Model Output Discussion - 19th - 25th December

[nick sussex]

Not the most exciting output this evening for those looking for some colder conditions.

There's very good agreement on the overall pattern from the operational runs although how far north any high pressure gets is a little more uncertain.

In terms of the upstream pattern in the USA its looking flat, although NOAA do mention moderate to large spreads over the sw Conus, east Pacific and more relevant to Europe in the eastern Atlantic in terms of the ensemble spaghetti diagrams.

An explanation of how these are used can be found here:

http://www.emc.ncep.noaa.gov/gmb/ens/spaghetti/spag_descr.htm

The suggestion from both the ECM ensemble mean and the clustering of its ensembles in the extended outlook is that any high pressure will be pushed south again and edged further west with the jet returning to a more west/east tilt.

[bluearmy]

Not the most exciting output this evening for those looking for some colder conditions.

There's very good agreement on the overall pattern from the operational runs although how far north any high pressure gets is a little more uncertain.

In terms of the upstream pattern in the USA its looking flat, although NOAA do mention moderate to large spreads over the sw Conus, east Pacific and more relevant to Europe in the eastern Atlantic in terms of the ensemble spaghetti diagrams.

An explanation of how these are used can be found here:

http://www.emc.ncep..../spag_descr.htm

The suggestion from both the ECM ensemble mean and the clustering of its ensembles in the extended outlook is that any high pressure will be pushed south again and edged further west with the jet returning to a more west/east tilt.

even you are struggling to find any positives for coldies from todays output nick. it looks as though the only offering apart from mobile w-e flow is a few days of anticyclonic gloom, especially for the south !!

[nick sussex]

even you are struggling to find any positives for coldies from todays output nick. it looks as though the only offering apart from mobile w-e flow is a few days of anticyclonic gloom, especially for the south !!

Well I'm not a politician so won't be able to spin this into something it's not!

The problem isn't seeing a high to the south, if its just temporary then at least there won't be any travel drama for people over Xmas, we'll have to see whether we can carve out a more favourable nw/se jet tilt later on, at least the stratosphere is moving in the right direction and thats my positive slant for the day!

[Robbie Garrett]

Like I've said previously I am not writing off winter till at least Mid-January, still Mid-Jan till at least March for some extreme cold? even April can throw some surprises, and saying that as far in as June/July. You never know with the weather these days, I am guessing we should just wait and see what happens, I am still in for a reverse of last year, i.e a cold blast in late Jan lasting till end of Feb.

We can only hope, but if it doesn't budge we have to thank the atmosphere for the fantastic winters that it has gave us over the last 3-4 year cycle, and I am not moaning as Summer to look forward with a nice thundery breakdown during the olympics or knowing our luck, during wimbledon play!

Edited December 19, 2011 by Robbie Garrett

[BurwellWeatherWatch]

I take it you have forgotten about December 2007? Remember when you said it was going to be a zonal fest and possibly a record break mild December and I pointed out that one or two ensembles were showing high pressure having more of influence? Lo and behold as the runs went by the high pressure influence increased and increased and we ended up with about a two week anticyclonic spell and an average December. Not saying that will happen this time but the point is we don't know with any degree with certainty.

Whilst the original post was clearly designed to subtly bait those with a disposition to more interesting weather patterns, that could well be the way that things turn out. Equally it might not be and the very nature of the UK's weather makes it impossible to know. Although there is nothing on the models tonight to suggest anything approaching a freeze, things could well change very rapidly following Christmas. I seem to remember a period of great doom and teeth-gnashing back around Christmas 2009, shortly before that very memorable cold spell of Jan 2010. I think a lot of the most memorable spells (mild or cold) pop up fairly suddenly out of the blue, so keep the faith everyone. However, on the models themselves - looks very mild mid week and fairly mild after that with the possibility of some chillier episodes interspersed.

Edited December 19, 2011 by themusicland

[Timmytour]

I'm a cold weather supporter.......when my team is 1-0 up I want them to score another and another and another!

Looking at the models at the moment.....I'd say my team is 2-0 down coming upto half time. I'm hoping the manager is set to make some changes at half time...I still believe we can come back and draw or even win the game, but that ain't gonna happen playing how we've been playing so far!!! :-)

[SNOWPLOUGH]

I'm a cold weather supporter.......when my team is 1-0 up I want them to score another and another and another!

Looking at the models at the moment.....I'd say my team is 2-0 down coming upto half time. I'm hoping the manager is set to make some changes at half time...I still believe we can come back and draw or even win the game, but that ain't gonna happen playing how we've been playing so far!!! :-)

I am a cold supporter too, I reckon we are about 30 mins in and 1-0 down and the other team have missed a penalty! we are less than a third through winter and so its not half time yet, given the overall pattern thus far and the teleconnections I reckon we are doing pretty good! I also have a feeling that messi is coming on at half time! ;D

Dan

[Great Plum]

http://www.wetterzentrale.de/pics/Rtavn3481.png

I know it's deep FI but the start of a signal for a more blocked Atlantic?

