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Model Output Discussion 25/11/2012 12Z onwards


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Posted
  • Location: Hayward’s Heath - home, Brighton/East Grinstead - work.
  • Weather Preferences: Snow and storms
  • Location: Hayward’s Heath - home, Brighton/East Grinstead - work.

Good Afternoon.

It is time for a new thread.

Please keep to the topic and include relevent charts where applicable. All views are welcome but please do back them up with appropriate charts and links. Any off topic or trolling posts are likely to be deleted.

Thank you.

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Posted
  • Location: Bearsden, East Dunbartonshire
  • Location: Bearsden, East Dunbartonshire

Good afternoon. As the centre of low pressure system moves further north east into the North Sea, later this afternoon and into the evening the rain associated with that low should be confined to north eastern parts of Scotland and the precipitation may fall as snow over the mountains. Skies across north eastern parts may still generally on the cloudy side, skies should be clearer in Northern Ireland, western Scotland as the sun sets and a belt of clearer skies should move further north through afternoon and evening across England. Meanwhile, across southern Ireland, the rain here should push into Wales, the south west and central parts of England later this afternoon and through the evening with some further heavy precipitation. Maximum temperatures today should range between 4 and 12C.

h850t850eu.png

ukmaxtemp.png

ukprec.png

Tonight, many parts of England and Wales should see some rainfall as the system moves further north. Wales and the south west may become drier later in the night as heavy showers move along the channel coast. The heaviest on the rain should be in northern England where there could be some wintry precipitation on the highest hills. A dry night for Ireland away from the east coast with some clear skies and some showers near the coast of Northern Ireland as the winds turn to more of a northerly here. In Scotland, there could be some rain near the borders but light rain should still linger around north eastern Scotland with further snow on the mountains. Some showers along the north and west coast of Scotland, but drier further inland with clear skies in the central belt. Overnight lows of 2 to 9C.

ukprec.png

ukmaxtemp.png

uksnowrisk.png

For Monday morning much of the rain should be over northern England but there could be some rain in parts of Wales as well as showers along the Channel and Moray coast and also the north and west coast of Scotland and Ireland. Dry conditions for Ireland, southern England and parts of Scotland with some sunny spells.

ukprec.png

During the afternoon the rain should be breaking up but there should also be further long periods of rainfall (heavy in places) for northern England and Wales and south eastern Scotland whilst there are further shows for the coasts. Some clear spells for parts of Ireland and western Scotland. Maximum temperatures 5 to 9C.

ukmaxtemp.png

Overnight - and there could be further rainfall across northern parts of England, Wales and into eastern Scotland and showers for northern Scotland and the seas surrounding Ireland and Wales. There could be some clear skies for Ireland, the very south of England and south western Scotland. Minimum temperatures of 2 to 8C as winds turn to a north easterly.

h850t850eu.png

Tuesday is looking like a much drier day for sunny intervals (for western areas in partcular). There could be a spell of light rain across south eastern England but this should clear southwards. It seems likely that there'll be some showers around, particulary for north eastern areas and these could be wintry - particular over the high ground. Maximum temperatures 5 to 8C.

GFS 06Z

h850t850eu.png

ECM 00Z

ecmt850.048.png

ukprec.png

With the north easterly wind, there will be further showers in places, possibly down the north sea coast of England but in general it should be a largely dry night with clear skies - most likely in western areas - and a cold night with lows of -1 to 6C.

h850t850eu.png

ukprec.png

Wednesday is looking a nice day for late November with crisp sunshine western areas, more clouds in the sky nearer to the north sea and across eastern Scotland with showers along the north sea coast. A cold day with maximum temperatures of 3 to 7C.

h850t850eu.png

ukmaxtemp.png

ukprec.png

There could be a widespread frost on Wednesday night with lows ranging between -2 and 5C. It should also be a dry night with only a few showers along the east coast of England but some light could be close to the very west of Ireland.

ukmaxtemp.png

ukprec.png

And a very similar story for Thursday with dry conditions away from the north sea and some crisp sunshine but there could possibly be some rain close to Ireland. A cold day with highs of 2 to 7C and similar story overnight with another frost for many with lows of -2 to 5C.

It could be a very seasonal start to December and winter 2012/2013 as we could see a more noticeable cold spell for next weekend.

GFS 06Z:

h850t850eu.png

uksnowrisk.png

ecmt850.144.png

uksnowrisk.png

ecmt850.168.png

Have a look at the maximum temperatures in Scotland on Sunday:

ukmaxtemp.png

And also the overnight lows:

ukmintemp.png

So the weather should be colder this coming week, and it should also be another exciting week of model watching as details emerge about the possible interesting weather for the weekend and it will be fascinating to see what sort of synoptics will emerge for beyond the weekend - at this stage we can only guess but by this time next week we should a much clearer picture and considering the background signals, there could indeed be some really interesting evolutions. We really are in interesting times and regardless of where we go from here, it should be an enjoyable rollercoster.

