Model Output Discussion 12z 07/11/2012

[Robbie Garrett]

Definitely agreed OldMetMan, it seems so long ago......

But at the current rate, we could be on for a repeat of November 2010. Not sure about December, but not even the MetOffice forecasted December mid-November.... the cold just continued and continued. We just have to wait for a pattern change, the pattern to submerge us and then remain in that pattern.

Obviously the first step we are looking for is a Pattern Change.

R..

Some typical November weather likely as per the models - at least until mid-term, with a succession of LPs running from slightly N of W.

However, the longer term has some interesting possibilities. The 00h GFS showed a significant cold plunge at the end of the forecast period - clearly not to be taken too literally - but some of the other output, including the GEM, show the possibility also.

The jet flow is changing gradually. There is still the strongest and most sustained jet over the W Pacific but further downstream we now have some more vigorous activity over the N USA with 2 streams combining and further downstream still, a strengthening WNW jet heading our way,

What I find significant about this arrangement is that, although the WNW jet seems likely to sustain mobile conditions for a while here, the alignment of the US jet would seem to be amplifying SE with the corresponding 500mb low going with it, resulting in rising pressure, and some blocking, developing off the E US and Canada.

Meanwhile, the tendency for the persistent upper low over the UK to recur is continuing to be shown by the models and it seems a logical development, given what's likely to happen upstream.

The persistence of the mobile pattern we have had so much of this year was largely due to the strong SW jet heading from the US to the UK. But, in spite of what I have said above, there is still quite some disjointedness to the jet, plus a fair degree of meridionality all the way from the Pacific which in my view would tend to favour blocking - this I base on what I have seen happen before.

I strongly suspect that within a couple of weeks there will be a major blocking setup with a strong upper ridge over the W Atlantic and a deep and broad upper trough covering much of the central and eastern Atlantic, including the UK, as hinted at by the GFS and GEM. I haven't checked out the 18Z GFS yet but it will be interesting to see if it brings this possibility back.

This raises the possibility of the W Atlantic HP extending towards Greenland and most of the LP energy on the forward side of the downstream LP heading into W and S Europe, which could bring a NE fetch our way.

Yes, a lot of ifs and buts here but I have to say there are some similarities between this November and that of 2010. I should add that on that occasion, the NE pattern developed very quickly in a matter of a few days.

I keep repeating this point but I think we are seriously overdue for some significant blocking that persists longer than a week or so. The repeat performance of an upper low and cold pool at our longitude gives me more confidence that this may indeed happen - and quite soon.

Edited November 8, 2012 by Robbie Garrett

[bobbydog]

18z not bad, still progged for a vortex shift. this is the key. don't be worrying about any 'mildness' here for now, we need to get some cold into europe first or the 'beast from the east' will have no teeth!!

[Gibby]

I'm not being too critical, I enjoy reading your posts even if I disagree here and there, i'm just pointing out that today's gfs 12z played out like todays update from the met office, which offers more encouragement for coldies beyond the next 10 days. As for next week, it does look mild for some of next week but for the north and west of the uk, apart from mon/tues, temps look much closer to the mid nov average.

Don't worry, I don't mind criticism as I am not a weather God and don't see everything right. There are many on here and elsewhere whose knowledge well surpasses mine. I just use the experience of nearly 50 years of enjoying weather, whatever it is and believe me it's amazing how much you can learn from just witnessing a lifetime of anticipation and disapointments over the years. Going back to an on topic perspective it's charts like I see tonight that make winter weather such a frustrating experience for cold lovers in the UK. With a Westerly flow that ebbs and flows but never goes away it really is like looking for a needle in a haystack trying to find the one outlet that could lead us to the synoptics we all want to see but unfortunately they're not shown tonight.

Edited November 8, 2012 by Gibby

[Cal]

Don't worry, I don't mind criticism as I am not a weather God and don't see everything right. There are many on here and elsewhere whose knowledge well surpasses mine. I just use the experience of nearly 50 years of enjoying weather, whatever it is and believe me it's amazing how much you can learn from just witnessing a lifetime of anticipation and disapointments over the years. Going back to an on topic perspective it's charts like I see tonight that make winter weather such a frustrating experience for cold lovers in the UK. With a Westerly flow that ebbs and flows but never goes away it really is like looking for a needle in a haystack trying to find the one outlet that could lead us to the synoptics we all want to see but unfortunately they're not shown tonight.

