Model Output Discussion - The final stretch to Christmas

[Jason M]

Well the good news is that the trend continues this evening for Scandi Heights. The bad news from my viewpoint is that I'm not sure much will come of it as the northern arm of the jet is now firing up and logically its going to be a sinker. In essence it will just delay the inevitable. Unless we can get some energy going south its a long road to nowhere.

The chart below is a good example with westerlies blasting across the far north of Scandinavia. This has two impacts. Firstly it will erode quickly any cold pool and secondly it will tend to sink the heights.

http://www.meteociel.fr/modeles/gfse_cartes.php?&ech=162&mode=0&runpara=1

If we get to that point, we will soon get to the chart shown below.

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

Then, its a very long way to anything worthy of being called a cold spell.

Interesting how the northerly has just degraded run by run to the point where its now not even worthy of the name. Suppose the one comfort is that it proves nothing is set in stone. Lets see what the ensembles and ECM say later. METO again the best chart tonight.

[Neilsouth]

Don't forget that the jet is also a forecast by a model(s), they can be both too strong or not strong enough and also positions can be inaccurate. 

[Froze were the Days]

I am a betting man and I'll bet the GFSop is the furthest out from being correct (28th December onwards) the model is renowned for not handling certain situations correctly and being Atlantic biased. We'll probably get a bit of 'middle ground' with High pressure once low pressure has cleared south eastwards from being over the country with the coldest air to the east and south over the continent.

[Met4Cast]

Well, the trend for Scandi height rises have certainly increased this afternoon and i'm glad to see the models slowly trending away from the Atlantic onslaught we saw a couple of days ago.

 

Until we get the tracking of this weekends low pressure nailed though looking beyond that just isn't worth it, if the low is modeled incorrectly we can't place much faith in the model beyond this point.

 

It's annoying that the GFS and UKMO are sticking to their guns, I was hoping at least one of them would back down so we could have a clearer idea. The South-East route is definitely best, a larger area would see some snowfall (though accumulation likely limited to higher levels) At the moment, given ECM/UKMO agreement i'd favour this option. It also leaves E/SE parts a window of opportunity for snow showers coming in from the East before high pressure builds in fully.

[Chris K]

i understand that nick, but does it totally mean the gfs is wrong? i see the 12z and again its sticking to its exit and flattening out the ridge.

mr cynical here is thinking that maybe people dont want the gfs to be right because quite frankly its a horror show for those searching for cold. im not suggesting it is right, but surely it has to be a possibility.

 

I mostly agree with you mushy ref. the possibility of the GFS being right, but the models still change smaller surface details right up to the day in question anyway. However when the GFS sticks to its guns, it has sometimes come out on top in the end. But vice-versa as well....it has just as often been clawed along to meet with the ECM & UKMO.

 

With the recent levels of inconsistency across the mainstream models (albeit each model beginning to have its own consistent solution), personally I think the fax charts (surface pressure analysis) updates by the MetO are useful and sometimes overlooked. They do of course also change (more so towards days 3-5), but I feel the fact that professional forecasters often input their modifications based on trained knowledge is valuable at times. Until the weekend's Low is sorted out (it's getting there!) I am a bit skeptical of where we are heading.

 

For those that may not be aware of these charts:

 

http://www.netweather.tv/index.cgi?action=fax;sess=

or

http://www.metoffice.gov.uk/public/weather/surface-pressure/#?tab=surfacePressureColour&fcTime=1419249600

[The PIT]

Well the good news is that the trend continues this evening for Scandi Heights. The bad news from my viewpoint is that I'm not sure much will come of it as the northern arm of the jet is now firing up and logically its going to be a sinker. In essence it will just delay the inevitable. Unless we can get some energy going south its a long road to nowhere.

The chart below is a good example with westerlies blasting across the far north of Scandinavia. This has two impacts. Firstly it will erode quickly any cold pool and secondly it will tend to sink the heights.

http://www.meteociel.fr/modeles/gfse_cartes.php?&ech=162&mode=0&runpara=1

If we get to that point, we will soon get to the chart shown below.

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

Then, its a very long way to anything worthy of being called a cold spell.

Interesting how the northerly has just degraded run by run to the point where its now not even worthy of the name. Suppose the one comfort is that it proves nothing is set in stone. Lets see what the ensembles and ECM say later. METO again the best chart tonight.

Annoying that the downgrades all well within the reliable time frame which echoes last year with all the cold disappearing 24 hours away.  Nothing to suggest this trend will cease either. No certainly on this weekends storm would be nice to get the cold air back but I suspect we won't.

