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phil nw.

Model Output Discussion 1st January 2014-06z onwards.

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A very optimistic outlook today. My only concern would be that there is an awful lot of latent "heat" lying around western Europe at the moment, and perfect synoptics next week may fail to deliver much apart from cold rain at low levels. We need 2-3 days of easterly feed to get ground and air temperatures down.

 

I don't necessarily agree with this statement. In a continental climate, if you have 850s plummeting then the surface temperature follows very quickly. I remember in Chicago a few years ago, I saw temperatures of 21oC on a Monday, and we were under 8 inches of snow by the Wednesday. 

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well the met office does not reflect the likely event of it lasting to long from there update which is a little concerning.

but if we can establish a 1020mb or above block over scandi then they can be pretty tough to breakdown.

 

although the ukmo super model likes the idea of the jet powering up and blasting the beasterly back east so can we agree with the super computer the other models don't seem to reflect what the 30dayer says.

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A very optimistic outlook today. My only concern would be that there is an awful lot of latent "heat" lying around western Europe at the moment, and perfect synoptics next week may fail to deliver much apart from cold rain at low levels. We need 2-3 days of easterly feed to get ground and air temperatures down.

 

From a IMBY point of view, I have a concern that we'll see the models pick-up on the dreaded short-wave in the Southern North Sea (due to the energy still available there), probably in the next 24 hours.  This will initially (at least) probably restrict the deeper cold to more Northern areas, in which case we'll need the blocking to be sustained for a couple of days, before those in the South get to join in the fun (assuming the broad pattern is correct).  

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With speculation rife regarding current cross modeled, and development further ie stick or twist.a certainty may well be some could do well as regards snowfall with some perhaps cold and wondering what the fuss is all about. Thats the nature of the BEAST,( pun Iintended).....but there again we will have to wait a little longer for more definite evolution/evolutions.

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From a IMBY point of view, I have a concern that we'll see the models pick-up on the dreaded short-wave in the Southern North Sea (due to the energy still available there), probably in the next 24 hours.  This will initially (at least) probably restrict the deeper cold to more Northern areas, in which case we'll need the blocking to be sustained for a couple of days, before those in the South get to join in the fun (assuming the broad pattern is correct).  

 

Yes, I agree with this sentiment. Any precipitation would probably fall as rain at first, then perhaps sleep/snow later on. North would be a different story, but heights always help. I still feel this is the first bite of the cherry though, and the real cold / snow is coming towards the end of the month.

 

Edit: Just to add it's mere speculation as trying to pinpoint falling snow is hard enough at T24 let alone now. Just basing on latest runs.

Edited by Glenn W
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Blimey, didn't expect those overnight runs. Form borderline promise to cross-model agreement on a cold and possibly snowy easterly. The GEM is crazy.

 

Posted Image

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Good old Joe laminate floori seems very bullish about the cold and snow.

 

Really?? Well that's a first... Posted Image

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Good old Joe laminate floori seems very bullish about the cold and snow.

Wish the met office were, perhaps tomorrow they will be. The models so far today are by far the most wintry since last spring.. Makes me wonder how wintry the models have to look before the met office react.
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From a IMBY point of view, I have a concern that we'll see the models pick-up on the dreaded short-wave in the Southern North Sea (due to the energy still available there), probably in the next 24 hours.  This will initially (at least) probably restrict the deeper cold to more Northern areas, in which case we'll need the blocking to be sustained for a couple of days, before those in the South get to join in the fun (assuming the broad pattern is correct).  

That's a good point Beng and for that reason we need to squeeze as much amplification from the upstream pattern, on two fronts this will help, firstly delaying the phasing time between the UK trough and the one further west and getting enough negative tilt to the troughing with as much energy going se, also a touch more westwards correction to add a bit more margin for error.

 

The ECM De Bilt ensembles for Holland are better today, the graphical ones do show the colder trend solidifying from the earlier two runs, last night and todays have been better: So from earliest to latest below:

 

post-1206-0-13729800-1389191318_thumb.pn

 

post-1206-0-94648800-1389191330_thumb.pn

 

post-1206-0-33005200-1389191336_thumb.pn

 

post-1206-0-02337200-1389191352_thumb.pn

 

The differently tabulated perhaps give a better idea of the actual synoptics on the ground with the operational and control in the colder cluster, some less cold options, then the major cluster cold so the issue of trough disruption still remains.

