Model Output Discussion - The Run In To Christmas

[kumquat]

Met Office very possibly wrong. Wouldn't be the first time. As per usual quite cagey and "safe" around the Christmas forecast (Christmas day, Boxing day) until the last second. I think that they disclaim all this by their wording anyway, so they've not committed either way thus far.

[Downpour]

I saw that too re the extended BBC outlook. That forecast of a milder Boxing Day doesn't seem to tally up with this though...

Strange forecast from Darren Bett - despite his personal preference for mild solutions I see little evidence from the models to support his analysis

[SMU]

The 18z can be summerised very easily-

 

18z GFS poor. ( not as good)

18z GFS (p) Great.

Edited December 17, 2014 by Steve Murr

[Captain Shortwave]

GFS

The Atlantic low is a pain and pushes in a ridge right over the UK, cold and frosty with sunny spells. That low looks like snatching defeat from the jaws of victory by forcing the ridge through the UK.

 

GFS parallel

Certainly potential for showers anywhere, wintry to low levels. A possibility of a white Christmas for some (especially over higher ground)

Large differences in how low pressure in the Atlantic is handled which potentially alters what weather we will see for the big day. We can't put this down to any model bias really as this scenario is poorly handled by all models. This saga could go on for days to come.

Low resolution of the GFS(P) will be fun......

Low resolution for the GFS is rage-worthy 

Edited December 17, 2014 by Captain shortwave

[Costa Del Fal]

Really remarkable differences between the GFS and GFSP across many runs. Just cant be sure which to believe really especially as the GFS 18z op seems more down to Earth, perhaps similar to the ECM on Boxing Day somewhat with a HP ridge to the South? Nonetheless, even better/stronger heights into Greenland this time but arguably too far west based to benefit the UK?

 

A cool/cold Christmas still looking likely but perhaps looking fairly settled with any wintriness likely to be pushed back or at least dictated by whether LP develops in the Atlantic?

 

Just the volatile and extreme changes between the 12z and 18z op are enough to stipulate that many significant changes will continue for much longer yet. The differences post Christmas between the 2 are ridiculous but not unsurprising. Mild or cold... anyone's guess.

Edited December 17, 2014 by Costa Del Fal

[bluearmy]

The gfs op solution is the west based -NAO which could be where Exeter is coming from. it should, however, end up with a euro trough as the depressions eventually clear east in week 2.

[Snowman.]

Holy amplification.

 

18z

 

12z

 

 

 

 

On the OP the jet is an absolute mess.

 

Edited December 17, 2014 by SN0WM4N

[snowice]

GFS

The Atlantic low is a pain and pushes in a ridge right over the UK, cold and frosty with sunny spells. That low looks like snatching defeat from the jaws of victory by forcing the ridge through the UK.

GFS parallel

Certainly potential for showers anywhere, wintry to low levels. A possibility of a white Christmas for some (especially over higher ground)

Large differences in how low pressure in the Atlantic is handled which potentially alters what weather we will see for the big day. We can't put this down to any model bias really as this scenario is poorly handled by all models. This saga could go on for days to come.

Low resolution of the GFS(P) will be fun......

Low resolution for the GFS is rage-worthy

The 18z can be summerised very easily-

18z GFS poor. ( not as good)

18z GFS (p) Great.[/quot

GPS (P) or gfs can someone please tell me the stats?also in the new year will gfs dissappear from meteociel and will it just be gfs parallel the updated version

Edited December 17, 2014 by snowice

[Jason M]

GFS opp going west based (as per a lot of the ensembles).

http://www.meteociel.fr/modeles/gfse_cartes.php?&ech=252&mode=0

GFS P much more east based. Lets hope with its upgrades its correct. Not massively cold as illustrated on this chart, but getting there and should be a good run!

http://www.meteociel.fr/modeles/gfse_cartes.php?&ech=210&mode=6&runpara=1

[snowking]

I have to keep my cautious hat on for now because we have seen too many times over the last few years, especially from the ECMWF, an overestimation of heights around the Greenland locale and resultant (or concurrent) trouble with phasing of lows crossing the Atlantic...

However, I would also caution that looking at such fine detail, including where the -10c 850 line is or isn't on each individual run, as well as the aforementioned phasing issues etc on day 6+ charts is very unlikely to ever lead to anything accurate in terms of projections.

