Model output discussion - 5th December 2016 - Into Winter we go

[blizzard81]

11 minutes ago, nick sussex said:

Who saw that coming. I hope the ECM is correct, good riddance to that Euro high.

I would be more dubious of this sudden change if it was post T168hrs but the changes start before that.

Thats all well and good as long as the plus 7 day charts come to fruition. If not, I fear a non stop zonal train for the rest of Dec. 

Edited December 8, 2016 by blizzard81

[cheeky_monkey]

13 minutes ago, nick sussex said:

Who saw that coming. I hope the ECM is correct, good riddance to that Euro high.

I would be more dubious of this sudden change if it was post T168hrs but the changes start before that.

i saw this coming see my post in the winter moans thread yesterday

[Frosty.]

Good to see two consecutive Gfs runs showing seasonal cheer during christmas week..more please. Ho Ho Ho

[doghouse]

18 minutes ago, nick sussex said:

Who saw that coming. I hope the ECM is correct, good riddance to that Euro high.

I would be more dubious of this sudden change if it was post T168hrs but the changes start before that.

GP

[snowice]

Well if this model tread was on life support yesterday,it will soon come back to life on the 12z fingers crossed.

[karlos1983]

2 minutes ago, snowice said:

Well if this model tread was on life support yesterday,it will soon come back to life on the 12z fingers crossed.

Just needed some CPR (Cold Pool Revival) 

[Summer Sun]

The GFS ens mean keeps pressure above 1020 right up to Christmas

Daytime temps struggling in low single figures the closer we get to Christmas whilst snow is looking unlikely for the foreseeable future a cold Christmas looks a good bet

[knocker]

I suppose this might illustrate that one should be careful what you wish for. The ext EPS means are certainly getting rid of the HP but with a trough to the north west and the Azores relegated away to the south west an upper flow just south of west becomes established with temps slightly above and then returning to normal.

Edited December 8, 2016 by knocker

[bobbydog]

30 minutes ago, blizzard81 said:

Thats all well and good as long as the plus 7 day charts come to fruition. If not, I fear a non stop zonal train for the rest of Dec. 

Well if the zonal train arrived in the form of the GFS parallel, we'd be riding the Polar Express....

[Frosty.]

1 minute ago, bobbydog said:

Well if the zonal train arrived in the form of the GFS parallel, we'd be riding the Polar Express....

I don't mind zonality as long as its cold zonality!

[Coopsy]

30 minutes ago, bobbydog said:

Well if the zonal train arrived in the form of the GFS parallel, we'd be riding the Polar Express....

Have we ever had a scenario like this actually happen to this degree?

Edited December 8, 2016 by Daryl Dixon

[Seasonality]

29 minutes ago, gottolovethisweather said:

Pattern change post my watch period (10th through 13th) I reckon. The models are struggling to get a grip on things as early as D4 and with all the differences noted intra-runs, may well be that Shannon has re-entered the room. I do feel, however, that, a colder than average period is upcoming for the second half of December. Your region and in particular Northwestern Scotland is likely to feel the brunt of it before hopefully extending south thereafter.

For those not in the know, this refers to Shannon entropy, named after the mathematician Claude Shannon who developed the concept in information theory. Entropy can be defined as the degree of disorder or randomness in a system. In the context of the model outputs, when Shannon entropy increases this means that there will be a greater variation of outcomes, greater volatility in the output. Lower Shannon entropy means more consistent output. So higher entropy explains the swings we're seeing.

[bobbydog]

Just now, Daryl Dixon said:

Have we eve had a scenario like this actually happen?

I'm not sure but if that continued to develop 'favourably', it would possibly lead to a country-wide blizzard that most of us would never have experienced in our lives!

[carinthian]

23 hours ago, carinthian said:

Morning this bigger picture of the 500mb flow from UKMO at 144 hours is not bad. Note the cross Polar high pressure link from Siberia to Western Canada with a extensive -AO flow ( east to west/north to south ) with little zonal flow across the Atlantic.  Looks like a split in the Polar Vortex , one in the NE Canada but the main one resident  in Northern Russia. So height rises again on the cards to dominate much of Europe in 6 days time, signs of heights start to  fall in the South Med. If that comes off we could get the Atlantic trough to dig SE wards and then bingo retrogression of the Euro high can take place. Keep the faith, we will get there . Its very much a different pattern to last years Zonal train.

