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chionomaniac

Model Output Discussion 25/11/2012 12Z onwards

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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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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 ?..

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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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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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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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is the gfs an american model or is it european

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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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The GFS is american, The UKMO is UK, ECM- European , GEM- canadian, BOM- Australian, JMA Korean.

S

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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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Is the jma not Japanese??

Yes, Japan Meteorological Agency.

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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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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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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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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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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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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.

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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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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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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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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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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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