Model Output Discussion - The Start Of Winter

[Barry12]

The theme continues on GFS 18z with the Azores high backing further west again, which results in the mild air being even more brief before the cold PM airflow moves in. Snow to lower levels in the North would be possible again from day 7 onwards if this run verified.

 

http://modeles.meteociel.fr/modeles/gfs/runs/2014121218/gfs-1-174.png?18

 

http://modeles.meteociel.fr/modeles/gfs/runs/2014121218/gfs-1-192.png?18

 

http://www.meteociel.fr/modeles/gfse_cartes.php?mode=1&ech=204

 

Mild air does return at 228 hours, but as ever will it make it into the reliable?

[Tim Bland]

Could be a nice end to the pub run! good Atlantic riding and WAA up to Greenland. Hopefully over the weekend we will start seeing hints of what the Metoffice are seeing for after Xmas

http://www.meteociel.fr/modeles/gfse_cartes.php?ech=336&code=code&mode=0&mode3h=0&runpara=0&carte=1

[Mark Bayley]

GFS 18z less of a horror show than the ECM. FI is colder rather than milder with the PV looking disrupted by the end of the run. Wintry showers in the north for Xmas day. Those expecting sustained cold before new year will be disappointed, although i'd happily take something akin to the 18z. I note the strat warming is slightly upgraded which should aid any PV disruption. Any SSW seems reserved for the new year.

Edited December 12, 2014 by Mark Bayley

[DAVID SNOW]

Could be a nice end to the pub run! good Atlantic riding and WAA up to Greenland. Hopefully over the weekend we will start seeing hints of what the Metoffice are seeing for after Xmas

http://www.meteociel.fr/modeles/gfse_cartes.php?ech=336&code=code&mode=0&mode3h=0&runpara=0&carte=1

 

Indeed Tim, but I will keep my powder dry until those 'hints' become a > probability.

Edited December 12, 2014 by DAVID SNOW

[festivalking]

Indeed Tim, but I will keep my powder dry until those 'hints' become a > probability.

hints>probability>potential>sub120>.........downgrade

[Vorticity0123]

For the ones looking for a nice new way of analysing weather synoptics (or charts), Meteociel has a chart viewing option which enables one to 'visualize' the flow in the atmosphere by means of an interactive 3D viewer (somewhat similar to earth.nullschool.net viewer, but then with a few more and different features). The link is given below:

 

http://www.meteociel.fr/modeles/gfse_3d.php?lat=49.75&lon=0.5&ech=138&zoom=6

 

A really nice example of this visualization can be found by checking the 'temp 2m + vent 10m' (2 meter temperatures and 10 meter wind), at Wednesday, 17 December, 19Z. As an illustration of what can be seen there, below is the 850 hPa temperatures forecast of the GFS for the same date, but then from the standard Wetterzentrale view (the Meteociél images cannot be uploaded in this way as far as I am aware).

 

GFS 850 hPa temperatures and surface level pressure, 18Z run, T+120 H.

 

From the chart given above, it can be seen that the south of the UK is located between two fronts, with the warm front being located over Germany (red line). Furthermore, a cold front is oriented ESE-WNW just to the north of the UK (which can be seen by the very sharp temperature gradient there, blue line). The southern part of the UK itself is therefore located in the warm sector. This is made evident by the fact that the southern part of the UK is located in very warm 850 hPa temperatures for the time of the year (over 10*C in the extreme south).

 

On the Meteociel charts given in the link above, this weather pattern is beautifully evident. This is definitely the case at the cold front, where the temperature gradient is very large (large change in temperature over a small distance), and there is also a pronounced wind shift (the wind blows from the northwest north of the cold front, and from the southwest south of the cold front).

 

With the Meteociél link, it is also possible to view ensemble forecasts from the GFS at any location. Also, GFS sounding forecasts can be accessed at any random location. This can all be done by clicking with the right mouse button on any location one wishes to analyse.

 

Hope you like it .