C

Just an up date from the post this time yesterday. Now at the critical time 240t the GFS charts are the best route to cold. Remember it beat all the other models at this time span in recently  sinking the UK high into Central Europe, now it has shown consistency in relocating the high centre again back with retrogression shown in its out puts in F1. Cross Polar high pressure link from Siberia to Western Canada is still shown post 240h. Eventually a fall in heights in Euroland will follow and then we will be in true -AO charts. I much prefer the GFS charts en- route to proper cold as opposed to this mornings ECM. The extended UKMO Atlantic charts out to 168h , possibly going with ECM but not sure how this will pan out. We do not want Atlantic zonal flow to take charge, so I am happy with the American models this morning.

C

Edited December 8, 2016 by carinthian

[Matthew.]

3 minutes ago, Frosty. said:

I don't mind zonality as long as its cold zonality!

The bonus with polar zonality is the sunshine increases in abundance with a healthy west of NW wind and nighttime frosts and if you head to the hills for a hol you'll find chances of snow tooThe profile pic illustrates.

[nick sussex]

42 minutes ago, blizzard81 said:

Thats all well and good as long as the plus 7 day charts come to fruition. If not, I fear a non stop zonal train for the rest of Dec. 

To be honest I'm normally in the hope the high retrogresses camp but we've been waiting for this to happen for weeks and ended up with zip. The ECM looks to have a more southerly tracking jet and more amplified upstream. At this point I'm willing to take the chance on removing the high. Also this has a better chance of bringing some snow to the ski resorts . As you say though it's whether this verifies because the more interest is past day 7.

[gottolovethisweather]

1 minute ago, Seasonality said:

For those not in the know, this refers to Shannon entropy, named after the mathematician Claude Shannon who developed the concept in information theory. Entropy can be defined as the degree of disorder or randomness in a system. In the context of the model outputs, when Shannon entropy increases this means that there will be a greater variation of outcomes, greater volatility in the output. Lower Shannon entropy means more consistent output. So higher entropy explains the swings we're seeing.

 

Thanks, Seasonality, I've learned something there. Not that I'm by any way sure I'm correct in using the word in circumstances such as these. I mention it as the period from around the 10th through to the 13th December when the PV initially splits has been one of great model confusion for the best part of a week now. Hence my hunch of a pattern change developing around said timescales. Whether it ends up as an HP dominated set-up or one with an increasingly active zonal flow with the Jet ever trending southwards I can't say, but something's up IMHO.

[Paul_1978]

12 minutes ago, Daryl Dixon said:

Have we eve had a scenario like this actually happen to this degree?

January 1984? At least I think it gave deep/heavy snow over a wide area from a north-westerly? At least it did in Bradford - I remember it being very deep indeed.

[bobbydog]

The 00z GFS(P) continues in a similar fashion  (if not quite as dramatic)

[Seasonality]

24 minutes ago, bobbydog said:

Well if the zonal train arrived in the form of the GFS parallel, we'd be riding the Polar Express....

Have you got a link to that run @bobbydog Struggling to find it on meteociel

[Southender]

18 minutes ago, Daryl Dixon said:

Have we eve had a scenario like this actually happen to this degree?

Yes, we have had PV lobes pay us a visit many times. It looks more dramatic than it actually is, as by the time it hits our shores it is massively watered down in terms of temperature profile. Still, gives us a shot at some colder and potentially snowy weather for some if it were to arrive.

Edited December 8, 2016 by Southender

[bobbydog]

3 minutes ago, Seasonality said:

Have you got a link to that run @bobbydog Struggling to find it on meteociel

Here you go-

http://www.meteociel.fr/modeles/gfse_cartes.php?ech=204&code=0&mode=0&runpara=1&carte=1

It is within the menu of the OP run on there though

(It has just updated to the 00z run, my first chart was the 18z run)

Edited December 8, 2016 by bobbydog

[Summer Sun]

 

[Ali1977]

2 minutes ago, Seasonality said:

Have you got a link to that run @bobbydog Struggling to find it on meteociel

It's in the options 850 , 2m etc on the GFS Europe tag 

[Seasonality]

4 minutes ago, Summer Sun said:

 

Definitely not a blowtorch Sou-Wester though.