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Winter Model Discussion 06Z 10/01/13>

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Despite the best efforts of the team, the last model discussion thread still descended at times into an outpouring of emotion and very little content was to do with what the models actually showed and how that translated into the weather we could expect.

Judging by comments in other areas of the forum, people have been put off coming into this usually 'highly thought of' part of Netweather because of the standard of posting and the abundance of comments that were nothing to do with the topic.

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As this is one of the busiest times in recent years, the team do not have the usual luxury of moving 'Off Topic' posts and you may find your contribution, if not relevant, will be deleted. Save everyone the time and effort in doing this by reading your post first and seeing if it meets the fairly simple criteria for inclusion in the MODEL OUTPUT DISCUSSION thread here.

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Another morning, another standoff, more misleading posts. They both stick to their guns which is remarkable considering the timeframe, ECM has not moved towards the GFS, I admit, for southerners it doesn't look as good if your looking at 850 temps however a hundred/200 mile shift and the whole country would still be game on. I think the ECM will be milder than the mean for the south of the UK, GEM and UKMO still cold too so basically, no real change this morning. GME looks good this morning aswell.

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snapback.pngmcweather, on 10 January 2013 - 08:30 , said:

I have great respect for you so perhaps you'd be good enough to give us your learned view on the overnights John.

I will post later this morning if I have time in here and the more sedate area

Many thanks John. Your measured view is always appreciated.

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This is the new Pluim. When you have a paid contract with MeteoConsult you get the Pluim so what earlier than officialy at the KNMI/ Weerplaza sites.

More uncertainty after 144h; which can be seen here too http://www.ecmwf.int/samples/d/inspect/catalog/samplers/banner/mean_sea_level_pressure_and_temperature_at_850hpa!168!pop!od!enfo!enplot!2012020700!!/

post-10577-0-71744800-1357807234_thumb.p

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Good morning. Here is the morning report on the 00z output from the big four, namely GFS, UKMO, GEM and ECM for today Thursday January 10th 2013.

All models show a colder and wintry spell spreading into the UK over the coming days. Today shows a chilly and cloudy day though with some bright intervals in places.as a slack area of Hugh pressure weakens further as a trough moves into the SW later bringing some rain. This trough weakens in situ tomorrow with a dry and cloudy day likely tomorrow before Saturday sees a more meaningful area of Low pressure move in close to the SW. With pressure building to the North a cold Easterly flow undercuts the rain area moving in from the West and SW with rain turning to snow later on Saturday and into Sunday when wintry showers move into Eastern areas too. Early next week then shows a strong divergence between the models.

GFS shows a ridge of High pressure drifting SE over the UK and on down into France. After a couple of days of cold and frosty weather milder SW winds move into the UK bringing rain and strong winds across the UK from the West towards the end of the week. In FI today the GFS operational shows a potentially wet and stormy period as deep Low pressures steam across the Atlantic and over the UK with frequent bouts of rain and showers falling as snow on Northern hills at times.

The GFS Ensembles show a short cold spell before a return to more average conditions as the Atlantic brings a return to wind and rain at times. This doesn't proclude the risk of some snowfall over Northern hills in the rather chilly conditions following the rain bands. The operational is a slightly warmer meber of the pack while the Control run shows a very deep cold spell late in its run.

The Jet Stream is a little disorganized at present with the main arm well South of the UK for some time to come. Later a strengthened arm moves East across the Alantic to the UK in a week or so.

UKMO for midnight on Wednesday shows High pressure to the North of Scotland with a ridge South over the UK. the weather would be very cold and frosty with some snow showers in the SE slowly dying out.

GEM shows High pressure North of the UK too at that time with a very cold NE flow over the South with further sleet or snow showers in places. Later in its run the cold weather persists with winds keeping an Arctic element to them with sleet or snow at times in very cold and frosty conditions.

ECM shows something a little different this morning with the cold Easterly flow more restricted to the North while Low pressure moving further North over the UK than previous output re-introduces milder air into the South with rain heare while the North sees more snowfall. However, the pattern remains essentially a very cold and unsettled one over the UK towards the end of its run with spells of sleet and snow for all at times.