 

Sources:

www.meteociel.fr/modeles/gfse_3d.php?lat=49.75&lon=0.5&ech=138&zoom=6

http://www.wetterzentrale.de/topkarten/fsavneur.html

http://www.atmos.illinois.edu/~snodgrss/Midlatitude_cyclone.html

Edited December 12, 2014 by Vorticity0123

[Tim Bland]

GFS (P) shreds the PV post Xmas

http://www.meteociel.fr/modeles/gfse_cartes.php?&ech=348&mode=0&runpara=1&carte=1

http://www.meteociel.fr/modeles/gfse_cartes.php?ech=360&code=code&mode=2&mode3h=0&runpara=1&carte=0&runpara=1&

Edited December 12, 2014 by Tim Bland

[Penrith Snow]

That's a good pub run, much more amplified in FI with cold weather sweeping south into the eastern US and Western Europe and not a Bartlett in sight.

Too much chopping and changing with the models and it's interesting that the MetO ignore all these swings in their MRF and I think from now on I will do the same.

So if is cold north westerlies over Christmas as indicated by the guys at Exeter I will not be complaining.

Andy

[Snowman.]

The Para does a better job at developing -EPO ridge but still nothing that impressive.

 

 

Take a look at the latest CFS run

 

http://www.meteociel.fr/modeles/cfse_cartes.php?ech=354&mode=0&carte=1&run=0

 

While a beauty look at what happens over the Eastern Pacific something to look out for as we head towards the new year to at least get us in a -AO pattern and disrupt the vortex.

Edited December 12, 2014 by SN0WM4N

[fergieweather]

Yes, the pressure patterns into Xmas week are very reminiscent of the Meto contingency planners outlook for winter,

very positive NAO at least for the first part of winter.

UKMO expect NAO phasing more neutral through the next week or so. First weakly -ve NAO cluster we've seen in recent EC-EPS now appears in back end of today's 12z suite but way out at T+360, needs to be taken with due caution(!). Nonetheless, shift remains in line with ongoing UKMO medium range expectation. Edited December 12, 2014 by fergieweather

[blizzard81]

UKMO expect NAO phasing more neutral through the next week or so. First weakly -ve NAO cluster we've seen in recent EC-EPS now appears in back end of today's 12z suite but wsy out at T+360, needs to be taken with due caution(!). Nonetheless, shift remains in line with ongoing UKMO medium range expectation.

Thank you for that update Ian. That is positive news for the coldies. We need consolidation on this solution from now on.

The best bit about this news from Ian is that there is some consolidation in the long term between ECM and Glosea5.

Edited December 12, 2014 by blizzard81

[fergieweather]

Thank you for that update Ian. That is positive news for the coldies. We need consolidation on this solution from now on.

The best bit about this news from Ian is that there is some consolidation in the long term between ECM and Glosea5.

Yes, but sizeable salt pinches required at this tentative juncture, plus clear recognition that even pattern change / -ve NAO shouldn't be confused with the guaranteed snowmageddon characterising the voodoo of Maddenology, versus the cautiously incremental analysis & prognosis expected from meteorology.

[Man With Beard]

Encouraging updates for coldies on charts we cannot see, then, but on the charts we can see, the overall conclusion must be more of the same for the next 7-10 days, with an ongoing tussle between an Azores High that occasionally suggests it wants to move into the UK, and a jet that hints at the occasional dive from NW to SE, bringing more of a cold bite on the back of passing depressions.

Neither camp seem to be making strong moves though, perhaps Azores High on ECM slightly, the northern lows having the edge on the GFS - but the moves are fairly indecisive, so the end result will probably be more NWlies rather than SWlies, cold enough for snow on northern hills for periods and possibly at some lower levels just for a few hours - frosts not uncommon - oddly though it won't really feel like a cold spell away from the north, the CET may manage to stay below average throughout the period, as the Azores High may fail to get in a position to give us more than transient mild spells.

Oh, and one or more storms to come for the north, and squally frontal bands pushing south every couple of days.

