Model Output Discussion - The Run In To Christmas

[BLAST FROM THE PAST]

What i dont understand is where have all the heights gone!! I mean we had some serious greenland heights at 1060 mb and they've just vanished to nothing in literally 24 hours! ! How om earth is that possible!!! Okay a slight downgrade is possible always but nothing to this extent! ! Something is seriously wrong with the models or theyve picked up on a change that wasnt expected.

That's the point, they weren't ever there and only projected to be there.  But we also have to say we aren't there yet so more changes could and probably will occur.

 

BFTP

[bluearmy]

How important is this - NAO and SSW?

It is talked a lot on here but is it the be all and end all?

 

 

a -NAO is simply the measurement of the pressure pattern to our west.  if you take it that an icelandic low and azores high will be strongly positive and a greeny/icelandic black and azores low strongly negative then you can fiddle around inbetween.

 

clearly a -NAO would statistically give the uk a better likelihood of cold conditions but it is possible to get cold without one. (ie scandi block with the uk just able to receive the continental flow before the atlantic takes it north)

 

SSW is statistically significant re cold and viewing the strat thread will assist. again, its not a precondition for cold here.

[West is Best]

That would likely make a cold spell unlikely till after mid January.

 

Any chance you could take silly posts like that off to the moan thread?

 

Not really sure why there is annoyance at the 06z GFS. It looks pretty spectacular to me for the third into fourth week of December. The storm on 27th has the potential to cause a lot of problems and will be far from mild, with snow potential still in the mix.

 

GFSP is terrific.

 

One thing I'd add: often when there's a pattern shift we go through these model wobbles. They may go down the ECM mild route but I'm not so sure, I'm not so sure ...

Edited December 20, 2014 by West is Best

[karlos1983]

a -NAO is simply the measurement of the pressure pattern to our west. if you take it that an icelandic low and azores high will be strongly positive and a greeny/icelandic black and azores low strongly negative then you can fiddle around inbetween.

clearly a -NAO would statistically give the uk a better likelihood of cold conditions but it is possible to get cold without one. (ie scandi block with the uk just able to receive the continental flow before the atlantic takes it north)

SSW is statistically significant re cold and viewing the strat thread will assist. again, its not a precondition for cold here.

SSW doesn't gaurantee cold for the UK though, just significantly increases the chances as it promotes Northern Blocking

BA I know you know this, just adding

Edited December 20, 2014 by karlos1983

[J10]

At least cold air is trying to push south, last winter was a cold free zone!

 

Indeed, Some people have already have more frosts than last winter, and more severe frosts than last winter already.

[Polar Maritime]

That's the point, they weren't ever there and only projected to be there.  But we also have to say we aren't there yet so more changes could and probably will occur.

 

BFTP

 

Exactly Fred, 

.

They were falsely modelled.

 

I like the way you put it.. But at the range it's been Model'd at reg the Greenland High it was always going to be false no matter what it shows.   :smiliz19:  

Edited December 20, 2014 by Polar Maritime

[karlos1983]

.

 

I like the way you put it.. But at the range it's been Model'd at reg the Greenland High it was always going to be false no matter what it shows.   :smiliz19:

[terrier]

Just looked at the gfs 06z run and that's a awful run for coldies. Think the ECM will be bang on the money. Yes it's been throwing out different output past t144 but we see that other models are moving towards the ECM solution. Also just read cohens update on the strat thread. And it's grim reading for a ssw. Now looking like late jan. I'm starting to wonder after all the background signals looking favourable if the mets lrf winter forecast will be spot on.

[ukpaul]

Just one chart posted in the last two pages.

 

I thought this was the model thread, if you don't back up your thoughts with evidence then why bother posting?

 

Most of this should be in the moan thread where it belongs. If each posted what they think is poor then we can judge them on it.

[johnholmes]

So up and down and round and round the synoptic models go. Are the anomaly charts any better-well yes but not resoundingly so?

Not looking prior to 5-6 days ahead as the anomaly charts start at day 6.

