Model Output Discussion: 12Z (20/11/12) And On...

[Zenarcher]

A great ECM tonight the GFS, UKMO and JMA are also pretty good as well but the GEM and NOGAPS are showing what we don't want to see. But I'm not concerned by them we have the 3 main models showing good outputs this evening.

Just looking through the ECM snowfall charts to see when snowfall would actually occur during it's run and shows it to happen around 180 hours when the low to the South of the UK helps bring this into play. Obviously it's 180 hours away but I was interested in seeing what would happen.

[Met4Cast]

Worth pointing out for people worrying

http://www.wetterzentrale.de/pics/archive/ra/2010/Rrea00120101121.gif

Massive amount of Northern blocking, but not particularly cold

http://www.wetterzentrale.de/pics/archive/ra/2010/Rrea00220101121.gif

We all know what followed. Blocking in place, the cold will come.

[Nick F]

One thing's looking more and more certain, it's going to turn colder next week, with an increasing threat of frosts. But, if it's snow you want from the northeasterly/easterly, then it could be a while to wait, if the blocking holds long enough to tap into deep enough cold air.

Having said that, anyone noticed sub 130dm 850-1000mb air dragged south across the UK next Tuesday on the 12z GFS? That would bring some marginal snow wherever we see heavier enough precip. Obviously no point in being specific in forecasting possible wintriness that far off. But surprise marginal snowfalls aren't out the question with colder air sinking south early next week - like that snow event we saw a few weeks ago in the west country.

Edited November 20, 2012 by Nick F

[SilverWolf]

There has been bickering in this thread for around 4 weeks, discussing the likelihood of a pattern change that the wider range of signals (teleconnections to some) have been suggesting may occur at the end of Nov / start of Dec (ish). Now the major models have CLEARLY indicated a pattern change there is bickering over whether the 850s are going to be cold enough for snow. When the 850s are cold enough for snow (and they will be - follow the pattern run to run, look at what the ECM is hinting at from the NE) there will be bickering over whether it will snow in the north east or the west or in my back yard. Winter is upon us and the only guarantee is point scoring and bickering in this thread. The signals are pointing towards at worst a much better start to winter than last year, and at best a repeat of 62/63. I will happily just follow what the broad range of signals are telling us and bet on a pretty good winter overall. Stand back people and look from an objective viewpoint - it's looking positive. There really is no more useful information than that to be had from any source of predictive weather data.

Lurker on here trying to get my head around the science and it's interpretation - very interested by recent model development, but I have to say this is the best post I've read today. Last winter for cold/snow lovers was frankly dire, all looks way more positive even for just frost and (freezing?) fog for maybe quite a few days.To me that means some potentially stunning and beautiful weather in the first 2 weeks of winter proper - leaving a further 10 weeks MINIMUM for more snow potential etc. So lets be happy at this likely outcome in late Autumn eh? Otherwise lurkers like me may end up getting annoyed and leaving an otherwise fantastic forum for somewhere where people behave better - and that's coming from someone who is basically an 8 year old when it snows!

[Frosty.]

Initially it'll be surface cold, widespread frosts developing, a lot of mist and fog around, some cold, dry autumnal weather. But we've got the block in place by then, the cold will be working its way into the flow and towards the UK. Now, can we all stop mentioning it?

That will only happen if the high drifts southeast across the uk in the further outlook, the GEFS 12z would keep the uk more unsettled with a large trough to the east/ne in control, cold and cloudy with cold rain and some sleet and wet snow eventually but not much chance of frost and fog until the skies clear and winds fall light, the gefs mean is not indicating that.

[Thundery wintry showers]

It depends on whether our initial cold is delivered from the north or east. As I indicated in my previous long-winded post, the easterly shown by the ECMWF would most likely bring a fair amount of stratocumulus/stratus trapped underneath an inversion (850hPa temperatures close to freezing and surface temps over the continent not much higher), but the northerly shown by GFS would bring clearer skies and thus more chance of overnight frost. I agree with Nick F that the GFS version could bring marginal snow events wherever we get heavy enough precipitation- I remember snow falling and settling fairly widely from trough activity with similar 850hPa temperatures in late-November 2005 and early-December 2008 and a cyclonic/northerly regime. Windward coastal areas would probably be wrong side of marginal though.

On the other hand I would suggest that from where we get to at T+240, the ECMWF version has the greater snowy potential- with extensive high pressure to the north and southerly tracking lows we would probably see much colder air moving in from the NE if the run extended much further.