Beyond that, well, waiting for the NH pattern to change feels like watching a set of dominoes, waiting for someone to push the first one and then the others will fall too. But there have been very few hints that this will happen even in the 10-15 day period. Still early days in winter, though.

[blizzard81]

Yes, but sizeable salt pinches required at this tentative juncture, plus clear recognition that even pattern change / -ve NAO shouldn't be confused with the guaranteed snowmageddon characterising the voodoo of Maddenology, versus the cautiously incremental analysis & prognosis expected from meteorology.

Feet always firmly on the ground Ian  

[blizzard81]

Much colder runs on the GFS 18z ensembles from Xmas Eve onwards compared to the 12z. Consolidation is the watchword

tonight. Lets see if we can consolidate on the 00z runs

Keep the faith coldies

Edited December 13, 2014 by blizzard81

[easton888]

I've just ordered 10 Kg of salt. Not to throw on the path when it starts snowing in London, but to chuck on the model updates every 6 hours. Should keep me going till the 25th.....

[Kentspur]

Some cracking beasterly CFS charts for second week of Jan showing out in FI - let's hope some of these start appearing over the next couple of weeks among the more accurate models in a closer time frame

[ItNeverSnowsInWindsor]

Has the GFS 18Z had a few cocktails or is it smelling the coffee and reflecting the Met office 'signal' in deep FI ?

[Recretos]

When that ridge starts crawling towards Greenland, dont forget which models were the first and most direct about it.

Before I go into more details, I wonder how many of you are familiar with NCEPs GEFS Reforecast 2 project/model?

To quote ESRL:

"The ESRL/PSD 2nd-generation Reforecast Project has produced a dataset of historical weather forecasts generated with a fixed numerical model, using the 2012 version of NCEP's Global Ensemble Forecasting System (GEFS). This Reforecast V2 dataset consists of an 11-member ensemble of forecasts, produced every day from 00 UTC initial conditions from Dec 1984 to present. The horizontal resolution of GEFS is T254 (about 50 km) out to 8 days, and T190 (about 70 km) from 8-16 days. Real-time forecasts are ongoing.

Among the advantages associated with this long reforecast dataset is that model forecast errors can be diagnosed from the past forecasts and corrected, thereby dramatically increasing the forecast skill. Past results have shown that the improvements may be particularly large for medium-range forecasts and for forecasts of relatively uncommon events such as heavy precipitation."

The FTP is offline atm. so I will plot the R2 a bit later. In the mean time, yesterdays ECM really began to spice up the Atl. ridge.

(image removed on request)

Edited December 13, 2014 by Recretos

[mushymanrob]

some premature posts writing off mild weather last night... both the ecm and gfs this morning (00z) have shifted towards a more mild outlook..

 

 

 

 

thats alot of milder days on these runs...

... now im not suggesting that these will verify... and this outlook may well have changed by the next runs, but cracking open the champagne everytime abit of mild is delayed really isnt the first sign of a pattern change until subsequent runs support it...

meanwhile

 

 

suggests a strong azores high ridging in towards the uk... and that would tend to support a milder outlook then a colder one.

itll be very interesting to see if stratospheric warming actually does bring about a major pattern change. being uneducated in these dynamics i remain sceptical until i see something in the reliable/semi reliable. and i dont mean that as any disrespect to the members who do have an understanding of the strat warming consequences, and that applies no matter what weather type such an event might produce.

Edited December 13, 2014 by Osbourne One-Nil
because there's no such word as varify

[TEITS]

some premature posts writing off mild weather last night... both the ecm and gfs this morning (00z) have shifted towards a more mild outlook..

 

In my opinion Mushy the model output shifted many days ago to a milder outlook as I have suggested in previous postings. Whilst we might see a very brief dip in temperatures around the 19th, thereafter milder weather is the trend and locations such as SW England could become very mild i.e temps 13/14C.