 

Last evening NOAA below

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

The chart in the UK area does suggest a colder spell over and beyond Christmas but no real deep cold. That is something they have never really suggested since they began this signal of a colder flow at 500mb from north of west into the UK and a fairly rounded trough over northern Europe. Both 6-10 and 8-14 show this. It was about 4 days ago that the ECMWF-GFS outputs started to suggest something along these lines but only 48 hours ago that NOAA began to pick this up.

Hindsight is a wonderful thing! Looking at these outputs from about last Monday and the split flow into the UK area on the ECMWF version, link below, initially way west

http://mp1.met.psu.edu/~fxg1/ECMWF_0z/hgtcomp.html

over N America, today showing into the UK. All week I have never really suggested, even on my Tuesday ‘ramp’ higher than a 35-40% probability of deep cold. This morning, in terms of anything long lasting from an Arctic source probably back to 25-30%

On all 3 charts the contour that ends up over southern England has begun its travels over N America south of Alaska then south of the Gt Lakes so no deep cold and a very long sea track rather than a contour coming down from northern Greenland or north of Jan Meyen. In other words all the time the air is Polar not Arctic in origin for most of the country. Nor is there any real signal out in the 8-14 NOAA chart of this flow changing markedly or the trough extending well south into Europe.

So overall I think we are set to have mainly Polar Maritime air, temporarily southern areas associated with one or more deepening lows, just about into winter style Tropical Maritime, thanks to the marked temperature contrasts, with more northern parts keeping, for the most part, air of Polar origin. Whether any further really deep lows expected post Christmas are likely again is impossible to say from the anomaly charts. Further wind for sure as systems move quickly in the strong flow over the Atlantic and how westerly or slightly meridional that may be still seems open to either pattern to me. As to where snow may fall on low ground then the Border counties north I would think but back edge snow MIGHT occur further south with the post Christmas storm. So quite good for the Scottish ski industry but not so good for many lower level European ski resorts.

A very difficult upper air pattern to really get right let alone the surface so lots of room for many ups and downs over the festive season for many cold lovers on here.

[J10]

Deleted  I was looking at the wrong version of GFS on NW.

 

Apologies.

Edited December 20, 2014 by J10

[Polar Maritime]

.

 

I like the way you put it.. But at the range it's been Model'd at reg the Greenland High it was always going to be false no matter what it shows.   :smiliz19:

Not really sure what your point is? I put exactly what BFTP put yet I'm somehow reading it wrong?

Edited December 20, 2014 by Polar Maritime

[492]

http://mp1.met.psu.edu/~fxg1/ECMWF_0z/hgtcomp.html

 

The 8-10 day 500mb anomaly charts show a strong northerly component across the UK with ridging to the W of the UK . The northern part of the ridging over Greenland is further east than yesterdays output as is the trough to the east. The last few days have seen variable patterns projected at this timescale at 500mb with the strong ridge extending west-east to the south of the UK now transferred westwards into the atlantic. It remain to be seen whether the latest forecast pattern will be replicated over the next few days but there has been a trend to a more favourable pattern for cold over recent days. Models are toying with the idea of cold outbreaks every few days. Even xmas day although not snowy looks pretty cold. With the close proximity of such cold air to our north and the presence of the Greenland Ice cap with some evidence of ice flows extending eastwards from the Greenland coast north of Iceland there must be a possiblity that any northerly outbreak although short lived could be potent bringing the prospect of snowfall to many parts.      

[Polar Maritime]

Just looked at the gfs 06z run and that's a awful run for coldies. Think the ECM will be bang on the money. Yes it's been throwing out different output past t144 but we see that other models are moving towards the ECM solution. Also just read cohens update on the strat thread. And it's grim reading for a ssw. Now looking like late jan. I'm starting to wonder after all the background signals looking favourable if the mets lrf winter forecast will be spot on.

 

Really?

 

[J10]

So up and down and round and round the synoptic models go. Are the anomaly charts any better-well yes but not resoundingly so?

