Model Output Discussion - The Start Of Winter

[SMU]

The ECM ensembles show that the Control is more than likely on a par with the operational with a quick swing at day 10-13 from atlantic profiled weather to air sourced from the North east.

 

http://www.weerplaza.nl/15daagseverwachting/?r=midden&type=eps_pluim

 

Very cold air arriving.

 

from my Winter forecast the closest 'dated' analogue to a xmas change was Dec 1968.

 

The benchmark is the first -2.5 AO reading.

1958 =  Dec 15th

1965 =  Dec NA

1968 =  Dec 25th

1976 =  Dec 18th

2009 =  Dec 10th

 

 

 

& whilst the AO hit -2.5 on the 25th the -EPO ridge was lurking some 4 days before-

http://modeles.meteociel.fr/modeles/reana/1968/archivesnh-1968-12-21-0-0.png

 

All in all a very positive eve in the 'bigger picture'

 

S

[snowice]

The ECM ensembles show that the Control is more than likely on a par with the operational with a quick swing at day 10-13 from atlantic profiled weather to air sourced from the North east.

 

http://www.weerplaza.nl/15daagseverwachting/?r=midden&type=eps_pluim

 

Very cold air arriving.

 

from my Winter forecast the closest 'dated' analogue to a xmas change was Dec 1968.

 

 

& whilst the AO hit -2.5 on the 25th the -EPO ridge was lurking some 4 days before-

http://modeles.meteociel.fr/modeles/reana/1968/archivesnh-1968-12-21-0-0.png

 

All in all a very positive eve in the 'bigger picture'

 

S

Hi Steve what is the percentage chance of above coming of and do you expect a big divergence in the model output in the comming days!

[SMU]

Hi Steve what is the percentage chance of above coming of and do you expect a big divergence in the model output in the comming days!

 

As a rudimentary figure I would day 70% odds on favourite for a NH pattern change between 25-27 December-

50/50 whether we lock into the cold, I would say as it stands the anomalies at least look in favourable locations..........

 

S

[phil nw.]

The GFS mean hts anoms. charts at T240 and then T384hrs illustrate the shift of the pattern post Christmas.

 

 

underlines what Chiono. and Steve have indicated.

 

Upstream  the newly formed Alaskan ridge impacting into the Atlantic via formation of that Canadian trough inducing ridging downsteam.On our side of the Atlantic a Scandianvian trough ejecting lower heights into Europe.

 

At this range still detail to be ascertained as the amount of ridging and placement of the main features but we can see some changes look likely between now and month endwith height anomalies rising over the Arctic.

Growing signs of a falling AO/NAO pattern but as ever in the UK getting the cold here is never a smooth transition.

 

Promising signs and plenty to keep us interested though.

Edited December 15, 2014 by phil nw.

[Polar Maritime]

Yes as Phil & others say, Some promising upstream signals in the models for some sort of change around the turn of the Month. And will hopefully will lead to some interesting viewing on the run-up to Christmas as they run through various solutions/outcomes. 

[knocker]

The GFS mean hts anoms. charts at T240 and then T384hrs illustrate the shift of the pattern post Christmas.

 

gensbcnh-21-5-240.pnggensbcnh-21-5-384.png

 

underlines what Chiono. and Steve have indicated.

 

Upstream  the newly formed Alaskan ridge impacting into the Atlantic via formation of that Canadian trough inducing ridging downsteam.On our side of the Atlantic a Scandianvian trough ejecting lower heights into Europe.

 

At this range still detail to be ascertained as the amount of ridging and placement of the main features but we can see some changes look likely between now and month endwith height anomalies rising over the Arctic.

Growing signs of a falling AO/NAO pattern but as ever in the UK getting the cold here is never a smooth transition.

 

Promising signs and plenty to keep us interested though.

 

Well Phil I'm looking at the ECM ens T360 anomaly chart and by that time we are supposed to be locked in to the cold. So this chart must be way out. I know it's 15 days hence but still.

And does NOAA support the cold post Xmas day scenario? Very dubious.

Edited December 15, 2014 by knocker

[Captain Shortwave]

Yes as Phil & others say, Some promising upstream signals in the models for some sort of change around the turn of the Month. And will hopefully will lead to some interesting viewing on the run-up to Christmas as they run through various solutions/outcomes. 