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Posted
  • Location: Napton on the Hill Warwickshire 500ft
  • Weather Preferences: Snow and heatwave
  • Location: Napton on the Hill Warwickshire 500ft

As for the ECM ensembles and remember during Dec 2009/2010 the extended ensembles were forever becoming less cold but this these became colder as the timeframe crept closer. Using your past experiences of following the models is always a good guide in helping you interpret the current model output. This is why im surprised some of the regulars are making the same mistakes!

There are verification stats for models but how does one learn to 'interpret' current model output ? Do you just through experience get to know that some models underestimate blocking, or overestimate the power of the Atlantic and its potential return?. Or as per SM posts which are more specific. 'GFS 06z tendency to plough the jet east' do you learn this through experience?. Do you just know some ensembles tend to be pulled more to the standard default mode in FI ?. How does one stop jumming on every minor change at T240 , know (even if its a gut feel) what charts to bin what to keep without any bias and then sit back and enjoy the next week of model watching and watch the cold arrive ?..

Edited by stewfox
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Posted
  • Location: st albans
  • Location: st albans

There are verification stats for models but how does one learn to 'interpret' current model output ? Do you just through experience get to know that some models underestimate blocking, or overestimate the power of the Atlantic and its potential return?. Or as per SM posts which are more specific. 'GFS 06z tendency to plough the jet east' do you learn this through experience?. Do you just know some ensembles tend to be pulled more to the standard default mode in FI ?. How does one stop jumming on every minor change at T240 , know (even if its a gut feel) what charts to bin what to keep without any bias and then sit back and enjoy the next week of model watching and watch the cold arrive ?..

Yes to most of that stew. however, the disppointing charts are sometimes right. (Infact, living on the edge of the atlantic, they are more than sometimes right!)

years and years of watching the damn frames come out in situations like this

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Posted
  • Location: Essex, Southend-On-Sea
  • Weather Preferences: Warm, bright summers and Cold, snowy winters
  • Location: Essex, Southend-On-Sea

General question do you believe that their will upgrades or downgrades in the models I personally don't believe we will see many upgrades if any at all. I was wrong about 2010 thou so I never know.

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Posted
  • Location: Gillingham, Kent
  • Weather Preferences: Snow, Thunderstorms,
  • Location: Gillingham, Kent

Just a word to anyone worried about the rise in ensembles out in FI.

Don't be. The increased amount of scatter within the ensemble suite in FI is bringing the mean up, remember that these ensembles are run at a lower resolution than the op so once you get past T144 they don't really have a clue and start to mute any blocking signal. The ensembles were constantly trying to rise in FI back in 2010 only to turn colder within the T144 time frame.

T144 down to T0 is where you want to pay attention, it's here we'll see the upgrades. Anything beyond that is pure conjecture

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Posted
  • Location: falkirk, scotland, 16.505m, 54.151ft above sea level
  • Weather Preferences: dry sunny average summers and really cold snowy winters
  • Location: falkirk, scotland, 16.505m, 54.151ft above sea level

is the gfs an american model or is it european

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Posted
  • Location: Calgary, Canada. Previously, Saffron Walden (Essex/Herts border), United Kingdom
  • Weather Preferences: Continental:Warm dry summers, cold snowy winters
  • Location: Calgary, Canada. Previously, Saffron Walden (Essex/Herts border), United Kingdom

Just a word to anyone worried about the rise in ensembles out in FI.

Don't be. The increased amount of scatter within the ensemble suite in FI is bringing the mean up, remember that these ensembles are run at a lower resolution than the op so once you get past T144 they don't really have a clue and start to mute any blocking signal. The ensembles were constantly trying to rise in FI back in 2010 only to turn colder within the T144 time frame.

T144 down to T0 is where you want to pay attention, it's here we'll see the upgrades. Anything beyond that is pure conjecture

Thanks a lot for this post, i was starting to get concerned with the lack of blocking after next weekend with the GFS,CFS and ECMWF but UKMO is staying strong with that block! So beyond T+1440, not worth reading into too much i should think?

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Posted
  • Location: falkirk, scotland, 16.505m, 54.151ft above sea level
  • Weather Preferences: dry sunny average summers and really cold snowy winters
  • Location: falkirk, scotland, 16.505m, 54.151ft above sea level

thanks steve i had a slight thought that it was american and i had no idea the jma was korean.

if the gfs is an american model would the ukmo and ecm not be better at the small details in our part of the world or does it not work like that

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Posted
  • Location: Carlisle, Cumbria
  • Weather Preferences: Atlantic storms, severe gales, blowing snow and frost :)
  • Location: Carlisle, Cumbria

Is the jma not Japanese??