 

post-1206-0-95796200-1389191711_thumb.pn

 

At this timeframes given the placement of the troughing at T96 and 120hrs and seeing as this is the key foundation for the easterly then I think we need to weight the operational higher because of its better resolution.

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A lot of posts in here recently would be more suited to the model ramps/banter/moans thread. Before hitting post, please just consider whether you're in the right thread or not:

 

Where to post in this area? We have 3 main threads running:

1. To hunt for the next sign of seasonal weather or the next cold spell predicted for 14 days' time, please use the Model Output Discussion thread.

2. For more in depth, objective summaries of the current model output please use the In Depth Model Discussion thread.

3. And finally, to go mad when a hint of cold weather is suggested and then despair when it fails to arrive, or to moan because it seems so unfair that we are an island surrounded by sea at the end of the Gulf Stream, please use the Model Mayhem, Moan, Ramp, Go Nuts thread.

 

With a cold spell looking more and more likely, it's harder for the team to adequately clean up off topic posts, so please help us out by just re-thinking your post before posting. Cheers :)

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Yes, I agree with this sentiment. Any precipitation would probably fall as rain at first, then perhaps sleep/snow later on. North would be a different story, but heights always help. I still feel this is the first bite of the cherry though, and the real cold / snow is coming towards the end of the month.

 

Edit: Just to add it's mere speculation as trying to pinpoint falling snow is hard enough at T24 let alone now. Just basing on latest runs.

 

yes, and for what it's worth (probably not much but....) the CFS has been adamant for a while now that spring, especially March, is going to see plenty of blocking and undercutting - similar to the synoptics progged for next week actually.

 

Posted Image

 

personally i find that a bit upsetting as i wasn't really a fan of last spring but there you go. I'm getting used to cold springs, now.

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That's a good point Beng and for that reason we need to squeeze as much amplification from the upstream pattern, on two fronts this will help, firstly delaying the phasing time between the UK trough and the one further west and getting enough negative tilt to the troughing with as much energy going se, also a touch more westwards correction to add a bit more margin for error.

 

The ECM De Bilt ensembles for Holland are better today, the graphical ones do show the colder trend solidifying from the earlier two runs, last night and todays have been better: So from earliest to latest below:

 

Posted Image060112.png

 

Posted Image070100.png

 

Posted Image070112.png

 

Posted Image080100.png

 

The differently tabulated perhaps give a better idea of the actual synoptics on the ground with the operational and control in the colder cluster, some less cold options, then the major cluster cold so the issue of trough disruption still remains.

 

Posted ImageDB.png

 

At this timeframes given the placement of the troughing at T96 and 120hrs and seeing as this is the key foundation for the easterly then I think we need to weight the operational higher because of its better resolution.

bang on again n, s im with you on that ie, operational. I await 12z with baited breath!
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I'm guessing the temp contrast over Lake Michigan aided the convection there. Unsurprisingly, SSTs over the North Sea are higher than average at the moment:

 

Posted Image

 

 

So if we can get an Easterly flow, that should help, one would think.

 

 

(BTW, nobody is allowed to tell their family/colleagues/pets about this possible cold outbreak. Understood?Posted Image )

Yes, a good point to pick up, could be a decent Lake Effect ...

 

Posted Image

 

Credit to Weatherquestions.

 

Just to show what a LE can actually produce given the correct fine details:

 

http://www.weather.com/news/weather-winter/huge-lake-effect-snow-expected-20140106

Edited by Glenn W
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Hello I was wondering if anyone could help me with the answer to a post I made last night.  I think in the excitement of the models changing so dramatically it rather got missed.  That and the fact I was working through the night so made it at 2am!

 

Also please feel free to redirect me where to post queries like these as I’m not sure this thread is where they should be.  Also how to quote multiple replies rather than having to copy and paste would be a useful pointer too!