Not looking prior to 5-6 days ahead as the anomaly charts start at day 6.

 

Last evening NOAA below

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

The chart in the UK area does suggest a colder spell over and beyond Christmas but no real deep cold. That is something they have never really suggested since they began this signal of a colder flow at 500mb from north of west into the UK and a fairly rounded trough over northern Europe. Both 6-10 and 8-14 show this. It was about 4 days ago that the ECMWF-GFS outputs started to suggest something along these lines but only 48 hours ago that NOAA began to pick this up.

Hindsight is a wonderful thing! Looking at these outputs from about last Monday and the split flow into the UK area on the ECMWF version, link below, initially way west

http://mp1.met.psu.edu/~fxg1/ECMWF_0z/hgtcomp.html

over N America, today showing into the UK. All week I have never really suggested, even on my Tuesday ‘ramp’ higher than a 35-40% probability of deep cold. This morning, in terms of anything long lasting from an Arctic source probably back to 25-30%

On all 3 charts the contour that ends up over southern England has begun its travels over N America south of Alaska then south of the Gt Lakes so no deep cold and a very long sea track rather than a contour coming down from northern Greenland or north of Jan Meyen. In other words all the time the air is Polar not Arctic in origin for most of the country. Nor is there any real signal out in the 8-14 NOAA chart of this flow changing markedly or the trough extending well south into Europe.

So overall I think we are set to have mainly Polar Maritime air, temporarily southern areas associated with one or more deepening lows, just about into winter style Tropical Maritime, thanks to the marked temperature contrasts, with more northern parts keeping, for the most part, air of Polar origin. Whether any further really deep lows expected post Christmas are likely again is impossible to say from the anomaly charts. Further wind for sure as systems move quickly in the strong flow over the Atlantic and how westerly or slightly meridional that may be still seems open to either pattern to me. As to where snow may fall on low ground then the Border counties north I would think but back edge snow MIGHT occur further south with the post Christmas storm. So quite good for the Scottish ski industry but not so good for many lower level European ski resorts.

A very difficult upper air pattern to really get right let alone the surface so lots of room for many ups and downs over the festive season for many cold lovers on here.

 

Excellent analysis there John. Completely based on facts and entirely objective.

[ukpaul]

People might want to see how the GFS translates into weather on the ground. As such here's the precipitation page, you can click around to check out potential snow depths.

 

http://www.meteociel.fr/modeles/gfs-para/royaume-uni/precipitations/3h.htm

[OldMetMan]

The models' ambivalence as to what happens on or after Christmas Day continues. The spectacular looking LP for 27th would indeed be interesting, but I guess the chances of anything like it happening at this distance are pretty remote, although having said that, it is a possibility.

 

What I find odd still is that there have been no real signs within the models of a pressure build from the NW after Christmas. Pressure rises to the S or SW yes, but that is all. Several days of cold air coming S across the Norwegian Sea, LP much weaker over Scandinavia, a situation which has in the past given rise to some noteworthy frontal battle grounds between cold and mild.

 

Here's a nice example from 1982.

 

 

That one produced significant snow across the S as an advancing frontal zone stalled as it pushed into the cold air to the N.

 

As always, I am aware that no 2 situations are ever the same, and I wouldn't mention it but for the indecisiveness of model output at that time, but it's an intriguing possibility and, dare I say it, no less unlikely than the GFS major storm!

 

It will be interesting to see later model output and whether we have any sort of consensus developing.

 

 

 

 

[Tamara]

Disappointing read to be honest. We were hoping for a SSW in late December/early January and now this is pushed back to late January (if it happens). It is becoming clear that the cold hearted winter forecast is in jeopardy!

 

With the polar vortex weakened natural state as it is this winter, we don't actually require an SSW this season. In many ways it might actually be preferable we didn't actually - but that is for another time and place and not this thread.

 

One thing that can be said with absolute certainty is that it is far far too premature to declare that last sentence.

