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

[Frosty.]

So after all the models are out IMO we have learnt zero about what to expect! Any cold doesn't appear till after 144hrs, the ECM departs from its earlier 00hrs run, the UKMO is saved a slating as we only see its output upto 144hrs. The GFS operational run looks out on its own even though its a loner in a sea of confusion anyway. The GEM looks better than this mornings run but still flatters to deceive. The rest of the wannabee models JMA, damp squib similar to the GFS let down, the NAVGEM so so, the CMA aka we should give up modelling and stick to oppressing Tibet model as they're much better at that than NWP, who cares! The BOM similar to the GFS.

 

Basically its a mess, we'll just have to wait till tomorrow for the mist to clear hopefully!

The Gfs 18z will save the day, not worth hiding behind the sofa though. All to play for, atlantic high still has a chance of pulling further west and building north to cut off the atlantic and the shape & potency of the scandi trough is nowhere near nailed yet, the fat lady can clear off home until the 00z...and who knows, the Ecm 12z ens mean might be more of a stonker than a stinker.

Edited November 28, 2013 by Frosty.

[Iceberg]

I would advise not to concentrate too much on the cold aspect. Otherwise you will miss the other possible weather. After going through the models and the various ENS one word springs to mind to describe the possible weather from the 5-10th of December "WOW".

As i am sure has been said already it all hinges on how the High and lows exit newfoundland between T144 and T192.  But the two main possibility groupings indicate either an extreme storm/wind event or and an possible high risk snow event. For me the chances of somewhere getting the storm component is very very high, mainly due to the ramped up jet and the large temp differential caused by the cold air flooding south into the atlantic.

Far too early to judge the models but the next 3-4 days look like must watching activity. Just don't concentrate on the snow aspect and don't get caught up my indervidual runs (i.e GFS ENS, ECM and GEM all back away from the GFS ops outcome).

 

Its going to be a nightmare to forecast thought

[Summer Sun]

Comparing GFS, ECM and GEM AT t192 and t216 ECM is by far the coldest

 

ECM

 

 

GFS has the coldest uppers missing most of England and Wales

 

 

And finally GEM

 

 

 

 

 

 

 

[Tamara]

No-one should take model output at face value of course but I think that the ECM 12z is a realistic enough expectation of what is to come and puts into perspective the much more amplified arctic blast of this morning. It depicts and illustrates well the theme of the winter forecast yesterday and the thoughts for December with a mix of occasional atlantic ridges/attempted amplification (at least so long as the Pacific ridge holds) and quite dominant spells of mid latitude High pressure giving drier than average conditions but seasonal temperatures thanks to inversion conditions whilst High pressure is close by.

 

This doesn't fit the mood and expectations of the thread I know, but then I think it better to look at what is more likely than what one hopes for

Edited November 28, 2013 by Tamara תָּמָר

[nick sussex]

I am not aware that cold was/is expected before that time scale anyway?

I would think 144h may see signs at synoptic level of this development.

It wasn't, any cold shown even if the models all agreed on the way forward is outside of the more reliable timeframe.  The foundations or lack of are messy and unconvincing, the synoptic evolution is not that of the normal northerly toppler we often see, the models are determined to throw in a shortwave and not just go the simple retrogression route via more amplification in the eastern USA.

 

The GFS IMO is often good at the bog standard northerly toppler , indeed I'd put it ahead of the ECM normally on that synoptic set up although it does have a bias for overdoing the cold and longevity come verification time but it normally at least picks the northerly. Even its making a pigs ear of the set up, I think the juries out on this one, once theres some coherence upstream then things might become clearer.

[cooling climate]

I think the UKMO is better than people give it credit for at 144 with that shortwave SW Greenland ready to slide SE and amplify the pattern

 

ECM at 168 not bad but we need that shortwave to develop SW of Iceland and less energy coming over our ridge from that phasing low.

 

As you say the UKMO chart at t144 is a very good chart and for me probably the pick

of the bunch at that range.

Nothing to get hung up about in the way the latest ECM run turned out its still a pattern

in development and at approx 8 day range little hiccups are to be expected.

Come Saturday we should know for sure whether we are in for a real taste of winter or

just a cold snap. I am happy to put my money on the former as I think the pattern will be

amplified enough to scupper any spoilers such as what the ECM is showing from t168 onwards.

