Model Output Discussion 13/11/12 18Z onwards

[Paul]

Here's the latest outlook for the upcoming 7 days from Michael Fish - rain and wind playing a prominent part!

[weather eater]

Thanks for all the likes and well wishes, no doubt that will be my only popular post of the winter, so I shall savour it.

The 12z continues with the blocking in FI with another variation on the theme, we have seen similar runs over the last few days with the initial high setting up over the UK before shifting NW, pretty much in keeping with GPs post earlier.

Edited November 15, 2012 by weather eater

[Geordiesnow]

ECM has now backed away of the low pressure for Sunday into Monday being deflected by the strong Euro high to the SE and its more in line with previous GFS set ups of having its track hitting the UK giving a spell of wet and quite windy weather, especially to locations which are on the southern flank of the low pressure system. Certainly one to watch as it could still deepen as it interacts with the jet stream and also due to the short distances between the polar and tropical airmasses.

This low pressure may open the gates for a spell of wet and windy weather, GFS has a slightly milder set up than the UKMO but the trend does look look like after a quieter period of weather of a more mobile set up.

As for cold prospects, then I still can't see many trends which suggests a cold set up is on the way? Maybe some hints of some sort of blocking trying to form but its hardly convincing and the timescale for such events is still way over 200+ hours away, plenty of weather going on before then therefore it will likely to change, whether that change will be a much stronger blocking signal or the complete opposite remains to be seen.

[Frosty.]

A stunning end to the Gfs 12z op run, yet another run showing a Northerly and once again a different evolution of how we get there with the large high which forms over the uk splitting in two with one part going east and the other goes west into the middle of the atlantic, the main theme of the run is the complex troughing which covers the uk north to south by this time next week, the whole trough clears away to the northeast and high pressure topples in from the northwest and becomes a major feature, filling the void left by the departed trough, this high becomes positioned in such a way as to drag easterly winds across the south but lighter to the north within the main core of the anticyclone, daytime temps of around 5-7c, so quite chilly and overnight slight frosts, the way the high splits in two is classic and a deepening trough then pushes east and finally opens up the floodgates for a very potent northerly, a few extra frames on the 12z would have brought the snow showers down across the uk with a really icy blast, a perfect start to winter that would be..

Edited November 15, 2012 by Frosty039

[mcweather]

A stunning end to the Gfs 12z op run, yet another run showing a Northerly and once again a different evolution of how we get there with the large high which forms over the uk splitting in two with one part going east and the other goes west into the middle of the atlantic, the main theme of the run is the complex troughing which covers the uk north to south by this time next week, the whole trough clears away to the northeast and high pressure topples in from the northwest and becomes a major feature, filling the void left by the departed trough, this high becomes positioned in such a way as to drag easterly winds across the south but lighter to the north within the main core of the anticyclone, daytime temps of around 5-7c, so quite chilly and overnight slight frosts, the way the high splits in two is classic and a deepening trough then pushes east and finally opens up the floodgates for a very potent northerly, a few extra frames on the 12z would have brought the snow showers down across the uk with a really icy blast, a perfect start to winter that would be..

The good thing about it as well frosty is that it is a classic evolution to cold that we have seen many times before down the years. The retrogressive high pulling west and north to open the door to thre arctic. Notice also the Aleutian/ Kamchatka high coming in over the pole as well to back it up.

Edited November 15, 2012 by mcweather

[AWD]

Looks like another foggy night to come across England & Wales tonight, although visibility shouldn't be as bad as last night;

http://www.weatheronline.co.uk/cgi-bin/expertcharts?LANG=en&MENU=0000000000&CONT=ukuk&MODELL=nae&MODELLTYP=1&BASE=-&VAR=visi&HH=18&PRINT=1&ARCHIV=0&PANEL=0&INFO=0&WMO=

and pretty chilly too, although most places should be above freezing, no doubt a ground frost for areas of Scotland.

http://www.weatheronline.co.uk/cgi-bin/expertcharts?LANG=en&MENU=0000000000&CONT=ukuk&MODELL=nae&MODELLTYP=1&BASE=-&VAR=tmp2&HH=18&PRINT=1&ARCHIV=0&PANEL=0&INFO=0&WMO=

[phil nw.]

The good thing about it as well frosty is that it is a classic evolution to cold that we have seen many times before down the years. The retrogressive high pulling west and north to open the door to thre arctic. Notice also the Aleutian/ Kamchatka high coming in over the pole as well to back it up.

What`s interesting is that T168hrs looks like the first stage of a change to our current setup where the UK trough shows the first signs of disruption and eventually being cutoff.

http://www.meteociel...&mode=0&carte=1

http://modeles.meteo...nh-0-216.png?12

Heights then able to build across the gap as the low heights to our north retreat.

