

The GEFS have it closer to hudsons than the pole later week 2. it does look likely to displace to the Canadian side due to the wave 1 forcing upcoming. 

[Iceberg]

As you would expect the vast majority of ens members from the 06z have cold and snow at t192 along with a good to strong Greenland high many go on to develop easterlies and or cold and snow 

[Summer Sun]

GFS 00z para gives 2 cold snaps the 2nd quite possibly the coldest one

[feb1991blizzard]

7 minutes ago, bluearmy said:

The GEFS have it closer to hudsons than the pole later week 2. it does look likely to displace to the Canadian side due to the wave 1 forcing upcoming. 

Slightly yes, I noticed a warming coming in from our side lately, would like to see the Altantic ridge further North though, at least up to 30 mb.

[bluearmy]

4 minutes ago, Summer Sun said:

GFS 00z para gives 2 cold snaps the 2nd quite possibly the coldest one

In the context of the thread, that was a post I found very confusing until I looked at your charts quite closely gavin. This weekend is no longer being discussed and the gfsp 00z run is one of the disappointments of the 00z output in general as it flattens through week 2. 

Edited December 30, 2016 by bluearmy

[stewfox]

It appears we now have a waiting game for UKMO 12z which I understand will come out between 1700-1800 (GMT)

We want it to go towards the ECM ,GFS solution

Yesterday the GFS 12Z was worse then the GFS 6z (stella) and GFs 18z not great (relative). Today The GFS 0z and 6z are a lot better

ECM good UKMO not feeling the love post T96 ? Although GFS 12z may have a word before.

 

Edited December 30, 2016 by stewfox

[Ali1977]

5 minutes ago, stewfox said:

It appears we now have a waiting game for UKMO 12z which I understand will come out between 1700-1800 (GMT)

We want it to go towards the ECM ,GFS solution

Yesterday the GFS 12Z was worse then the GFS 6z (stella) and GFs 18z not great (relative). Today The GFS 0z and 6z are a lot better

ECM good UKMO not feeling the love post T96 ? Although GFS 12z may have a word before.

 

UKMO 1530-1630

[stewfox]

1 minute ago, Ali1977 said:

UKMO 1530-1630

Is this link now out of date ?

 

[Iceberg]

Ens mean temps for central England drop down to -8 850s at 210hrs that's quite an incredible feat for a 20 member ens

[bluearmy]

Incidentally, the 46 was pretty cold for  weeks 3, 4 and 5

[IDO]

Well the D8 GEFS now 100% support for the second trough to drop with a significant westward correction compared to the 0z suite.

It will be a bit of a disappointment if we don't get some snow out of this, the means:

From there on, great uncertainty as to how the pattern develops, but remaining colder than average for the 5 days after at least.

 

[Jason M]

And for once were talking D8 and not day D15 charts

Edit - GEM ensembles are on the same page.

 

 

Edited December 30, 2016 by Jason M

[West is Best]

Some astonishing synoptics at the moment. I guess those of nervous disposition will be pretty scared with this kind of set up, whilst those who want to see mild in anything will do so (and doubtless irritate people in the process), but these runs do remind me very very much of 1978/9. That was an extraordinary winter of snowy and cold not just cold: off north west to north east low pressure cells and instability. I much much much much much much much prefer this kind of synoptic set up than a boring bone chiller such as we had in February 1986 when it was relentlessly dry and bitter off an easterly: hardly a flake fell all month and it was simply brrrrrrrrr. This has mahooosive snow potential.

The 6z is 1978/9. Awesome. Just awesome.

[karyo]

5 minutes ago, IDO said:

Well the D8 GEFS now 100% support for the second trough to drop with a significant westward correction compared to the 0z suite.

It will be a bit of a disappointment if we don't get some snow out of this, the means:

From there on, great uncertainty as to how the pattern develops, but remaining colder than average for the 5 days after at least.

 

That's very pleasing to see! Hopefully the UKMO will back off later.

[jvenge]

Nothing mild showing on the GEFS for the UK, but they are more split in the medium term outcome than the 0z and less members going for deeper cold into the UK towards the end.

By the way, since when did day 15 charts cause so much excitement here? :-)

[Summer Sun]

ECM weeklies keep temps below average till the 22nd the odd less cold spell can't, of course, be ruled out during this period but overall it looks chilly

[Derecho]

Hello, I thought I would provide an analysis to demonstrate how we can get a strong cold spell and summarise the model output from this.

There are 3 steps

STEP ONE: Avoid a sinking high to the south - this can cut off the northerly flow being shown later next week.

 - UKMO Meh... probably the least likely evolution at this point though.

- ECM - bingo!

STEP TWO: Get the low west of Iceland moving eastwards to Scandi

 - GFS 06Z doesn't manage this so we get an unsettled NW flow instead that cannot get the really cold air towards the UK. Also risks the cold air staying out to the West.

STEP THREE: Develop heights towards Greenland

This releases all the cold air from the arctic into our path

 - P11 of the 06Z is the best example, although a few others get close.

It can easily go wrong but I think we will probably get past step one.

If we don't get the heights over Greenland then we will hopefully get a shot of cold air from Scandi. Not much has changed from yesterday and the chances of some really sustained cold are still there (although low at this point still - as many things need to come together!)