[No Balls Like Snow Balls]

several hundred miles perhaps?

A couple of hundred miles at 4 days away in the grand scheme of things is a pretty similar placing of the LP in my book. Of course i accept there is always a queue of people waiting tp prove you wrong and be pickey.

[frosty ground]

i understand that nick, but does it totally mean the gfs is wrong? i see the 12z and again its sticking to its exit and flattening out the ridge.mr cynical here is thinking that maybe people dont want the gfs to be right because quite frankly its a horror show for those searching for cold. im not suggesting it is right, but surely it has to be a possibility.

Mr Cynical...... could it be that the gfs is out on its own with not a great deal of support across the range of models?

If I was cynical I would suggest people want the gfs to be right because they wanna see the world burn..... but I'm not cynical I am a realist and don't by snake oil in the form of it's the form horse etc etc

[Aiden2012]

Well the wait for the ecm lets hope something good comes out of it.

[SLEETY]

Where is SM.He must be laughing at gfs now.I bet anything its totally wrong .You only have to look back over the last few years to confirm that.Always has everything too far East in these situations.

[mushymanrob]

Mr Cynical...... could it be that the gfs is out on its own with not a great deal of support across the range of models?

If I was cynical I would suggest people want the gfs to be right because they wanna see the world burn..... but I'm not cynical I am a realist and don't by snake oil in the form of it's the form horse etc etc

 

... cynically when the gfs was showing cold options recently it was suddenly a great model!

now its not, its suggesting mild/average, it has 'no support' (ok not you said that).... or does it?

 

 

looks pretty flat to me, looks like support to me.

my point is that i dont think it can be ignored , thats realism.

Edited December 23, 2014 by mushymanrob

[MR EXTREMES]

Day 5 charts

GFS

Northerly, main low tracking east with the secondary feature pushing south towards Italy

 

Parallel

Main low tracks south east down the east coast of the UK.

 

UKMO

Similar track to the GFS(P) but much quicker, cold easterly flow across the south eastern third of the UK

 

GEM

Another bizarre evolution from this model.

 

The GFS remains the odd one out with the main drive of that low, though there are plenty of options on the south/south easterly track of the low. A cold block remains the favour solution near the UK, though again the chances of snowfall remain limited.

Good post captain and there's no question now the models are in an agreement !.

Once we get the mlb in place over the uk you can be sure cold surface nice lid on the cold air and possible easterlies and this block could well stick around for sometime it also will hold back the zonal flow I got a feeling we will start seeing lows heading se and a slow progression to a colder and colder output as we head into the new year!.

And I'd bet a bottom dollar the ukmo and ecm will be pretty much onboard with each other.

I've seen these set ups many a winter and there is no doubt in my mind that it's certainly going to be a wintry feel even in the sunshine overall I'm happy with tonight's and this mornings model outputs I think there's most certainly a close similarities between them.

Sold colder than has been just recently.

[karlos1983]

... cynically when the gfs was showing cold options recently it was suddenly a great model!

now its not, its suggesting mild/average, it has 'no support' .... or does it?

 

814day.03.gif

 

looks pretty flat to me, looks like support to me.

my point is that i dont think it can be ignored , thats realism.

I agree it shouldn't be ignored, it's a legitimate model, so it can't be dismissed, but it would need more support than it's getting currently to worry me. Personally

[frosty ground]

... cynically when the gfs was showing cold options recently it was suddenly a great model!

now its not, its suggesting mild, it has 'no support' .... or does it?

 

814day.03.gif

 

looks pretty flat to me, looks like support to me.

my point is that i dont think it can be ignored , thats realism.

It looks flat therefore surface conditions can be attained...... does that chart contain the 12z runs?

[phil nw.]

I posted earlier regarding the differences wrt Canadian tough and the split of the jet into the Atlantic and it's still showing there between the UKMO and both GFS models.

It can be seen at T96hrs again and it starts even earlier with the UK model much firmer on that downstream ridging towards Greenland.

This of course means the whole downstream pattern is more progressive from the American models sending the UK low on a more northerly path and eventually builds only a transistional High further south.

Anyway the ECM is coming out so we shall see how it handles the upstream modelling around T96hrs. 

[mushymanrob]

anyway, why are so many knocking the gfs? in the more reliable timeframe its COLDER then the ecm..

