Model Output Discussion - The Start Of Winter

[Captain Shortwave]

Well the next 7 days tends to be dominated by more milder airmasses overall, so I would expect the CET to rise from its current slightly below average value to above average. This morning though it does look like it will begin to turn colder around Christmas with the cold front forecast to push south on the big day itself being shifted to Christmas eve.

So we have this for Christmas day

Still only looks like being Scottish hills which could get some snow, but a chilly and sunnier day for most compared to previous runs.

Beyond Christmas day, still looks good from the ECM which will begin to bring much colder air down from the north by day 10.

Edited December 16, 2014 by Captain shortwave

[Mucka]

ECM quite a bit different by 192h compared  to GFS due to how it handles upstream developments. 

A much deeper trough by the 24th

 

 

and a chilly Northwesterly established by Christmas day.

 

 

That would be ideal for my part of the world, please Santa.

Atlantic ridge ultimately  foiled once more though, so still no Operational output showing the Atlantic being blocked off for any length time.

Edited December 16, 2014 by Mucka

[MR EXTREMES]

incredible massive blob of cold air around the northern hemisphere from the ecm.

Certainly wintry out there today fog and frost here on the sunny costa del south coast very pleased to see 

Edited December 16, 2014 by emotional rollercoaster

[knocker]

The ecm going for nippy NW on Xmas day.

Chart courtesy weatherbell

 

[Dorsetbred]

The ecm going for nippy NW on Xmas day.

Chart courtesy weatherbell

And a fair bit warmer in our neck of the woods, out of the direct blast.

[strathearn snow]

00Z EC joins the Xmas party with a chilly NW'ly for Xmas Day - wetterzentrale.de/pics/Recm2161.… - Increasing confidence now for Xmas not to be mild

7:00am - 16 Dec 14

[Gavin Hannah]

This mornings 00Z run obvously hasn't had it's coffee this morning because it went from this in the pub run last night...

to this...

 

 

 

 

So it's the usual flip flopping untill the weekend by which point we should know which way the cookie is going to crumble.  

[Frosty.]

Something wintry is definitely brewing for later next week with an increasing risk of snow showers and frosty weather. In the meantime, although the next few days will be milder, it turns colder and showery from the NW for friday and Saturday,then milder wet and windy and then colder and showery again. The festive period itself could be dominated by frosty & snowy weather. :-)

[IDO]

  MattHugo81
Amazing change to the EC Seasonal with such a strong +ve height anom over the pole for Jan/Feb/Mar. It's playing catchup once again.
16/12/2014 07:17

 

Good news the background signals are still going to plan. Looking at the CFS Monthly Feb-March was always looking blocked and Jan has been flip flopping between blocked and not, so I suspect the change sometime in Jan.

 

In the medium term, say till the end of December a continuation of the pattern with possibly a fleeting Northerly due to transient heights in the Atlantic/Greenland. Looking synoptically more likely than the non-Northerly of last week but again it remains one of about three clusters so it remains fluid. The Christmas Day and Boxing Day means:

 

  

 

More green than white to my eyes. The London temps (uppers) for the next 8 days suggests more milder days than cooler and the cooler look close to average (2m temps) so the south remains relatively average to above:

 

 

 

In the 10-16 day period no real change in our region, a continuation of current synoptics looks the most likely. ECM at D10 (as it will) slightly more amplified trough but followed by a more amplified ridge. With a flat upstream:

 

 

 

Mixed messages from the GEFS out in FI re the "possible" Alaskan Ridge. These potential heights are looking more mobile and less members are linking the polar heights with that ridge so looking less of a block and more of a mobile flow. Could be just run so more runs needed.

Edited December 16, 2014 by i'm dreaming of...

[BlueHedgehog074]

In a way, Christmas Day is still far enough away for things to improve with regards to cold weather possibilities. On a personal level, considering how uninspiring last Winter was for low level snow, it'd be nice to see something a little white for Christmas. The models do seem to be playing about with some kind of amplification to our West towards Christmas - whether it's a mid-Atlantic ridge or heights building over Greenland like on the GFS Paralell run. Both scenarios of which could produce a Northerly (even if it's just brief) if the High Pressure to our West can amplify enough. And also if a piece of the Vortex can get pushed to our East to allow room for High Pressure to amplify to our West. I suppose having read Tamara's post yesterday, she did seem to give the impression to not panic if you're after a different weather pattern setup and that a change to cold shouldn't be ruled out yet.

