Model Output Discussion - Late October Onwards

[Backtrack]

The raw, daily CFS is not bias corrected - you need to understand the model and it's inherent biases a bit more if you want to read into it's output, and even then you need to view it for trends over many days/weeks to really start to glean anything..

I've been viewing the model on the Weather Online website everyday for a few weeks now, they've been fairly consistent with a cold spell around the end of November/start of December. Nothing major, perhaps the first low land snow for Scotland/Northern England.

By making note of these trends, do you think it could be deemed accurate?

[SP1986]

I'm not even sure you can read much off a weak La Nina. Last year we had a very cold December, obviously, but even that December was 'hanging in the balance'. If we had witnessed a west based -NAO for example, things would have been much different.

I personally cannot foresee a quick change to cold in the next 2 weeks, but that's not to say it won't happen there after.

as for beyond that, well..

[No Balls Like Snow Balls]

Looking at the last few runs with all the 3 major models it looks as though we can be certain about one thing and that is that daytime temperature's will fall back close to average / just above from the end of this weekend onwards. Some teasing in FI on the GFS 12z for cold fans. TBH I don't know why a lot of people are down beat about the last few runs in the models, to me they could quite easily evolve into something a lot colder and they are a lot better looking than they have been for the last few weeks.

Edited November 1, 2011 by Jimblob

[feb1991blizzard]

Some decent Northern blocking showing on the GFS from about 150 right the way through to the end of low res, no cold pooling though. Unless i see at least the 528dam line consistently modelled on at least 2 models in a reasonably reliable timeframe or the Met Office friday update suggests otherwise then i will stick by my prediction of no potent cold in November, however common sense tells me that if we get some Northern Blocking in a month that the atlantic usually dominates in and is projected to, even if it doesnt deliver what we want then thats still a good sign going forward for the winter.

[johnholmes]

re the CFS comments above following on the post from Paul M about bias.

the only way to use ANY output is to see how it performs over a long period. Keep a record of what it showed for particular time periods, don't rely on your memory, its far from accurate!

Using both raw CFS and the other version in the light hearted look at Christmas Day over the past 7-8 weeks I honestly have not observed any trend from either version. That is not so much for Xmas Day as most folk on here know my views on trying to forecast for a single day 3 months in advance. Its a view from doing a brief summary for EACH run day by day with raw CFS and the other output whenever it updates for the 3 months of official winter. Its into week 9 this week and I'll post that along with the usual daily comments once I get a view of the Tuesday output.

About all I could say about both versions is that they have varied from week to week, indeed the raw CFS from day to day.

There COULD be a pattern beginning to emerge but its not one I would use at this point to do any predictions.

Take a look for yourself on the Christmas thread-

the link is

http://forum.netweat...60#entry2151378

Edited November 1, 2011 by johnholmes

[feb1991blizzard]

re the CFS comments above following on the post from Paul M about bias.

the only way to use ANY output is to see how it performs over a long period. Keep a record of what it showed for particular time periods, don't rely on your memory, its far from accurate!

Using both raw CFS and the other version in the light hearted look at Christmas Day over the past 7-8 weeks I honestly have not observed any trend from either version. That is not so much for Xmas Day as most folk on here know my views on trying to forecast for a single day 3 months in advance. Its a view from doing a brief summary for EACH run day by day with raw CFS and the other output whenever it updates for the 3 months of official winter. Its into week 9 this week and I'll post that along with the usual daily comments once I get a view of the Tuesday output.

About all I could say about both versions is that they have varied from week to week, indeed the raw CFS from day to day.

There COULD be a pattern beginning to emerge but its not one I would use at this point to do any predictions.

Take a look for yourself on the Christmas thread-

the link is

http://forum.netweat...60#entry2151378

Thanks for the link,

[Summer Sun]

With all the talk of when snow may arrive just compare these GFS charts year on year

November 2nd 2011

November 2nd 2010

Not much difference apart from low pressure is further west of us this year with more high pressure to our east.

[Isolated Frost]

[Liam J]

With all the talk of when snow may arrive just compare these GFS charts year on year

November 2nd 2011

November 2nd 2010

Not much difference apart from low pressure is further west of us this year with more high pressure to our east.

