Model Output Discussion - The Start Of Winter

[Captain Shortwave]

Day 6 charts

Westerly flow established, any cold weather being rather brief.

UKMO

Slightly better with the cold digging a little further south and with greater longevity.

GFS

Again brings the -8C isotherm briefly over the whole of Scotland before Atlantic westerlies bring a warm up in conditions.

GEM

Again oddly it makes nothing of the cold air pushing south. Only 850s of -4C reaching Scotland.

 

There seems to be good agreement on a mobile and slightly milder westerly pattern developing from the end of next weekend, just a case of how much cold we can eek out of this week, and the mid-week storm of course.

[knocker]

From Friday to Saturday the GFS runs through a rapidly moving surface analysis. A north westerly on Friday as the low moves away north east, a very brief ridge on Saturday before the next system comes along with south westerlies. Temps below average but becoming above average by Tues. The detail is of course subject to revision.

 

The ECM has a slightly different take by delaying the ridge

 

Charts courtesy weatherbell

Edited December 8, 2014 by knocker

[shaky]

Ridiculous differences this morning at just 96 hours across the uk!! Gfs doesnt have nowhere near as deep a low as ukmo and ecmwf and is also slightly further south!!!

[bluearmy]

Gem uppers in a cold scenario (apart from continental flow) are notoriously conservative. I was rather hoping that the upgrade may have fixed this.

Edited December 8, 2014 by bluearmy

[IDO]

The good news first, warming looking like a consistent feature after D12 and at D16 at 10hPa:

 

The GEFS at D16 have two HLB and about 3 others showing some NH ridging potential: 

 

Hopefully they can build on that trend.

 

The bigger picture remains with a period of Atlantic dominated weather for around two weeks (plus). GEM is stalwart in bringing 3-4 days of mild uppers in a SW flow:

 

 

Not sure of that. Only 4 GEFS have this TM shot but none are quite so warm. So maybe an outside chance at the moment.

 

ECM plays around with D10 charts upstream (today heights over N.Canada) but they rarely get into the reliable so just concentrating on our sector; it is a zonal flow after the brief Northerly toppler, and at D10:

 

GFS op & C:  

 

With regard to backedge snow Friday morning for the south, the front maybe weak for the far south but the Midlands should get some after the initial rain:

 

 

 

A very windy week for the NW from Tuesday-Thursday.

 

 

[shetland islands]

Unfortunately, it does look as if the models are trending to a more westerly flow come the new week. The models show a variation in extremes during this week, but unless you live in western, central, northern Scotland, the far north of northern ireland and the northern Pennines it will probably be a standard wintry affair.

The differences in the UKMO still highlights the uncertainty during this week.

Edited December 8, 2014 by shetland islands

[bluearmy]

The day 16 GEFS mean anomoly would have been a good chart to post IDO. Might have even got you a star!

[nick sussex]

This mornings headlines !

 

UKMO once again more amplified but has backtracked somewhat, I don't think this comes as too much of a shock given its having serious issues at the moment.

 

The ECM reverts to its progressive run of yesterday morning by bringing the low near Greenland quickly se which cuts off the cold flow, thereafter its similar to last nights 12hrs run with the Azores high failing to rub salt into the wounds by getting into the Med, its upstream pattern later is better than the GFS and shows some hope for a change towards Christmas.

 

The GFS prolongs the cold but thereafter is much flatter over the USA, so its better earlier and not so good after that point, however it also fails to bring the Azores high into Europe which at least is a positive.

 

Overall then a coldish week, possible  problems if that shortwave develops like the ECM, to the north of the low centre could be some significant snow especially to higher ground, on the southern flank some very strong winds, as heights drop to the nw some moderation in the cold with temps returning closer to normal.

 

In terms of any snow for more central and southern areas, its marginal and still uncertain, the ECM is least positive for this, the GFS and UKMO better but again I think higher ground will be needed.

 

Although on the face of it prospects aren't great currently for some deep cold its best to look at this from a glass half full perspective, even with the PV cranking up it still on current output fails to deliver the winter nemesis and thats the Azores high pushing into the Med and the jet running ne.

Edited December 8, 2014 by nick sussex

[Gibby]

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

NEXT UPDATE TUESDAY DECEMBER 9TH 08:00

THE CURRENT GENERAL SITUATION A ridge of High pressure will cross the UK from the West today and tonight followed by a trough reaching the NW tomorrow in a strengthening SW flow.

MODELS-2 WEEK HEADLINE Rather cold and windy for most with wintry showers or longer spells of rain or sleet with snow on hills especially in the North later this week. Perhaps milder especially in the South next week. Some night frosts where skies clear.

THE JET STREAM ENSEMBLE FORECAST The Jet Stream Ensemble forecast shows the strong flow continuing just to the South of the UK this coming week before it eases North for a time but continues in an undulating fashion in conjunction between Low pressure to the North and High pressure well to the SW.