Yes, Japan Meteorological Agency.

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Guest Kent-Weather

JMA Korean.

Always thought it was Japanese myself "Japan Meteorological Agency". Learn something new every day. Models seem to be happy for a cold spell to happen. This does appear to pretty much set in stone. NetWx extra 16 day detail keeps locally here very cold too. Great potential but will wait until the mid-latter part of this coming week before getting too excited of course. Loving the UKMO output

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Posted
  • Location: Basque Country - Northern Spain
  • Location: Basque Country - Northern Spain

thanks steve i had a slight thought that it was american and i had no idea the jma was korean.

if the gfs is an american model would the ukmo and ecm not be better at the small details in our part of the world or does it not work like that

The models divide the northen hemisphere in several chunks. Those chunks are bigger in the GFS than in the ECM, that's why the ECM is more accurate. On the other hand, every model is better in their own place, because they have more information.

Is the jma not Japanese??

According to Meteociel: Ces cartes présentent les prévisions du modèle JMA (modèle japonais) pour les 8 prochains jours. So it's Japanese

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Posted
  • Location: Castle Black, the Wall, the North
  • Weather Preferences: Spanish Plumes, Blizzards, Severe Frosts :-)
  • Location: Castle Black, the Wall, the North

General question do you believe that their will upgrades or downgrades in the models I personally don't believe we will see many upgrades if any at all. I was wrong about 2010 thou so I never know.

I think there will be more upgrades than downgrades, more peaks than troughs so to speak..hope that helps..mild weather is not going to bother us for a good while.smile.png

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Posted
  • Location: St Albans, 95m asl
  • Location: St Albans, 95m asl

Out at day 6, the three main ensemble means give us a very similar prognosis:

gensnh-21-1-138.png?6naefsnh-1-0-144.png?12EDH1-144.GIF?25-12

Anyone who is still in doubt that we will not see mean trough to our east with HP ridging up towards Greenland and a Svalbard high of some kind needs a serious reality check (barring a MAJOR model screw up). And when you take a look at the three of them, not only does it become apparent that the GFS is underplaying the svalbard high (as even its own ensemble mean mashed with the GEM still produces a stronger high), but I am also encouraged by the fact that the ECM is 10mb stronger in this region (still the model to watch IMO despite the UKMO consistency)

Beyond this the spread becomes large. The slightly stronger theme across the NAEFS and the ECMWF by 240 is for an atlantic undercut with HP still in place to our north:

EDH1-240.GIF?25-12naefsnh-1-0-240.png?12

However, the spread in the solutions is evident by the lack of detail within the ensemble mean by this timeframe (as well as the large scatter amongst the plotted graphs)

So, up until 144 looks pretty set in to me at the moment, its still beyond that which is presently unclear.

Cooling down for all though significantly, with the slightly more favoured solution beyond this an undercutting of our Svalbard-Greenland HP

SK

Just for good measure, the GEM ensemble mean out to 240 very clearly illustrates the undercut

gens-21-1-240.png

Edited by snowking
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Posted
  • Location: Glasgow, Scotland (Charing Cross, 40m asl)
  • Weather Preferences: cold and snowy in winter, a good mix of weather the rest of the time
  • Location: Glasgow, Scotland (Charing Cross, 40m asl)

Just a word to anyone worried about the rise in ensembles out in FI.

Don't be. The increased amount of scatter within the ensemble suite in FI is bringing the mean up, remember that these ensembles are run at a lower resolution than the op so once you get past T144 they don't really have a clue and start to mute any blocking signal. The ensembles were constantly trying to rise in FI back in 2010 only to turn colder within the T144 time frame.

T144 down to T0 is where you want to pay attention, it's here we'll see the upgrades. Anything beyond that is pure conjecture

Quite right. What I have noticed from the GFS ensembles in particular is that they've been just as volatile as the operational output. The NAEFS and ECM ensembles are generally more stable but perhaps it's just a case of comparing like for like runs. Yesterday's 6Z ensembles were, I believe, much milder than the 00Z and people started talking about how there was now a trend away from cold etc.until the 12Z came out.

Overall I see nothing in this morning's output that seems like a set back. We have another slightly different set of evolutions from yesterday but that is to be expected and I expect we'll see the models toying with a few more. Fundamentally, though, everything appears to be moving forward nicely, and even the worst solutions still have the polar vortex shot to pieces even in FI.

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Posted
  • Location: North Devon, All of 6M ASL :/.
  • Weather Preferences: Continental climate suits me very fine.
  • Location: North Devon, All of 6M ASL :/.

Would anyone mind explaning to me what a short wave looks like on the charts. Is it the horn shaped thing that moves from west to east across the atlantic with higher uppers?