What was the point of posting these charts? run through the archives and the pattern last November is nowhere near what the models are progging as we move into Nov 2011

http://www.meteociel.fr/modeles/archives/archives.php?day=9&month=11&year=2010&hour=0&map=0&mode=0

[mountain shadow]

I think perhaps the point is you can take a chart from the 2nd of November in any year and it won't have any factor on the weather a month down the line.

[Gibby]

Good evening. Here's a look at the 12zs from GFS, UKMO and ECM.

GFS tonight shows a strong Southerly flow developing over the next 24hrs in association with deep Low pressure in Mid Atlantic. A cold front meanders East over the UK on Wednesday night and Thursday followed by some clearer weather with some heavy thundery showers. The weather will continue to be on the mild side, though tempered by the wind. As Low pressure then drifts into France and pressure rises further North rainfall will continue for Southern and Eastern parts over the weekend while the North becomes drier with all areas becoming less mild. Further out in FI and High pressure becomes the driving force of the UK weather, centred to the East and then North by the end of the run with winds from an East or SE point. The Atlantic still feeds some rain into the UK at times as Low pressure slides against and under the block. Temperatures would be much closer to average for the latter stages of the run with a chilly east wind in the South.

The GFS Ensembles continue to show 850's on the warm side of average in the next couple of weeks with the operational a cold outlier for a while towards the end of the run for London.

UKMO shows the same Low pressure and rainfall as GFS up to the weekend when Low pressure winds up somewhat over France giving what would probably be a very wet weekend for Southern Britain. Further North things would dry up somewhat while as we move into next week Low pressure has filled over France with a slack Low pressure area remaining over the South maintaining the risk of showers while the North stay drier under a ridge of high pressure. After a mild rest of week things would become somewhat cooler for all by the weekend and it would no doubt feel cold in the rain over the weekend.

ECM tonight also shows an unsettled weekend for the South though not as extensively so as UKMO. By Monday a ridge is lying NE over Britain with quieter more settled conditions with the chance of mist and fog at night increasing. As we move through next week we need no prizes for guessing where we go once High pressure strengthens over NW Europe and winds get sucked up from the Med over the UK. The weather would become very mild once more though if winds stay light enough at night and skies clear chillier nights are likely with the chance of fog.

In Summary the jury is still out on developments next week. The weather remains unsettled and mild up to the weekend when the South looks like they could have some particularly wet conditions. Thereafter High pressure is shown to become influential with the position crucial in what weather is experienced. The GFS route would deliver normal temperatures and a chilly SE breeze at times while ECM looks like throwing yet another wave of very mild air North over the UK.

[johnholmes]

With all the talk of when snow may arrive just compare these GFS charts year on year

November 2nd 2011

November 2nd 2010

Not much difference apart from low pressure is further west of us this year with more high pressure to our east.

I would differ with that viewpoint Gavin. There is a pretty extensive trough on one almost down to 40N with the other having a much more zonal upper flow.

Neither of course has anything to do with what did occur last year nor what may ocur this year.

The change in the upper pattern last year began about 5-7 days later.

What was the mechanism behind that I am unsure and I suspect so is everyone else.

Edited November 1, 2011 by johnholmes

[Isolated Frost]

All with a slight ne/e'ly flow joggs. LP to the south so rain possible in southern parts. I expect low cloud and maybe drizzle for the rest; but i'm not sure yet.

[Frosty.]

Still some differences between the Gfs & Ecm 12z for this weekend with the gfs having the azores ridge further north but the ecm further south. Into next week there is a battle of sorts with a low pressure near iceland trying to push east but coming up against the blocking anticyclone across mainland europe, the high seems like it will win next week after a brief skirmish with fairly mild SE'ly winds which could tend more E'ly with time dragging in slightly colder air from eastern europe but that's a long way off and the ECM is not showing any cold T850 hPa even by T+240 hours but the gfs 12z does have a colder long range pattern. For the time being it looks like the models have agreement on a more anticyclonic longer range outlook which may or may not lead to a wintry snap later in the month but no signs of any stormy cold zoneality in the next 2 or 3 weeks.

Edited November 1, 2011 by Polar_ Low

[damianslaw]

Short term - more of the same but gradually trending cooler for all by the weekend thanks to some trough disruption. The north of the country could see some bright weather especially the NW which makes a change! - the SE will suffer with wind and rain/drizzle.