[gareth73]

As a novice I find how people get really hot under the collar in this forum about the various outputs.  I always think take them all at face value and wait for an outcome. In 2010 winter really did not start till Fri 17th Dec and then it really did kick in till mid Jan.  I am waiting and seeing. If it comes off we will love it, If does not then we will save on our fuel bills and the elderly will be better off.

[Gibby]

Here we are copied across from my website from my own fair hand tonight. I wish it was a good omen for cold and snow but having seen the 12zs I'm afraid it's not.

 

Good evening. Here is the report from the 12 noon outputs from GFS, UKMO, GEM, NAVGEM and ECM for tonight Thursday November 28th 2013.

 

All models illustrate a spell of anticyclonic gloom coming to an end briefly as a cold front crosses SE across the British Isles tomorrow bringing cleaner and fresher air to all areas by tomorrow evening. Winds will strengthen markedly from the NW and could carry a few showers to NE Britain for a time before Saturday sees decreasing winds with quite a pleasant day for many before cloudier weather spills down from the NW to land us back to square one on Sunday with largely cloudy and non-descript weather to start next week with temperatures remaining close to the seasonal average as High pressure maintains a ridge across Britain from the West. Frost and fog would be relatively limited in amount through this spell with Friday and Saturday night's the only nights at substantial risk.

 

GFS then shows a weak series of fronts cross SE soon after midweek with a little rain ahead of a colder phase, especially across NE areas while elsewhere stays dry and probably quite bright and only a little colder. By the weekend wet and windy weather spreads first across Northern Britain and then on to all areas as a deep Low crosses East to the North of Scotland and down over NW Europe. The cold front would bring a short spell of cold NW winds and potentially wintry showers of sleet and snow in the North before a ridge of High pressure brings a change to increasingly milder weather with any rainfall becoming more and more confined to Northern areas as Southern Britain sees some potentially very mild weather for a time.

 

UKMO today shows High pressure well under control of the weather still over the UK with a strong ridge across Britain from a centre over mid Atlantic. The quiet and benign weather of early in the week looks like persisting with perhaps a few more brighter interludes by day and clearer interludes at night to promote a little more in the way of frost and fog.

 

GEM shows a front moving South midweek with some occasional rain for a time before clearer conditions move down from the North and then another band of more coherent rain spreads down behind on a more active front and this time is followed by a spell of cold NW winds with wintry showers and night frosts to end the run.

 

NAVGEM too shows a couple of fronts moving SE through the middle of next week, the second of which brings a spell of cold and showery weather with sleet or snow showers over all high ground and frost at night.

 

ECM tonight shows a brief spell of rain midweek behind which a cold NW flow brings some wintry showers to the North and East before High pressure slides over from the West keeping things cold but bringing dry weather with frost and fog. By Day 10 it looks like Northern areas will see milder air moving in off the Atlantic while Southern areas stay flat calm under High pressure.

 

The GFS Ensembles show a short colder interlude towards the back end of next week before the general trend is for thing to return to average by the end of the period. The current High pressure and precipitation less weather that we are currently experiencing  will most likely continue for the next week or so before it is shown to give way to somewhat more unsettled conditions from many members later. Tonight's mild ending shown by the operational was a big mild outlier at the end of the run.

 

The Jet Stream tonight shows the flow remains to the North of the UK before it is directed SE over the UK later next week. thereafter, the flow becomes indeterminate and hard to find a pattern from with many options possible.

 

In Summary tonight there is still a week of High pressure based weather to wade through with benign and cloudy conditions with just a brief window of colder and fresher weather for 36-48hrs from Friday. Later next week still looks like turning cold across the UK with the threat of some sleet or snow in parts of the North especially but most output still indicate the North flow providing the cold being shunted East quite quickly and replaced by High pressure with frost and fog possibilities late in the period. It should also be noted that there still is a good chance that some milder weather will return over the UK late in the period as High pressure may become flattened to the South.

[Barry12]

Here we are copied across from my website from my own fair hand tonight. I wish it was a good omen for cold and snow but having seen the 12zs I'm afraid it's not.

 

The ECM has -8 uppers over the whole of the UK, with -10 uppers over parts of Scotland at day 8 and 9, how is that not cold?

 

Edited November 28, 2013 by Barry95

[Fozfoster]

Phew, just cought up. Some great posts tonight, but you know what!Still none the wiser :-)but its worth it!!!!!!! Luv this thread :-)

1

[Gibby]

The ECM has -8 uppers over the whole of the UK, with -10 uppers over parts of Scotland at day 8 and 9, how is that not cold?

