Model Output Discussion 18th Nov.2013-12z onwards.

[Skyraker]

@IANF

 

Any chance of the UKMO 168 ?

[Gaz1985]

The GEM was seen as an outlier solution and ditched by NOAA this evening, the JMA is the Brut of the aftershave world.It's really what the GFS/ECM/UKMO agree on that will decide things. There are no guarantees either way regarding the northerly, it might get watered down. Certainly makes for avid model watching, its the first real drama of the season!

 

True and still 5 days to a week before this potential cold snap arrives (if it does), it may get watered down to not much like the last one or maybe more potent, I won't put confidence on it happening until all the main models are on board and that includes JMA - which I think is a good model and better than GFS. As ever it's a waiting game.

Edited November 29, 2013 by Gaz1985

[Catacol]

Ian-

 

rem what I said last year - 2 lows separating over Greenland ( West coast)

http://modeles.meteociel.fr/modeles/gfs/runs/2013112912/gfsnh-0-180.png?12

 

not as good as 2010 but a split flow none the less normally means no toppler-

 

All the atlantic low will do is disrupt out & slide SE...

 

UKMO 144 upper air is EPIC- deep cold waiting in the wings.

 

I'd love to believe that the high wont topple, but I just cant see it. We are looking at a deflecting blow that will flatten fast. Lots of fun for some in the north and parts of the west for a day or so, but I must be spoiled by the synoptics of the last few years because I just cant get particularly excited by this. Still - pretty good for the first week in December I suppose and perhaps a sign that we can see more of this kind of northerly with longer lasting potential as we go though the winter. 

[legritter]

Many happy posters tonight ,but we need a little bit of support from tomorrows runs with no big downgrades ,no big Stella runs just steady as we go .with a bit of luck and i think we are moving in the right direction, this cold[ Period ]could deliver for some and if synoptics set up just right some surprises which at this range remain a mystery .Dont get too down if high pressure is modeled to be very close in later stages of the runs this can always set up in a favourable position later .so lets enjoy the ride ,Razors prozack and straws at the ready .

[johnholmes]

 

 

 

Im off out-

 

I would just offer 1 word of caution

 

This Shortwave is the one to watch with keen eyes-

 

ALL the models even possibly the UKMO recurve this SE NOT north up through Greenland

 

ECH1-144WAVE2.jpg

 

If theres to be any downgrades from the ECM they will come from this -

 

However if ECM Is correct- remember its against every model then every model will UPGRADE!

 

S

Sorry Steve

http://forum.netweather.tv/topic/78508-model-output-discussion-18th-nov2013-12z-onwards/page-136#entry2849015

 

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

If it is the Newfoundland one then it is hardly a shortwave; it is a fully fledged low pressure are at the bottom of a marked upper trough?

 

sorry about the mess up quoting Steve twice

 

Looking at the predicted upper air pattern about 6 days ahead, around the time of the chart shown by Steve, the output for this evening has not yet become available

http://www.cpc.ncep.noaa.gov/products/predictions/610day/500mb.php

 

and the version from the ECMWF-GFS output this morning

http://www.meteo.psu.edu/~fxg1/ECMWF_0z/hgtcomp.html

 

None of them really suggest long lasting cold to me. They do offer the probability of cold shots from time to time. Also the probability of fairly deep lows looking at the strength of the 500mb flow. The pattern of course will at times become more zonal but then tend to become more meridional after the passage of these fairly major systems (IF they materialise), or that is the way I see it.

Indeed the 12z GFS seems to have gone along that path as it tracks this low into the UK area. I know some of us disagree with the usage of short wave etc. Whatever term it is a largish 'hole' in the atmosphere with a lot of weather with each of them.

Edited November 29, 2013 by johnholmes

[The Northern Ramper]

Not really seeing the optimism for a longer protracted spell of cold to be honest as much as I would like it. ECM shows a 4 day cold snap but at 216, 240 you can see a Vortex re forming flatter surpressed and high pressure west/over UK after day 4 of the cold snap.

 

High pressure to west of us or over us and ties in with anomaly charts.

 

After the cold northerly we sort of await the next chapter:-)

 

After the Northerly on the ECM that high is definitely eyeing up Scandinavia.

[UV-RAY]

You think the uppers will be cold enough at -6/-8 or are we looking at marginal conditions away from the peaks etc?

Uppers would be fine as would dew points, even coastal areas would see sleet/wet snow. That's for the North and NW areas. Edited November 29, 2013 by Sceptical Inquirer

[Matty M]

The ECMWF would give 70% of the British Isles some snow cover which would be a brilliant result.

 

Obviously not looking like being prolonged but a real 3 day cold plunge.