Let's just hope that the models don't play the role of Grinch and throw a spoiler shortwave on their output on Christmas day.

Plenty of water to get under the bridge before then

Including some very mild weather through the middle of the week.

Temperatures do drop back to average, though nothing particularly cold until potentially after Christmas. At this moment I would put the chance of a white Christmas as pretty slim. But maybe I might see some snow during my trip back to Norfolk before New Year

[SMU]

Well Phil I'm looking at the ECM ens T360 anomaly chart and by that time we are supposed to be locked in to the cold. So this chart must be way out. I know it's 15 days hence but still.

 

Please post said chart.....

[knocker]

I can't ©     But the NOAA 8-14 isn't a million miles away although it has less emphasis on the Alaskan ridge  and southward influence of the Scandinavian trough so not really that helpful in that respect.      

 

EDIT

This answer is redundant as IF has replied with more detail.                  

Edited December 15, 2014 by knocker

[phil nw.]

Well Phil I'm looking at the ECM ens T360 anomaly chart and by that time we are supposed to be locked in to the cold. So this chart must be way out. I know it's 15 days hence but still.

I don't think anyone has proclaimed UK cold by then Knocks-i certainly havent- but we can see the changing placement of height anomalies in the GFS mean anomls.

Of course you have the advantage on the ext.ECM ens. so i can't comment on them really except to say if you are just looking at the mean it will be give a clouded picture at that range.

At this stage it is case of watching to see how things evolve.I did say  getting cold here wasn't straightforward.

Edited December 15, 2014 by phil nw.

[fergieweather]

Well for what it's worth campers a quick look at the ECM T360 anomaly.

 

Strong ridge Alaska; flattish across the US and eastern seaboard but quite a marked Azores/ Greenland ridge orientated NW/SE just west of the UK. Trough Scandinavia into Europe. Which on a surface analysis would bring the Azores HP into prominence.

 

Largest 12z cluster at T+360 (22 members) does indeed ridge the Azores high up to SW/W of UK as you say, with the associated 500hPa anomaly stretching up to Iceland. Second cluster (15 members) has axis more SE-NW, as you describe, with underpinning down in Biscay/Iberia, stretching up to Greenland. All 3 clusters concur on some S-N orientated ridged solution in the broad same areal sense (either to W or over UK), with trough to E, but any attempt at detail / over-analysis obviously pointless at this juncture. Similar variations of these signals also occur earlier in the EPS clusters. As we've been pointing-out via GloSea, it's currently impossible to say where blocking, if it occurs, might become cemented proximal to the UK at end of month/early Jan, albeit that model's signal for this possibility out at that range is still a repetitive one of late.

[IDO]

I am in the minority I think with respect to any Atlantic/Greenland ridge at around D10-12 in that I believe it is not a pattern change, is just transient, and is nothing to do with the early stage development of the Alaskan/Pacific ridge, just a "possible" short term amplification (one of several clusters on the GEFS) as the US ridge vacates from the Conus. The GEFS have been advertising this for sometime and it has always been transient, except when the Polar Heights migrate to Greenland; however the consensus is that those heights will slide to the Alaska region to promote the -ve Pacific Ridge. The wave from the Pacific Ridge surely won't affect the downstream UK region till at the beginning of January?

 

For instance it is only on the 31st December that WAA really starts to amplify the Alaskan Ridge on the GFS: 

 

The NOAA 8-14: 

 

Only my opinion but it looks like the last week of December is just a variation on the upcoming theme.

[knocker]

I don't think anyone has proclaimed UK cold by then Knocks-i certainly havent- but we can see the changing placement of height anomalies in the GFS mean anomls.

Of course you have the advantage on the ext.ECM ens. so i can't comment on them really except to say if you are just looking at the mean it will be give a clouded picture at that range.

At this stage it is case of watching to see how things evolve.I did say above getting cold here wasn't straightforward.

 

Just quoting SM Phil

 

 

As a rudimentary figure I would day 70% odds on favourite for a NH pattern change between 25-27 December-

50/50 whether we lock into the cold, I would say as it stands the anomalies at least look in favourable locations..........

 

[Severe Siberian icy blast]

Well Phil I'm looking at the ECM ens T360 anomaly chart and by that time we are supposed to be locked in to the cold. So this chart must be way out. I know it's 15 days hence but still.