 

Edited December 23, 2014 by mushymanrob

[LomondSnowstorm]

It's very rare for one models to be right if almost all the other models take a significantly different route *edit* at Day 4 (seen it happen a few times Day 6 onwards), it's rarer still for that to happen when the model in question is the (old) GFS and the difference largely stems from it being less amplified than the rest of the NWP. *If* the ECM remains broadly the same with the track of the low as it was this morning I'd say it's highly likely that the more southerly tracking low with a cold block building in behind will be closest to the mark. Much as posters are understandably annoyed by the lack of decent low ground snow (or any low ground snow for those in the south and other unfavourable locations) since March 2013, it still isn't the case that the most progressive solution is automatically right, and hopefully that pessimism will be alleviated somewhat if we manage to get at least some low ground snowfall over the Christmas period. It's certainly far from the worst Christmas period outlook I've seen - Christmas Day 2011 was warmer here than many days in the following July, 2012 was a complete washout and 2013 saw transient cold before some incredibly stormy conditions returned.

Edited December 23, 2014 by LomondSnowstorm

[Captain Shortwave]

... cynically when the gfs was showing cold options recently it was suddenly a great model!

now its not, its suggesting mild/average, it has 'no support' (ok not you said that).... or does it?

 

814day.03.gif

 

looks pretty flat to me, looks like support to me.

my point is that i dont think it can be ignored , thats realism.

Probably should wait for the NOAA chart for today which should be released shortly I believe. 

ECM backs the UKMO btw

An area of 850s of -8C close to the south east, so wintry showers in that north easterly flow with the risk of snow even getting to low levels.

Edited December 23, 2014 by Captain shortwave

[Matty M]

The EC 12z may be about to tease us!

 

[phil nw.]

I posted earlier regarding the differences wrt Canadian tough and the split of the jet into the Atlantic and it's still showing there between the UKMO and both GFS models.

It can be seen at T96hrs again and it starts even earlier with the UK model much firmer on that downstream ridging towards Greenland.

This of course means the whole downstream pattern is more progressive from the American models sending the UK low on a more northerly path and eventually builds only a transistional High further south.

Anyway the ECM is coming out so we shall see how it handles the upstream modelling around T96hrs. 

If we compare the 2 Euro models with the 2 GFS the difference is clear at T96hrs.Much better ridging on the Euros again.

Edited December 23, 2014 by phil nw.
spelling!

[Matty M]

Comedy gold from the ECMWF,

 

If this was to come off, would make a mockery of looking at Ensemble means etc..

 

Edited December 23, 2014 by Matty M

[gottolovethisweather]

Two days on from this post, and both the UKMO and the GFS P continue to toy with the idea of lowering heights across Europe and a colder Northeast to Easterly flow incoming to our shores post the 27th/28th problem low.

 

https://forum.netweather.tv/topic/82046-model-output-discussion-the-run-in-to-christmas/?p=3093572

 

Don't expect to tie down any snow potential events until within 24 hours but yet, the 27th and 28th December depression may yet be a snow-producer for a fair few of us, given last evening's encouraging 10-day media forecast.

 

Not much has changed to alter my views from many of my recent posts, even back on 16th December when you I suggested the broader weather pattern could be developing into a colder one. As long as one cares not to look into things too deeply, the bigger picture hasn't changed much.

 

Is still a long-shot for any lowland snow down South I guess but you never know. What I will enjoy, once I've shifted this winter bug of mine are some crisp frosty and bright days which to me are much more seasonal than what we are enduring right now.

 

Over to the ECM to continue the colder scenario post D5. 

 

Happy Christmas all. 

 

PS ECM delivers as promised, still t+120 hours but hopefully the broader viewpoint is coming off.

Edited December 23, 2014 by gottolovethisweather

[mushymanrob]

It looks flat therefore surface conditions can be attained...... does that chart contain the 12z runs?

 

dont think so, and data will change that far ahead. i totally accept the gfs might well be a complete outlier, im just suggesting that theres a chance it might not. realism. '

[Geordiesnow]

I think a lot will depend just how much amplification we will get and how that will affect the sinking low will depend how quick any threat of the Atlantic coming back, you can clearly see not only the low tracks in a different direction, any amplified ridge is not as strong as on the UKMO and ECM. 

 

In the realiable timeframe, the outlook is a cold one if not especially snowy but some seasonal weather is on the way for sure. Another thing, detail at this stage will be sketchy so i would not rule out anything just yet, especially if the Euros are right.

[Banbury]

this evenings GFS is even quicker than the last at flattening the pattern and only one way of going and that is a azores blowtorch grim for all coldies out there

 

GFS is correct then? Can you explain why you think this is the correct outcome??  Cheers