 

Yes it is cold and I agree but in the general view of things I think most people know what I mean.

[Captain Shortwave]

The ECM has -8 uppers over the whole of the UK, with -10 uppers over parts of Scotland at day 8 and 9, how is that not cold?

 

I think the eye is in the beholder, for long term cold it doesn't look encouraging at the moment, but the models do suggest a period of colder weather, in fact cold enough for snow to low levels for a time (couple of days), which is what is said in the summary to be honest

At the moment out of the 3 solutions I said were possible for the UK, it looks like solution number 2 is the most likely (A northerly toppler). But if we get some good fortune it might last more than 48 hours or so and potentially deliver snow to many areas. Of course with this solution the length and depth of cold will be up for grabs even within a couple of days of the forecast event.

[Summer Sun]

Welcome back Gibby, pleased to see you posting your analysis again

 

Edited November 28, 2013 by Summer Sun

[SMU]

http://www.knmi.nl/exp/pluim/Data/PLUIM_06260_NWT.png

 

The raw 10 day ECM shows at day 10 the op is 2 or 3 degrees above the general clustering showing it *MAY* be producing on onshore flow to fast..

 

Expect changes a plenty in the next 2 days - some good - possibly some not so good-

S

[Iceberg]

Worth comparing the end of the semi-reliable timeframe at T168 for the GFS latest and previous run. Particularly the high with has been replaced with a low around newfoundland. But also a very different n.hemi pattern on the two runs.

Its really unusual to have this much global pattern uncertainty at this range, hence why they models even at T120 are changing so much.

A little bit of consistence on a global pattern would be nice before we start to exam too closely how its going to effect the UK.

[Summer Sun]

Tonight's ECM ensemble shows -5 850's over a lot of the UK at either t192 and or t216 depending on your location, t240 shows less cold 850's approaching the west

 

Edited November 28, 2013 by Summer Sun

[radiohead]

12Z ECM ENS mean T192 - T240

 

[Andy H]

Welcome back Gibby, pleased to see you posting your analysis again

 

Welcome back Gibby love your input, only thing is Summer suns post count is going to dramatically drop

[Skyraker]

I've simplified the ENS watch.

 

Four locations, only -10C 850hpa counts.

 

[terrier]

Great to see gibby back. Like I said earlier his posts make it so much easier for novices like me to understand. And like he keeps saying this looks nothing more than a short sharp blast. And it seems the met office agree in today's update. With westerly winds becoming established again. But I do understand these updates can and do change.

[bluearmy]

http://www.knmi.nl/exp/pluim/Data/PLUIM_06260_NWT.png The raw 10 day ECM shows at day 10 the op is 2 or 3 degrees above the general clustering showing it *MAY* be producing on onshore flow to fast.. Expect changes a plenty in the next 2 days - some good - possibly some not so good-S

The spread at day 10 has the clustered mean ridge further west. There appears to be a clustering that brings a more developed depression around the Atlantic ridge days 9 and 10 and into s UK. South of the PFj, that would allow for something significant for n England. Because even the poor sypnotic outcomes at day 10 are likely to be v cold at the surface, the London ens will not tell us too much tonight.

[cold snap]

Any sort of substational pressure getting Into Greenland is unlikely with vortex at present time ,

Scandinavia high seams more likely.

Looks like your bog standard toppler to me

Hope I'm wrong

[Frosty.]

To my eyes, the Ecm 12z ensemble mean looks significantly more wintry than the 00z mean, I would say it's 50 percent better with the arctic air having more of a swipe at the uk, especially the north and east..all to play for since the timeframe of most interest is beyond T+144 hours. :-)

[fergieweather]

Just a note on shorter-term modelling, for those interested - after much work over many months by UKMO and BBC Weather, we've just (an hour or so ago) migrated our 0-48hr mesoscale TV graphics across from the former (modified) NAE-driven version we've used for many years (farewell!) to the new high-res UKMO Euro4 (4km) data feed. So, in broadcasts later this evening at regional and national level, you will probably notice a difference in how cloud/rain/winds etc are morphed and animated; i.e. with more realistic hourly speed and localised detail.... the move to Euro4 is the reason why!

[Convective]

What's to say it won't change back by tomorrow morning? B.R.E.A.T.H.E people..