Longer term - hard to say where the current heights to our east will eventually position themselves. GFS suggesting they could ridge nw in time ushering in some cooler uppers and every chance of something much colder by mid month, but ECM not keen on this suggestion. I do rate GFS over ECM when it come to development to our NW and if it continues to suggest strengthening heights in this region and more energy being fired into the southern arm of the jet then we really shouldn't be writing off such an evolution. But at this stage we can't say with any confidence yet just when and if we will see a major pattern change as we head into the middle of the month.

I suspect heights will languish over N germany/s scandi next week which will pull in some cooler uppers and increase chance of fog and frost - but what happens to the jet I have no idea, it may split and allow a surface high to develop over the country. Indeed this may be a very plausible set up as we head into the middle of the month, but for longer term cold, we need the energy in the jet to transfer southwards not northwards. By this weekend things will become much clearer.

Edited November 1, 2011 by damianslaw

[ITSY]

no unusual or noteworthy cold (or even cool) weather to speak of on the 18Z GFS

[Snowmad79]

Pretty much the same theme going on this morning with rinse and repeat output being shown in terms of HP to our east and LP out to west with a SWerly/Southerly flow, respites from HP building over us before the pattern reloads the same senario. The differences in the NH pattern start at 144hrs to 168 where the ECM has this morning gone back to showing hp over the pole which is important in terms of reducing the westerlies being added to the flow around the pole and taking some of the punch out of the strengthening pv. GFS again having none of that paticular senario.

They model HP over the pole, drop it the next day and then show it the following day closer towards the more reliable time frames. If I'm honest, model watching is painfull right now, not because the output doesnt show anything cold for us but because its to hard to tell if the current pattern is going to keep reloading or whether a change will come.

[Gibby]

Good morning. Here's my take on the 00zs this morning.

GFS shows a strong Southerly flow for the next 48hrs with an active front crossing East in the next 24-36hrs. Heavy rain will accompany the front and will be followed by less windy and showery conditions with some possibly heavy and thundery showers in the SW. In the SE further rain may spread North late tomorrow. Over the weekend as the trough disrupts Low pressure forms over France and could give a very wet day on Saturday for England and Wales. High pressure to the NE extends a ridge over Northern Britain over the weekend and start of next week giving drier conditions here. Then Southeast winds take hold as pressure falls to the West with a spell of rain at times again before through FI when High pressure over (which remains over Europe throughout) extends further West at times bringing drier, Autumnal weather with the risk of frost and fog becoming much more likely. After a very mild start temperatures look set to fall to near the seasonal normal or a fraction below by the end of the operational.

The GFS Ensembles maintain slightly above average 850's right out to the end of the run in both London and Aberdeen. A few more members take uppers down to -5 at times but there is still little support to offer anything more than the risk of Anticyclonic cold in fog and frost so far.

UKMO today also shows a cold front moving East across the UK tomorrow with its heavy rain and strong winds ahead of it. The weather then turns more showery as winds fall light and transfer to an Easterly direction as Low pressure develops to the SE. This could throw further rain North over the weekend, especially towards the SE. This gradually recedes as we move out of the weekend and into next week with the North seeing drier weather from Saturday on. After a mild start temperatures would return nearer to normal over the weekend and beyond.

ECM finally differs in keeping the French Low further East and less influential over the weekend. Instead it delivers a strong ridge up from the SW to from an Anticyclone close to Eastern Britain by Monday. After tomorrows rain and Friday's showers the weather would settle down away from the SE with cooler nights with some fog and a touch of frost for a while. However, as the High moves away East later next week mild Southerlies return with Atlantic wind and rain drawing close to Western Britain by the runs end.

In Summary today the weather remains fairly benign for widespread cold. Instead after this weeks unsettled and mild conditions an attempt is made by the models to introduce quieter and cooler conditions with the risk of frost and patchy fog early next week but this seems quite temporary as the majority of members from the ensembles and the operational push the ridge away to Europe and re-introduce the Atlantic again soon after. Although the air would be less mild than recently I can see nothing colder than average for the next two weeks in any meaningful form from the models today. No doubt some of the other members on the forum may dig deep and shape things rather differently.

[Methuselah]

Thanks for the summary, Gibby.

[feb1991blizzard]

I Like the latest GFS FI, while it doesnt actually bring us anything wintry it is keen to develop a greenland block and you can see how things could develop quite nicely from there. I think its the 324 chart thats the best, from that chart if we didnt get a greeny block i fail to see how we couldnt get a scandi block. I cant post the chart though, it wont allow me to anymore.

