Model Output Discussion 4th Dec.2013-12z onwards.

[TSNWK]

Out to 240 and no change, another symptom of a locked in greenland vortex and associated euro high pattern FI starts much later and there is much less inter model variability.

The pattern looks locked in now until at least the middle of week commencing 15th December and that is being conservative., without some tangible changes in the plus 240 frames soon then it's more of the same until Christmas

And guess what we get a cheeky little northerly for Christmas Eve..

Edited December 8, 2013 by TSNWK

[MrSunshine]

Final frames of the 18z GFS look a tad more encouraging in my opinion, FI I know but we shall see. I expect changes in the model runs next week regarding the Christmas period. 

[snowmadchrisuk]

18z another run that wants to bring a low pressure over the Uk during the Christmas period , setting up a temporary mid Atlantic toppler and filtering down some Colder air ..... that's about 8 runs in a row ive seen that now, Could be one of them things it will drop and then bring back .. 

[Richie V]

Well from a cold point of view the 18z goes down like a cup of cold sick.

Most of April was colder than this run.

[Jason M]

Ensembles out to day 10. If its cold weather your after they are just plain ugly. Some fantastic summer charts on show.

Hopefully it will change but this does look a robust pattern we are in.

Jason

[TSNWK]

No tangible changes on this mornings metoffice run or GFS up to 240. Pattern remains locked..

[That ECM]

No tangible changes on this mornings metoffice run or GFS up to 240. Pattern remains locked..

I guess it depends on what you mean by changes. GFS between t180 and t240 is being modelled differently to previous output. There is more opportunity IMO to see the high move more north. Agreed at the surface it would feel not to different to what was being shown before, all be it cooler.Slightly encouraged this morning but that would not have been hard considering what we have looked at the last few days.

[Great Plum]

No tangible changes on this mornings metoffice run or GFS up to 240. Pattern remains locked..

I wouldn't expect any differences for the next 10 days or so - it's the post 240hrs where any major change will occur...Look at the ensembles... - little change until the 14th at the very least...http://www.wetterzentrale.de/pics/MT8_London_ens.pngChance of something cooler as keeps cropping up in FI...http://www.wetterzentrale.de/pics/Rtavn2881.png Edited December 9, 2013 by Great Plum

[Beaufort12]

ECM cooler this time +168 with -4 uppers flirting NW Ireland and Scotland. HP further East in Europe

[That ECM]

The differences between ECM and GFS at t192 would suggest that fi starts around this time frame. Prob 24 hours before. At least with model disagreement it creates some interest and discussion. Sorry not able to post charts.

Edited December 9, 2013 by That ECM

[ARNOTT ad]

Ecm much better potential this morning. Seems weird that we are having to like stronger SW wind charts but it simply holds more potential with lows closing in and high drifting away.

[IDO]

The models for the start of the weekend:

 

GEM at T120:  GFS:  ECM: 

 

Settled in the south, jet running Birmingham north varying per model, but similar synoptics.

 

As you were from there, with the MLB, but no model consensus to how far the HP sinks, and where the zonal weather crosses the UK:

 

GEM at T240:  GFS:  ECM: 

 

My preference is GFS then ECM. To be decided...

Edited December 9, 2013 by i'm dreaming of...

[Frosty.]

I think we could be in for another stormy and potentially colder spell beyond the next 7-10 days, the atlantic will be bottling up an incredible amount of energy as increasingly vigorous depressions are backed up to the sw / w / nw........the Gem & Ecm 00z show the atlantic breaking through by the end of the week or early next week and the ukmo 00z shows the high drifting further east/se, only the gfs 0z op run turns into an anticyclonic bore fest, hopefully the unsettled outlook with the jet digging south will be the way forward as we head into the christmas period with a growing risk of cold incursions.

[Nick F]

Ecm much better potential this morning. Seems weird that we are having to like stronger SW wind charts but it simply holds more potential with lows closing in and high drifting away.

Can't see any potential, for cold anyway, from this morning's ECM deter. Low heights dominate close to the NW and HP over the near continent dominating throughout the run. GFS does at least have slight amplification upstream in low resolution, which allows HP to build north across the UK - but with low heights still dominating to the north - it would be a struggle to evolve from there to something more than HP surface cold. Edited December 9, 2013 by Nick F

[Frosty.]

Can't see any potential, for cold anyway, from this morning's ECM deter. Low heights dominate close to the NW and HP over the near continent dominating throughout the run. GFS does at least have slight amplification upstream in low resolution, which allows HP to build north across the UK - but with low heights still dominating to the north - it would be a struggle to evolve from there to something more than HP surface cold.

That can easily change though, i'm already seeing signs that the euro high might not be quite the limpet it looked on previous runs, the ecm / gem are pointing to a much more unsettled outlook with a fired up atlantic.

[shedhead]

Can't see any potential, for cold anyway, from this morning's ECM deter. Low heights dominate close to the NW and HP over the near continent dominating throughout the run. GFS does at least have slight amplification upstream in low resolution, which allows HP to build north across the UK - but with low heights still dominating to the north - it would be a struggle to evolve from there to something more than HP surface cold.

Indeed Nick, the mild pattern is locked in for the foreseeable, but looking at the overnight outputs there's still a fair degree of uncertainty regarding just how zonal things become, with GFS keeping pressure considerably higher and even bringing a large anticyclone back as we enter FI.

 

 

ECM for the same time is not buying it though and is busily winding up a system out west.

 

 

Edited December 9, 2013 by shedhead

[Ian Brown]

Indeed Nick, the mild pattern is locked in for the foreseeable, but looking at the overnight outputs there's still a fair degree of uncertainty regarding just how zonal things become, with GFS keeping pressure considerably higher and even bringing a large anticyclone back as we enter FI.

 

 

ECM for the same time is not buying it though and is busily winding up a system out west.

 

 

Morning Shed, yes some intensely low heights becoming firmly established to the NW especially on the ECM. Would expect the METO to adjust their outlook later today.

[Gibby]

Good morning. A new week but will the weather be any different as we continue the run up to Christmas 2013. Here is my visualization of the output from GFS, UKMO, GEM, NAVGEM and ECM for today Monday December 9th 2013.

 

All models continue to show a period of benign weather for most areas of the UK away from the NW where it will be cloudy and windy but mild with rain at times through the coming week. Towards England and Wales the weather remains more settled and with a SW wind backing towards the SE for a day or two midweek it will become less mild for a time with a greater risk of mist, fog and a touch of overnight frost slow to clear for several days. However, by the end of the week and certainly through the weekend SW winds will bring milder air back across all areas and as winds increase generally the risk of some rain increases as weak fronts are shown to cross the UK by some output delivering occasional rain for some, even in the South.

 

GFS shows this well next weekend with one such band of rain crossing early in the weekend and another on Monday with the general trend to change the orientation of the wind flow to more of a West or NW directon as High pressure builds from the SW this time. Eventually this is shown to cover the UK with a marked drop in temperature and delivering much colder nights with widespread frost and fog problems but some crisp winter days with plenty of sunshine. The customary collapse of the High SE is shown right at the end of the run with milder SW winds slowly returning.

 

UKMO shows a weak front crossing East at the end of the week with a little rain for a time before the pattern resets somewhat though there would be more wind and troughs look like having a greater impact on many areas as we move towards next week in a mild SW flow.

 

GEM gradually shows things becoming much windier next week with the North in particular shown to experience gales and heavy rain at times as small depressions zip NE. Rain will reach the South too at times where it will stay mild but windy here too.

 

NAVGEM too recedes High pressure a little right at the end of the run but the pattern remains the same with High pressure to the SE and Low to the NW with a mild SW flow carrying troughs NE across the North and bringing these areas rain at times and there are hints that this may reach the South too with time.

 

ECM shows signals today of a much more mobile pattern eventually showing up later next week. Before we get there though there are many days of benign and quiet weather with mild SW winds just bringing the occasional weak trough East across the South next weekend while the NW sees more in the way of wind and rain throughout. Low pressure then looks like digging in closer to the WNW of the UK with troughs making inroads to more areas, but it should stay reasonably mild.

 

The GFS Ensembles are a little better this morning with the trend at least the right way for more average levels of temperatures, both aloft and at the surface to show up. It may come at a price of wind and rain at times but never much in the SE.

 

The Jet Stream continues to orientate itself NE across the Atlantic to the NW of Britain for some considerable time to come. The only change of note is likely to be a shift towards a more West to East orientation across the Atlantic and the UK at least for a time in Week 2 but there is no major signs of a major shift that would deliver anything cold to the UK as of today's output.

 

In Summary then there remains little to offer in the way of colder weather for the UK as a whole from this morning's output. With pressure high to the SE and the South later, West or SW winds are likely to predominate throughout. Through this week it looks like there may be a few days of chillier air across the South with fog and frost possibilities but these look like being swept away by the weekend by an increasing SW breeze and a little rain at the weekend. The trend thereafter appears to be a slow progression to more changeable weather with rain at times in a fresh to strong SW flow later next week.

[Nick F]

That can easily change though, i'm already seeing signs that the euro high might not be quite the limpet it looked on previous runs, the ecm / gem are pointing to a much more unsettled outlook with a fired up atlantic.