That's a brilliant post Gibby! Bit of a down to earth reality showing over the next 10 days or so, however, most of us can remember the synoptic output from Nov/Dec 09 thinking what an earth are the Met O long range forecasts on about? Slowly but surely the ensembles showed it, yet the Met O kept banging on about below ave temps at the end of the month into dec09, it never came out on the 'control run' till mid/late Nov 09, yet 95% on here were adamant it wouldn't happen and were confused as to why when the models kept churning out the mild stuff.... You speak what you see, so fair play...until the models agree on a pattern wherby the forum goes into meltdown then you carry on kid well old man !

[Robbie Garrett]

Interestingly looking at the NAO forecast, it's already forecast to go back to a more negative state.

Polar Vortex looking likely to set-up shop over Scandinavia. I suspect that it would likely also bring it a first polar low towards our shores. As some green/yellow's head towards Greenland/Cananda providing support for the block. I suspect the Arctic looks likely to become blocked looking at the NH 500 hPA chart.

Edited November 9, 2012 by Robbie Garrett

[Timmytour]

Reputation on the line here....so nothing to lose!!

But I'm looking at this on the GFS +72....(and first of all I'm peed off I can't seem to post underneath it!) but I'm saying it's wong thereafter...the low won't progress as far east as modelled and the UK weather will develop more from the east

Sorry if off topic.....but a big change is on the way and a lot sooner than even some coldies think!

[pyrotech]

I think we need to look back at the model runs this year.

Firstly strong heights have been persistant over Greenland and no signs that will change.

High possability of a Scandi high and eventually negative AO

So the models later this month will pick up signs of this,probably GFS first.

About GFS this models seems to pick up trend changes, in deep fi, drops them medium term and bring them back fairly like original in reliable frame. Discount GFS at your peril as it does that fairly often.

Something the models do not pick up on is the sleeping sun, A long very low minimum and now a very low maximum suspot count.

I Would expect a short cold snap around Very late November and early Dec. Then more average conditions following.

Winter as a whole will have sinifigant snow fall more likely than not especially into 2013.

Every thing points in this direction in the climate models all it needs is pieces put in right location.

Snow cover is fairly extensive already in Northern Europe-.

We have alot of factors to look at, but its all very positive for winter as a whole.

The models will pick it up and i would expect signs of brief cold spell to show up in fi by last quarter of this Month.

Remember the models react to slight changes now and will only show changes from a SSW if it had become evident now, that may have a lag from discovery of 3 weeks to efffect AO. The models are more reactive than proactive.

Some may not like it, but imho the sunspot cycle if it stays the same may have a rather large efffect over next few years, Will the models struggle with that, i think they might.

So is my discusion about watching models for next few weeks and expect signifigant snow this year based on any facts?

Yes, Heights over Greenland and negative AO, because everything seems right for this to occur.

We discuss the models, yet we seem to forget to study them. A trend has been stubborn over last few months for heights to build again and again over Greenland. Just part of many pieces of a pussle that allow -AO and others there too.

Watch for this trend in the models and you will hopfully see the other factors including positions of the high(s) for colder plume

This is looking for trends in the models rather than specifics.Could we have strong -AO and NAO and not have cold and snow - yes, but its the historic way for cold spells so i call it positive for cold lovers. The most exciting bit for me is much longrt term with sunspot cycle.

WhaT EVER happens i hope we can learn from it.

The models will react to effects caused by sunspot cycle , but will not predict the effects in weather patterns seasonally or likely changes to global or continent temperatures over longer term. This is another part of the complicated patterns the models try to digest on their runs based mainly reactively.

Edited November 9, 2012 by pyrotech

[IDO]

The GFS 0z shows a really flat pattern on this run with any trough activity not progressing further than mid France. The Azores high settles in, over Europe, from T276 till the end of FI, putting the UK under a classic zonal flow. Temps are consistently average through the run with no frosts or anything wintry, apart from mountain tops.

The Arctic still showing blocking at the end of FI:

gfsnh-0-384.png

But again no sign of the cold dissipating our way. All heading to the Eastern Seaboard and Siberia:

gfsnh-1-384.png

The GEFS control also on the same song sheet:

gensnh-0-0-384.png

Any cold 850s on a different axis. So the NH looks to be heading for a cold spell at the end of the month, as forecast by the knowlegeable here. At the moment the models are forecasting this at 90 degree axis east and west of the UK. This may put us in line for a mild spell, bearing in mind the amplified upstream pattern. Too early to call yet but a possible pattern change now may start to be shown in late FI. The Broken Jet, late in FI highlights this:

http://cdn.nwstatic..../372/hgt300.png

Edited November 9, 2012 by i'm dreaming of...