Apart from the cold possibilities towards Christmas and/or after, the weather for the next few days is likely to bring a mixture of rain, showers (some wintry over high ground to the North-West) and some drier interludes. Some days being on the chilly side, especially late this week and into the weekend with a cool/cold North-Westerly flow establishing.

I really wonder how *seagulls would cope with cold weather? (*that should help the other hosts/mods/admins with their weather Model game they're playing - don't ask. )

[johnholmes]

it is of course entirely possible that one possibly even 2 days in the Christmas period might rate rather cold by official standards but I have to say again that there is nothing to suggest any more than this. Which day or two is still not clear if either in fact occur. It is now 9 days from the 25th so watch each model for the same time over the next 3-4 days don't compare the 00 to the 06 and the 06 to the 12 etc. Checking the same time output is far more likely to reveal a trend than the other way. By all means from 144h then each run is a fair enough thing to do as by then later data may give a better update on what the actual may turn out to be.

But looking 6-15 days ahead nothing suggests any marked cold spell is yet in sight. I know some deride the anomaly charts but in spite of a post last evening suggesting otherwise they are a far better guide than the 4x or 2x model outputs at beyond 6-7 days ahead. They have been the reason I have not given any suggested marked change other than the mild to less mild they predicted some 7-8 days prior to the last week or so of somewhat below average temperatures with a fairly mobile westerly as the average direction at 500mb. I did rigorous checks over 3 years that proved this. In all honesty I can only think of 4 maybe 5 instances in that time that the synoptic models picked out a change of type in a consistent manner before the anomalies did. But we all have our favourites and it all adds to the interest on here.

 

The post by IDO above with charts is again the most level headed and realistic outlook so far this morning-just my view!

 

this also sums up the rest of December in my view from Gibby

While long term projections from the experts remain positive for a change of pattern later in the Winter it looks unlikely that any major shift will occur until early 2015 at the earliest which means we have to be satisfied with the same old brief incursions of cold from the NW over the coming weeks which will probably disappoint all but those living on the highest ground of the North or the ski resorts of Scotland if it's snow your looking for.

Edited December 16, 2014 by johnholmes

[nick sussex]

I'm somewhat underwhelmed by the outputs this morning, more especially the ECM which phases that USA troughing with that low off the eastern seaboard of the USA.

 

That small low needs to do one asap!

 

In terms of trend upto T240hrs the GFS P is the best as it doesn't phase the trough with the low and is more amplified upstream.There are quite a few changes this morning in terms of how the models bring about that colder flow into Christmas, the ECM looks a bit quick over the USA and has a broader trough digging south.

 

Overall it does look colder for Christmas but the depth of cold to tap into this morning bar the GFS P isn't really going to deliver more nationwide.

 

ECM ensembles out shortly, hopefully they're a bit more amplified upstream.

[TonyH]

it is of course entirely possible that one possibly even 2 days in the Christmas period might rate rather cold by official standards but I have to say again that there is nothing to suggest any more than this. Which day or two is still not clear if either in fact occur. It is now 9 days from the 25th so watch each model for the same time over the next 3-4 days don't compare the 00 to the 06 and the 06 to the 12 etc. Checking the same time output is far more likely to reveal a trend than the other way. By all means from 144h then each run is a fair enough thing to do as by then later data may give a better update on what the actual may turn out to be.

But looking 6-15 days ahead nothing suggests any marked cold spell is yet in sight. I know some deride the anomaly charts but in spite of a post last evening suggesting otherwise they are a far better guide than the 4x or 2x model outputs at beyond 6-7 days ahead. They have been the reason I have not given any suggested marked change other than the mild to less mild they predicted some 7-8 days prior to the last week or so of somewhat below average temperatures with a fairly mobile westerly as the average direction at 500mb. I did rigorous checks over 3 years that proved this. In all honesty I can only think of 4 maybe 5 instances in that time that the synoptic models picked out a change of type in a consistent manner before the anomalies did. But we all have our favourites and it all adds to the interest on here.