And does NOAA support the cold post Xmas day scenario? Very dubious.

Well it's not dubious though is it ? The second chart would give us a good northerly of sorts maybe Northwest . Good ringing into Greenland . Just no low hights into Europe but quite a good chart if you ask me

[phil nw.]

Fair points IDO and indeed although there are signs of an adjustment/change post Christmas we cant  ascertain how this plays out for us and whether this will be temporary.

I don't think we can expect any real change in that 8-14 day pattern yet anyway.

As Ian F said above it's too early to consider details towards month end but it does make for some good debate. 

Edited December 15, 2014 by phil nw.

[knocker]

Well it's not dubious though is it ? The second chart would give us a good northerly of sorts maybe Northwest . Good ringing into Greenland . Just no low hights into Europe but quite a good chart if you ask me

 

I didn't say it wouldn't give a NW just that a pattern change was dubious.

[Barry12]

Only my opinion but it looks like the last week of December is just a variation on the upcoming theme.

 

But, it would still bring cold and widespread snow to the UK...

 

 

Which is what most of us are looking for!

[Mucka]

If speculation and post activity were any barometer then we would be expecting an upcoming change in our weather.

Which is what this forum is all about so no problem with people tapping the gauge to make sure the needle isn't stuck, especially at this stage.  

 

Anyhow 18z rolling out and ready to muddy unclear waters which won't stop us detailing what may be lurking beneath the surface of course. 

I've gone a bit analogy mad this evening haven't I? 

 

anyhow the pub runs looked slightly more amplified upstream in the early going but let's see what develops.

Edited December 15, 2014 by Mucka

[johnholmes]

 

 

The NOAA 8-14: 814day.03 (1).gif

 

Only my opinion but it looks like the last week of December is just a variation on the upcoming theme.

Indeed it is and until they change nothing major or even fairly minor in terms of any cold other than coldish as we have had over the past week or so. Great to speculate but if it is a scientific appraisal then in 8 out 10 cases the anomaly charts will be the guide. Be that to show no change or to indicate the likely change in pattern to bring more substantial cold or mild into the UK. The minor changes the main 3 are showing, have done for several days in differing areas of the chart, is not yet an indication of the major wavelengths changing in my opinion in the time scales they represent, 6-15, maybe even 17-18 days ahead.

[Ali1977]

-10c uppers into Northern Scotland by Boxing Day....great pub run

Edited December 15, 2014 by Ali1977

[Great Plum]

Taking the 18z as gospel (which it isn't of course!) it's a green christmas for most...

http://www.wetterzentrale.de/pics/Rtavn2401.gif

Maybe not a green Boxing Day for some...

http://www.wetterzentrale.de/pics/Rtavn2641.gif

And the -5 air is over all the UK by 27th!

http://www.wetterzentrale.de/pics/Rtavn2882.gif

We can but dream!

[cyclonic happiness]

F.I. looks very, very low resolution and sparse to be taken seriously. We still have no idea or resoultion as to how it will go after the 23rd. 

[Mucka]

-10c uppers into Northern Scotland by Boxing Day....great pub run

 

 

We can do better than a transient Northerly though can't we?

At least that is what a lot of us will be hoping.

 

Parallel looks mildish for Christmas day but promising upstream at 222.

Edited December 15, 2014 by Mucka

[Long haul to mild]

Indeed it is and until they change nothing major or even fairly minor in terms of any cold other than coldish as we have had over the past week or so. Great to speculate but if it is a scientific appraisal then in 8 out 10 cases the anomaly charts will be the guide. Be that to show no change or to indicate the likely change in pattern to bring more substantial cold or mild into the UK. The minor changes the main 3 are showing, have done for several days in differing areas of the chart, is not yet an indication of the major wavelengths changing in my opinion in the time scales they represent, 6-15, maybe even 17-18 days ahead.

Now this is where I get confused. John says the anomaly charts show no change to the current pattern whereas others have posted anomaly charts showing expected HP into Greenland with resultant troughing to the East, which seems like a pattern change to me? Are different models showing different anomalies because I'm losing track!

Apologies if I'm just being slow on the uptake.

Edited December 15, 2014 by Long haul to mild

[Mucka]

Parallel day 10

 

 

ECM day 10

 

 

I would take either of those at this stage.