 

http://max.nwstatic.co.uk/ensimages/ens.20141213/00/t850Cambridgeshire.png

[IDO]

The GFS op is in line with one of the clusters where the PV gets reorganised during week 2 and turns the UK milder:

 

 

Unfortunately this has been just a strong signal in FI than the more amplified cluster. The GFS P offers another cluster, where the PV remains mobile and disorganised but with little sign of blocking:

 

 More average temp wise on this run.

 

Looking at the ensembles and this morning compared to the 12z little change. They may be in the throws of working out a pattern change (ridge towards Alaska) or it could be background noise. No definitive trend from the 12z so a watching brief. However even at D16 in the meridional members are really still not getting the cold to the UK yet (end December). So early January looking the most likely call for a trop led pattern change if the signal grows. However a continuation of the current pattern remains the most likely scenario even then.

 

In the next 10 days it remains clear in the UK sector that we remain under the zonal flow, consisting of PM and TM flows. On this run an equal mix of the two so averaging out:

 

ECM @D10:   GEM: 

 

London 2m temps for the next 16 days. Not much sign of cold there: 

 

Good confidence in the lead up to Christmas 22-24th for a UK warm sector.

 

 

 

[tinybill]

Much colder runs on the GFS 18z ensembles from Xmas Eve onwards compared to the 12z. Consolidation is the watchword

tonight. Lets see if we can consolidate on the 00z runs

Keep the faith coldies

i agree  f1 starting  to look better reg xmas    the charts are looking like they could be going colder by the end of next week we might be able to call it  far to early at the moment!!!

[Gibby]

HERE IS MY LATEST ANALYSIS FROM THE OUTPUTS OF THE WEATHER COMPUTER PREDICTION MODELS FOR TWO WEEKS FROM 8AM TODAY SATURDAY DECEMBER 13TH 2014.

NEXT UPDATE SUNDAY DECEMBER 14TH 20:00

THE CURRENT GENERAL SITUATION A ridge of High pressure will cross SE across Britain today followed by a milder SW flow ahead of a cold front approaching the North and West of the UK tomorrow.

MODELS-2 WEEK HEADLINE Remaining changeable with rain at times especially across the North and West. Temperatures generally close to or a little above average but a few colder periods over the North when showers could turn wintry.

THE JET STREAM ENSEMBLE FORECAST The Jet Stream Ensemble forecast continues to show signs of maintaining a West to East flow in the vicinity of the UK over the next few weeks. However, the speed of the flow is looking like weakening with time as the Jet flow filters first further north over the UK and later back South to lie South of the UK post Christmas.

GFS OPERATIONAL The GFS operational this morning shows a continuation of the Westerly flow through the next 5- 7 days with rain at times and further wintry showery incursions across the North. In the days that run up to Christmas pressure rises over the South with drier and more settled conditions possible with frost at night while the North maintains a Westerly feed with rain at times and milder periods. Late in the period with High pressure over SE Europe the weather become milder again in a SW flow across the UK.

THE GFS PARALLEL RUN The GFS Parallel run is broadly similar in structure with latter details day to day not mportant at this range but with the jist of it showing higher pressure developing close to the South of the UK near Christmas with bands of rain off the Atlantic principally affecting the North more than the South with frost and fog patches possible under the ridges more likely over the South later before High pressure ridges North over the Atlantic at the end of the run with a cold North flow affecting all then..

THE GFS CONTROL The GFS control run today maintains a basically mobile Westerly flow across the UK over the period leading up to Christmas. There will be spells of milder and rainier conditions alternating with short colder periods with showers especially across the North. Later in the period a more pronounced push of High pressure affects the South at times with colder and less breezy weather more common with frost and fog patches at night between short periods of rain and cold conditions with snow on hills as Low pressure sinks SE across the UK post Christmas.

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 continue to be dominant through much of the period but the trend towards a weaker Jet profile and weaker pressure gradients over the UK opens the door for other solutions including cold ones under Northerly winds to be shown within the ensemble pack.

UKMO UKMO today shows a strong Westerly flow across the UK towards the middle of next week with deep Low pressure to the North. With temperatures close to average it will feel chilly in the wind and all areas will see further spells of rain and showers at times with a some snow on the higher Northern hills in the showery periods between rainbands.