However it`s much later in the output before the real mcoy appears building towards Greenland

http://www.meteociel...&mode=0&carte=1

-which would be a nice start to Winter.

Nice but lets get rid of that trough first then see where we are.

[Frosty.]

The good thing about it as well frosty is that it is a classic evolution to cold that we have seen many times before down the years. The retrogressive high pulling west and north to open the door to thre arctic. Notice also the Aleutian/ Kamchatka high coming in over the pole as well to back it up.

Yes mcweather it's a truly stunning evolution, and the Northerly looks like it would last at least a few days (probably even longer) and back northeasterly after, not a quick toppler, it's just a shame the run ended before it got really exciting for all of us.

Edited November 15, 2012 by Frosty039

[nick sussex]

An okay run from the GFS but still that trough refuses to tilt favourably and we have to wait for it to split and weaken.

The GEM looks similar in pattern at 144hrs, the UKMO once again underwhelms me with a flatter upstream pattern and the troughing further east, although the UKMO in recent days have been modifying their raw data in the fax charts which suggests they think their operational output isn't up to much. We can only hope that this is the case as it looks like a long road to anything colder on that output.

Having just checked the latest verification stats they show the UKMO performing woefully in recent days, indeed at this rate it could be keeping the NOGAPS company!

Edited November 15, 2012 by nick sussex

[The PIT]

After this weekend plenty of mild weather around as GFS continues it swing back to a milder outlook. A bit breezy weather Monday but nothing really of note.

[AWD]

GFS ensembles show a general cooling trend throughout the last third of the month and into December.

Suggestive of a cool weekend, with a milder recovery for the first half of next week before cooling off again though out the rest of the month.

A large scatter as you would expect in FI.

http://www.meteociel.fr/cartes_obs/gens_display.php?ext=1&x=463&y=4

[nick sussex]

Modifications are part of the process throughout every day...I think they're broadly happy with where their GM sits presently amongst other operational models... for example, as of 09z this morning they'd been making (and notifying us of) these sorts of mods to the UKMO-GM output, alongside the usual regular comparative comments and analyses they provide us versus output from EC, ARPEGE, NCEP, JMA etc:

"3. Modifications:

T+96-T+120: Low moved a little further west and frontal clearance across E’ern parts of the UK

delayed.

T+132/T+144: A more substantial wave has been developed and allowed to spread another spell

of rain across many parts of the UK."

As for the longer-medium range etc, i.e., end Nov into Dec., my discussion with them today rightly continues with the "no strong defining signal", at least in summary.

Oh and PS - don't forget the FAX charts don't necessarily tally with what the raw UKMO-GM output shows. Indeed it frequently doesn't. The FAX charts are heavily modified with forecaster input and without blinkered following of their own models in isolation.

Thanks for that. All models go through good and bad patches but for some reason over the last few days the UKMO has fallen off a cliff in terms of its anomaly correlation.

It's most evident at 144hrs, I know they have that new ensemble system which helps them rather than using the ECM ensembles.

So I would expect those modifications occured with those taken into account. Don't get me wrong I like the UKMO and generally place it above the GFS at that range, at the moment the ECM looks most stable out of all the global models.

[mcweather]

Modifications are part of the process throughout every day...I think they're broadly happy with where their GM sits presently amongst other operational models... for example, as of 09z this morning they'd been making (and notifying us of) these sorts of mods to the UKMO-GM output, alongside the usual regular comparative comments and analyses they provide us versus output from EC, ARPEGE, NCEP, JMA etc:

"3. Modifications:

T+96-T+120: Low moved a little further west and frontal clearance across E’ern parts of the UK

delayed.

T+132/T+144: A more substantial wave has been developed and allowed to spread another spell

of rain across many parts of the UK."

As for the longer-medium range etc, i.e., end Nov into Dec., my discussion with them today rightly continues with the "no strong defining signal", at least in summary.

Oh and PS - don't forget the FAX charts don't necessarily tally with what the raw UKMO-GM output shows. Indeed it frequently doesn't. The FAX charts are heavily modified with forecaster input and without blinkered following of their own models in isolation.

Hi fergie thank you for your information. Your last paragraph is very telling because for most of the time I've been on here those supposedly in the know always told us that the Met office never considered other models (apart from the ECM for the medium range outlook).

[bluearmy]

ian - you are going to be the most popular poster on here if stewarts thoughts verify !!

[bradymk]

I know a lot of people express that the CFS is rubbish but the monthly anomalies it has been chucking out the last few days for December are great.

