Model Output Discussion - The Run In To Christmas

[MR EXTREMES]

Comments on latest NOAA and general comments following on from that for the Christmas period

 

6-10 from far w of chart and trough ridge along with -/+ve suggestions looks about same as last issue-canadian trough is looking about the same, re position/intensity-ridge/+ve heights and the +ve heights remains around 370dm + which is certainly a significant +ve height anomaly and it coincides with the ridge-this as before causes the 500mb flow to move towards the uk with a direction well n of west, with still quite a rounded trough over the uk along with some SLIGHT extension into Europe but NOT much.

Height over far s of uk=remains a touch over 546dm

The 8-14 and it looks pretty similar to me in all aspects to the last issue; possibly the slightest extension s of the uk trough, height far s of uk=546dm/touch above much as 6-10 so the pattern looks likely to be as shown on both these over the 6-15 day time scale.

For ski fans (like myself, we could do with the extension s of the trough into the uk to bring snow in decent quantities to lower levels than many resorts have had for a week maybe longer!

For the UK, remembering these are mean charts over the period given then the probability of sharper extensions is present. Small, relatively, upper troughs are best left to the synoptic models at shorter time scales.

Perhaps we can take a look at the 2 major synoptic outputs, maybe 3 if we use the UK model?

For some obscure reason folk want to know weeks in advance what it will do on the 25^th of this month, never any other month and some do get worked up when the models cannot do this, be it 240h or 96h out but never raise a murmur on 25^th of any other month. Scientifically this is totally illogical but never mind.

Link to NOAA output

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

For details on how this and EC-GFS were summed up from this morning please see the post with links in the technical thread. It is NOT technical.

A link to see how the EC and GFS models at 00 and 12z have coped with this from 240h down to today is below.

The GFS 12z version from 240h and it has some similarities, at least not showing any flow from the SW. The 00z a little more consistency on most runs, again no SW flows shown

ECMWF 12z and 00z perhaps not quite the consistency of either GFS runs?

Anyway I will leave it to the reader to make their own mind up.

What I am trying to illustrate is that, to me if not you the reader, the anomaly charts have been more consistent than the synoptic charts in predicting this substantial build of pressure in the southern Greenland area for a number of days. Once the +ve heights began to show substantial numbers east of the Canadian trough, this partly the cause of the trough moving west, then the pattern they show for 6-14/15 days ahead looked fairly clear.

This build of heights and surface pressure below it is the cause of the lows/depressions running east not NE if you look at the Fax chart, link below

http://www.weathercharts.org/ukmomslp.htm#t0

If you look at their raw data below the Fax charts out, currently, to 25 December note how the 552dm line is pushed south with colder upper air pulling in behind it. Also the transfer south of the surface trough to cover most northern areas by Christmas Day. Still held up as it often is by the ‘lee’ low that often develops in Arctic flows over Iceland. This will not change much until/IF the upper flow turns north of west over the UK as the trough then extends into Europe. At the moment there is no sign of that happening.

Will it happen, sorry do not know. The next further out link I use is the MJO and that is currently and predicted to be in a very low orbit. This usually means that the weather patterns over the UK are likely to be much as they are for some time to come. How long? Again I do not know but the MJO change to a relatively reasonable orbit may signal a change. Again to what I have no idea. Perhaps the other links we read in the OPI or Stratosphere thread may give us more guidance there.

 

Finally how active is this incursion of colder air likely to be? That can only come from shorter time scale guidance using the synoptic models. Judging by the quite strong indication from UK Met, they are fairly convinced it is going to quite marked in one or more parameters, be it wind, rain or snow.

 

If things look to be changing I will post again over the next few days. Some look like having snow on the ground or falling over the Christmas period. Stay tuned as no doubt on here we will be treated to all manner of ups and downs before Christmas Day and after.

Sorry John but I really want to re post this !.

I'm not expert but the recent run of models but not the latter ecm don't that pretty much match what we're seeing tonight ?

That looks rather promising from noaa so clearly there really could be some really wintry weather on its way.