Please read the more knowledgeable GP's latest thoughts in the in depth thread!

[pyrotech]

Whilst the original post was clearly designed to subtly bait those with a disposition to more interesting weather patterns, that could well be the way that things turn out. Equally it might not be and the very nature of the UK's weather makes it impossible to know. Although there is nothing on the models tonight to suggest anything approaching a freeze, things could well change very rapidly following Christmas. I seem to remember a period of great doom and teeth-gnashing back around Christmas 2009, shortly before that very memorable cold spell of Jan 2010. I think a lot of the most memorable spells (mild or cold) pop up fairly suddenly out of the blue, so keep the faith everyone. However, on the models themselves - looks very mild mid week and fairly mild after that with the possibility of some chillier episodes interspersed.

It is true that all the models show no sign of a sustained cold spell at the moment, but a cold spell in mid to late january is more than possible. What is obviously needed is blocking and right through and into Fi there is no sign of this at the moment. All the models conccur on this.

However signs are starting to become evident that the AO is beginning to weaken and will continue to do so which can give more credability to a blocking pattern. I would be looking at deep Fi for first signs of this around the new year, probably showing on the models for around the 12th/13th of Jan 2012. Lets face it winter has only just really began and our best Months would normally be Late january Through February anyway. In the mean time it looks like its going to remain unsettled and changeable. When the models show consistancy and similarity for a trend they normally get it right (trend wise) but i would be very surprised if those wanting cold do not see a new patern emerging in the models as we cross into 2012, albeit it will be in Fi when we see it, it will then become an interesting 2 weeks watching it become reality. I see GFS has cooked the storms up over next two weeks more than ECM, i did start to think they had corrected that, or perhaps they have and GFS is right. What will really be interesting is what model will pick up a blocking patern from weakening AO first.

http://www.wetterzen...s/Rtavn3481.png

I know it's deep FI but the start of a signal for a more blocked Atlantic?

Please read the more knowledgeable GP's latest thoughts in the in depth thread!

I think that will end up being slipped by at least a week and GFS has jumped the gun, but i would love to be proved wrong and find that GFS has spotted a weakening AO and see it happening quickly. I think we will see this appear sporadically on a fe runs until a trend between models suddenly nails it. I think it will happen but that gfs is two quick with the blocking.

[feb1991blizzard]

I thought someone would have commented on the 18z GFS by now, not a snowfest by any means but there are some very very tiny positives for people looking for colder weather. In the short term the very mild uppers give way at the end of the week to some uppers which may be conducive to snowfall in Northern Britain.

http://hw.nwstatic.co.uk/gfsimages/gfs.20111219/18/96/h850t850eu.png

The precipitation type chart shows some not insignificant snow for Western Scotland, Cumbria, and even as far south as Manchester,

http://hw.nwstatic.co.uk/gfsimages/gfs.20111219/18/96/prectypeuktopo.png

Normally one would think that on future runs any snowfall will be restricted to Scotland as the low gets shunted further North, this occurs quite regularly with these setups, especially with the GFS which also tends to overdo the area of snow on PPN type charts but it is model output and we are really struggling for any cold charts to post!

Also the rest of the run does show more cold, albeit very brief zonal coldish spells and some surface cold giving some low nightime temps with potential frost and fog, which may be slow to clear in parts, interspersed with some very mild South Westerlys, not really anything to float my boat but i just thought i would try to give some positives as its like a mauge in here!

[davehsug]

Correct me if I'm wrong, but I thought the AO & NAO are driven by the synoptics & do not drive them? Aren't they merely products of pressure differences?

[phil nw.]

Correct me if I'm wrong, but I thought the AO & NAO are driven by the synoptics & do not drive them? Aren't they merely products of pressure differences?

Your correct Dave.They change with each run reflecting the sypnotics of that run.

They are not a forecasting tool as such.

Latest NAO graphs here

http://www.cpc.ncep....a/nao.sprd2.gif

The red lines into January are the GEFs members for that run.

Edited December 19, 2011 by phil n.warks.

[Duane S.]

Correct me if I'm wrong, but I thought the AO & NAO are driven by the synoptics & do not drive them? Aren't they merely products of pressure differences?

That's exactly what they are. Reflections (and predictions) of pressure anomolies in set places.

Taking the models at face value, which is never wise, today has been pretty horrific in terms of cold weather potential. Yesterday there were more hints at a cold shot than today for sure, perhaps the 18z is the pick of the bunch with its FI but its pretty desperate stuff. Perhaps we can console ourselves that despite many deluding themselves that we are stuck in some sort of perenial rut, that things will more than likely change in plenty of time before winter's end. In the same way as 1963's and 1947's are rare so are 1988/89 type winters.

Here's a pretty nasty looking 850 chart for Boxing day in Europe, it can't get any worse at least, can it???

[davehsug]

Thanks for the replies, it confirms what I believed. I see so many posts saying, that the AO or NAO is progged to go negative/positive & this will lead to blah blah...without any correction. I wondered if the noggin was playing tricks

[Robbie Garrett]

Model wise, I am surely thinking this is a step in the right direction? But looking at GFS, ECM any heights to the north seems to get blasted! Maybe I am looking too far into FI?