 

The post by IDO above with charts is again the most level headed and realistic outlook so far this morning-just my view!

Agreed no snow away from Scottish Mts on the Big Day is what the models scream out. IDO seems to have a fine handle on the models yes.

[Gibby]

HERE IS MY LATEST ANALYSIS FROM THE OUTPUTS OF THE WEATHER COMPUTER PREDICTION MODELS FOR TWO WEEKS FROM 8AM TODAY TUESDAY DECEMBER 16TH 2014.

NEXT UPDATE WEDNESDAY DECEMBER 17TH 08:00

THE CURRENT GENERAL SITUATION A ridge of High pressure across the UK will move away East with an active warm front following bringing very mild WSW winds across the UK tomorrow.

MODELS-2 WEEK HEADLINE Remaining changeable with rain at times especially across the North and West with snow on hills there at times. Temperatures alternating close to or a little above or below average day to day but overall no severe weather expected over the period.

THE JET STREAM ENSEMBLE FORECAST The Jet Stream Ensemble forecast continues to show the flow moving West to East across the UK in an undulating form as the polar front moves South then North again within the west to east flow.

GFS OPERATIONAL The GFS operational this morning shows a pattern which changes little over the period. Yes there are variations in day to day conditions with mild winds and rain alternating with colder and more showery interludes but away from high ground most areas away from Northern high ground will see nothing wintry falling from the sky through the period up to the New year with frosts at night patchy and occasional.

THE GFS PARALLEL RUN The GFS Parallel run does show a window of opportunity around Christmas of a period of Northerly winds and some snow showers mostly iver the North while the South sees some rain or sleet for a time but other than that the pattern of High down to the South and SW and Low to the North persists or indeed returns after Christmas on the run up to the New Year.

THE GFS CONTROL The GFS control run shows conditions which are conducive to a Westerly flow of weather being maintained with some days when mild and wet conditions prevail and then a couple of colder polar maritime air type days when sunshine and wintry showers dvelop along with a pathsy frost. Late in the run the weather is shown to become more deeply unsettled for all with rain and windy weather for all but still with colder periods with wintry showers, always most likely over the North.

THE GEFS ENSEMBLES The GEFS Ensembles members in very basic terms though not without exception look like the best chance remains with a continuation of the Low pressure vortex lying to the North of the UK and High to the South all the way up to and including the New year period. In weather terms this means more rain and showers across the UK with average temperatures or a little above at times alternating with brief colder interludes with wintry showers in the North.

UKMO UKMO today shows the UK under a strong Westerly flow to start next week lying between High pressure to the South and Low to the North. A cold front is shown to be approaching the UK from the NW early next week which will likely replace mild weather with some rain with colder and more showery weather as we move towards Christmas though with any wintry showers confined to the high ground of the North.

THE FAX CHARTS The Fax Charts today show a complex series of troughs crossing East over the UK from later today until Friday in moist and mild air. On Friday cold fronts move SE down over the UK clearing the UK by the weekend bringing a temporary colder and brighter NW flow with scattered wintry showers over the North.

GEM GEM also maintains a mild Westerly flow predominating across the UK with just short colder injections of air with wintry showers in the North for a time this weekend and again over Christmas when more prolific amounts of frost may develop over the South for a time as High pressure moves in from the West, slowly slipping away SE post Christmas.

NAVGEM NAVGEM maintains the strong Westerly flow often mild and cloudy with rain mixed with some short 24-48hr periods of brighter and colder weather when wintry showers could occur across the hills of the North.

ECM ECM this morning shows a mobile and strong Westerly type pattern through the period with spells of rain and mild weather alternating with colder and brighter weather with wintry showers in the North. There are two separate shots of colder polar maritime air shown, one this weekend and another coinciding with Christmas but away from northern hills the chances of snow on lowland UK remain low over the period.

ECM ENSEMBLES The ECM Ensembles on face value do not look over inspiring though for the first time there is evidence of change afoot the other side of the Atlantic as Low pressure over Canada looks like beginning to support a rise of pressure over Greenland which although at this stage will mean little longer term a rise of pressure there could raise tha chances of a pattern change for the UK.