 

No-one can deny that expected, and very well reasoned, evolution to a dominant -AO pattern has been put back. But then again it was being viewed at the outset from an accelerated track - faster than some of the coldest winters ultimately have delivered- and herein lies the perspective we should currently take with the outlook into the New Year. Which clearly means that there is a lot of winter to get through yet

 

But back to the beginning : Customary lack of apology extended here for snippets from a previous update a few days back as a usual attempt to try to provide continuity and progress..and most of all perhaps for purposes of this thread, some perspective. I think we need to remind ourselves where we stood earlier this week. A lot to take in since then

 

---------------------------------------------------------------------------------------------

 

<There is no surprise at all to see indeterminate suggestions from G5 and ECM ensemble data for the further outlook from Christmas itself and beyond New Year

< a panacea of solutions appear in the modelling.... including cold pattern solutions.

<This suggested upstream change, courtesy of continued modelling of GWO heading to phases 1 and 2 in conjunction with falling AAM is well advertised now across the modelling.

<The turn of the year and early part of 2015 is going to be very tricky to predict I think, and we should be prepared for quite possible sudden and significant changes of travel for that trend period in the lead up to Christmas.

Slower flow leaves room for better jet amplification. However, taking into account present conditions over the polar field with zonal winds only just set to start falling once again over this period in response to fresh wave activity on the vortex, then calculating amplification equations is going to be difficult. Much easier for the models to handle much more predictable faster zonal flow.

If WAF really ramps up, as it may well do in the days to come - then the calculations will increasingly become more and more in our favour and the type of alluring GFS output we are currently seeing in FI may become more and more plausible sooner rather than later. Caution advises, as reasoned later in this post, that it might be a little premature at this time - but all bets are off as stated in the extended period.

< the EPO ridge heading into the pole over forecast period will prompt further attacks on the vortex.

With that in mind, and with the polar profile improving once more after the recent lull - as zonal winds slow more and more over the remainder of December courtesy of the resumed wave activity on the vortex - could it be that the amplification signal being picked up in the last week of this month leads us to simultaneous timing of vortex demise and flip in the NAO from the persistently + signal we have been seeing... early in January?

There are dominoes to fall that need a little luck (for coldest outcomes)

Hopefully the troposphere/stratosphere relationship (allied with the atmosphere calling in a favour for us) will do the rest....

Edited by Tamara תָּמָר, 16 December 2014 - 19:05

-----------------------------------------------------------------------------------------------.

 

And so it is proving very tricky, and even more complex to see the way forward than could have been anticipated

 

The greatest uncertainties of all lie in the upcoming tropospheric/stratospheric direction of travel. Much hinges on these developments to take advantage of what could be a big opportunity to flip the pattern properly colder in the shorter/medium term. Much as has been written about in detail in recent times.

 

There continues to be a further possible bite at the cherry upstream for atlantic amplification potential and there is still ensemble support for this to happen this morning. It is not time to throw in the towel on the Christmas/New Year week just yet. This further amplification in turn would provide the wave 2 activity that would be the catalyst to undermine further a very weak and vulnerable vortex and which would get us to a more sustainable cold pattern relatively quickly. Much as highlighted a few times previously

.

The GWO is fast orbiting Phase 1, and Phase 2 (atlantic amplification phase) is proving too much of a 'pit-stop' first time around. This is behind the current erratic chopping and changing and apparent frustrating atlantic pattern phasing through the festive week

 

The sequence upstream ( underlined by -AAM tendency which on its own makes model tracking harder anyway) is accordingly fast moving, and is set to be punctuated by a brief poleward westerly burst (30N).

 

 

 

This is behind some of the flatter modelled scenarios cropping up in the modelling. No surprise in the absence, yet, of zonal winds across the polar field being reduced sufficiently, to see the modelled mid latitude ridge response over Christmas itself and hence the more flattened first attempted atlantic amplification than seemed apparent a day or two back. The knock-on effect of this is that we require greater things from any second round of amplification - which is the gist of what bluearmy has said this morning

　

 

GWO forecasts over the next day or two will continue to give us a guide as to where models take their cue regarding further attempted amplification. There remains guidance this morning for rebound to Phase 2 from 3/4 and this supports NOAA guidance for ensemble amplification support

 

.