THE FAX CHARTS The Fax Charts show a couple of occluded fronts crossing SE over the UK in the coming days bringing rain at times and showers behind them, wintry over hills in the North. Towards midweek a warm front with a more proniunced warm sector crosses England and Wales with rain at times before the North sees a cold front cross midweek with a return to colder and more showery conditions once more. Generally quite windy at times.

GEM GEM shows little change in conditions to that we have experienced over recent days with spells of rain alternating with colder NW winds with showers, wintry in the North. Later in the run the trend towards pressure rising across the South and later to the West over the Atlantic brings quieter and more settled conditions across the South with some patchy frost and fog at night. As we approach Christmas High pressure is shown ridging North over the Atlantic with a spell of mild westerly wins being replaced by colder northerlies in the days up to the big event with wintry showers developing over the North.

NAVGEM NAVGEM continues to show the pattern to which we have become accustomed of late with deep Low pressure to the North and High pressure to the SW sending spells of milder west winds and rain over the UK alternating with colder, windy and showery NW winds when showers turn to snow over high ground in the North. It too shows hints of pressure rising North over the Atlantic late in the run.

ECM ECM this morning shows a mobile Westerly type pattern maintained through it's duration this morning with all of the UK weather through the period generated over the Atlantic. As of late there will be spells of rain alternating with colder and windy periods with showers, wintry in the North. High pressure does show signs of becoming somewhat more influential in the South later by a reduction in the amounts of rainfall and in the North by bringing strong but milder Westerly winds for longer periods than currently. It currently shows a mild and benign looking Christmas over the UK as a whole..

ECM ENSEMBLES Due to work commitments I am unable to report on these this morning as of time of release of this report they had not been issued.

NOTABLE TREND CHANGES FROM PREVIOUS RUNS A slow trend for more members within model groups that a trend towards High pressure ridging North into Southern Britain at tmes or North over the Atlantic later in the period towards Christmas is indicated this morning but progress and extent is very sketchy and limited currently.

MY THOUGHTS In these thoughts of mine this morning I am not going to dwell on the fact that the models continue to show variations on a well worn track that Westerly winds between Low pressure to the North and High pressure to the SW continue to be the overriding factor within the models again this morning. However, reading between the lines there are a few small and some would say minute but subtle differences in the pattern that show up towards Christmas and more likely thereafter. It looks increasingly likely that High pressure will gradually exert more influence of primarily Southern britain in the run up to Christmas. This will of course mean mild Westerly winds over the North with further rain at times and perhaps less interventions of colder polar maritime air for a time. In addition behind each cold front comes another surge of High pressure eventually from the West which shows more inclination in trend to push north over the Atlantic with time and although in the time frame of this morning's output this is not achieved to any great extent it could spell the first signs of a pattern change as High pressure becomes more dominant to the West of the UK and later NW as the Jet flow pattern continues to show signs of weakening in response to other factors within the atmosphere towards the New Year. I continue to maintain that our best chance of cold weather this year will be from the North and not East and although there is little concrete evidence to support this in a huge way this morning the first baby steps are there but it is a long way to go before a change in pattern will achieve a common theme within extended outputs but I believe the first steps of change are beginning to become apparent within the longer term outlooks this morning and if the info supplied from the Met who have access to much more than we can see is to be right then we could begin to realise what they say about conditions by early January could begin to bear fruit soon within the models. Watch this space.

[mushymanrob]

In my opinion Mushy the model output shifted many days ago to a milder outlook as I have suggested in previous postings. Whilst we might see a very brief dip in temperatures around the 19th, thereafter milder weather is the trend and locations such as SW England could become very mild i.e temps 13/14C.

 

http://max.nwstatic.co.uk/ensimages/ens.20141213/00/t850Cambridgeshire.png

 

you may well be right dave, i suspect it but am not convinced. i certainly wouldnt like to call it as a cold pattern could emerge.