NOTABLE TREND CHANGES FROM PREVIOUS RUNS Trends away from the current pattern of weather across the UK remain weak and ill defined with the overwhelming majority in favour of only small variations in the overall pattern the most likely this side of the New Year.

MY THOUGHTS The models continue to yo-yo between mild and strong Westerly winds with rain at times alternating with colder polar maritime air with wintry showers across the North. There are two separate attacks of the colder air from the NW, one this weekend although away from windward coasts and the usual hotspots in the North snow showers are unlikely on low ground but more widespread frost is likely over Friday and Saturday night. Then another perhaps more substantial attack over Christmas itself when if a lot of todays charts verify would mean we would wake to a sparkling and cold, frosty Christmas morning in a NW flow which I'm sure many of us would take over the mild and damp and sometimes wet conditions which prevail before and inbetween these two incursions. Having said all that though the pattern remains stubbornly resilient to meaningful change with the polar vortex remaining in place to the North of the UK and after a temporary weakening of High pressure to the South mid period the end of the run shows the status quo resumed with more periods of rain and wind on a Westerly flow around a strong Azores High and temperatures close to average or alternating just above or below as each front passes. While long term projections from the experts remain positive for a change of pattern later in the Winter it looks unlikely that any major shift will occur until early 2015 at the earliest which means we have to be satisfied with the same old brief incursions of cold from the NW over the coming weeks which will probably disappoint all but those living on the highest ground of the North or the ski resorts of Scotland if it's snow your looking for.

[knocker]

The ECM ens for Xmas day

Charts courtesy weatherbell

 

Edited December 16, 2014 by knocker

[IDO]

Confirmation from the ECM mean that the D10 amplified pattern in our sector is the usual ECM teaser. The mean has more in common with the GEFS than its own op:

 

  GEM also: 

 

I suspect it is the same situation as the GEFS, a cluster of members with the more transitory amplified Atlantic but the majority of members having a flatter pattern. So the ECM op remains a possibility but as usual with these "Northerly's" more than likely a non-event south of the M62.

 

 

[mushymanrob]

when i first joined the site nearly ten years ago, the first 'lesson' learned was dont trust fi as its usually nothing more then fantasy. im abit bemused then that theres are discussions going on about t384!!! and the only reason such discussions are going on is because it shows a possible colder outlook.

what does fi @ t384 show this morning?

 

 

the gfs suggests the post crimbo ridge (where the azores links with the greenland high) isnt the precursor to a pattern change but a temporary, transient feature  before the jet powers through it again, returning us to a mobile regime.

im not saying the pattern wont change at this juncture, im saying that the hoped for pattern change to cold isnt the only option. and these transient ridges in mobile westerly patterns are common enough features.

Edited December 16, 2014 by mushymanrob

[frosty ground]

Confirmation from the ECM mean that the D10 amplified pattern in our sector is the usual ECM teaser. The mean has more in common with the GEFS than its own op:

 

EDM1-240.gif  gens-21-1-240 (3).png GEM also: gens-21-1-240 (4).png

 

I suspect it is the same situation as the GEFS, a cluster of members with the more transitory amplified Atlantic but the majority of members having a flatter pattern. So the ECM op remains a possibility but as usual with these "Northerly's" more than likely a non-event south of the M62.

Not sure how much use the mean is, surely the best way of looking at these long range charts would be to use the ensembles and look for groupings rather than looking at the mean of all the runs together, (I acknowledge the information to do this with the ECM is not freely available The GFS on the Other hand) 

 

[frosty ground]

when i first joined the site nearly ten years ago, the first 'lesson' learned was dont trust fi as its usually nothing more then fantasy. im abit bemused then that theres are discussions going on about t384!!! and the only reason such discussions are going on is because it shows a possible colder outlook.

what does fi @ t384 show this morning?

 

Rtavn3842.gif

 

the gfs suggests the post crimbo ridge (where the azores links with the greenland high) isnt the precursor to a pattern change but a temporary, transient feature  before the jet powers through it again, returning us to a mobile regime.

im not saying the pattern wont change at this juncture, im saying that the hoped for pattern change to cold isnt the only option. and these transient ridges in mobile westerly patterns are common enough features.