 

Thanks for helping

 

 

Trom, on 08 Jan 2014 - 01:38, said:

 

Yes thanks - I understand friction is lower closer to the surface, but I've read that the effect is  10 - 15 degrees deviation in direction between boundary airflows and those at surface level coming in off the ocean, and around 40 - 50 degrees from the land.  I'm lacking a relative scale, I understand it puts the centre of the low further forward but am not sure to spot this from the model output.  Is the best method simply looking at model output at different levels of the troposphere?  I guess I'm looking for output that would show wind spiralling towards the low pressure centre, or out from a high pressure centre, at the surface layer, compared to a bigger swing right at higher boundary levels if the Coriolis effect dominated the pressure gradient at this height?

 

The impact would appear significant to me but I lack the experience or confidence in how all the variables interact to work out whether I should be obsessing about this.  It just seems a big deviation, and as a economics lecturer and financial modeller it stood out.  As said I'm very new to this but I am enjoying watching mathematics versus mother nature.  Almost as interesting is the range of posts on this board and the topic of behavioural finance.  Some might call it human nature but then I'd be out of a job. Best call it cognitive dissonance and confuse people with terminology!

 

On a side note I think I'm an fan of extremes hot, cold, windy or whatever.  Watching the models of these brutal lows steaming in off the atlantic and then seeing the effect has been a buzz.  Hey I got stuck on a steam train visiting Santa with a four year old and one less than two, due to a fallen tree.  When you've survived three hours of that and the blitz spirit being rekindled by railway enthusiasts singing Rudolph the red nosed reindeer you know its been an amazing period of weather. I've learnt a lot seeing the pressure gradients and temperature differentials between Canada/US and the warmth of temperate air from the South fuelling the Atlantic to unbelievable levels.  Not cold for the UK but amazing to watch and a rare event. 

 

 

john w, on 07 Jan 2014 - 23:49, said:

Hey,

 

Generally, friction becomes more dominant at the surface whereas the pressure gradient force and coriolis effect tend to balance each other out aloft. Now of course you get rising and falling air etc etc, so air will always converge towards the low centre and diverge from the high centre, but crossing of isobars is more pronounced at the surface.

 

Make sense?

 

 

Trom, on 07 Jan 2014 - 23:15, said:

Hello 

 

As a newbie I have a question regarding air circulation around high and low pressure areas and how to interpret them on the various models.  I'm not sure if this is the right place to post but the site is fairly daunting with the sheer volume of message boards so apologies if I'm in the wrong place (please feel free to point me in the right direction).

 

Anyway the question is when looking at airflows hitting a low pressure area on one of the models output pages: how can you infer whether the Coriolis effect will dominate or the pressure gradient force?  Also I'm struggling with how to interpret the impact of friction on the Coriolis effect and whether I really need to consider it if the airflow is a westerly, given it's coming of the ocean?

 

I'm sure these questions betray my own ignorance but an answer would help me in interpreting model output even if it's "You are missing the big issue and focusing on a small/irrlevant one muppet!"

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I'm guessing the temp contrast over Lake Michigan aided the convection there. Unsurprisingly, SSTs over the North Sea are higher than average at the moment:

 

Posted Image

 

 

So if we can get an Easterly flow, that should help, one would think.

 

 

(BTW, nobody is allowed to tell their family/colleagues/pets about this possible cold outbreak. Understood?Posted Image )

 

I'm surprised that Lake Michigan is showing as being warmer than average given that the upper Midwest has been frozen solid since early December! 

Anyway, lake effect snow is very rare in Chicago. The general setup is systems approaching from the NW drag in very mild air from the Southern US/Gulf region, and then a powerful cold front drags the much colder air from Northern Canada. It's unusual to get winds from the NE which would fire up lake effect snow; Indiana and Michigan tend to get much more snow in this way. 

 

In the case of continental Europe, the colder air is dragged in from the N and E, but the principle is much the same; so long as we're tapping into sufficiently cold air, then the current temperatures do not matter.

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Wish the met office were, perhaps tomorrow they will be. The models so far today are by far the most wintry since last spring.. Makes me wonder how wintry the models have to look before the met office react.