[Tom Montalbano]

GFS yet again, albeit at the end of week 2 into week 3, persisting with the idea of a fragmenting and displaced PV and heights rising over the Arctic.

Just before that fragmentation occurs, signal for strong upper ridge to develop between Aleutian Islands/Kamchatka area.

http://cdn.nwstatic....324/npsh500.png

http://cdn.nwstatic....384/npsh500.png

Regards,

Tom.

Edited November 9, 2012 by TomSE20

[lorenzo]

GFS operational 00z off on one this morning with a monster Atlantic Low leading to the last week of the month.

Jet pattern increasingly meridional behind it as per OMM post pointing to the changes late last night.

Towards the very end of the run so some time to see if this is GFS dartboard 940mb low is out in la la land or picking up on the Atlantic steaming through before a pattern change..

[Gibby]

Good morning. Here is the latest review from the 00zs of GFS, UKMO, GEM and ECM as well as the GFS Ensembles and the Jet stream report too.

All models look monotonously similar right out to the middle of next week and beyond with a cold front currently shown to be crossing SE over the UK carrying a band of rain with it, reaching the SE after dark today. Behind it a showery and rather colder airflow follows lasting through Saturday and into Sunday with Northern and Western areas seeing the heaviest showers where some could fall as snow on hills. Through Sunday a ridge of high pressure is shown to cross the UK later in the day allowing showers to decay as winds fall lighter briefly. A chilly night Sunday night will be chased away by a freshening SW breeze as a warm front moves in from off the Atlantic with a spell of rain and drizzle for all in milder air. Once passed the models show winds settling SW for several days and it looks like it will become very mild in the South and particulary the Southeast with 13-14C possible or more in any brightness. Here it would likely stay dry while Northern and Western areas are more likely to see rain and drizzle at times in a continuing mild SSW wind.

GFS then moves into the second half of the week with a cold front moving erratically Eastwards over the UK bringing a band of rain slowly East with it, lowering temperatures to nearer normal values as it does so. By the weekend a new Low pressure winds up in the area of Iceland with a broad and strong SW flow over the UK with further rain and drizzle sweeping NE over the weekend, heaviest in the North and West. It will become somewhat milder again. Through FI the pattern remains virtually unchanged with further rain at times for all in a strong and blustery West or SW wind with just the hint of something a little colder in the far reaches of FI once more as winds turn more Northwesterly dragging colder air South.

The GFS Ensembles show the pattern as before with a notable reduction in the amount of rainfall expected over Southern Britain next week under the closer influence of High pressure over Europe. Next week looks very mild over Southern Britain before temperatures fall to average at the surface as 850's fall closer to the long term mean. Rainfall amounts increase again then in the South as the influence of Low pressure to the North extends to all areas of the UK. This would likely allow temporary incursions of rather fresher and showery conditions at least to the North at times where the tops of hills and mountains above 2500-3000ft could see some snow.

The Jet Stream ridges over the Atlantic currently and then cascades South over the UK. As time passes it undulates close to our latitude and turns North or Northeast over the top of the European anticyclone through next week.

UKMO shows a slightly different picture at midnight next Thursday with a closed Low pressure centre over Ireland and a cyclonic Southerly flow over the UK bringing rain at times for all in temperatures close to normal.

GEM shows a broad trough South near Western Britain at the same time which ambles East and weakens through Friday. By the weekend the pressure pattern simplifies as Low pressure out to the NW drives a return of mild SW winds and milder air NE again to all areas over the weekend.

ECM places Low pressure further North than GEM and UKMO at 144hrs with a mild Westerly flow and a front crossing East in the flow, most active in the North. This Westerly mild weather with occasional rain continues until near the end of the run when a temporary turn of winds from North of West brings a snap of rather colder air with showers which could turn wintry in the North. There is a chance at this point that the Low in mid Atlantic could bring about a pattern change if it is prevented from moving NE and bringing back the Atlantic train once more. It is sheer speculation at this point but I'm sure many of you will be discussing it through the day.

In summary the pattern remains very flat and mobile this morning. A very mild SW flow looks like taking shape next week with not much rain in the SE and most of it in the NW where it will be very windy at times. In the second week a stronger and somewhat cooler westerly flow develops for all with rain more widespread and evenly spread throughout the UK with the chance of something a little colder from the North in 10-14 days time.

[Frosty.]