[ukpaul]

No Parallel? That's a blow; the op's massive shifts haven't caused the wailing and gnashing of teeth as they would have done previously, given that there was a comparison to be made. Just at the wrong time, too, when we are wanting to look at the hours out that are on the edge of the credible. Given the bizarre chart that the ECM threw out earlier I think the ensemble spread of both will be a workable alternative.

 

Edit: and the UKMO of course, just remembered that it's coming in range.

Edited December 20, 2014 by ukpaul

[Altohumorous]

I've been looking at a pattern in the model forecasts that to me has existed through the autumn but of more relevance since the onset of the darkest months. to me this pattern has been consistent and the models have been overall correct - we remain, as we have done since early November, in a very very gradually cooling scenario.  And the patterns predicted for the rest of the year continue overall that gradual, very gradual, cooling trend.

The weather not surprisingly overall is very undramatic. This reflects the majority model output. We appear to be in a continuing trend of very gradual cooling overall. It's like Sisyphus and his rock and the hill. I think we get a little closer each time, though she knows the outcome is impossible.

[Trom]

ECM London ensembles.

 

 

control goes into deep freeze after a brief warm up.

 

I know GFS ensembles are showing a toppler and fairly short lived cold spell but as I have said previously, any modeling that shows a remotely organised PV into January needs to be treated with suspicion.

IF we get a good start and decent amplification and strong Atlantic ridge I think we will quickly see the length and severity of the cold being upgraded across GFS ensembles.

The scenario they show with the PV moving back West and reorganising is unlikely given the strat warming and likelihood of an Atlantic and EPO ridge. Far more likely will b a split with the dominant half of the PV setting up home to the East.

 

My concern is only that we get a good start rather than the halfhearted ECM attempt.

I really think we are on the verge of something special developing in January but want to see ECM get fully on board with the initial cold spell first.

 

The spread post 27th is dramatic suggesting the models are struggling.  Picking a model or run or ensemble member is too tough to call.  The volatility run to run and between models is extreme right now with more cold trends appearing but far from being convincing on anything..  

[Jonan92]

Don't like the 00z run, quite a chunck of the polar vortex is transferred to the Canada area, that energy doesn't allow the height to build up nicely and there is just a short cold snap, if the trend continues the atlantic side would get a lot of energy to keep going on

[Mucka]

Output going the wrong way this morning unfortunately with the shortwave to the NW being held up a la EM and UKMO also phase it with the shortwave to the SW

 

 

GFS a little better

 

 

But as with UKMO far too much energy coming over the block.

 

 

So every way you can think of the cold spell being wiped out is pretty much being modelled one way or another though there should still be some cold air around.

I'm not too dismayed because there is till hope yet and even if it does go TU I think we will get another shot first week of January.

Amazing how the weather seems to always find a way of scuppering UK cold but plenty more twists and turns to come. 

 

EDIT

 

GEM at least keeping the faith

 

 

Though it does topple the ridge fairly quickly afterwards.

Edited December 20, 2014 by Mucka

[Mucka]

GFS ensembles are  a horror show with plenty showing this sort of thing for day 6. I will check back if they improve in FI

 

 

Starting to look like ECM picked this out unfortunately.

 

 

EDit

 

GFS ensembles are about 50/50 colder/blocked milder/zonal once into FI proper (day 8+) after the messy mid term which shows there is still hope of new cold pattern setting up from the aftermath.

Edited December 20, 2014 by Mucka

[TSNWK]

But the issues are apparent from day 6 and ECM is top of the board for 144 verification, it has also been rather persistent the past couple of days in offering a different view of the situation.. ECM is known to flip flop day 8 onwards but is one mighty steady eddy under 168'

I posted the above last night,unfortunately for us coldies this mornings runs are suggesting a definite trend towards the way the

ECM has been seeing things the last couple of days.

[chicken soup]

Why is it like pulling hens teeth to get cold and snow in this country....does my head in every winter....i refuse to believe another model run again beyond 48hrs.

