Model Output Discussion - 28th November - 4th December

[damianslaw]

Reliable timeframe is about 96 hrs at present. Its a very volatile situation, models in such set ups understandably will toy around with varying scenarios - placing troughs and lows in different positions.

UKMO often does very well in these situations and it has been performing rather well lately, my eyes will be on the FAX this evening and how strong it develops the low pressure system due to hit us on Wednesday.

Too early to be discussing with any confidence if heights will strengthen sufficiently northwards to Greenland - lots of hurdles to get through before this time next week.

I do think heights will ridge in from the SW in some shape or form next weekend - but not speculating how just yet.

[kold weather]

From the looks of things on here I imagined the ECM to be a really poor run, but really its not too bad. Obviously not as good as the GFS which really does produce some fun and games and the ensembles are pretty good as well.

I'd probably suggest the ECM is closer to the mark but the idea of a high pressure intrusion into Europe is a fairly solid one IMO...now that doesn't obviously go against the UKMo or GFS because they too do move a HP cell into Europe, just its centered far enough north for us to really benefit.

[bluearmy]

the ecm ens spreads are interesting. the trend from the 12z suite is definitely to support the solution of the 12z gfs op. now a strong jet being forced well to our north pumping lots of 'warm' air into a frigid arctic - cant think what might come of that :winky:

[kold weather]

ECM ensemble mean is very close to the op run though at 144hrs, so looks like the ECM is something of a middle ground at that point between the possible solutions.

Still by in large the ECM ensembles seem to suggest a WNW/NW at 168hrs, quite a few like the GFS as BA said.

[bluearmy]

ECM ensemble mean is very close to the op run though at 144hrs, so looks like the ECM is something of a middle ground at that point between the possible solutions.

Still by in large the ECM ensembles seem to suggest a WNW/NW at 168hrs, quite a few like the GFS as BA said.

i was referring to later in the run Kold, given the way the gfs op built a substantial ridge (that failed to survive low res). the possible northerly incursion in a weeks time holds little interest for a fair chunk of the country - the possibilities thrown up by a large block over nw europe/eastern atlantic extending northwards regarding the last third of the month is what has my attention.

Edited December 3, 2011 by bluearmy

[kold weather]

At this time of year with the set-up the GFS tries to kick-start, any easterly would probably ve very marginal for snow anyway. Probably the coldest solution actually is to get a brief northerly followed by a toppler high over the UK...I'm betting that'd be colder than a half-baked easterly with very moderated temps due to the north sea...and 'wintry showers'.

[lorenzo]

Firstly, my comments we're in reference to tonights 18 Z onward not 12Z.

2. Where did I make reference to it been mild (subtropical)

3. T+96 is FI at the min let alone the cherry picked T+126 hrs chart in your post.

The pattern 12 Z is "serving" is liabale to severe changes even at your belovid (Chosen by you range) T=126 chart

Sorry if you did not read my post with the comedic intentions.If they were not comedic they were playful.

I feel you have taken a personal slight to matters which is not my intention, i enjoy this forum for its candour of all else, it is polite and erudite.I have not picked any chart at all, certainly not picked one to your detriment, as my post history will illustrate similar concern with the time frame you reference @ +96, even as early as around 8am today I cited this.

Sorry you felt the need to vent, and lastly i do not hold charts in a beloved status.

What I do enjoy just now are certain synoptics making the most of situations unexpectedly, weak MJO Pattern , non influence of GLAAAM, limited or Waning La Nina signature, high PV forcing, spin off lows, trended pacific ridge muddling amplification beyond ' cherry picked' FI. cross model disagreement in longer term.

So am happy to settle with the cold incursions from the NW and the excitement they bring.

[Grimsby Snow Lover]

Well up to next Saturday and things on the 18z run are not a million miles away from the previous run. High pressure is still extending towards Greenland.

http://www.wetterzen...s/Rtavn1561.png

Should bring a nice seasonal feel if nothing else. All we need now is for it to either build towards Greenland and form a block (unlikely) or extend towards Scandinavia.

Edited December 3, 2011 by Grimsby Snow Lover

[kold weather]

Broadly similar evolution on the 18z GFS with a HP cell forming in the Atlantic and spreading eastwards with cold air down on the eastern flank. Nice run so far for below average conditions.

[conor123]

18z shows potential for a Cheshire Gap streamer Friday, will change anyway but seems odd forecasting 6c with uppers so cold.

[Liam J]

Well the GFS and ECM couldn't look much different to each other, ECM catapults deep depressions over the Atlantic with a very flat pattern and remaining very disturbed but the GFS builds high pressure over the UK which would result in nice crisp winter days and below average temps with pretty cold uppers locked in.

Not so clear cut at all in the medium term, FI is about as close to the reliable time frame as it gets!

Edited December 3, 2011 by Liam J

[nick sussex]

Surely not, whilst attention has been on the will it won't it northerly the models have craftily slipped in a route to a much more seasonal feel, false dawn or another trend?

The evolution is perfectly plausible and you can get some decent cold even with a cold stratosphere if the PV sets up far enough west, in the lower resolution the GFS sinks the high but given the changes over the last few days who would bank on any outcome.

The ECM still seems most bullish about pushing the PV eastwards and flattening the pattern so at this time the odds still favour any high being sunk but we'll have to wait and see if we can actually get agreement between the operational runs on the pattern within 144hrs.

The latest UKMO fax chart for 120hrs sticks with the raw output and hasn't been modified towards the ECM.

Edited December 3, 2011 by nick sussex

[kold weather]

Interesting 18z, synoptically it looks like a mild run in FI, but we manage to keep just enough influence of the high pressure and clear skies to keep temps on the low side of what you'd expect pretty much till the bitter end of the run.