Looking at the Gfs 00z ens mean out to T+240 hours, the generally very unsettled pattern shows no sign of ending, it does relax it's grip for a time, this weekend looks like an improving picture with showers fading although it will be rather chilly with temps of 7 to 9c, a touch of overnight frost but plenty of sunshine, especially on sunday, monday becomes wet, windy and milder as a depression moves in but then we start to see a nw/se split develop through most of next week, northern and western britain continue unsettled and relatively cooler but the south and east turn milder, drier and brighter thanks to high pressure over the near continent, however, by later next week onwards, low pressure moves down from the northwest to bring gradually colder and very unsettled conditions back to all areas with the PFJ being pushed well south of the uk and an increasing risk of snow on northern hills/mountains and frost where skies clear, beyond T+240 I would think the main trough could push a bit further east opening up even colder air from the northwest.

Edited November 9, 2012 by Frosty039

[bradymk]

Matt on twitter saying that the ECM 32 day model is sticking with its previous output with "N blocking late Nov/early Dec with cold temps & a likely risk of wintry weather"

[IDO]

Matt also says the latest ECM seasonal forecast is for a mild and wet Winter over the Uk...as per their last update.

[Tim Bland]

However. ECM seasonal model going for a mild winter with lower pressure to our north and higher to our south. It's strange that they are conflicting, unless early Dec blocking is short lived?

[georgiedre]

I was wondering that too and i asked chino about this and his reply was:

I don't know how accurate they are, having not really followed them. Matt Hugo has suggested that they have been unreliable. Let's hope he is right.

Edited November 9, 2012 by georgiedre

[snowking]

However. ECM seasonal model going for a mild winter with lower pressure to our north and higher to our south. It's strange that they are conflicting, unless early Dec blocking is short lived?

From memory it has done that consistently...for about the last 3 years

SK

[Tim Bland]

Maybe it's like some human forecasters.... Go mild / zonal and you will be right 9/10 was supprised that BBC did a video yesterday showing Easterlies and blocking at the end of the month. Shows Meto are confident that the ECM 32 dayer is on the money. It's on my twitter page -@timbland36 if anyone wants to see it

[lutfishah]

CFS 18z showing really cold air of -8 uppers from 25th of November and staying with us till 5th of December.

[Tim Bland]

Could someone post. Link to CFS please. Re 06z, it shows an Atlantic ridge in FI and PV fragmenting. It's always the last few frames though, never seems to get any closer! Sorry I can't post charts, on phone bored out my brain on M1 closure for the last 2 hrs!

[Mark Neal.]

Could someone post. Link to CFS please. Re 06z, it shows an Atlantic ridge in FI and PV fragmenting. It's always the last few frames though, never seems to get any closer! Sorry I can't post charts, on phone bored out my brain on M1 closure for the last 2 hrs!

CFS Charts are on here what i look at- http://www.meteociel.fr/modeles/cfse_cartes.php

Hope this helps

[Paul]

Can we stick with the model output in here please, chat about seasonal forecasts and the like are better suited to the winter thread

[offerman]

Looking good toward the end of November for cold spell potentially lenghty one as warm air gets pushed in to Greenland from Mid-Atlantic displacing the normal cold high cell over Greenland and pushing it in to the Atlantic just west of Ireland. These setups can change so far out but if these runs keep repeating then late Novemeber earluy december could be interesting.AIMHO of course. I`m no expert

Edited November 9, 2012 by offerman

[Frosty.]

The Gfs 06z is a rollercoaster of a run with mild and cool, even cold spells and generally unsettled throughout but with exceptions, during next week it does turn mild, temps widely up to 13c next tuesday but then trending nearer average but still mild and drier at times towards the southeast with the best of the weather, fairly benign conditions briefly down there but most areas more unsettled and windier, some stormy spells in FI and a general trend away from mild with a strengthening westerly airflow, when you follow the isobars back you can see the air was originally sourced in the arctic so temps falling below average with wintry spells for northern hills and overnight frosts where skies clear, one very vigorous depression later in FI would be the trigger for an arctic outbreak later in the month but the main feature of the 6z is the persistent nature of the unsettled weather for almost the next 384 hours with power to add. Today's 6z is an upgrade on yesterday's 6z in terms of a colder further outlook with more wintry potential

Edited November 9, 2012 by Frosty039

[johnholmes]

Looking good toward the end of November for cold spell potentially lenghty one as warm air gets pushed in to Greenland from Mid-Atlantic displacing the normal cold high cell over Greenland and pushing it in to the Atlantic just west of Ireland. These setups can change so far out but if these runs keep repeating then late Novemeber earluy december could be interesting.AIMHO of course. I`m no expert

where do you get information to suggest 'potentially lengthy one' re cold?