Model Output Discussion - The Start Of Winter

[Newberryone]

PM shots aplenty this coming week with quite a potent one featuring next Fri/Sat, however latter stages of this am's Ecm op look very uninspiring with what has been described on here as that wretched Azores high, as it yet again threatens something less favourable from a coldies perspective 

Edited December 6, 2014 by Newberryone

[mushymanrob]

Knocker you've been banging on about this mild weather for weeks now, I still don't see any sign of it on the models apart from in FI

 

you keep going on about people 'going on' about mild...ive not seen one post anywhere that ramps mild more then what has been shown on the models, and just a week ago we had 15c !!! was that not mild?

of course we could turn this around and ask wheres all these pattern changes to cold (as in deep cold) that have been promised ever since all that northern blocking earlier last month? all those 'building blocks' that were supposed to lead to a cold spell as vaunted by some came to nothing..... nor did the eastern block that followed.

so no, theres no mild spells expected, nor are there any real cold spells for all, as nick l posted - average - below average which in december is cold (but not the deep cold most here seem to want).

[IDO]

Yes models are slowing down the overall zonal pattern so the topplers are slightly less transient and the following ridge showing slightly more respite. GEM never really goes more than average for the PM shot and continues to bring some warmer uppers in from D9:

 

   

 

No surprise that last night's 12z outlier is not repeated and GFS op is much flatter before D10: 

 

ECM also trending more towards GEM at D10: 

 

A cooler period but no widespread snow at sea-level and really nice seasonal feel as we continue to wait for blocking to develop.

 

Looking at the D16 GEFS the signal for heights to build near Greenland have all but gone as they now show a persistent mean area of low pressure in that region; the main PV lobe is in  Siberia, and any amplification now appears to be W.US and Pacific:

 

 

But to be honest there is no real signal for a HLB cluster in our region and the Russian/Siberian high may be more of a driver (small cluster) as it eases west. Still warming starting at D12 and continuing at D16:

 

 

Not all things going to plan in the strat but the chances of an SSW in January probably remain higher than no SSW.

 

Next week's storm, some "bombogenesis" incoming:

 

  NWSOPC
00Z OPC 48-Hour surface forecast w/hyperactive Atlantic, storm force lows in W & E Atlc, bombogenesis near Greenland. http://t.co/f3qDzCInhS
06/12/2014 07:22 Edited December 6, 2014 by i'm dreaming of...

[knocker]

The 00z NCEP ens. Quite similar to last night's other models.

 

Edited December 6, 2014 by knocker

[Frosty.]

My ticket for the polar express has just arrived..and in mint condition too

 

The Gfs 00z op run shows a triple whammy of cold incursions throughout the run, the most potent being late next week but it's a recurring theme of reloading cold shots from polar regions so we should all see at least some snow in the next few weeks along with sharp frosts at times..all aboard..choo choo  

[Long haul to mild]

you keep going on about people 'going on' about mild...ive not seen one post anywhere that ramps mild more then what has been shown on the models, and just a week ago we had 15c !!! was that not mild?

of course we could turn this around and ask wheres all these pattern changes to cold (as in deep cold) that have been promised ever since all that northern blocking earlier last month? all those 'building blocks' that were supposed to lead to a cold spell as vaunted by some came to nothing..... nor did the eastern block that followed.

so no, theres no mild spells expected, nor are there any real cold spells for all, as nick l posted - average - below average which in december is cold (but not the deep cold most here seem to want).

 

There is certainly a pattern change afoot in that only a week ago the models were touting the Azores High to be the main player in the UK weather this coming week and there was plenty of talk about the pleasant anticyclonic, quiet weather it would bring.

 

Now however, we are looking at a wet windy and cold week ahead, with increasing chances of Northerly incursions.

 

What this has taught relatively inexperienced people like myself is that the models are frequently wrong after about 7 days. That doesn't mean I don't value their existence or LRFs etc, but only for gaining more knowledge in the overall patterns that make up our weather. Actually trying to get into specifics is fraught with danger.

 

So I take no notice of a mild forecast at 14 days out in the same way as a cold one.

Edited December 6, 2014 by Polar Maritime
To remove off topic reverences.

[Polar Maritime]

A few post's have been moved, Model Discussion only please in here.

 

PM

[nick sussex]

Maybe its too early but I'm still trying to decide what this ECM ensemble spread shows:

 

Pressure:

 

 

The 850's:

 

 

It does seem that over the west of the USA and Canada theres room for a more amplified set up which would explain that drive of warmer air north.

 

 

 

 

 

 

[Gibby]

HERE IS MY LATEST ANALYSIS FROM THE OUTPUTS OF THE WEATHER COMPUTER PREDICTION MODELS FOR TWO WEEKS FROM 8AM TODAY SATURDAY DECEMBER 6TH 2014.

NEXT UPDATE SUNDAY DECEMBER 7TH 08:00

THE CURRENT GENERAL SITUATION A cold front will move down over the UK from the NW later today and tomorrow followed by a cold and showery WNW 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. Some night frosts where skies clear.

THE JET STREAM ENSEMBLE FORECAST The Jet Stream Ensemble forecast shows the flow positioned to the South of the UK with cold zonal weather the most likely with rain or showers for all falling as sleet and snow at times in bluster west or NW winds.

GFS OPERATIONAL The GFS operational this morning shows a lot of rather cold and unsettled weather across the UK as the pattern of Low to the North and occasionally NW and NE and High to the SW persists. There is spells of wet and windy weather shown for all at times followed by spells of colder and clearer weather with wintry showers across the North and West in particular. It is shown to be often windy too.

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

THE GFS CONTROL The GFS control run maintains a similar pattern to the operational with winds from a Westerly point alternating with more NW or even North winds at times as each weather system moves away East. Occasional rain followed by wintry showers will be a repeated process through the run with snow at times over most high ground.

THE GEFS ENSEMBLES The GEFS Ensembles maintain a period of zonal Westerly winds over the next two weeks circulating around Low pressure to the North and High to the South. As a lot of colder air interjects at times there will be wintry showery type weather for many areas too with frost and snow at times over even modest high ground on occasion.

UKMO UKMO today shows deep Low pressure to the North of the UK with a strong, cold and unstable Westerly flow over the UK. Showers or longer spells of rain with sleet and snow at times over high ground look the most likely scenario for all areas later next week.

THE FAX CHARTS The Fax Charts show a cold front moving SE across the UK tonight and again towards midweek, each accompanied by strong winds cloud and rain. In between will be a cold and showery WNW flow particularly later in the period with some frost by night early in the week as a ridge topples across the UK from the West.

GEM GEM this morning shows a very unsettled and cold period next week as a deep Low crosses East to the North of Scotland and then SE down over NW Europe tutning winds into the NW or North with wintry showers and strong winds for many as a result. Later in the run pressure is shown to rise markedly as a ridge moves across from the West with widespread frost before milder Westerly winds cross the UK from the Atlantic later with rain at times.

NAVGEM NAVGEM also shows strong Westerly winds developing through next week and once a band of squally rain moves through cold and showery conditions will prevail and as winds turn more NW later in the week wintry showers across Northern and Western hills could extend to all areas later.

ECM ECM this morning shows a variation on the same theme as the others with a chilly and unstable WNW flow across the UK following the band of squally rain towards midweek. Troughs in the flow enhance the showers at times before winds turn more NW later and rising pressure from the SW dampens down the showers from the SW late in the period. Many of the showers will be wintry especially on higher ground and this may extend to lower levels too at times especially later in the week and next weekend.

ECM ENSEMBLES This morning's Ensemble data maintains the pattern of Low tpressure to the North and High near the Azores but this is made up of a variation of options some of which do include Northerly incursions with snow showers in places and others with a milder Westerly pattern with rain at times so clearly nothing definitive can be drawn from these this morning.

NOTABLE TREND CHANGES FROM PREVIOUS RUNS The main theme is for a lot of rather cold zonal Westerly winds to prevail across the UK between deep Low pressure to the North and High pressure near the Azores with the usual ebbs and flows in the flow as each weather system passes to the North.

MY THOUGHTS The pattern most commonplace within all the output this morning is for a sustained period of rather cold and unstable, strong Westerly winds to blow across the UK over the next couple of weeks. With the air source often coming from Newfoundland or Greenland the air will be none to warm at times and with sufficient instability in the form of showers there will be loads of wintry showers peppering our Northern and Western areas in particular driven well inland at times in the strong flow. There could also be minor disturbances within the flow delivering more prolonged rain or sleet at times too and with time the flow could tilt more NW or even North which will enhance the wintriness within the showers to even more areas at even modest height levels later. However, the distribution of showers will shift more towards the North and sheltered Southern and pater Western areas would see less showers and possible frosty nights as pressure rises somewhat from the SW. So having dealt with the pattern of the next few weeks where will that leave us as we approach Christmas. Well I still feel as yesterday that it's too the North we have to continue to look for our cold weather this side of the New Year and I'm fairly certain that there will be some interesting weather not too dissimilar to the pattern we are looking towards currently to maintain at least the interest and possibility of snow over the Christmas week and nowhere over the UK could be immune. I do feel though that it will be made up of fleeting snowfalls chiefly over the hills and lying snowfall may well be very temporary at best on low ground and in the South but if our friend the Azores High is allowed to ridge North over the Atlantic at some point over the next few weeks as others on here I wouldn't be surprised to see a plunge into a more sustained and UK wide cold shot from the North develop but for the moment I think the current expected pattern shown for later next week could stick around for quite a while. Having said that it is at least a more seasonal outlook than the benign mild weather with High pressure over Europe than we endured a few weeks back.

[fergieweather]

Re 'pattern change': not something UKMO expect into next 10-15d, with both EC and GloSea5 showing strong dipolar anomalies (low heights N of UK, high to S) with strong jet continuing westerly mobility theme. Colder outbreaks will occur periodically but they reckon temperature overall coming out as average or a tad above through this forecast period (NB not 'mild'). Frequently very windy. Shannon Entropy low into this trend period, indicative of decent confidence on broad theme.

(Edit: Thus supporting Gibby summary above)

Edited December 6, 2014 by fergieweather

[bluearmy]

I think the upstream situation is dependant upon the split flow off the eastern seaboard that will become more of an issue through week 2. At the moment, the ens behind day 10 are not best resolved to work this out. the general continuation of jet nw/se axis with depressions running west to east then dropping heights to our east with the Azores ridge rising and falling in tandem with each surge of the jet across the Atlantic. As time has ticked down, we have seen ops both over amplify the ridge and also flatten the pattern somewhat. So it's not a straightforward 'flatter pattern nearer the time' set up.

whilst the major anomolys week 2 remain high w Russian, canada, w Atlantic and low n pacific and east Siberia, there remains plenty of wriggle room for the detail to be decided in Europe. as I said, I think the energy distribution of the upstream split flow will dictate where we go.

[phil nw.]

We are having to remove comments and the odd post, which are nothing to do with model discussion.

Just a request to keep to the charts/data not individuals.

Cheers all.

[IDO]

I think the upstream situation is dependant upon the split flow off the eastern seaboard that will become more of an issue through week 2. At the moment, the ens behind day 10 are not best resolved to work this out. the general continuation of jet nw/se axis with depressions running west to east then dropping heights to our east with the Azores ridge rising and falling in tandem with each surge of the jet across the Atlantic. As time has ticked down, we have seen ops both over amplify the ridge and also flatten the pattern somewhat. So it's not a straightforward 'flatter pattern nearer the time' set up.

whilst the major anomolys week 2 remain high w Russian, canada, w Atlantic and low n pacific and east Siberia, there remains plenty of wriggle room for the detail to be decided in Europe. as I said, I think the energy distribution of the upstream split flow will dictate where we go.

 

I think the long wave pattern is quite set in the 8-14 day period, as the GEFS have been suggesting for a while. NOAA are giving "high confidence" in the US pattern, so downstream as you say the UK is subject to variations in the overall theme. That signal is a broadly westerly flow with possibilities of a flat to a more amplified shortwave ridge-trough combo. There is no sign of a ridge developing into a mid-latitude high or a trough digging south/SE and amplifying the Atlantic. The surface conditions will no doubt be cooler if there is more amplification, but in most of these cases the models meet in the middle; so just normal December weather looks the call IMO.

 

The 2m temps for London:  NOAA 8-14: 

[Summer Sun]

The latest snow accumulation map shows the snow risk getting much further south on this run during the next 3 to 6 days totals for parts of western Scotland look to be really mounting up could be looking at a foot of snow for some of the highest parts by later next week

 

[TonyH]

The latest snow accumulation map shows the snow risk getting much further south on this run during the next 3 to 6 days totals for parts of western Scotland look to be really mounting up could be looking at a foot of snow for some of the highest parts by later next week

 

Pity no scale on that SS

[Nick F]

Re 'pattern change': not something UKMO expect into next 10-15d, with both EC and GloSea5 showing strong dipolar anomalies (low heights N of UK, high to S) with strong jet continuing westerly mobility theme. Colder outbreaks will occur periodically but they reckon temperature overall coming out as average or a tad above through this forecast period (NB not 'mild'). Frequently very windy. Shannon Entropy low into this trend period, indicative of decent confidence on broad theme.

(Edit: Thus supporting Gibby summary above)

 

Yes, some conflicting signals from different sources, if we get to phase 7-8 of MJO potential for a pattern change in next few weeks. However, reading the latest AER analysis and forecast issued yesterday, they seem to think the AO will be neutral/+ve for the next few weeks, the NAO perhaps strongly +ve with a temporary strengthening of the PV, also wave propagation weakening. But, they seem confident of AO dropping by the end of the month, with even a hint at a SSW in January:

 

https://www.aer.com/science-research/climate-weather/arctic-oscillation

 

However, depsite the strong vortex to our north over Greenland and Norwegian Sea, we are seeing cold zonality and also enough amplification over the Atlantic following the mid-week's low track towards Norway to keep the cold feed going until next weekend at least ... so we are doing well I think, very well, out of the current pattern. Even hints of temporary snow across central and southern areas later next week on GFS ... but plenty of snow to come for northern areas over the coming 7 days, even to lower levels at times.

[Duane S.]

Re 'pattern change': not something UKMO expect into next 10-15d, with both EC and GloSea5 showing strong dipolar anomalies (low heights N of UK, high to S) with strong jet continuing westerly mobility theme. Colder outbreaks will occur periodically but they reckon temperature overall coming out as average or a tad above through this forecast period (NB not 'mild'). Frequently very windy. Shannon Entropy low into this trend period, indicative of decent confidence on broad theme.

(Edit: Thus supporting Gibby summary above)

With the current setup and teleconnections in the medium term I can't say I am surprised at all other than the 'temperature overall coming out as average or a tad above' comment. I would have thought average and a tad below  is more likely but guessing the Met see more of a westerly then Northerly element.

[winterof79]

Yes, some conflicting signals from different sources, if we get to phase 7-8 of MJO potential for a pattern change in next few weeks. However, reading the latest AER analysis and forecast issued yesterday, they seem to think the AO will be neutral/+ve for the next few weeks, the NAO perhaps strongly +ve with a temporary strengthening of the PV, also wave propagation weakening. But, they seem confident of AO dropping by the end of the month, with even a hint at a SSW in January:

 

https://www.aer.com/science-research/climate-weather/arctic-oscillation

 

However, depsite the strong vortex to our north over Greenland and Norwegian Sea, we are seeing cold zonality and also enough amplification over the Atlantic following the mid-week's low track towards Norway to keep the cold feed going until next weekend at least ... so we are doing well I think, very well, out of the current pattern. Even hints of temporary snow across central and southern areas later next week on GFS ... but plenty of snow to come for northern areas over the coming 7 days, even to lower levels at times.

Hi Nick,just read that update on the strat thread.Fantastic insight and a few would do well to digest it.Model watching prior and during the festive period will be eagerly anticipated.I agree we are for once about to be on the favourable end of the spectrum of weather that is available to us under the current set up.Enjoy the polar westerlies I say,there will always be fronts embedded in the flow to look out for.

[Captain Shortwave]

With the current setup and teleconnections in the medium term I can't say I am surprised at all other than the 'temperature overall coming out as average or a tad above' comment. I would have thought average and a tad below  is more likely but guessing the Met see more of a westerly then Northerly element.

The ensembles for week 2 do such that the trough over or east of the UK will begin to lift out suggesting a return of a milder westerly regime.

GFS looks a little better

GEM ens suggest a westerly pattern

That said can the ensembles be trusted at this timeframe? Not too sure on that.

[Long haul to mild]

We are having to remove comments and the odd post, which are nothing to do with model discussion.

Just a request to keep to the charts/data not individuals.

Cheers all.

Fair point and apologies if my original comment took the discussion off track; that was certainly not my intention. My point was more that I never see any model output here that could possibly lead to some of the very specific forecasts we see being made for dates almost three weeks hence.

On to the 6z Gfs and still looking like a windy week ahead with some secondary depressions spawning off the main trough.

[IDO]

Three PM shots in the next 6 days:

 

Tomorrow:   Later Tuesday:  late next week: 

 

None initially look likely on the GFS 06z op of bringing snow at sea level south of Birmingham. However knowing the 06 there should be some amplification from D7.

[ItNeverSnowsInWindsor]

Some big differences showing between the GFS 06Z and 00Z at T162 with a strong mid-Atlantic ridge showing in the 06Z.

 

Edited December 6, 2014 by prolongedSnowLover

[stratty]

............6z showing interest down south for snow for next weekend with the heavier precipitation (can't post charts atm)

[The Eagle]

6z prolongs the polar maritime regime. The jet pattern is consistently northwest/southeast. Good for some at times and would deliver snow to many occasionally.

[Barry12]

IDO, you've used the 7am chart on Sunday, when the cold doesn't move in until the afternoon/evening. Monday is also looking like being the coldest day, and you've completely missed it out...

Edited December 6, 2014 by Barry95