GFS OPERATIONAL The GFS operational this morning shows little change from the pattern that has been shown for some while. The model shows a sustained period of strong Westerly winds between Low pressure to the North and High to the SW of the UK. From time to time the flow turns more NW dragging colder uppers down across the UK before milder air returns East behind. This means that rain at times will be mixed in with periods of brighter and colder conditions with showers turning wintry over the hills, more especially in the North.

THE GFS PARALLEL RUN The GFS Parallel run is not available until Monday of next week.

THE GFS CONTROL The GFS control run also shows a similar pattern to the operational above but shows a more defined pull of milder tropical maritime air across the UK in conjunction with higher pressure over France through week 2 with less rainfall likely too especially over the South.

THE GEFS ENSEMBLES The GEFS Ensembles are indicative that Low pressure to the North of the UK and High to the South and SW will be the dominant pattern over the whole period. There will be alternating periods of cold and showery weather mixed with milder air at times with the trend for more of the air to be milder in the second week than week 1 as the jet flow edges North somewhat to the East of the UK.

UKMO UKMO today shows deep Low pressure to the North and later NE of the UK with a brief cold period of 24 hours or so around the start of next weekend. Very windy conditions will be dominant this week with showers or longer spells of rain at times falling as snow on Northern hills and in the South too possibly briefly at the weekend. The Day 6 chart shows milder winds encroaching over the UK from the West as winds back towards the West later with further rain at times with any snowfall becoming more and more confined to northern hills again early next week.

THE FAX CHARTS The Fax Charts show a very deep depression well to the North of Scotland with gale or severe gale West winds and rain or showers becoming increasingly wintry over the hills of the North innitially with further troughing crossing the South later this week with more prolonged rainfall here for a time.

GEM GEM this morning shows a cool and very windy period this week, often cold with snow showers over the hills especially in the North but the South too briefly near this coming weekend. As we move into next week a more pronounced shift towards milder winds from the SW will engulf the UK with some rain at times across the North and West.

NAVGEM NAVGEM this morning also shows the pattern of cold and windy conditions predominating this week with rain and showers with snow on the hills before a shift towards somewhat milder but still breezy West winds take hold at the end of the run covering the period of the beginning of next week.

ECM ECM this morning shows a very mobile Atlantic flow across the UK throughout the period of it's run this morning. The pattern will alternate between milder and windy weather with rain for all and colder and more showery periods when showers will turn to snow over the hills of the North principally but not exclusively. Temperatures overall will be close to average or somewhat below at times across the North and occasionally a little above in the South with frost restricted towards the colder and showery interludes akmost anywhere.

ECM ENSEMBLES This morning's Ensemble data remains unchanged with the overriding factor likely to be one of Low pressure situated to the North of the UK and High pressure to the SW. There will be spells ofstrong winds, rain and showers likely across all areas interspersed with colder and more showery spells with snowfall on Northern hills at times. Overall temperatures will be in the range of near or slightly below normal at times over the North and near to or slightly above average at times in the South but windchill will be a notable factor at times.

NOTABLE TREND CHANGES FROM PREVIOUS RUNS Changes in trend to the continuing strong Westerly flow of weather across the UK are slow or non-existent with some output still showing a somewhat milder trend for next week than the week to come as High pressure edges closer to the South and SE of Britain.

MY THOUGHTS The pattern of weather over the next couple of weeks illustrated by the latest outputs indicate little change in what has been shown over recent days. In basic terms there will be a lot of days when strong winds occur with rain at times in the form of showers or brief periods of more prolonged rainfall. The main interest in this otherwise static pattern is the ingress of colder polar maritime air across the UK bringing the possibility of some snowfall in places. As is always the case this is focused most towards higher ground over the North and only briefly reaching the South for a time this coming weekend as a brief shift of winds towards the North is well documented by all output. Then next week as winds back towards the West some output shows a milder phase of weather even across the North as pressure rises to the South of the UK coupled with a change of axis to the Jet flow with rain at times for all. However, there is still some evidence that the pattern will remain mixed with further colder injections around the Southern flank of depressions North of the UK through next week too as the ECM operational illustrates well today. So in my opinion the next few weeks will remain unsettled and often windy with rain at times for all and occasional snow showers over northern hills. It looks unlikely that snow will become anything other than interest value only for the vast majority of the populous of the UK with any notable settling snow reserved to hills and mountains above 300-400mtrs in the North and many will see none at all. Nevertheless, with such a volatile pattern across the UK and Northern hmisphere in general coupled with stark temperature contrasts North and South of the Jet flow across the South of the UK there will be plenty of interest from other elements of the weather other than snow to keep us on our toes and I continue to feel that at some point in the near future a flood of cold air from the North will likely give us our first main shot of Winter weather at some point in the not too distant future.