Edited December 20, 2011 by Robbie Garrett

[Uncle_Barty]

That's exactly what they are. Reflections (and predictions) of pressure anomolies in set places.

Taking the models at face value, which is never wise, today has been pretty horrific in terms of cold weather potential. Yesterday there were more hints at a cold shot than today for sure, perhaps the 18z is the pick of the bunch with its FI but its pretty desperate stuff. Perhaps we can console ourselves that despite many deluding themselves that we are stuck in some sort of perenial rut, that things will more than likely change in plenty of time before winter's end. In the same way as 1963's and 1947's are rare so are 1988/89 type winters.

Here's a pretty nasty looking 850 chart for Boxing day in Europe, it can't get any worse at least, can it???

Looks lovely to me, to be honest. Will be good to watch the Boxing Day footie without freezing my bits off and having to dab constantly streaming eyes! Would bank that till the end of March.

Looks zonal and "best in the south" out to FI on the 00z GFS. Not a lot for coldies in that run.

[weathe20]

Lots of comments regarding 'not good for coldies'. I think the models are showing what they should be according to NW LRF. Maybe things will on change on the output over the next week or so.

[Great Plum]

The 0z GFS ensembles are showing more of a spread in FI...

http://www.netweather.tv/index.cgi?action=charts;type=ens;sess=

Notice how after 1st Jan a few cooler members appear. The op also repeats its earlier view of cooler weather... (very deep FI though!)

http://www.wetterzentrale.de/pics/Rtavn3481.png

For the big day:

http://www.wetterzentrale.de/pics/Rtavn1321.png

http://www.wetterzentrale.de/pics/Rtavn13217.png

Not widespread double digit temps - in fact the CET are looks distinctly average!

[bluearmy]

The cooler ens members reflect a mid Atlantic ridging - some the usual zonal one, some in response to a sharpening of the scandi trough. None of them reflect a pattern change though.

[shedhead]

We are certainly looking at some intensely low heights to the North going forward, it wouldn't be the greatest surprise if High pressure were to extend a little further North, but the general pattern is obvious and we see the jet advancing to Western Russia.

Yep, given the model output this morning it's impossible to draw any other conclusion... least it should be. I was hoping to see signs of HP developing over the UK between Xmas and New Year, but it just cannot seem to get a grip even in the south, with the dreaded Euro high firmly in place with both of the big players at T+192hrs. Gonna take some time to break this pattern, that's for sure, with the first taste of very mild conditions still looking very likely for many through the middle of this week.

[phil nw.]

Yes the pattern still looks very solid overall with that still strong vortex planted around Greenland and High pressure extending from the Azores into France.

http://hw.nwstatic.co.uk/metoimages/20111220/00/npsh500.120.png

Not mild all the way as the PFJ wavers around our latitude.

A brief colder 48hrs. or so at the end of the week looks likely but nothing really wintry except perhaps over the Scottish highlands.

No signs of a change going into next week

http://hw.nwstatic.co.uk/gfsimages/gfs.20111220/00/168/h500slp.png

as solid a +NAO pattern as you could wish for or dread--depending on your taste.

[rich1]

Charts indicating one of those irritating Brian Gaze colloquilaisms i.e Zonal-Bartlett, if you are in to that kind of dinner mashing terminology which I personally despise

not every day will be 10c plus, but this xmas period is turning in to one I will be quickly forgetting.

Edited December 20, 2011 by phil n.warks.
Removed whining comments-there is a thread for that Rich.

[OldMetMan]

Not a lot can be said about today's runs in terms of any potential change of pattern. Basically the main models are in general agreement, with a SW-NE mobile pattern, with pressure fairly high over the south of the UK.

Only a couple of things I picked up on today, the first was from the GEM model which I rarely consult, which shows more of a meridional flow within 7-10 days, and HP pushing N over the UK towards the Norwegian Sea. The other is the transference of the lowest thickness values from N Canada towards to pole on the GFS, to be expected really at this point in the winter, I suppose but interesting. It does suggest the possibility of pressure buildup over Canada, and the resultant change in the downstream upper wave pattern - upper trough over the W atlantic and ridge mid- to east Atlantic. Plus the GFS seems to be building pressure more over Greenland towards the end of the run as the cold there and to the north intensifies.

The big, fat HP over central Asia is still shown to ebb away by the models but I still maintain that there is a possibility of it reforming to the W of its current position. Also, it needs bearing in mind that there was a HP for weeks over E Europe throughout late autumn/early winter so this again suggests a recurrence of the block.

In the meantime, we'll see if any of the other models start to hint at more of a meridional flow late Dec/early Jan.

[tinybill]

YEP ITS f 1 we need something to like this to lift the gloom like going back to work after xmas to this ex me new job in the new year

[swilliam]

Bit more interest on the 06Z with a high developing near Iceland

Didn't last long though!

Edited December 20, 2011 by swilliam