I would say when there is  consistency over a few days, I mentioned over in the MetO thread that I would expect them to come on board by Friday if the models are still  on the  money for cold. 

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yes, and for what it's worth (probably not much but....) the CFS has been adamant for a while now that spring, especially March, is going to see plenty of blocking and undercutting - similar to the synoptics progged for next week actually.

 

Posted Image

 

personally i find that a bit upsetting as i wasn't really a fan of last spring but there you go. I'm getting used to cold springs, now.

Think it's coming earlier this year NFG, was actually expecting Feb, but now the last third of Jan looks increasingly like it may be back in the frame.  Looking at the shorter term I'm not yet convinced that next weeks first bite of the cherry will leave more than teeth marks or perhaps split skin, but thereafter we may see the whole thing absolutely inhaled.

Edited by shedhead
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Just had my first chance to view the whole of the 06z run, a slower evolution than the 00z but still a good run, hopefully it will be the first bite of the cherry with something more and maybe better to come for the end of the month and into Feb. Of course we have a way to go before we know exactly how the synoptics are going to look for the start of next week and we will see changes, these are inevitable. Now I know I know this is not what some will want to hear but these things seem to have that habit of downgrading more often than upgrading IMO and even when they don’t the path to cold and snow nirvana is often rocky. As I’m sure Nick Sussex would say, expect short wave drama or low pressure drama for those that prefer that term.

 

So a small plea because with the models trending in the way that they are this place is likely to get very busy. Can we just discuss the models without berating others just because their interpretation of the models is different from yours, or because they choose to highlight other areas other than cold and snow. For example when the pattern will or looks likely to break down, or berating them for not being positive enough, the clue to what this thread is about is in the title, positive and negative have nothing to do with it, and while people making posts just to wind others up is dull and we know they do, so also is reading through pages of tit for tat moans or having digs at people just because their preferred weather type is not the same as yours/bulk of members, it’s not a closed shop, there is not a rule that only coldies can post. OK I’m not a mod, so I guess that some members will think that I don’t have the right to make such a plea, but I am a member who would have a lot more posts to my name had I not got so bored and jaded with bickering, bickering which has a tendency to increase the more the models point at a potential cold spell.

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Critical 12z's today.

All the output today offers some cold/wintry weather for most of the UK (Not Northern hills as alluded to in the meto update).

So,we can expect one of two things,a continuation of the excellent synoptics via NWP and a climbdown by the METoffice tomorrow,or,well im not even contemplating the other option...

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At this timeframes given the placement of the troughing at T96 and 120hrs and seeing as this is the key foundation for the easterly then I think we need to weight the operational higher because of its better resolution.

 

Even more, the control and the oper are closely matched. So the difference is made by the differences made in the output. Every member gets his own lightly disturbed begin situation.

 

The dutch text, please use translate google, if you want to read more about use an ENS. (I presume this explanation is the same, somewhere at the UKMO site ;))

De onzekerheid in de weersverwachting

De onzekerheid van de verwachting neemt toe met de termijn van de verwachting. Met het Ensemble Prediction System (EPS) van het ECMWF wordt een schatting gemaakt van die onzekerheid. In het EPS wordt de operationele ECMWF verwachting (T1279, roosterpuntsafstand ~16km) herhaald met 51 verwachtingen met een model met lagere resolutie (T639, roosterpuntsafstand ~ 32 km) om rekentijd te besparen. Ieder van die verwachtingen heeft een licht verstoorde begintoestand, om het effect van onzekerheden in die begintoestand te simuleren. Iedere individuele modelberekening geeft zijn eigen verwachting voor temperatuur, luchtdruk etc., alsmede voor weerselementen zoals neerslag, 2m temperatuur, windsnelheid. De zgn. EPS pluim geeft verwachtingen voor neerslag, 2m temperatuur en windsnelheid in 1 roosterpunt. Duidelijk is te zien hoe de onzekerheid in de verwachting groter wordt naarmate de voorspeltermijn toeneemt. Ook zijn soms verschillende scenario's te herkennen.

http://www.knmi.nl/exp/pluim/

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Before the 12'zs here's a quick comparison of the big 3 850's at t144

 

Posted ImagePosted ImagePosted Image

 

ECM was by far the coldest of the main 3 this morning with UKMO 2nd and GFS the least coldest in 3rd

Even more, the control and the oper are closely matched. So the difference is made by the differences made in the output. Every member gets his own lightly disturbed begin situation.