[Long haul to mild]

So just a brief toppler on the GFS this morning but that still looks like a nasty storm, especially for the Eastern side of the UK.

For what it's worth I don't think the evolution between Christmas and New Year is anything like nailed yet.

[Ali1977]

I have a feeling the ECM is about to flip cold, just to complicate matters.

[Captain Shortwave]

Well the GEM is finally out so day 6 charts

UKMO

GFS

GEM

UKMO looks like it is struggling to be honest. GFS is ok with the ejecting low from the Atlantic trough developing into a deep depression which runs down the north sea. Snow possible behind the wind and rain as a cold northerly feed establishes briefly. The GEM is by far the best of the three with a Greenland high developing with a cold northerly flow.

Edit - ECM

Again worst of the bunch with a deep Atlantic trough beginning to form. Saving grace is the ridge to the west of this has a much better angle to it than the UKMO/GFS.

A real mess this morning, would not like to make a call beyond Boxing day for our part of the world (dry/wet/mild/cold). 

ECM finally finds its cold mojo at days 9/10 but you cannot have any trust in the output by then.

Edited December 20, 2014 by Captain shortwave

[LomondSnowstorm]

The upstream modelling has been abysmal frankly - I don't see how you end up with a chart like the UKMO when there was cross model agreement on a proper inland runner 12 hours ago. Having a positively titled US trough would be far worse than any of the Atlantic shortwave shenanigans going on as at least they don't just shut down the blocking altogether. Hopefully the EC looks a bit better on this front and saves this, even if we miss out on the cold at first.

It's a mess again at +144 with a UK high trying to set up but at least it looks better upstream than the UKMO, cold at the surface

Edited December 20, 2014 by LomondSnowstorm

[Mucka]

ECM no go.

 

 

Might offer some compensation later in run,

Edited December 20, 2014 by Mucka

[Long haul to mild]

Significant differences between GFS and ECM at T168, will have to be resolved soon surely?

 

http://modeles.meteociel.fr/modeles/gfs/runs/2014122000/gfs-0-168.png?0?0

 

 

http://www.meteociel.fr/modeles/ecmwf/runs/2014122000/ECM1-168.GIF

 

Edit : ECM at 192 still going for its Caribbean to Russia low pressure belt too as with last night's 12Z!

Edited December 20, 2014 by Long haul to mild

[IDO]

Yes just subtle differences at D8:  

 

   

[IDO]

As Dr Cohen's update suggests a period of -AO is upcoming and as in cases like this we will need the luck within the NH to get some of the mid-latitude cold. Looking at the last few runs the trend is for the 850s PV to slide its cold in the wrong areas again for the UK:

 

We can see the current D3 cold, around the Arctic: 

 

At D8 the mean is spilling cold to mid-latitudes but a direct miss for the UK: 

 

At D16 we have to rely on the crumbs as the real cold has been piling in to the US: 

 

We really need to be lucky with localised HLB to divert some of the cold especially when the default of late has been to send cold to the US when we get these phases. They need to be more than just what has been showing up, like both the GFS and now the D10 ECM toppler:

 

 

Again the core cold goes to the US at D10 but with a weak Greenland ridge we at least get some transient cold diverted our way before our normal warm sector follows in. It does look like the trop led NH cold spells are not going to be kind to us this early Winter and we can only hope it is not a portent of the pending SSW.

[Man With Beard]

The thing of real note for me this morning is the absence of any lasting cold spell on any charts. Whether it's a GFS superstorm on 27th or ECM's slow sinker by 29th, I think 2 or 3 days of cold is the best any model produces this morning. Ah, the perils of trying to get a Greenland High established.

(Though if the NOAA anomaly charts are to be believed, they may all be sinking the pattern too soon...)

[KTtom]

So to sum up the likely conditions for the 28th December from the overnight runs......

 

Temperatures will range from 2 to 14c in a slack southwesterly flow or a storm force northerly. It could be dry and sunny or very wet with blizzards in the north!

 

That clears things up!

[bluearmy]

as ever, a repeating ECM op is onto something. However, we are are not past the point of no return on this. By tomorrow evening, all should become clear with the handling of the Atlantic 'short waves' and their phasing by Boxing Day. That should mean the models have a handle on what to do with the whole thing thereafter and we see if we are likely to get a cold shot/spell post next weekend as per the ECM ens (very strong on that) or just a brief toppler type scenario with the Atlantic ridge sinking se. hopefully, the scenario over the next 5 days re the interaction of the cut off Atlantic low and the other shortwave features coming into the n Atlantic basin will not be repeated and we can expect a smoother transition to cold when the next cycle appears. low heights in that area carry potential for us moving forward - perhaps short term pain for long term gain. Anyway, the absence of sm for the past few runs tells you much about where we are - too many Xmas parties!

[Matty M]

ECMWF 0z backs up 12z and brings the UKM with it!

[TEITS]

The outlook this morning is much clearer to me and my observations are based on all the output.

 

So Xmas day a relatively weak N,ly across the UK. During Boxing day a ridge of HP from the S will bring settled conditions but still cold. The 27th/28th/29th will see the return of milder, unsettled W,lys as the HP sinks S and LP becomes centered towards the NW of the UK. Beyond into the New Year a much colder spell could develop.

Still think my post from yesterday morning is the most likely outlook and pretty much reflects this mornings ECM. However a couple of things I am unsure of is how long will the spell of SW,lys last and will a severe storm develop i.e GFS 0Z. At the moment I would say the mild SW,lys will last for around 2-3 days and then the cold returns around the 29th. I am more concerned with the storm that will blow E Anglia away because the GEFS control also develops this.

 

http://modeles.meteociel.fr/modeles/gens/run/gens-0-1-180.png?0

 

So I continue with the same outlook but im not totally dismissing the storm that the GFS predicts!

[Duane S.]

So to sum up the likely conditions for the 28th December from the overnight runs......

 

Temperatures will range from 2 to 14c in a slack southwesterly flow or a storm force northerly. It could be dry and sunny or very wet with blizzards in the north!

 

That clears things up!

 

That is actually the tuth of the matter though! The Xmas period must sure class as a high shannon entropy period, Ian F? And don't forget the inevitable missing data come that time as well (sorry, couldn't resist)

 

It is all about upstream events and does seem to rest on amplification and the Eastern Pacific ridge. The good news is there is still an appetite across the various moels this morning for a classic 2 wave Western Conus / Mid Atlantic poleward ridge which would very likely have the net effect of giving us our cold spell. However there are also plenty of perfectly viable variations on the theme. Notably too much energy in the Greenland locale inhibiting WAA from heading into and giving what most of us crave.

 

It is a very unusual setup, be in no doubt about that, so analogues are of little use right now.

 

Not that I am necessarily more right than wrong normally but 99% of the time I am at least confident enough to give it my opinion of what I think will occur. This falls into the 1% catagory, from mild SWerles and an almost Bartlett type setup to a proper Greenland High and frigid cold air entrentched before NYD. Looking at the background signals I feel any mild (albeit quite possible) will be short lived but frankly, who knows!?

[MR EXTREMES]

im confused in this thread as much as strat thread and this to does not make for good readying perhaps the higher solar output has put the spanner in the works.

winters in this country are getting harder and harder to get cold.

 

i would not be suprised to see this nightmare runs go on and on.

rinse and repeat although could have settled conditions to start jan.

 

all in all dreadful really really frustrating.

[bluearmy]

  

It is a very unusual setup, be in no doubt about that, so analogues are of little use right now.

?

it's the detail that makes each scenario unique. However, the bigger picture tends to over ride the small detail in the end so the models could well be over complicating things. I wouldn't discount analogs but at the same time, the outcome is never going to match the analog either.

as someone who would like to see some proper cold winter after last years effort, the annoyance with that w Atlantic depression is tempered by my belief that it will do us good in the longer term.