Above are the anomalies from the last 4 day runs, all going for high heights to our NW, i might be completely reading these charts wrong so please correct me if I am

Regards,

Matthew

[Methuselah]

Thanks for that, Ian F. It's a lesson, for us all, in just how hard weather-prediction really is!

Hi fergie thank you for your information. Your last paragraph is very telling because for most of the time I've been on here those supposedly in the know always told us that the Met office never considered other models (apart from the ECM for the medium range outlook).

True, mc. And most of those seem to have some kind of antipathy towards the MetO...

I know a lot of people express that the CFS is rubbish but the monthly anomalies it has been chucking out the last few days for December are great.

Above are the anomalies from the last 4 day runs, all going for high heights to our NW, i might be completely reading these charts wrong so please correct me if I am

Regards,

Matthew

But, what if they turn-out to be wrong?

[bradymk]

But, what if they turn-out to be wrong?

Yes true, but just showing what trend the model has been showing now for several consecutive days, hopefully it will continue to show this, but you never know with the CFS.

[SMU]

http://www.meteociel.fr/modeles/ecmwf/runs/2012111512/ECH1-168.GIF?15-0

Best 168 Chart for a long time-

S

[EML Network]

http://www.meteociel...H1-168.GIF?15-0

Best 168 Chart for a long time-

S

Agreed we have the "H" pattern beginning to emerge , which can never be a bad thing at this time of year :-)

[Ian Brown]

The ensemble mean data consistently pointing towards an anticyclonic phase as next week's trough migrates eastward and fills / disrupts. Thereafter, the trend (with excellent teleconnective support) is to introduce a stronger mean ridge towards the north-west (favoured spot southern tip of Greenland to Iceland) during final week of the month delivering T2 anomalies around -0.5C through -1.5C. With a strengthening ridge in the North Atlantic, the flow will pivot around this drawing in a more northerly or north-easterly component.

Modelling has generally rushed this synoptic evolution IMO, but possibly CFS v2 week 3 and 4 a little slow in bringing the evolution, but gathering support for this type of set up for late Nov / early Deccember which asks some rather immediate questions of ECM,GLOSEA and EUROSIP seasonal forecast (CFS starting to sniff the coffee).

Note the persistence of the Kamchatkan / Aleutian ridge there.

Interesting GP, but synoptically if the heights are not high enough - i.e low pressure crosses the Greenland plateau, then it serves to sink the block.

Promising GFS but nothing to suggest anything to be too bullish about IMO.

[Geordiesnow]

http://www.meteociel...H1-168.GIF?15-0

Best 168 Chart for a long time-

S

For less knowledgeable posters, explain why this is the best 168 hour chart for a long time? Obviously I can sort of see the potential there but other posters will be confused why a chart showing mild southerly winds is a good thing.

As it happens, the trend for tonight in the short-medium term is after the brief polar westerly which will deliver a chilly but bright weekend for most parts, is one of turning mild again with mild Atlantic based winds. The trough that people are talking about may undercut which may force an easterly of some sorts but that is a long way off at this stage but the 168 hour chart does have potential for that to happen if nothing else.

[Ian Brown]

ECM at T192 and potentially promising.

[Matty M]

There is no cold anywhere to our east or on the continent. While the PV is setting up shop in an area we REALLY don't want it, northwest of Greenland.

http://meteociel.fr/modeles/ecmwf/runs/2012111512/ECH1-216.GIF

[phil nw.]

For less knowledgeable posters, explain why this is the best 168 hour chart for a long time? Obviously I can sort of see the potential there but other posters will be confused why a chart showing mild southerly winds is a good thing.

As it happens, the trend for tonight in the short-medium term is after the brief polar westerly which will deliver a chilly but bright weekend for most parts, is one of turning mild again with mild Atlantic based winds. The trough that people are talking about may undercut which may force an easterly of some sorts but that is a long way off at this stage but the 168 hour chart does have potential for that to happen if nothing else.

Both models show a very similar evolution with a UK trough disrupting and splitting with a build of pressure through the gap in week 2.

It looks like the trend is to look north west for any future building blocks rather than further east.

Edited November 15, 2012 by phil n.warks.

[nick sussex]

Impressive continuity from the ECM with this run a mirror image of its earlier 00hrs.

Still the matter of the UKMO and if you look at that at 144hrs and compare it to the ECM theres a big difference. Certainly we need to see the UKMO come on board as thats still a concern with the trough much further east and the pattern upstream already flattening out.

At 240hrs take a look at the NH chart, that Aleutian high is about to carve its way cross polar !

Edited November 15, 2012 by nick sussex