In Summary the stand off between GFS and the rest persists this morning. Never in the history of my model watching which in some shape or form has been over 20 years have I witnessed such a stark contrast between one model and another meaning totally different weather conditions to be experienced at the surface. The Euro models maintain a basically cold and wintry outlook though widespread snowfall looks less likely from the UKMO output away from the East after the weekend.. ECM does also show a hint of milder air making inroads into Southern Britain early next week just for a while. But it's GFS that still shows nothing particularly wintry at all going for wet and stormy weather as it's likely outcome in association with deep Low pressure rushing east from the Atlantic. It's Ensembles also suggest a very brief cold blip followed by a return to normality spare the Control run. I wouldn't want to be a professional forecaster today as they must begin to feel pressured on making a call on where the weather is likely to go as we move into next week.

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The Ecm 00z has become a lot messier and more complex this morning compared to yesterday when the cold trend and cold outlook was clean cut and more emphatic, there are now a lot more uncertainties but ironically because the ecm is more low pressure dominated and cold, major snowfalls would be the result rather than wishbone Northerlies with showers draped around the coasts, the one major ingrediant in our favour is the SSW which could and should ultimately be the deciding factor.

post-4783-0-58163700-1357807168_thumb.pn

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Another morning, another standoff, more misleading posts. They both stick to their guns which is remarkable considering the timeframe, ECM has not moved towards the GFS, I admit, for southerners it doesn't look as good if your looking at 850 temps however a hundred/200 mile shift and the whole country would still be game on. I think the ECM will be milder than the mean for the south of the UK, GEM and UKMO still cold too so basically, no real change this morning. GME looks good this morning aswell.

Good summing up of the models without the emotions of some of the other members earlier posts. I suppose one of the problems is that some of the previous runs from the big 3 have been so good that a downgrade had to come.

Lets face it if there were upgrades this country would have had serious problems if they verified!

To add further confusion itv's day break weather presenter at 8.30 mentioned the newspaper headlines of the big freeze. She then went on to add that it would become very cold with snow risks over the weekend and she reiterated that the cold spell would last for at least 2 weeks.

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Still by in large same set-up form all the models, IE the GFS utterly on its own with its evolution on the shortwave, all other models broadly have a similar looking set-up though how they handle the small features is different. Interestingly the GFS ensembles have moved towards its op run, so it'd be a bit daft to rule it out.

With that being said, for now its hard to believe that many other strong models have got it wrong, but the GFS is VERY good at handling these sorts of shortwaves, I'd argue better than the ECM.

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thanks Kold-a very sensible post; we simply cannot yet know just what the evolution is going to be. This is where heart and head are so difficult to reconcile even for trained forecasters. The ops room in Exeter must be a very busy place over the past 2-3 days as they struggle to try and make sense of the conflicting models.

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http://www.cpc.ncep....O/foregfs.shtml

I notice the GFS MJO forecasts are now stalling in Phase 6 - which is not what we want to see really (for cold at least). I suspect if GFS is correct about the upstream pattern, then it may be too flat at day 6 - with more blocking likely to hang on around UK/Europe and the cold not as easy to push away as modelled.

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CMA120

cmanh-0-120.png?00

How long has this model been running, any stats for it yet?

T144 looks amazing!

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copied from the other thread as it may help new folk

thanks to Gibby for his outputs

For those new to model interpretation, simply read the two summaries above by Gibby. It shows quite clearly how over a 12 hour period the emphasis can change.

last evening

In Summary the cold spell is well and truly on the way. After a gradual cooling of conditions over the coming days the weather turns decidedly wintry as we move through the second half of the weekend and (as much of the output shows) much of next week too.

this morning

In Summary the stand off between GFS and the rest persists this morning. Never in the history of my model watching which in some shape or form has been over 20 years have I witnessed such a stark contrast between one model and another meaning totally different weather conditions to be experienced at the surface.

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So the ECM v GFS stand off goes on and on. I seem to recall the ECM has more form on 11th hour stand downs then the GFS? As many have speculated before the truth is probably somewhere between the two. This may make for something more interesting or if we're really unlucky we'll end up with some slushy horrible polar maritime nonsense that deliver little but is still cold! Lets see what the next couple of model runs deliver! I don't think we've seen the end of this roller coaster by a long chalk....