 

The degree of amplification upstream after Christmas will determine the aforementioned wave 2 activity on the vortex that in turn is required to get us to any immediate longer term cold pattern ( if it is going to happen) faster.

 

In the absence of this (or it being too insufficient) the reset pattern, (much under discussion already elsewhere in reaction to the latest Cohen blog) is the slower train to cold coming from the east - and that prospect is clearly going to prove quite unacceptable in this thread!!  But here we should remind ourselves that we don't need an SSW to get us a sustained cold spell. December/Jan and Dec 10 are very good recent examples

 

Plenty of very good information has been written by members in the strat thread in the last day or two indicating possible split vortex potential courtesy of this wave activity around day 10. Lets hope that these signals verify into something concrete - the coming few days will tell us more about this though and best to avoid pre-emptive assumptions in the meantime

 

Uncertainty can be a good thing as well as bad - and in the face of such outlined complexity then best to make no predictions and see what the coming days brings as further changes are likely to come

 

Frustrating at the moment I understand it may be, but lets please at least hold off indirect winter obituaries via direct LRF obituaries. We can only reason the way ahead but ultimately, no-one, not even the professionals in the METO and elsewhere, can control and 100% predict the weather.

 

There is far too much short term knee-jerk reaction in this thread each day as it is, without terminal seasonal knee-jerk on top of this..

　

　

　

[KyleHenry]

Just looked at the gfs 06z run and that's a awful run for coldies. Think the ECM will be bang on the money. Yes it's been throwing out different output past t144 but we see that other models are moving towards the ECM solution. Also just read cohens update on the strat thread. And it's grim reading for a ssw. Now looking like late jan. I'm starting to wonder after all the background signals looking favourable if the mets lrf winter forecast will be spot on.

1st of March 2015 for revision of long range forecasting.

Regards the SSW being delayed this was always a possibility and if it results in it being 3 weeks further forward, it was still a great forecast from Chino and Tony.

They assessed all the data and made a great call. What could not have been seen was the last months increase in solar energy output.

But looking at what Judah states regarding the modelling of the AO in next 5-7 days and it turning negative with the NAO following suit, I'm convinced that the anomaly charts are correct with the Greenland ridge prediction.

In the end it's personal what your feelings are but the models are struggling, some aren't even functioning (GFS P) and ECM outliers are numbering 2 runs now.

So going by Judah's forecast A -AO this week. Not that long to wait and see if true.

[ukpaul]

1st of March 2015 for revision of long range forecasting.

Regards the SSW being delayed this was always a possibility and if it results in it being 3 weeks further forward, it was still a great forecast from Chino and Tony.

They assessed all the data and made a great call. What could not have been seen was the last months increase in solar energy output.

But looking at what Judah states regarding the modelling of the AO in next 5-7 days and it turning negative with the NAO following suit, I'm convinced that the anomaly charts are correct with the Greenland ridge prediction.

In the end it's personal what your feelings are but the models are struggling, some aren't even functioning (GFS P) and ECM outliers are numbering 2 runs now.

So going by Judah's forecast A -AO this week. Not that long to wait and see if true.

 

The GFS P is actually back (quicker than expected) and I hope that people take note of it (at least in its high resolution period).

[West is Best]

Just looked at the gfs 06z run and that's a awful run for coldies. 

 

How exactly is this chart for Christmas Day morning 'awful for coldies'?

 

If you had offered this chart to the forum a fortnight ago 9/10ths of us would have frostbitten off your hand for it.