I will finish on this note though - that is a stunning EPS mean. I have seen it swing either way from there still, but at face value as a mean (and indeed from the clusters Nick so kindly provided) it's pretty encouraging.

SK

Edited December 17, 2014 by snowking

[Jason M]

The gfs op solution is the west based -NAO which could be where Exeter is coming from. it should, however, end up with a euro trough as the depressions eventually clear east in week 2.

I was thinking that as well. That really is the only logical explanation from what we are seeing. Should just delay things, so not the end of the world but since the weekend gefs have been strongly hinting at a west based set up (they could easily be wrong though)

[Ice Day]

The 222hr on the GFS(P) is a beaut. Hopefully, the 'P' is onto something as the operational is comparatively pretty poor !

 

[kumquat]

GFS Op Old V GFS Parallel

 

Discuss!

 

Anybody got any real insight or verification stats?

Edited December 17, 2014 by kumquat

[Mark Neal.]

Great GFS P. Cold uppers treading there way down. Low pressure around too. Not bad aye!

[Geordiesnow]

Met Office very possibly wrong. Wouldn't be the first time. As per usual quite cagey and "safe" around the Christmas forecast (Christmas day, Boxing day) until the last second. I think that they disclaim all this by their wording anyway, so they've not committed either way thus far.

 

Conversely the Met Office could be right, problem on here, everyone can be quite quick to assume this will happen basing on a few runs or a few trends. Maybe the UKMO does not show the set up the GFS is showing hence the different forecasts?

 

As I said earlier, its too uncertain to know what will happen in the Xmas period, what is fairly safe to say we will see a swing from mild to chilly weather then mild again but perhaps more mild days than chilly ones, especially in Southern areas. 

 

I wouldnt be too surprised if what the GFS shows is gone by the 06Z run but if we can find some trends then that is more encouraging signs.

[chionomaniac]

The GFS is dead. Long live the new GFS! LOL

[Jason M]

Getting colder and colder under this stagnant set up I'd have thought.

http://www.meteociel.fr/modeles/gfse_cartes.php?&ech=240&mode=0&runpara=1

Imagine the storms if pressure profile set up in the summer!!!!

[Mark Neal.]

That is a fanatastic GFS P. Then brings a band of snow into the South.. Lovely stuff. GFS though is poor with a west based. Interesting viewing!

.

[johnholmes]

Question to JH.Are the 500mb charts you use showing any change yet?

Thanks in advance.

hi joggs

As posted over the last 24 hours the anomaly charts are fairly similar to one another in the way they are trending. For once, assuming the prediction turns out correct, it is the EC-GFS outputs leading the way. Both have shown for a couple of days the idea of a ridge (upper air that is) starting to develop east of Canada and this, very slight as it is shown on the morning issue, along with the +ve heights is shown edging east. NOAA only last evening began this move as well and does continue it tonight. It is too early to be sure if the ridge will amplify and that in turn would sharpen the currently predicted fairly flat trough currently west of the UK and out into Europe, into southern Scandinavia and Europe. These two upper air features would put the UK on the cold side of an upper ridge. IF it does occur then how long this might last is impossible to day, 48h or maybe longer who knows as it has yet to form and the upper air pattern east and west of it to be clear. In terms of probabilities, after not before Xmas then I would say it has gone from 30% 3-4 days ago to a bit over 40% this evening. Note this idea does not alter the idea of a short cold snap leading into Christmas before milder air takes over for, what would be a short spell IF the idea suggested in this post does happen.

Edited December 17, 2014 by johnholmes

[BlueHedgehog074]

The NOAA 8 to 14 day 500mb anomaly chart, I feel, seems to show possible hints of the UK heading in a generally cooler direction. Some fairly strong higher than average heights out in the Atlantic (red dashed lines) with a little bump in the green 500mb flow line in the mid-Atlantic suggesting ridging of High Pressure to our West. And, as such, is quite fitting with many of the models' ideas of throwing up ridging to our West. Also, that green contour line suggests a flow at the 500mb level from the North-West through the UK with some troughing to our East. This may (but not definite) help to provide something chillier straight from the North at some point, otherwise it would probably look like we would see a flow between the West or North-West, but maybe of the cold and/or wintry variety. The big dip in the green line over Eastern Northern America would perhaps indicate some notable troughing in that area and perhaps help along with amplifying the pattern downstream towards the UK, and especially if a major chunk of the Vortex does indeed shift to our East. The anomaly chart does, at least, show lower than average heights (the blue dashed lines) mostly concentrated to our North and East. Plus, the combination of higher than average heights over Western Northern America along with a noticeable bump in the green line there, suggests another ridge of High Pressure (the Pacific ridge?) which, as some mentioned, could be another ingredient to help out with blocking opportunities to our West or North-West. I think, personally, though, it perhaps would be ideal to see more of a bump in the green line in the Atlantic as their could always be a risk of Low Pressure systems towards Eastern America flattening out ridging to our West, unless the Lows/troughs in that region can dig far enough South to keep High Pressure amplified in the Atlantic.