[Methuselah]

I'd love to believe that the high wont topple, but I just cant see it. We are looking at a deflecting blow that will flatten fast. Lots of fun for some in the north and parts of the west for a day or so, but I must be spoiled by the synoptics of the last few years because I just cant get particularly excited by this. Still - pretty good for the first week in December I suppose and perhaps a sign that we can see more of this kind of northerly with longer lasting potential as we go though the winter. 

Apart from on 2 occasions - 1981 and 2010 - all very early cold-incursions have been transitory in nature; and, it didn't seem to have any deleterious effects on the following winters...Was it the last Saturday in November 1969, or the first in December, that produced blizzard-conditions in Tunbridge Wells - for one day?

 

​IMO, the short blast of Arctic air currently being predicted by some model-runs is nothing out of the ordinary...

[Purga]

After a brief northerly toppler which will bring some welcome cooler weather neaxt weekend, the default mild pattern of High pressure over Europe and Low pressure strongly centred over Greenland looks the form horse.

 

 

At least the far end of FI shows the jet displaced south and has a bit of promise.

The ENS show the brief cool down before a strongly mild and zonal type regime exerts its grip in the run up to mid month.

[tight isobar]

Sorry Stevehttp://forum.netweather.tv/topic/78508-model-output-discussion-18th-nov2013-12z-onwards/page-136#entry2849015 http://www.wetterzentrale.de/topkarten/fsavneur.htmlIf it is the Newfoundland one then it is hardly a shortwave; it is a fully fledged low pressure are at the bottom of a marked upper trough? sorry about the mess up quoting Steve twice Looking at the predicted upper air pattern about 6 days ahead, around the time of the chart shown by Steve, the output for this evening has not yet become availablehttp://www.cpc.ncep.noaa.gov/products/predictions/610day/500mb.php and the version from the ECMWF-GFS output this morninghttp://www.meteo.psu.edu/~fxg1/ECMWF_0z/hgtcomp.html None of them really suggest long lasting cold to me. They do offer the probability of cold shots from time to time. Also the probability of fairly deep lows looking at the strength of the 500mb flow. The pattern of course will at times become more zonal but then tend to become more meridional after the passage of these fairly major systems (IF they materialise), or that is the way I see it.Indeed the 12z GFS seems to have gone along that path as it tracks this low into the UK area. I know some of us disagree with the usage of short wave etc. Whatever term it is a largish 'hole' in the atmosphere with a lot of weather with each of them.

...more than fair quotations JH, but as again (thats the issue) shortwaving is development and or can be LPS.and can and usuall dictate or otherwise long term outcomes of HP regression/ wanning,or ultimatly suppresion.thus no matter Lp, develop and or in premature develop...It's whom viewing that takes the reigns of overall outcome/outcomes.

[terrier]

Even if the ECM only delivers a 3 day event that would do for a lot of coldies. Then let the pattern reset itself for a more prolonged spell late dec early jan.

[Joe Levy]

We will, inevitably, at some point get a westerly this winter. It could be after the Northerly that is predicted for next weekend, however not necessarily. I could be wrong, but if I remember correctly a westerly has been progged several times in the last few weeks and I must admit, the outcome has been far from mild, at least in how it feels outside. The models' different versions of events rely on a specific set of circumstances occurring and the further from the present we get, the more those specific circumstances result in huge deviations. However, if one of those circumstances suddenly changes, such as the positioning of a short wave, or the angle of the jet, then it can change completely. So we may lose our Northerly for next weekend, but if we don't we may also increase the chances of prolonging cold. This is why model watching is always interesting because just when you think everything is set in stone, something slightly changes and the whole pattern starts altering in response!

[Methuselah]

...more than fair quotations JH, but as again (thats the issue) shortwaving is development and or can be LPS.and can and usuall dictate or otherwise long term outcomes of HP regression/ wanning,or ultimatly suppresion.thus no matter Lp, develop and or in premature develop...It's whom viewing that takes the reigns of overall outcome/outcomes.

That's true, ti...But why can't we all agree to use nomenclature that we can all understand? What's wrong with 'old-fashioned' terms like 'major, minor, wave' depressions?

[Matty M]

Interesting, increased Ensemble support for Northerly to 6th/7th but wide spread of solutions thereafter with the OP being on the mild site of the spread.

[johnholmes]

After the Northerly on the ECM that high is definitely eyeing up Scandinavia.

 

erm, can you explain why you feel that will/may happen please. Both the 500mb charts show an upper trough over Scandinavia, and over the past few days there has been no sign of the upper high moving on them to where you suggest?

honest question

[Bristawl Si]

Phew! That was a rollercoaster ride through the last 3 hours of posts!

I can't wait until 6th December to see what actually happens, weatherwise!