Edited December 20, 2014 by West is Best

[Summer Sun]

Its one of those years where snow just doesn't want to fall and lay at lower levels

 

The best I can find away from Scotland is this

 

 

Day 10 sees the highest totals over northern Scotland starting to drop

 

 

Christmas day look dry fine and bright after a frosty start with temps around 3 to 6c

 

 

Boxing day looks a bit milder away from Northern Scotland for those heading to the sales, football matches or what ever else you may have planned

 

Edited December 20, 2014 by Summer Sun

[Banbury]

sorry frosty but to me it looks mild upto Wednesday then perhaps a fleeting cold snap over xmas. Before we're back in the milder air. The models have taken a huge jump away from cold over last 36hrs.

According to GFS as that goes so far out ???

Edited December 20, 2014 by Banbury

[snowking]

 

 

There continues to be a further possible bite at the cherry upstream for atlantic amplification potential and there is still ensemble support for this to happen this morning. It is not time to throw in the towel on the Christmas/New Year week just yet. This further amplification in turn would provide the wave 2 activity that would be the catalyst to undermine further a very weak and vulnerable vortex and which would get us to a more sustainable cold pattern relatively quickly. Much as highlighted a few times previously

.

The GWO is fast orbiting Phase 1, and Phase 2 (atlantic amplification phase) is proving too much of a 'pit-stop' first time around. This is behind the current erratic chopping and changing and apparent frustrating atlantic pattern phasing through the festive week

 

The sequence upstream ( underlined by -AAM tendency which on its own makes model tracking harder anyway) is accordingly fast moving, and is set to be punctuated by a brief poleward westerly burst (30N).

 

 

 

This is behind some of the flatter modelled scenarios cropping up in the modelling. No surprise in the absence, yet, of zonal winds across the polar field being reduced sufficiently, to see the modelled mid latitude ridge response over Christmas itself and hence the more flattened first attempted atlantic amplification than seemed apparent a day or two back. The knock-on effect of this is that we require greater things from any second round of amplification - which is the gist of what bluearmy has said this morning

　

 

GWO forecasts over the next day or two will continue to give us a guide as to where models take their cue regarding further attempted amplification. There remains guidance this morning for rebound to Phase 2 from 3/4 and this supports NOAA guidance for ensemble amplification support

 

.

 

The degree of amplification upstream after Christmas will determine the aforementioned wave 2 activity on the vortex that in turn is required to get us to any immediate longer term cold pattern ( if it is going to happen) faster.

　

 

As always another wonderful post Tamara, and the point above is a key one in to the medium term

 

The GWO forecast linked is a GFS-derived forecast....and that sort of GWO projection ties in pretty well the strongest day 15 ECM EPS cluster upstream with around 20 solutions (by my own manual counting) re-developing some form of North Atlantic ridge, and most members agreeing on a continued amplified trend, courtesy of our -EPO ridge (in turn driven by the well advertised Aleutian low - which of course is also helping to drive the next strong phase of Wave 1 activity).

 

ECMWF, which led the way with the last major Kelvin wave, keen on driving us back around the MJO phases too:

 

 

Ultimately we would like to end up somewhere towards phase 7:

 

 

Whilst I can understand why those who may have built up shorter term prospects a little prematurely are a little disappointed there is still very little reason to be despondent in to the mid-range

 

SK

[phil nw.]

A lot of uncertainty going forward but i think these are the best times for chart viewing,especially wrt to the constant attempts of ridging into the vortex.

Short term a couple of milder days before the cold air comes south again on Christmas eve.

 

It looks very changeable after the Boxing day ridge collapses as a new low heads NE from the S. Atlantic and now the track looks further north it will bring some milder air back in for a short while.

 

Very up and down then next week with mainly dry and colder Christmas and Boxing days before the unsettled spell kicks in.

 

Longer term i don't see any prolonged cold or mild as the jet pattern looks very amplified with continuing transitions between the 2 weather types into the New Year.

 

A quick glance at the London 2m Temperature ens graph

 

shows a wide spread but interestingly quite a bunching of cold members as we enter January.

A look at the Naef's and ECM t240hrs anomalies

 

still show those Atlantic heights and the troughing to the east.

Not a bad set overall with no real sign of a change to prolonged mild and more chances of some cold incursions from the north or north west.

Edited December 20, 2014 by phil nw.