So in 10 years you have yet to come to the understanding that people will look for cold weather in winter?   

Long range models and other sources are indicating a pattern change, I think it's perfectly reasonable to look for any sign of this change in the models, you are of course free to discuss what you like, not sure why your interested in talking about other peoples interest 

[Polar Maritime]

An odd post Mush..All part of model discussion, As im sure all members are aware that looking further into the runs are a little speculative whether showing mild or cold. Most are looking at small changes in upstream signals and makes for interesting viewing and lots to learn for members which is what this thread is all about. I would of thought after 10 yrs you would have been wiser to this.

Edited December 16, 2014 by Polar Maritime

[IDO]

Not sure how much use the mean is, surely the best way of looking at these long range charts would be to use the ensembles and look for groupings rather than looking at the mean of all the runs together, (I acknowledge the information to do this with the ECM is not freely available The GFS on the Other hand)

Hi. I agree and if you re read my post, I did add that exact point! Though the majority go for a flatter pattern so that is probably the most likely outcome without discounting the possibility of more amplification.

[Summer Sun]

A head of the next cooler spell from the north west we have a couple of very mild days away from Scotland

 

Temperatures tonight will be rising as the hours go on we could see a transient spell of snow on higher ground in Scotland as the rain moves in

 

 

By 7am most parts of England a wales are in or very close to double figures

 

 

13:00 & 16:00 see's temps in parts of the south close to 13c

 

 

Very mild away from Scotland Wednesday night and into Thursday these are the minimum temps

 

 

Thursday could see temps around 14c for some parts of Scotland remain cold with temps just above freezing for some

 

 

By Friday the south holds onto the mild weather but its becoming cooler from the north

 

 

By Saturday temps are back around average for England and wales

 

[Snowman.]

Some large differences early on for the 6zOP.

 

0z6z

 

Makes a big difference later on with the cold sweeping south faster.

 

0z6z

Edited December 16, 2014 by SN0WM4N

[Ali1977]

The GFS is quite different this run even by Sunday, 4c uppers replaced by -4c uppers in Scotland.....Thats a big change at relatively short range.

Edited December 16, 2014 by Ali1977

[Nick F]

when i first joined the site nearly ten years ago, the first 'lesson' learned was dont trust fi as its usually nothing more then fantasy. im abit bemused then that theres are discussions going on about t384!!! and the only reason such discussions are going on is because it shows a possible colder outlook.

what does fi @ t384 show this morning?

 

Rtavn3842.gif

 

the gfs suggests the post crimbo ridge (where the azores links with the greenland high) isnt the precursor to a pattern change but a temporary, transient feature  before the jet powers through it again, returning us to a mobile regime.

im not saying the pattern wont change at this juncture, im saying that the hoped for pattern change to cold isnt the only option. and these transient ridges in mobile westerly patterns are common enough features.

 

If  you are looking at an operational run in isolation, yes, but it's perfectly legitimate to get broad clues from ensembles and their means out at those ranges for a pattern change IF they are continually showing that change.

 

There has been a pattern change consistently been flagged upstream over NE Pacific and N America by GEFS and EPS.

 

This pattern change takes place way upstream with signs of the N Pacific jet stream retracting and the Aleutian low retrogressing in the means by day 10, thus leading to a ridge pushing north across Alaska and Yukon towards the pole ... ridging north over Siberia too perhaps leading to cross polar HGT rises. Downstream, a trough is forced south over central Canada and US Plains intially before transfering to eastern N America by day 10. This forces ridging north over the Davis Strait and Greenland.

 

 

This ridging in the far NW Atlantic is not looking to form a block with current guidance - as John H and others suggest ... but may hang on enough to drop some deep cold south across the UK around 26-29th. Low heights are still going to be a problem to shift over Nern Canada and Greenland, so any ridge north over the NW Atlantic will struggle to form a block, though there are signs of the AO going -ve later this month:

 

 

Vertical wave propagation has been rather weak of late given the zonal nature of the flow in the northern hemisphere, but with these changes upstream and signs of wave number one kicking in, we could see more blocking reappear as we had into the New Year, all this without signs of the potential SSW yet, of which there appears an increased chance of in Jan.

Edited December 16, 2014 by Nick F