Edited November 20, 2012 by Thundery wintry showers

[Frosty.]

i still find it hard to under stand why people post things like the col locked in now when the models have done such a poor job this week.the forecasts have been so poor in my area again much like most of the year.the cold is still more than a week away so much could change look at last years modeling for winter and it was shocking.the cold is not set it could all change either way it will not be cold next week just less mild cooler.

It's trending colder next week, no chance of mild next week onwards as winds will be going around to between northerly and easterly, a slow but certain colder outlook locking in, probably too much cloud, breeze and precipitation for frost and fog to become a widespread hazard until beyond T+240 hours.

[Continental Climate]

I suppose the later stages of the ECM highlight just how diffiecult it is to get sustained snowy weather into the uk!! The charts are fantastic snoptically wise but are just missing the one ingredient that is needed ie cold. Im sure that had the ecm went to 264 it would show much colder 850's heading our way. It is all a matter of whether the block will hold long enough!! I am hopeful that it will, I just hope we havent used up all our luck to early in the season.

[Geordiesnow]

Its interesting too see both the GFS and UKMO both showing the Arctic high trying to come into play, which is probably a better route to get colder upper air temperatures than what perhaps the ECM shows but the ECM to me has the most potential in terms of a few changes which may colder upper air down and to sustained any blocking pattern for longer.

Its still a little bit outside of the reliable timeframe to know for sure whether any proper blocking set up will form so in terms of upper air temperatures I won't be too concerned but at the time, be wary of the thought we may have blocking angled in a poor position which will make it harder for the cold uppers to sink south and westwards.

No doubt the output will be quite variable so I really won't get hung, drawn and quartered on every run and each model will show different set ups but hopefully maintaining the trend of blocking on our side of the Arctic will occur.

[swfc]

Phew!!!!!Anyway the models and various outcomes remains still up in the air post"in my opinion" 140hrs.Great synoptics on offer for the time of year and many avenues to go down one way or the other pv,nao ete wise.It may be an idea for some folk to stick to the "fax or ukmo" charts to avoid dragging there heals and getting wrapped up in "maybes"!!!!!!!.To look at some comments regarding the runs "ecm at 240hrs is a classic"-"but gfs at 190hrs is sus"does slightly ring of selective viewing to be honest.I often find the building blocks and build up to a cold spell the most interesting part of model watching.Whatever the weather enjoy and listen to the more respected and experienced on here and maybe the tramadol may be left in the meds cupboard

[UV-RAY]

I sometimes wonder if my computer operates in the twilight zone, because the charts that are showing on mine scream potential for a prolonged cold spell, by prolonged I mean ten days plus. Now hopefully someone will tell me if it is my computer at fault and what is really showing is a cool snap followed by raging zonality.

[Glacier Point]

If you didn't need any more instruction as to why following individual operational models beyond day 7 is folly, take note..

TODAYS GFS AND ECMWF ENSEMBLE MEANS ARE IN GOOD AGREEMENT WITH THE LONGWAVE

PATTERN FEATURING STRONG RIDGES OVER THE BERING SEA AND NORTHEAST ATLANTIC AND

AN AMPLIFYING TROUGH ACROSS THE EASTERN HALF OF THE NATION. THE VERY LARGE

POSITIVE 500-HPA HEIGHT ANOMALY CENTERS AT THE BERING STRAIT (MORE THAN 300

METERS ABOVE NORMAL) AND SOUTHEAST OF GREENLAND (MORE THAN 200 METERS ABOVE

NORMAL) ARE WELL AGREED UPON BY ALL ENSEMBLE MEAN SOLUTIONS. OPERATIONAL MODEL

RUNS WERE NOT USED IN CREATING THE MANUAL 500-HPA BLEND DUE TO POOR CONTINUITY.

Taken from:

http://www.cpc.ncep....day/fxus06.html

and FWIW, the 8-14 day anomaly pattern is a stonker.

http://www.cpc.ncep....14day/500mb.php

Edited November 20, 2012 by Glacier Point

[johnholmes]

Again, I stress the need for a cold air source for snow. It can't just simply snow if the uppers are not cold enough man! I've been on this forum 4-5 years now and I've never heard anything like that.

If my memory allowed me I could quote at least 3 winters when pretty much that happened, in the teens to snow overnight in one instance, I think, January 1955, and at least two others.

[johnholmes]

If you didn't need any more instruction as to why following individual operational models beyond day 7 is folly, take note..