[fergieweather]

Hopefully a timely interjection, but UKMO caution (again) that medium range NWP may not be adequately reflecting ultimate broadscale outcome. First tentative signs emerging, they suggest, of *possible* pattern change (weakening of MSLP anomaly; transition to -ve NAO) second half/later December, with GloSea5 continuing to yield interesting stratospheric signals later this month. So, without wanting to sound like a stuck record, I do urge 'elasticity of thought' when assessing distant reaches of EC/GFS suites.

[IDO]

The day 16 GEFS mean anomoly would have been a good chart to post IDO. Might have even got you a star!

 

Hi BA. I was not being "funny". Looking at D16 charts from the GFS of late has been rather a chore. But there are signs that the pattern is amplifying; at least compared to a couple of days ago, when they were flat. Out of little acorns grow...

 

Anyway a soft signal for "possible" changes and one to watch.

 

The ECM mean at D10 again opposes the op height build over the N. Canadian region: 

 

A pretty flat upstream like the GEFS. We know the half life on the upcoming pattern is small and late Dec-early Jan remains my call for some potential blocking. The CFS Daily is right on cue:

 

 

The means for Jan-Mar heading that way, so T-588 and counting:

 

  

[garbagebags]

Looks like the UK may see its first 850 -10 line this weekend.

 

I have to say, its a bit sad to see everyone looking way into next week and beyond and getting down about it. I think there is a case of "not being able to see the woods for the trees" going on here (I too am guilty). 
I mean, here we are, just over a week into winter and we have -10 line forecast to hit the british Isles. God, compared to last winter thats a near miracle.

[garbagebags]

The bigger picture remains with a period of Atlantic dominated weather for around two weeks (plus). GEM is stalwart in bringing 3-4 days of mild uppers in a SW flow:

Really? I wouldnt Say this is Atlantic dominated.

[Gavin Hannah]

Really? I wouldnt Say this is Atlantic dominated.

 

 

It may not be blocked high goodness anytime soon but the LP to the north is going to give the UK a good wintry blast this week into the weekend. After that, its pointless trying to nail down the pattern but just looking at the GFS ops last night and this morning, I would say it's an upgraded in terms of cold.  The HP to the south east not as dominant. Hopefully as time progresses, we would perhaps even see this HP migrate NW. 

[IDO]

Really? I wouldnt Say this is Atlantic dominated.

 

 

Anomaly charts at that range can really mislead, especially one chart that has no context. Here are the charts for the day before and after:

 

 

There is slight transient amplification in the shortwaves allowing for a PM flow but it is Atlantic driven. The Jet highlights this:

 

 

 

And later in the run you have the split jets re-emerge double barrelling the UK:  

Edited December 8, 2014 by i'm dreaming of...

[Polar Maritime]

I've moved a few post's, Please only discuss the Model output's in here.

 

Thanks, PM.

Edited December 8, 2014 by Polar Maritime

[garbagebags]

The 06 has deepened the midweek low slightly. Really glad Im not on a boat near shetland this week. 

 

[winterof79]

How about this for verification by the under fire GFS

Here is what was predicted for today on the 30th November.

 

http://modeles.meteociel.fr/modeles/gfs/archives/gfs-2014113000-0-192.png?0

and the jet forecast

http://modeles.meteociel.fr/modeles/gfs/archives/gfs-2014113000-5-192.png?0

Here is the present set up

http://modeles.meteociel.fr/modeles/gfs/runs/2014120806/gfs-0-6.png?6

and the jet

http://modeles.meteociel.fr/modeles/gfs/runs/2014120806/gfs-5-6.png?6

 

Not bad at all.A milder interlude looks possible prior to Christmas,then we can look forward to things finally dropping into place with luck.Last winter may become a distant memory.Snow on the hills and cars this am.

[Mucka]

GFS 00z and GEM still phased the trough to our NW which accounts for the flatter patterns and AH riding in more strongly again this morning -  they are likely wrong but TWT.

 

 

While the Euros do not

 

 

Keeping the pattern more amplified. 

ECM is an improvement over yesterday while UKMO is not quite as good as it was yesterday but both maintain a cold zonal flow with only brief ridges giving temporary respite. It still looks good for a transient snow event to low levels at some stage so given we have no blocking and it is early Dec I think the output is rather better for coldies than the overall mood would seem to indicate this morning.

 

GFS 06z is a slight improvement as it looks the model is finally figuring out the energy will remain separate once again day 5 even though it quickly fails wit the upstream pattern once more making the same mistakes over and over but expect further improvement this afternoon with the GEM also looking very different to this mornings run in FI if and when it also gets to grip with the upstream pattern.

 

 

The only negative is that any sign of blocking developing after mid month is more muted this morning within GFS ensembles though we can expect any signal that far out to wax and wane. 