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CMA144...Yes looks a cracker....There was some detail on this model in previous thread......Nick Sussex posted an excellent document from Met office over on the Strat thread and this model seemed not to engage in any strat dynamics in its current of future output which will put some off.....verification stats seem hazy..bit like everything coming out of China these days

cmanh-0-144.png?00

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the simple way of looking at all this and to be honest until this morning is that the jet and the azores heights are not helping the midterm outlook.

i also strongly believe now that heights around greenland iceland and scandi are less likely although vortex dissplacement is evident its from this source that these developments from the northern states that are still putting tomuch energy into the alantic.

and this is why i believe the gfs could well be onto something although teleconnections still could favour cold by the end part of january i do believe now that 1 the jet still to strong 2 vortex still spawning deep enough and disruptive enough low pressure systems not to favour heights to our north not allowing time for things to settle.

and the azores heights really are pretty strong and maintaining there influence on our weather in the uk.

in the shorterm there is cold and snow to be had but because of the genral movement of low heights and ridge from the south things are messy.

http://www.cpc.ncep....O/foregfs.shtml

I notice the GFS MJO forecasts are now stalling in Phase 6 - which is not what we want to see really (for cold at least). I suspect if GFS is correct about the upstream pattern, then it may be too flat at day 6 - with more blocking likely to hang on around UK/Europe and the cold not as easy to push away as modelled.

but this is ment to support mid alantic ridge or not?

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briefly...

Next week's forecast looks horrid and complex. I would go below average and becoming increasingly cyclonic. That brings an attendant snowfall hazard.

Ironically, day 10+ might be less problematic to get a broad view on.

Tendency in relative angular momentum is very likely to spike in the next few days. That will shoot the Global Wind Oscillation towards high amplitude phase 4. That teleconnects with the core of the +ve height anomalies in a triangle between eastern Greenland, Svalbard and northern Scandinavia.

GEFS has trended this way in the last 24 hrs, as has ECM. Also trending is the development of some energy off the residual pv over Canada into the North Atlantic, which most likely to reinforce the blocking signal further north and NE. Low pressure signal over Europe still very strong. Interestngly this perhaps resolves CPC's teleconnective issues w/r/t Greenland and Pacific blocking structures.

So period 14-21 Jan looking cold and unsettled with wintry mix. Thereafter, signal for renewed push of Arctic air from the NE.

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http://www.cpc.ncep....O/foregfs.shtml

I notice the GFS MJO forecasts are now stalling in Phase 6 - which is not what we want to see really (for cold at least). I suspect if GFS is correct about the upstream pattern, then it may be too flat at day 6 - with more blocking likely to hang on around UK/Europe and the cold not as easy to push away as modelled.

its also worth noting the gfs wiped the floor with the ecm when it came to strat warming.

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Still by in large same set-up form all the models, IE the GFS utterly on its own with its evolution on the shortwave, all other models broadly have a similar looking set-up though how they handle the small features is different. Interestingly the GFS ensembles have moved towards its op run, so it'd be a bit daft to rule it out.

With that being said, for now its hard to believe that many other strong models have got it wrong, but the GFS is VERY good at handling these sorts of shortwaves, I'd argue better than the ECM.

Yes, the GFS is very good in that area. I think talking about the ECM and how far North/South the snowline will be is an irrelevance because we are now in a situation where the ECM is at zero margin for error at T96/120 having had only very little margin for error on it’s 12z last night.

Is this simply a shortwave issue or are there other factors involved on why we cannot get a negative –NAO ? Would appreciate GP’s take. Either way it always a learning experience for all of us – not least the METO !

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Thanks GP – strongly disagree with the assessment for next week – don’t forget in December that the Cheltenham meeting that you thought would be off due to snow ended up being ran in double figure temps and pouring rain !

I hope you are right with your assessment and going forward with the blocking but I really can’t see it.

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What a bewildering (but fascinating) time for a newbie to start chart watching! Anyway, I have GFS/ECM/UKMO open in 3 windows and as I step through I can see the divergence emerge after T48.

At T72, ECM begins to do its own thing, but GFS and OKMO are still close (to my novice eyes).

UKMO

UW72-21.GIF?10-06

GFS

gfs-0-72.png?0?0

It's then that things begin to really change, but it seems a shame to me that neither UKMO nor ECM provide the 6h or 12h updates at that stage as GFS does so you can really watch the evolution in detail. So the question it leaves me is, leaving the models aside, are there any compelling physical reasons why that low would track E/NE rather than SE?

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weres all the blocking to the south i really do think now that something in the mid term is less cold than our 3 day cold snap still happy that we might see some wintry stuff but no cigar yet more time needed end of jan start of feb.

ECM1-96.GIF?10-12

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