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Posted
  • Location: East Anglia
  • Location: East Anglia

Stewfox, I would say this, I think without a doubt there are some things that you can look out for in terms of bias that the models may have, for instance I think the GFS breeds SWs like bunnies and has a tendency to over deepen them. but I don't think you need to worry to much about them.

The best method is show extreme caution with output post 144hrs or better still post 72hrs, trends only, forget the detail.

Compare and contrast

How does the current operational compare to previous runs.

How does it compare to how the other models are evolving the synoptics

Where is the point at which they start to diverge?

Think as long term as you can, what did yesterdays runs show and the day before.

I don’t worry about the ensembles either, I find them as fickle as the operational’s, how often do you see the ensembles point to a cold outlook on the 06 run and by the 12z run they are pointing at a milder evolution. And remember the models do not stand still, they constantly evolve, by the time we see an operational its already out of date.

Edited by weather eater
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Posted
  • Location: Batley, West Yorkshire
  • Weather Preferences: Heat and Snow
  • Location: Batley, West Yorkshire

Thanks a lot for this post, i was starting to get concerned with the lack of blocking after next weekend with the GFS,CFS and ECMWF but UKMO is staying strong with that block! So beyond T+1440, not worth reading into too much i should think?

T1440 defo not worth listening too :p

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Posted
  • Location: Beccles, Suffolk.
  • Weather Preferences: Thunder, snow, heat, sunshine...
  • Location: Beccles, Suffolk.

The tension rises: panic-buttons are being pressed; the wine, Scotch & vodka bottles are being opened; the cigarettes are burning away furiously and members' fingernails are being chewed in anticipation...Is the GFS going to making mazy runs towards Snowmageddon - or will they be blindsided by a one-off counter-attack by the Atlantic Short Waves?

Who knows...Game on!

Edited by Rybris Ponce
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Posted
  • Location: Reigate Hill
  • Weather Preferences: Anything
  • Location: Reigate Hill

Just a word to anyone worried about the rise in ensembles out in FI.

Don't be. The increased amount of scatter within the ensemble suite in FI is bringing the mean up, remember that these ensembles are run at a lower resolution than the op so once you get past T144 they don't really have a clue and start to mute any blocking signal. The ensembles were constantly trying to rise in FI back in 2010 only to turn colder within the T144 time frame.

T144 down to T0 is where you want to pay attention, it's here we'll see the upgrades. Anything beyond that is pure conjecture

However if there was a clear cold pattern forming, that is, sustained cold in FI, then the ensembles would reflect this, they don't.

At that range all they can tell us is what are the chances of cool/cold continuing or cool/average taking over. The scatter tells us that there is no clear signal; 50/50 at the moment.

When we see the mean drop to say -2c in FI ensembles then we can garner from this that the cool/cold option is the trend.

Even in FI the ensemble mean gives us some sort of indication as to patterns. Thats why the current trend is saying that the confidence in the maintaining of the really cold temps is reducing, they are not saying it will turn milder.

It is suggested experience tells you something different, the models are poor after T200 in such a set up, etc; Could be true but read the following:

http://www.weatherweb.net/wxwebtvsimonnew.php?ID=538.

"For now I am sticking with a colder last part of December, despite the overwhelming evidence from the analog above (not even one of the comparable years were cold in the 15 to 28 day period)" ...!

Statistics don't lie, or do they?

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Posted
  • Location: Catchgate, Durham,705ft asl
  • Location: Catchgate, Durham,705ft asl

No surprise to see the AO (Arctic Oscillation) about to tank negative with the sort of charts

we are seeing at the moment,and timed perfectly for the start of winter.

Looking forward to GP's winter forecast.smile.png

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Posted
  • Location: Longwell Green, near Bristol
  • Weather Preferences: Storms, Gales, frost, fog & snow
  • Location: Longwell Green, near Bristol

Looks like a hell of a lot of scatter in the ensembles to me, especially the further into Europe you go;

http://www.null/two/ensembles/

Plenty of cold continuity there, but looking at FI is fruitless currently with so many varying options.

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Posted
  • Location: Gillingham, Kent
  • Weather Preferences: Snow, Thunderstorms,
  • Location: Gillingham, Kent

However if there was a clear cold pattern forming, that is, sustained cold in FI, then the ensembles would reflect this, they don't.

At that range all they can tell us is what are the chances of cool/cold continuing or cool/average taking over. The scatter tells us that there is no clear signal; 50/50 at the moment.

Whilst generally true, just a few days ago the ensemble mean was above -5c but it's dropped below now that the time frame is getting closer and the models are upgrading the low temperatures.

Until we get the short - medium term modelled correctly and we get the placements of short waves then how can we take anything in FI to be true? The scatter is down to each ensemble modelling the short waves/troughing slightly differently which leads to a different outcome.

Background signals and teleconnective signals all point towards a sustained period of blocking.

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