Edited November 2, 2011 by feb1991blizzard

[Backtrack]

I Like the latest GFS FI, while it doesnt actually bring us anything wintry it is keen to develop a greenland block and you can see how things could develop quite nicely from there.

I know it's deep FI but I don't really see how at this stage in the year that blocking would benefit us.

The high moves over us rather quickly and produces Easterly winds, and there's no cold pooling on that run for Europe.

It will most likely be gone on the next run anyway. The ensembles show that operational to be a bit of an outlier too.

[feb1991blizzard]

I know it's deep FI but I don't really see how at this stage in the year that blocking would benefit us.

The high moves over us rather quickly and produces Easterly winds, and there's no cold pooling on that run for Europe.

It will most likely be gone on the next run anyway. The ensembles show that operational to be a bit of an outlier too.

The ensembles havent come out yet for that run but point taken an easterly is unlikely to deliver and yes i agree even if the greeny block did link up with the atlantic high that the atlantic would still probably be to potent for any lasting blocking to occur but IF we could see some form of blocking to the North in the traditional atlantic season, dont you think that might be a good sign further on down the line.

Ive already wrote November and the first week of december off, the best we will do it a brief PM blast/ 24 hour toppler, all i want is to at least se some signs by december, hopefully involving a stratosphere warming event.

Edited November 2, 2011 by feb1991blizzard

[Alex]

As GP said yesterday the GFS is being too progressive with the whole Greenland blocking scenairo and I agree that sticking with the ECM is best for now.

[Met4Cast]

The ensembles havent come out yet for that run but point taken an easterly is unlikely to deliver and yes i agree even if the greeny block did link up with the atlantic high that the atlantic would still probably be to potent for any lasting blocking to occur but IF we could see some form of blocking to the North in the traditional atlantic season, dont you think that might be a good sign further on down the line.

Unless of course the Jet Stream continued to undercut the High and head South, which would just pump up the high and make the block stronger. Though, this is of course pure speculation, it couldn't really be more in FI if it tried.

The ECM is still having none of it and wants to keep High Pressure stuck over Europe, leaving us in Southerly winds. It really is interesting me how both models are predicting very different outcomes, but yet both models continue to stick to their guns about it. The GFS does seem to be shunting Northern Blocking further back with each run, with it now projected to come into play around the 18th, this suggests to me that we're not really any closer to getting that block in place, or to knowing whats going to happen. You can see the stark difference on the 500MB anomaly map.

Whether it's going to lead to cold or not remains to be seen, but one thing you can't argue with is how bullish both models are being with their outcome, and how interesting model watching will become over the coming days if things continue to go down this path.

[Backtrack]

The ensembles havent come out yet for that run but point taken an easterly is unlikely to deliver and yes i agree even if the greeny block did link up with the atlantic high that the atlantic would still probably be to potent for any lasting blocking to occur but IF we could see some form of blocking to the North in the traditional atlantic season, dont you think that might be a good sign further on down the line.

Oh damn, I always forget the ensembles are a little later than the operational, my bad!

I don't really know if I would even class that as a block? It's only there for a very short time and then the high moves over us, which is a bad position especially at this time of year. As for signs, I'm not really sure. I suppose it can only be a good sign, but then again the weather doesn't follow any rules.

Unless of course the Jet Stream continued to undercut the High and head South, which would just pump up the high and make the block stronger. Though, this is of course pure speculation, it couldn't really be more in FI if it tried.

The ECM is still having none of it and wants to keep High Pressure stuck over Europe, leaving us in Southerly winds. It really is interesting me how both models are predicting very different outcomes, but yet both models continue to stick to their guns about it. The GFS does seem to be shunting Northern Blocking further back with each run, with it now projected to come into play around the 18th, this suggests to me that we're not really any closer to getting that block in place, or to knowing whats going to happen. You can see the stark difference on the 500MB anomaly map.

Whether it's going to lead to cold or not remains to be seen, but one thing you can't argue with is how bullish both models are being with their outcome, and how interesting model watching will become over the coming days if things continue to go down this path.

Hi Daniel,

Where can i find those charts? I have a link to one site but it's on a very fast loop and I don't have time to look at them before they change. :lol: