Model Output Discussion 29th December - Into mid-Winter.

[mulzy]

2 minutes ago, snowking said:

0z (Blue) vs 12z (Red) EPS (Note this is T2M max rather than average):

As Matt says, warmer in the mid range but pretty identical beyond that average wise, but notice the larger spread of the dataset on the 12z highlighting increased uncertainty

Hi SK - which location is this for?

[snowking]

3 minutes ago, mulzy said:

Hi SK - which location is this for?

Hello.

That is for Heathrow

[phil nw.]

Just taking a step back from the variations in the fine detail and really the overall NH pattern hasn't changed with modeling still showing the Pacific and Atlantic prone to further bouts of amplification through the next couple of weeks.

This continues to feed deep cold south from the Arctic into Europe and Scandinavia during the first half of January

Some perspective here.This first northerly was never modeled to be more than a brief affair and a short term rise in temperatures has been consistently modeled following that.

We are then looking at another round of Atlantic ridging which may bring a northerly next weekend but it could be a near miss and the risk of a high close by the UK at that time again has been in many of the gefs.Having said that the ensembles are remaining solid in a return to colder weather by day 8 as lower uppers are modeled to move in from the north east. 

A look at yesterday's and today's 12z ECM mean charts for the same dates -compare and notice the consistent pattern shown.

 

 

                                                                     

Glancing through those ECM ens charts shows the outlook hasn't really changed since yesterday-still getting colder again in week 2 with the Atlantic still looking quite blocked.What we are not yet seeing is a snowy setup such as many of us are keen to see but if that is to evolve then it looks likely that will be beyond the 10 day range and has never been an option in the ensembles before that.

The main point is we have wave breaking into both sides of the trop.vortex which is a much better place to be for further cold and hopefully snow than in an undisturbed full on zonal pattern where the deeper cold remains locked up further north.

 

Edited December 30, 2016 by phil nw.
corrected images

[knocker]

So what do the anomalies say after the trauma of today. Nothing significantly different to my eyes albeit the EPS does have a little variation

So upstream strong Aleutian ridge and Canadian vortex with cold trough orientated SW down North America with another trough over eastern Europe. The next Atlantic wave is still being initiated in this period with some high amplification to the west of the UK which settles down with strong positive anomalies and ridging mid Atlantic with a NW upper flow over the UK The EPS differing with this interpretation and has the ridge more negatively aligned which, although retaining a NW upper flow, will keep the UK more under the influence of the high pressure with systems tracking further east rather than dropping over the UK. Obviously the position and orientation of the ridge is crucial to the evolution of the det runs and until that  is sorted they will continue to differ.

Not to be forgotten in all of this is the trough and upper low to the south of the Atlantic HP as it's playing an important  part in the saga. .It certainly isn't cut off as energy is feeding into it from upstream keeping it activated and it's also diverting energy from the south arm of the jet south.

Looking at the 10-15 period (8-14 NOAA) still no significant change upstream and we are still looking at quite amplified ridging and positive anomalies loosely around the Iceland area. The problem is still the orientation of the ridge with the EPS still going for a negative tilt with the other two favoring a positive. The percentage play is still for ridging west of the UK, precisely where will dictate the surface weather, and obviously this will get sorted over the next few days. It should be noted the confidence level with NOAA for both time frames is well above average so I'm taking a punt on a quite few dry cold days. How cold I'll just take a rain check.

 

 

Edited December 30, 2016 by knocker

[Seasonality]

1 hour ago, Changing Skies said:

Well, that goes completely out the window when something unconventional is being shown ie. not long drawn southwesterlies, we're proably looking at 4% at best. The MetO outlook all but cemented our misfortune  

'A colder north to north-easterly is likely to become established from Friday onwards, with frequent wintry showers.." Then comes along the UKMO resolute, the GFS hops on board and now the ECM. It is looking highly unlikely for it to have been a bad day at the office. Our much touted N'ly for next weekend seems to be in precarious ground, contradictory to the GEFS which are 70/30 on a northerly. Not the end of the world it may have only been an appetiser, very uncertain outlook, one thing I'm confident on it will be cold but fingers crossed it isn't the anticyclonic kind with blocking slap bang over the UK, I think we're all getting sick to death of it! 

4% at best? Where did you get that verification stat from? Just for sake of accuracy.

[Cheshire Freeze]

It's heartening to see the CFS churn out this sort of scenario run after run

[Ali1977]

Ok so here comes the pub run , I am pretty sure we'll get a slight move back towards last nights runs but and bring back some king of Northerly next weekend, fingers crossed. 

[SMU]

Evening All -

so for your perusal before the 18z..

So lets move on from the UKMO saga with the footnote for those that did - dont ever ignore the model again, especially forecasting cold blocking & sliders--

& for clarity what has moved - The GFS & ECM have moved in terms of low pressure placement now taking the low @T120 south down the western side of the high instead of South East down the Eastern side of the block -

What we need to review is what the next steps might be post that as once again there is an ECM/GFS V UKMO scenario @ 144 (&168)

* Firstly the UKMO makes apparent 'ok' viewing at 144 with the ridge that was wNorth west of the UK forced east to Scandi & at face value there could be some trough disruption leading to an easterly/North Easterly- however the updated 168 makes very poor viewing with the atlantic jet overpowering the blocking to keep us mild -

* The GFS/ECM blend whilst moving to the UKMO with the energy dropping south - do re-engage the high pressure link ups leading to a similar pattern pre UKMO catastrophy pattern....

* Heres the rub, picture in your mind the 2 differeing scenarios from what we thought was going to happen to whats now likley to  happen with the low - mainly where the high pressure will sit as a result of it...

heres yesterdays day 7 first & todays day 6

 Yest today

the key here is the assuming the 2 highs do re-engage as per todays ECM the bottom end of the block will be further southEast-

Note the 192 chart today V the 216 yesterday - In terms of WAVE AMPLITUDE

Yest

Today

* Whats crucially important for a scandi high & UK cold is the CORE of the high pressure ( heigher heights that 560 yellow line ) gets up to iceland, its not how far the ridge gets (544 line)

so taking the x2 days you will see as a result of a move towards the UKMO - the subsequent repercussions have a probable negative effect on the wave height into scandi -

The net effects are felt the most the further west you come through Europe so no difference really for say Germany- but debilt will be nearer the cusp as a result & London will be ever further away from the cold - note the 2c mean increase for debilt tonight from the 0c 00zs to 2c 12z  ( day 10-13 maxima)

So I hope that helps people, in a nutshell if the UKMO 120-144 varifies then goodbye cold -

If we see a move ( or all 3 ) back to the ECM blend then cold yes circa -4 to -6 uppers at day 10 but there will need to be significant troughing coming south through scandi to create a westward push of the cold under the weakened high to get the deep cold over the UK

ECM/GFS V UKMO 50-50 tonight for 120-144

S

PS you will never find this level of detail in the anomalies or anomaly charts as today is a classic example of them appearing the same, but for the UK its the micro scale changes that have to be scrutinised to really get into the specifics....

 

Edited December 30, 2016 by Steve Murr

[johnholmes]

7 minutes ago, Steve Murr said:

 

S

PS you will never find this level of detail in the anomalies or anomaly charts as today is a classic example of them appearing the same, but for the UK its the micro scale changes that have to be scrutinised to really get into the specifics....

 

The anomaly charts, whichever one uses should never ever be used to give any micro guidance. They are only to be used, ahead of the synoptic models, whatever time scale, to give guidance, and quite often, reassurance about what major patterns are going to occur in those time scales.

Edited December 30, 2016 by johnholmes

[Tamara]

Some happy post Christmas shopping and been reading back the last couple of days and quite some capricious responses not just from NWP and but also observers alike, and seemingly from all levels of the debate, but I will continue to plough a lone furrow and send an auto repeat message as per the last week or two.   As gently suggested previously, the end of year/start of January amplified Atlantic ridge scenarios I think are the garden path to avoid in the shorter term (to accord with Nouska's lovely little tit-bit of advice in terms of post day 6) Which has indeed stayed at and mostly beyond day 6.

However, the nearby grass is still green enough as the mid latitude holding pattern offers seasonal weather.

As previously said, I'm watching for the starting pistol real amplification signal. Without it the Atlantic ridge will keep playing garden path northerlies

It might be worth waiting for this link to update because it is highly accurate. That might take some further time however bearing in mind the website 2 day lag times and slowness to keep up with those . I won't suggest patience as that is taboo for here I know, but for what little it might seem to be worth to the majority of NWP junkies on here, you can count a couple of weeks or so from the time that the pistol fires.....

@blizzard81  Hi I can only speak for myself and my own interpretations. The posts as always are based on continuation summaries and they are meant to speak for themselves, within my own ability anyway  

 

 

 

 

Edited December 30, 2016 by Tamara

[SMU]

13 minutes ago, johnholmes said:

The anomaly charts, whichever one uses should never ever be used to give any micro guidance. They are only to be used, ahead of the synoptic models, whatever time scale, to give guidance, and quite often, reassurance about what major patterns are going to occur in those time scales.

Yes John, however for the UK the micro patterns make all the difference - hence more of a deep dive into that...

[Gibby]

Today has I hope been a steep learning curve for 'newbies' entering Winter Model watching for the first year. For the rest of you 'well we've been here before.' It's hard not to be driven by the excitement of each operational run from each model and yes there has and still is reasonable optimism for a cold spell to come but lets face the facts. We live on an island on the Eastern end of a large ocean where the prevailing wind is SW. To get cold in this country all the dice have to fall on 6 and as the amount of significant cold snowy weather spells in the last 200 years leaving aside Global changes etc are minimal so its odds on that even with all models looking severe in 10-14 days time the odds of it actually happening are better compared to how many times it has actually happened in the past.

Back on topic and for what it's worth the ECM 10 Day Mean Chart has changed little since this morning whereas the operational has. Another reason why I use this chart on my Facebook Kilmersdon Weather Page Forecasts and not the operational. It's worked for me so far as I don't have to suffer the wild changes that each operational throws at me hence I don't over react. On tonight's forecast I have given my verdict on the next two weeks weather encompassing the upcoming cold spell or not based on what I've seen collectively today.

http://old.wetterzentrale.de/pics/Reem2401.gif

 

[booferking]

Low looking better around spain if it can stay strong and not move West were in business..

[Froze were the Days]

2 hours ago, BLAST FROM THE PAST said:

has any model gone slippy slippy? A few hrs ago 38 out of 51 suites went for the Shabang COLD outcome, now they have flipped?! Anyone else confused at what the route ahead is? Are the models of any use, are the suites of any use?  We seem to know the MJO isn't.

For me jam is still coming - mid month on for main surge....and potent surge for me.

 

BFTP

Don't curse it Fred - you were pretty 'hot' on a cold spell come mid-December which never materialised, fingers crossed and anything that can be...we need some luck on our tiny Isles!

[Seasonality]

20 minutes ago, johnholmes said:

The anomaly charts, whichever one uses should never ever be used to give any micro guidance. They are only to be used, ahead of the synoptic models, whatever time scale, to give guidance, and quite often, reassurance about what major patterns are going to occur in those time scales.

Wise words. As you yourself have said many times the anomalies give us a very good broad scale picture the majority of the time. And indeed the overall NH pattern has been well forecast of late, the UK of course being but a small island in rather difficult to forecast location.

Edited December 30, 2016 by Seasonality

[Weathizard]

2 minutes ago, booferking said:

Low looking better around spain if it can stay strong and not move West were in business..

That low is much further east on the 18z (when you consider its only 75 hours away) 

[Iceberg]

Quite a significant movement back to the better 06z on this run from the gfs. Still to early to see what will happen though 

[Mucka]

Just now, Weathizard said:

That low is much further east on the 18z (when you consider its only 75 hours away) 

18z already looking better, should be a decent run

[SMU]

16 minutes ago, Iceberg said:

Quite a significant movement back to the better 06z on this run from the gfs. Still to early to see what will happen though 

Yes 18z - always report on what were seeing - 

more blocking through the gap @ 102 should send the low to the east... 

its like an episode of Eastenders...- what a mess @108...

Edited December 30, 2016 by Steve Murr

[IDO]

Looks like another variation at D4 with respect to the Azores trough and phasing of the energy from the south. It is slower by about 12 hours to cut through the eastern flank of the Azores trough. It's  enough to keep the high in the Atlantic rather than further east over the UK. That delay  allows it to merge with the parcel of heights ejected into the western Atlantic at D4-5.

We get that link up on this run: 

Hopefully this will allow some amplification to the Atlantic high.

 

Edited December 30, 2016 by IDO

[booferking]

1 minute ago, Weathizard said:

That low is much further east on the 18z (when you consider its only 75 hours away) 

And thats a good thing thats what we want to see now see high pressure build in atlantic.

[Iceberg]

T114 and I am calling it. An almost complete back track to the 06z. The high instead of drawing into Europe is being drawn to the west Atlantic.  Job done. 

[knocker]

31 minutes ago, Steve Murr said:

 

 

PS you will never find this level of detail in the anomalies or anomaly charts as today is a classic example of them appearing the same, but for the UK its the micro scale changes that have to be scrutinised to really get into the specifics....

 

Using det, runs and anomalies does not make them mutually exclusive. A common sense approach is obviously use both. If nothing else, as John has already pointed out, it should at least alleviate the stress when the det. runs go off on one and help keep a sense of proportion.

[Ali1977]

1 minute ago, Iceberg said:

T114 and I am calling it. An almost complete back track to the 06z. The high instead of drawing into Europe is being drawn to the west Atlantic.  Job done. 

Yep this looks much better, just need some decent amplification now 

[bluearmy]

The fi pattern (as stewart alluded earlier) is pretty solid with high heights to our north and low heights to our south. How these orientate and where we sit between them remains uncertain. the Azores low behaviour re the 12z runs seems to increase the chances of the high heights being closer to the uk and therefore the coldest air advected to our south. however, we are far from knowing the actual outcome.

let's  try and enjoy the ride rather than getting sucked into expecting snowfall with the better coldie runs and them being disappointed with the next run if it swings th other way.