Edited December 8, 2014 by Mucka

[Gowon]

I know it might be gone on the next run but, there might be a bit of snow for the southerners Friday night into the morning..

 

Edited December 8, 2014 by Vivian

[IDO]

GFS 00z and GEM still phased the trough to our NW which accounts for the flatter patterns and AH riding in more strongly again this morning -  they are likely wrong but TWT.

 

 

 

While the Euros do not

 

 

 

Keeping the pattern more amplified. 

ECM is an improvement over yesterday while UKMO is not quite as good as it was yesterday but both maintain a cold zonal flow with only brief ridges giving temporary respite. It still looks good for a transient snow event to low levels at some stage so given we have no blocking and it is early Dec I think the output is rather better for coldies than the overall mood would seem to indicate this morning.

 

GFS 06z is a slight improvement as it looks the model is finally figuring out the energy will remain separate once again day 5 even though it quickly fails wit the upstream pattern once more making the same mistakes over and over but expect further improvement this afternoon with the GEM also looking very different to this mornings run in FI if and when it also gets to grip with the upstream pattern.

 

 

 

 

If you look at the ECM members at D5: 

 

The  two main clusters are split 18:17 and the op and control are in the 17. The largest cluster is more like the GFS. So it is clearly a very close call as to the transient D5 amplification. Some may say that the op and control at this range would be the call, others may say that the ECM bias on the hi-res to over amplify may suggest the other cluster? Too early to call who is right but the long and the short of it is that by D7 our sector either way is back in a westerly flow. Though the GFS 06z also hinting at Round 2 for the PM flow at around D10:

 

 

 

Interesting 06z run, though probably change by the 12z. However it develops a low on Friday in the Bay of Biscay that stalls the cold front in the south of the UK:

 

 

On the 0z the cold front headed south towards the Alps. Not saying it will be snow at sea level, though the Downs & Reigate Hill would get some IMO.

[bluearmy]

IDO - you are rightly chastised for evaluating day 16 Gfs output but no one will have issue with a day 16 gefs anomoly being posted.

It does point to the Atlantic ridge trending towards s Greenland which could tie in with Ian earlier post.

A bit more patience required

[Polar Maritime]

A cold wintry and stormy outlook continues  from the N/W, With -10 uppers close to Scotland further into the run giving blizzard conditions for parts in the North, And Snow possibility's extending further South.

 

 

[Team Jo]

Just wanted to chuck this in here from Fergie as a point of interest.. - it's in the Banter thread for those that want to view the original...

 

PS: MOGREPS & 00z EC ENS stamps now agree on signs of westerly waning into trend period. Circa 40% now show some form of continental block.

[Mucka]

 

If you look at the ECM members at D5: EPS_members.png

 

The  two main clusters are split 18:17 and the op and control are in the 17. The largest cluster is more like the GFS. So it is clearly a very close call as to the transient D5 amplification. Some may say that the op and control at this range would be the call, others may say that the ECM bias on the hi-res to over amplify may suggest the other cluster? Too early to call who is right but the long and the short of it is that by D7 our sector either way is back in a westerly flow. Though the GFS 06z also hinting at Round 2 for the PM flow at around D10:

 

gfs-0-240 (3).png  gfs-1-240.png

 

Interesting 06z run, though probably change by the 12z. However it develops a low on Friday in the Bay of Biscay that stalls the cold front in the south of the UK:

 

114-574UK.gif114-7UK.gif

 

On the 0z the cold front headed south towards the Alps. Not saying it will be snow at sea level, though the Downs & Reigate Hill would get some IMO.

 

 

I suppose I am presuming GFS is wrong somewhat and it has support from GEM. I can't tell from the ECM postage stamps as the phasing of the trough happens over Canada.

As far as the flow thereafter is concerned you  will always get a temporary westerly flow as the next low pushes in, the differences are how brief that flow will be and how deep the cold incursion behind as the more displaced the AH is to the SW the deeper and better defined the mean trough will be.

 

It may not be completely obvious that the Euros have colder zonal patterns due to keeping this upstream energy separate because of variance within the pattern overall but if you take GEM against ECM from this morning it should make it more conspicuous.

 

ECM/GEM 120

 

 

You can see how the next low is forced on  a more Easterly path with GEM while ECM slides it S/SE with the end result.

 

 

And

 

 

So while there will always be temporary spoiler ridges thrown in by the AH and the flow will always via westerly at times but the mean outcome will be a more amplified colder flow without that upstream energy merging because the AH wil lbe less influential.

There will still be colder/milder variances within these different set ups which confuses the issue but in general terms we want that low over Canada to remain a closed low and not phase with the trough as it allows the AH to ridge in, which makes the trough shallower which flattens the pattern which gives a predominantly W/SW flow rather than W/NW from day 5+ (accepting there will be variations within this theme)

Edited December 8, 2014 by Mucka