 

The dutch text, please use translate google, if you want to read more about use an ENS. (I presume this explanation is the same, somewhere at the UKMO site Posted Image)

De onzekerheid in de weersverwachting

De onzekerheid van de verwachting neemt toe met de termijn van de verwachting. Met het Ensemble Prediction System (EPS) van het ECMWF wordt een schatting gemaakt van die onzekerheid. In het EPS wordt de operationele ECMWF verwachting (T1279, roosterpuntsafstand ~16km) herhaald met 51 verwachtingen met een model met lagere resolutie (T639, roosterpuntsafstand ~ 32 km) om rekentijd te besparen. Ieder van die verwachtingen heeft een licht verstoorde begintoestand, om het effect van onzekerheden in die begintoestand te simuleren. Iedere individuele modelberekening geeft zijn eigen verwachting voor temperatuur, luchtdruk etc., alsmede voor weerselementen zoals neerslag, 2m temperatuur, windsnelheid. De zgn. EPS pluim geeft verwachtingen voor neerslag, 2m temperatuur en windsnelheid in 1 roosterpunt. Duidelijk is te zien hoe de onzekerheid in de verwachting groter wordt naarmate de voorspeltermijn toeneemt. Ook zijn soms verschillende scenario's te herkennen.

http://www.knmi.nl/exp/pluim/

 

Probably best to translate that here

 

The uncertainty in the forecast

The uncertainty of the expected increases with the period of expectation . With the Ensemble Prediction System (EPS ) from ECMWF is an estimate of the uncertainty . The EPS is the operational ECMWF forecast ( T1279 , grid point distance ~ 16km ) repeated 51 expectations with a model with lower resolution ( T639 , grid point distance ~ 32 km ) to save . Computing Each of these expectations, it has a slightly disturbed initial state , in order to simulate . The effect of uncertainties in the initial state, Each individual model calculation gives his forecast for temperature, pressure , etc. , as well as weather elements such as precipitation , 2m temperature , wind speed. The so-called EPS plume gives forecasts for precipitation , temperature and wind speed 2m in one grid point . Shows how the uncertainty in the forecast increases as the forecast period increases. Clear Also, sometimes to recognize different scenarios.

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I've been wondering for some time what happened to the GME full content, we only get to see its output upto T72hrs, has the German model been reduced in length because they now just use the ECM past that point.

 

Anyway not long to go now before the GFS comes out, nerves shredded for coldies, we don't want to see any shortwave drama, I think we've suffered enough over the last month of relentless zonal dirge.

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Before the 12'zs here's a quick comparison of the big 3 850's at t144

 

Posted ImagePosted ImagePosted Image

 

ECM was by far the coldest of the main 3 this morning with UKMO 2nd and GFS the least coldest in 3rd

 

Probably best to translate that here

 

The uncertainty in the forecastThe uncertainty of the expected increases with the period of expectation . With the Ensemble Prediction System (EPS ) from ECMWF is an estimate of the uncertainty . The EPS is the operational ECMWF forecast ( T1279 , grid point distance ~ 16km ) repeated 51 expectations with a model with lower resolution ( T639 , grid point distance ~ 32 km ) to save . Computing Each of these expectations, it has a slightly disturbed initial state , in order to simulate . The effect of uncertainties in the initial state, Each individual model calculation gives his forecast for temperature, pressure , etc. , as well as weather elements such as precipitation , 2m temperature , wind speed. The so-called EPS plume gives forecasts for precipitation , temperature and wind speed 2m in one grid point . Shows how the uncertainty in the forecast increases as the forecast period increases. Clear Also, sometimes to recognize different scenarios.

thanks for translation ss.the bear basics essentially as things stand is, the coldIis coming whether it be a shot or spell. However there any many solutions and outcomes on the table atm.hence, more evolution required.

Lets see what the 12z have in store .starting with GFS......

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