TODAYS GFS AND ECMWF ENSEMBLE MEANS ARE IN GOOD AGREEMENT WITH THE LONGWAVE

PATTERN FEATURING STRONG RIDGES OVER THE BERING SEA AND NORTHEAST ATLANTIC AND

AN AMPLIFYING TROUGH ACROSS THE EASTERN HALF OF THE NATION. THE VERY LARGE

POSITIVE 500-HPA HEIGHT ANOMALY CENTERS AT THE BERING STRAIT (MORE THAN 300

METERS ABOVE NORMAL) AND SOUTHEAST OF GREENLAND (MORE THAN 200 METERS ABOVE

NORMAL) ARE WELL AGREED UPON BY ALL ENSEMBLE MEAN SOLUTIONS. OPERATIONAL MODEL

RUNS WERE NOT USED IN CREATING THE MANUAL 500-HPA BLEND DUE TO POOR CONTINUITY.

Taken from:

http://www.cpc.ncep....day/fxus06.html

and FWIW, the 8-14 day anomaly pattern is a stonker.

http://www.cpc.ncep....14day/500mb.php

Yep, it and the other 2 along with NAEFS have consistently trawled this pattern for well over 10 days whilst many on here have gone up and down as the model run changed almost daily. Yet again folks, unless you really enjoy the roller coaster, take a deep breath, join the 500mb VERY small supporters team and give yourself a break. When it gets into a more reliable time frame and all 3 models can be compared to one another then okay follow each run for the twists and turns. By T+144 the models MAY even get the 850mb temperatures correct but I bet they are a fair way off the mark for 'will it snow in my background' type posters.

From T+120 then the most accurate chart will almost always be UK Met Fax, and even that is often changed as they see later data in the short time frame but it is the best guidance for centres and fronts.

Edited November 20, 2012 by johnholmes

[Methuselah]

I sometimes wonder if my computer operates in the twilight zone, because the charts that are showing on mine scream potential for a prolonged cold spell, by prolonged I mean ten days plus. Now hopefully someone will tell me if it is my computer at fault and what is really showing is a cool snap followed by raging zonality.

Either that, or Steve has hacked into your system...Or even (just to stay on topic) ECM.

[johnholmes]

I sometimes wonder if my computer operates in the twilight zone, because the charts that are showing on mine scream potential for a prolonged cold spell, by prolonged I mean ten days plus. Now hopefully someone will tell me if it is my computer at fault and what is really showing is a cool snap followed by raging zonality.

much as I have posted at least once-7 days minimum and possibly 14 days and who knows beyond that as it takes us into about 10-12 December!

[Downburst]

Fantastic to see these charts and so early on the season. That's the main thing for me. Good work from GP and indeed from the Met Office and ECM 32 etc in catching this well out. John of course with the 500mb charts. Over the last 5 years forecasts are improving so much. Not expecting 2010 just yet but of course it won't be 97/98 so happy to watch. We will have to see. No need BTW to write war and peace on each run.

[Liam J]

Has anybody set eyes on the rather epic JMA 12z? 1050mb Arctic high + much colder uppers arriving by T192.....

Very similar to the ECM, look at the heights stretching from Greenland to Russia.

http://www.meteociel...&nh=1&archive=0

Edited November 20, 2012 by Liam J

[chionomaniac]

For the fearful 850 warriers - get a load of this!

Yes - the intermediate ECM ensembles - operational at the top end!

[weather eater]

Re GPs post I don’t think I’ve seen a statement like that from the NWS before, unfortunately it’s still going to fall on a lot of deaf ears especially those whose preference is over analysing every run in a kind of sadomasochistic fashion.

[fergieweather]

FYI - just in from Chief Forecaster at UKMO - we're upgrading to Amber Warning tonight across SW / W Country. Concern growing markedly over impacts in this region from tonight's wave & rain event.

[Paul]

Quick reminder, we do have some severe weather about over the next 48 or so hours, heavy rain, flooding, high winds all in the mix. Discussion over here:

http://forum.netweat...2/page__st__160

[chionomaniac]

Posts starting to go in the bin that are not related to the models. Don't let your posting ability follow suit!!!

Time for the 18Z. Please keep relevent to the thread. In depth analysis great, humour alllowed, inane banality in the bin!

[swfc]

FYI - just in from Chief Forecaster at UKMO - we're upgrading to Amber Warning tonight across SW / W Country. Concern growing markedly over impacts in this region from tonight's wave & rain event.

hi ian,you posted earlier that you would give your thoughts on any snow which may or may not occur over the next few weeks???

[chionomaniac]

For the fearful 850 warriers - get a load of this!

Yes - the intermediate ECM ensembles - operational at the top end!

And extended ensembles none too shoddy either;

I like the cold outlier!