Always the optimist and I mean that in a good way. But this pattern we're in looks pretty locked in and don't think anyone can be confident in a pattern change yet to bring a chance of cold weather. Really need to shift those low heights close to the NW, either eastwards towards scandi or through retrogression.

[shedhead]

Hi Ian...yes the PV on ECM looks very menacing, both regard to intensity and it's position over Baffin. I too was surprised at METO's wording yesterday and fully expect a volte face from them today.

 

GFS has the mild air getting close to the Urals next week....next stop Ojmjakon...

 

Edited December 9, 2013 by J10

[Purga]

What a scorcher for friday!

Pretty toasty for Scandinavia right through to deep into Russia so even an easterly would be mild

Looks like Turkey is the place to head to if you want any hint of cold.

Christmas cold Turkey then it is - sorry couldn't resist...

[Tom Quintavalle]

Can't see any potential, for cold anyway, from this morning's ECM deter. Low heights dominate close to the NW and HP over the near continent dominating throughout the run. GFS does at least have slight amplification upstream in low resolution, which allows HP to build north across the UK - but with low heights still dominating to the north - it would be a struggle to evolve from there to something more than HP surface cold.

 

Totally agree with that Nick. The 06z Gfs does allow some slight amplification at the end of the high resolution part of the run, as those low heights around the Aleutian Islands/Alaska area fill out somewhat but on into the low resolution part of the run pressure falls again in that area. We then see a repeat pattern of an Atlantic high drifting across the UK and taking up residence to our east (obviously not to be taken as gospel, as its way out at the end of the run) and with those low heights seemingly entrenched to our NW, over Greenland, any attempt at blocking further north is going to be futile, as the strengthening PV looks to boss the pattern, over our neck of the woods.

As Tamara, Nick S, amongst a few other posters, have alluded to so well recently, we really do need to see a return of those strong heights over the N.Pacific (around the Aleutians/Alaska region), to re-amplify the pattern and shake things up, over our side of the pond. It's very much a case of patience being the watch-word but it's looking increasingly unlikely that anything particularly cold and wintry will be reaching our shores, this side of the Festive period.

 

Tom.

Edited December 9, 2013 by Kentish CZ

[fergieweather]

Always the optimist and I mean that in a good way. But this pattern we're in looks pretty locked in and don't think anyone can be confident in a pattern change yet to bring a chance of cold weather. Really need to shift those low heights close to the NW, either eastwards towards scandi or through retrogression.

Yes, the Shannon entropy for the pattern over at least next 10 days is low so good confidence on broadscale. Given the sizeable degree of baroclinicity in the pattern to W/NW & EC continuing to splatter 930MB lows into it south of Iceland, the key forecast challenge is just how such developments may become realised & impacts for e.g. NW Scotland. MOGREPS holds-on to the more anticyclonic feed across S/SE for longer but Exeter favour the EC/GFS more progressive story from weekend into next week. Edited December 9, 2013 by fergieweather

[Ian Brown]

Yes, the Shannon entropy for the pattern over at least next 10 days is low so good confidence on broadscale. Given the sizeable degree of baroclinicity in the pattern to W/NW & EC continuing to splatter 930MB lows into it south of Iceland, the key forecast challenge is just how such developments may become realised & impacts for e.g. NW Scotland. MOGREPS holds-on to the more anticyclonic feed across S/SE for longer but Exeter favour the EC/GFS more progressive story from weekend into next week.

Thanks Ian, why were the METO talking about below average temps in the extended period yesterday ? Perhaps waiting for the next EC32 dayer to confirm a lengthy zonal SWerley period ? 

[johnholmes]

The 500mb anomaly charts have been pretty consistent as to where the 500mb ridge centre of gravity will be, mainly around the southern end of Sweden/north Denmark. Of course then the question of where will the surface high be-hard to say, not far from there but it could be E-N-S-W and that would of course make some difference to the low level air flow but not to the overall blocking pattern east of the UK.

An interesting change shows on the ECMWF output this morning, see below. That shows a separate area of +ve heights and a ridge in the Azores are allowing the trough, so long way west to re orientate itself so that it affects the UK, still with a 500mb flow from s of west. Interesting but it will need NOAA to start to follow that idea and also the GFS 500mb anomaly to do the same to give any confidence in that becoming the pattern. Just what it would mean in the longer term, post 14 days is certainly not clear.

The MJO is predicted to finally move away from close to the origin t 2 then 3. Neither of which suggests a 500mb ridge well north of the UK. At best a broad band of upper heights between 50 and 60N from N America across the Atlantic over the UK and east into Europe and Russia. Make of that what you can, IF it turns out to be true.

http://www.meteo.psu.edu/~fxg1/ECMWF_0z/hgtcomp.html

Edited December 9, 2013 by johnholmes