Genuinely, i've bookmarked that day.

Will Steve M's forward thinking analysis be proved correct (remember, he's been calling cold & possibly snowy shots, well ahead of model output for a few days now) OR

will Gibby's 'no risks/deviations from the model output everyday' be proved more accurate.

Cant wait to find out. But nicely interrupted by Spurs/Manure at midday on Sunday.

[johnholmes]

We will, inevitably, at some point get a westerly this winter. It could be after the Northerly that is predicted for next weekend, however not necessarily. I could be wrong, but if I remember correctly a westerly has been progged several times in the last few weeks and I must admit, the outcome has been far from mild, at least in how it feels outside. The models' different versions of events rely on a specific set of circumstances occurring and the further from the present we get, the more those specific circumstances result in huge deviations. However, if one of those circumstances suddenly changes, such as the positioning of a short wave, or the angle of the jet, then it can change completely. So we may lose our Northerly for next weekend, but if we don't we may also increase the chances of prolonging cold. This is why model watching is always interesting because just when you think everything is set in stone, something slightly changes and the whole pattern starts altering in response!

 

 

I think perhaps you misunderstand how weather models operate. There is no set of circumstances that occur other than those created by the model as it follows strict mathematical formulae to solve complex (hugely complex) physics, largely thermodynamics. So the positioning of short waves, the jet etc are all part of this complex process. Or am I misunderstanding your post?

[radiohead]

CFS 1 is interesting for mid-December. "That CFS?"

 

[Matty M]

Dublin Ensemble showing cold trend and large spread at end of run.

 

 

[tight isobar]

That's true, ti...But why can't we all agree to use nomenclature that we can all understand? What's wrong with 'old-fashioned' terms like 'major, minor, wave' depressions?

..fair comment, I,ll revert to yours quoted...apologys ..

[Joe Levy]

I think perhaps you misunderstand how weather models operate. There is no set of circumstances that occur other than those created by the model as it follows strict mathematical formulae to solve complex (hugely complex) physics, largely thermodynamics. So the positioning of short waves, the jet etc are all part of this complex process. Or am I misunderstanding your post?

I think I didn't communicate myself correctly! Basically I am trying to simplify what you have just said! But my understanding of thermodynamics and physics is limited so perhaps think of a shortwave as many many specific "circumstances" as I called them. My point is more that tiny factors can change a lot and so in spite of what is being shown now, the outcome could be very different indeed.

[johnholmes]

...more than fair quotations JH, but as again (thats the issue) shortwaving is development and or can be LPS.and can and usuall dictate or otherwise long term outcomes of HP regression/ wanning,or ultimatly suppresion.thus no matter Lp, develop and or in premature develop...It's whom viewing that takes the reigns of overall outcome/outcomes.

 

I think I had better give up trying to get folk to not use the term, it is, quite often in here, used incorrectly. However, if the majority like its use and understand what it is then best I leave things alone. I know US forecasters use it but you will rarely find a UK forecaster doing so which is where I was brought up.

developing low/short wave as you wish.

So long as you all understand the short wave is NOT the cause of the change. That can be found in the upper air pattern that allows it to form.

[Cloud 10]

Excellent support for the 12z ecm operational run from the ensemble mean at 168 hrs.

 

 

 

 

Quite a rapid transfer of the polar vortex towards Canada by T240 and high pressure

close to the UK,so looks like a fairly short (4 days?) but potentially very sweet cold plunge.

 

[gottolovethisweather]

Phew! That was a rollercoaster ride through the last 3 hours of posts!

I can't wait until 6th December to see what actually happens, weatherwise!

Genuinely, i've bookmarked that day.

Will Steve M's forward thinking analysis be proved correct (remember, he's been calling cold & possibly snowy shots, well ahead of model output for a few days now) OR

will Gibby's 'no risks/deviations from the model output everyday' be proved more accurate.

Cant wait to find out. But nicely interrupted by Spurs/Manure at midday on Sunday.

 

Let's not isolate the few other folk who were also shouting the odds over five days ago, either please. They know who they are, but shall remain nameless.

 

 

http://forum.netweather.tv/topic/78387-south-westcentral-southern-england-regional-weather-discussion-061113-0000z/?p=2844673

 

 

Oh and the ensembles trend from the unlauded GEFS 12z (Berkshire only) three days ago showed the following. 

 

 

Now three days on they show the following, the trend is our friend.

 

 

 

 

Things are still on a knife-edge in terms of determining whether one will get SNOW and another three days will buy some more time to perhaps finally answer how prolonged this spell will be and whether snow is likely in your own location.

 

I'm loving the chase that is for sure.

Edited November 29, 2013 by gottolovethisweather