Overall, it's possible that those who enjoy the cold weather may indeed be in for a wintry surprise during the Christmas period. And if the anomaly chart can show an even stronger signal for ridging in the Atlantic (at least when focusing on the green contour line), then that 'surprise' might just be fulfilled.

(In spite of having used these quite a few times in that past, those with much more experience are free to correct any elements I haven't observed correctly).

Edited December 17, 2014 by DiagonalRedLine

[ukpaul]

Remember that there is a marked difference between the old and new GFS resolutions at a crucial time - i.e. between 192h and 240h. There shouldn't be any of the changes that low res. has often brought as soon as you get past day eight, now it will be day ten!

[ukpaul]

...and just in case anyone was wondering what might happen up above us. This is something that has been hinted at on a few runs now, but the first chart showing suggestions of a further warming as the upcoming one diminishes, this time on the Atlantic side.

 

At that range I wouldn't count on it but it appears plausible (the parallel keeps the existing warming stronger for longer with no subsequent developments visible as yet).

 

Edited December 17, 2014 by ukpaul

[johnholmes]

The NOAA 8 to 14 day 500mb anomaly chart, I feel, seems to show possible hints of the UK heading in a generally cooler direction. Some fairly strong higher than average heights out in the Atlantic (red dashed lines) with a little bump in the green 500mb flow line in the mid-Atlantic suggesting ridging of High Pressure to our West. And, as such, is quite fitting with many of the models' ideas of throwing up ridging to our West. Also, that green contour line suggests a flow at the 500mb level from the North-West through the UK with some troughing to our East. This may (but not definite) help to provide something chillier straight from the North at some point, otherwise it would probably look like we would see a flow between the West or North-West, but maybe of the cold and/or wintry variety. The big dip in the green line over Eastern Northern America would perhaps indicate some notable troughing in that area and perhaps help along with amplifying the pattern downstream towards the UK, and especially if a major chunk of the Vortex does indeed shift to our East. The anomaly chart does, at least, show lower than average heights (the blue dashed lines) mostly concentrated to our North and East. Plus, the combination of higher than average heights over Western Northern America along with a noticeable bump in the green line there, suggests another ridge of High Pressure (the Pacific ridge?) which, as some mentioned, could be another ingredient to help out with blocking opportunities to our West or North-West. I think, personally, though, it perhaps would be ideal to see more of a bump in the green line in the Atlantic as their could always be a risk of Low Pressure systems towards Eastern America flattening out ridging to our West, unless the Lows/troughs in that region can dig far enough South to keep High Pressure amplified in the Atlantic.

Overall, it's possible that those who enjoy the cold weather may indeed be in for a wintry surprise during the Christmas period. And if the anomaly chart can show an even stronger signal for ridging in the Atlantic (at least when focusing on the green contour line), then that 'surprise' might just be fulfilled.

(In spite of having used these quite a few times in that past, those with much more experience are free to correct any elements I haven't observed correctly).

17th dec noaa aniomaly chart.gif

 

no major issues DRL, see my post above and various recently using these charts. The next time will be sometime tomorrow with a link, they are very useful or at least I find they are

[nick sussex]

GFS Op Old V GFS Parallel

 

Discuss!

 

Anybody got any real insight or verification stats?

Here you go:

 

http://www.emc.ncep.noaa.gov/gmb/STATS_vsdb/12Z/

[BlueHedgehog074]

no major issues DRL, see my post above and various recently using these charts. The next time will be sometime tomorrow with a link, they are very useful or at least I find they are

Will do.

I think as you talked about in the past, the anomaly charts can be handy for looking at the overall picture and getting some ideas of the sort of direction we could head in. I suppose, as well, they do tend to not have the wild swing in changes that the operational models can have from run to run.

Edited December 17, 2014 by DiagonalRedLine