[BLAST FROM THE PAST]

That is the whole point of my post. Look at the big picture, not the swings and roundabouts produced by every run.

What's the big picture? We aren't in it now are we....more amplified and a colder set up than was anticipated? Why is it going to be returning to flat? Aren't we supposed to be flat now? Just would like to know where the background signals should have us now and down the line...want to grasp it.

UKMO painting a more and more interesting picture folks and again one cannot ignore it, GFS bringing heights more and more north for potential cold shot 3rd week. Very interesting outlook for sure.

BFTP

Edited December 3, 2011 by BLAST FROM THE PAST

[Snowmadsam]

What's the big picture? We aren't in it now are we....more amplified and a colder set up than was anticipated? Why is it going to be returning to flat? Aren't we supposed to be flat now?

UKMO painting a more and more interesting picture folks and again one cannot ignore it, GFS bringing heights more and more north for potential cold shot 3rd week. Very interesting outlook for sure.

BFTP

It most certainly is liking GFS alot

[ribster]

What's the big picture? We aren't in it now are we....more amplified and a colder set up than was anticipated? Why is it going to be returning to flat? Aren't we supposed to be flat now? Just would like to know where the background siganls should have us now and down the line...want to grasp it.

UKMO painting a more and more interesting picture folks and again one cannot ignore it, GFS bringing heights more and more north for potential cold shot 3rd week. Very interesting outlook for sure.

BFTP

Indeed blast, we are supposed to be flat now, and in a milder setup. We keep on hearing about a flat pattern, strong pv, cold strat, without acknowledging the synoptics that we currently have and what they are delivering, despite those other factors being against us. It's about time some realised that they are not the be all and end all. I think some like to be au contraire for the sake of it. On a side note, what happened to Eugene?

[BLAST FROM THE PAST]

Indeed blast, we are supposed to be flat now, and in a milder setup. We keep on hearing about a flat pattern, strong pv, cold strat, without acknowledging the synoptics that we currently have and what they are delivering, despite those other factors being against us. It's about time some realised that they are not the be all and end all. I think some like to be au contraire for the sake of it. On a side note, what happened to Eugene?

No idea, yep conspicuous with his absence. I enjoy Nick Sussex updates and he has pointed this out as have many, encouraging to see what we have at present. What I will say is that if one takes El Nino or La Nina over a century or so there is no prevalence of cold, average or mild winters. What is the primary driver? Is there a primary driver?

BFTP

[davehsug]

No Blast, but there are basic rules. With a PV as strong as we have now, even if it pulls West a touch, there is no way a real anticyclone can form right next door to it over Greenland. We might get some occasional amplification of the jet, as we have now, but there's only one way it can go while the PV remains so strong. IMO any model output showing anything else has to be wrong.

[nick sussex]

No idea, yep conspicuous with his absence. I enjoy Nick Sussex updates and he has pointed this out as have many, encouraging to see what we have at present. What I will say is that if one takes El Nino or La Nina over a century or so there is no prevalence of cold, average or mild winters. What is the primary driver? Is there a primary driver?

BFTP

Thanks.

Yes I have mentioned the likelihood of the pattern upstream deamplifying as the east Pacific ridge is expected to flatten out however the degree of this is uncertain,but I did mention a few days back chances of high pressure ridging far enough north to bring a surface cold feed into the UK but didn't expect the GFS to deliver the easterly tease!

We don't need a highly amplified pattern for that but would certainly need the PV to remain far enough west, the big sticking point is the ECM being a misery in even developing a decent mid Atlantic ridge within 144hrs.

I wonder if the models are reacting to some temporary warming forecast in the stratosphere at the 30 and 10 level, normally there would be a large time lag for its effects to be seen in the output, maybe it's alot more sensitive because of certain other factors.

It's not really my forte, maybe if Chiono is around he'll update us.

[lorenzo]

No idea, yep conspicuous with his absence. I enjoy Nick Sussex updates and he has pointed this out as have many, encouraging to see what we have at present. What I will say is that if one takes El Nino or La Nina over a century or so there is no prevalence of cold, average or mild winters. What is the primary driver? Is there a primary driver?

BFTP

I would stick money on the MJO being the main Teleconnector blast.. this recent cold interlude a result of phase 2 action not impacting stratosphere as severely as last winter due to strong PV, in some respects defelction.

You have got to include sunspot cycles as being the only factor outwith the norm from the pattern.

[kumquat]

No Blast, but there are basic rules. With a PV as strong as we have now, even if it pulls West a touch, there is no way a real anticyclone can form right next door to it over Greenland. We might get some occasional amplification of the jet, as we have now, but there's only one way it can go while the PV remains so strong. IMO any model output showing anything else has to be wrong.

It's the amplification of the jet that will help initiate the SSW (or, at least, that will be one factor). People here are so set in their ways. Whoever said look at the bigger picture had it correct.

Edit: by the way, it's (SSW) already started happening.

Edited December 4, 2011 by kumquat

[lorenzo]

http://wekuw.met.fu-berlin.de/~Aktuell/strat-www/wdiag/ts.php#fig2

60N ??????

[kumquat]

Yes..It's bottomed out.

[legritter]

morn all ,itried posting earlier but cocked it all up , dont know where i sent post , anyhow i like thursdays fax , a bit of meat on the bone .you never know what a cold front can throw up .i know the state of the stratosphere is a player in polar physics etc ,but im sure in years to come if money is invested in this field we will find some interesting discoveries . looking at the models at the moment is a bit of a rollercoaster , but the end is always changing . yes we have had some good shots over the last 3 winters , but in my opinion we need some damn good luck with getting high pressure north scandy finland way , also ,something to change down the azores ,regards for now .

[lorenzo]

http://www.esrl.noaa.gov/psd/map/images/gcm/gwo_40d.gif

whats stopping it... !