Model Output Discussion: 12Z (22/11/12) And On...

[Mucka]

Twist in the tale tonight, a lot of GFS ensembles want to break blocking down in the mid range.

Tense day tomorrow.

[Severe Siberian icy blast]

just look at this northern blocking at t90hrs with the vortex ripped apart, yes this is 4 days away.

Blocked atlantic anyone?

>>

Really is amazing northern blocking there with amazing synoptics, really are in a fantastic position hear if its cold and snow you want. Dont concern yourself with upper air temps, get the right synoptics and the cold will come.

>>

I really dont feel iv saw this in my time following the models, not in terms of how extensive the blocking is.

>>

Now if thats not a signal for a prolonged cold spell with hights strongly building over greenlands i dont no what is.

Just sit back and enjoy this amazing cold spell unfold, feel this could be a speciall two wks .

Edited November 22, 2012 by shaun wilmer

[phil nw.]

http://www.meteo24.f...html?eps=london

Coldest ecm suite for a few runs. The op on the cold side days 8 and 9.

We are looking at a cold first week of winter. Mean maxes in the capital around 3c.

Looking further east Nick - Berlin going sub-zero.

They have dropped quite a bit since yesterday-if memory serves me correctly

How long before we get some of that i wonder?

[LomondSnowstorm]

yes i no its fi and will change but on the past few runs at 384 there has being a break down of pressure over greenland

By that point in the run the small initial errors have accumulated and multiplied so much that it's really not at all worth considering. In these instances also the models really struggle with the breakdown, even once the blocking is at T+0, so even at +168 or +144 it can change very significantly. The real concern for the moment is how the blocking aligns itself, whether shortwaves will hinder our chances of cold etc.

[Cheshire Freeze]

Yes a lot of the ensembles drop pressure over Greenland fairly early and eject energy into the North Atlantic which prevents Atlantic/Arctic high link up. It's a concern but rolled on to 240 hours I think a percentage of those ensembles would come good anyway. Epic model viewing ahead tomorrow one way or another.

[Met4Cast]

Twist in the tale tonight, a lot of GFS ensembles want to break blocking down in the mid range.

Tense day tomorrow.

I'm not sure about that

http://www.meteociel.fr/modeles/gefs_cartes.php?ech=0&code=4&mode=0&carte=0

Some VERY good blocking setups in the ensemble members, some arguably better than what the GFS Op shows

[SMU]

18z Ensembles. Says it all.....

just as bad as the 06z ensembles-

S

[lorenzo]

Through the floor...

[samadamsuk]

Hey all.

Looks to me like once we've adjusted to the slight downgrade in the near future, the charts aren't shying away from precip across the country when the colder air starts to approach and we could get stung over a number of days given the marginal temps predicted... Very interesting times and uncharted territory for me personaly (probably because of my bad memory!) - one hunch of mine is that as we get towards dec 1, the models seem toget a grip on the airmass mixing more exactly, and the cold air that is currently modelled to be to ournorth could easily be mixing across us with more developed lows as the time approaches - gut feel is some major snow events possible here.

Cheers, Sam

[Mucka]

Yes a lot of the ensembles drop pressure over Greenland fairly early and eject energy into the North Atlantic which prevents Atlantic/Arctic high link up. It's a concern but rolled on to 240 hours I think a percentage of those ensembles would come good anyway. Epic model viewing ahead tomorrow one way or another.

Yeah that may be so, as you say just a worry the latest output would want to go that way instead of reversing the trend.

We always get wobbles once the blocking is well in hi res whether or not the cold charts verify.

[snowking]

Latest update of the ECM 32 day control:

Big change from the previous update, this time rather than signalling raging zonality, it builds in a big scandinavian HP at around +400 mark to repel any attempt from the atlantic to get back in, LP from the atlantic undercuts the block and i'll leave you to guess what that leads too

For the remainder of the run its much the same, blocking transferring between our NW and NE, repeated undercutting scenarios (including one showing on xmas eve) and generally cold

So from the control run its a case of a continuation of prevalent northern blocking in our part of the world, over to Matt in the morning to see what the full ensemble suite shows

SK

[Cheshire Freeze]

Yeah that may be so, as you say just a worry the latest output would want to go that way instead of reversing the trend.

We always get wobbles once the blocking is well in hi res whether or not the cold charts verify.

It's a perpetual cycle....stunning 18z op run but poorer ensembles; poorer 0z op run but more promising ensembles, indifferent 6z op run and poor ensembles, better 12z run etc etc. So many times I've gone to bed on an epic op run only to wake up to a let down in the morning!

[Mucka]

I'm not sure about that

http://www.meteociel...&mode=0&carte=0

Some VERY good blocking setups in the ensemble members, some arguably better than what the GFS Op shows

Set it to around 150 and flick through you will see. Definitely a lot more energy bursting through the ridge and quite a few runs look in trouble at that stage.

The renewed WAA toward Greenland saves a few but not all. Just something to watch - the overall output is positive.

It's a perpetual cycle....stunning 18z op run but poorer ensembles; poorer 0z op run but more promising ensembles, indifferent 6z op run and poor ensembles, better 12z run etc etc. So many times I've gone to bed on an epic op run only to wake up to a let down in the morning!

Yeah it is easy to over analyse things when we are on the verge of a good cold spell. Let's see what tomorrow brings.

Edit.

Looking at FI some of the iffy runs still manage to find a different to route to cold and some of the better ones bring in some deeper blues - I imagine the graphs wont reflect the mid term wobble at all and look quite cold.

Edited November 22, 2012 by Mucka

[bluearmy]

One thing i took from the 12z gefs was the massive scatter in slp after a few days. My 4 year old looked like he'd done them. I really have low confidence with the individual members as the moment. The anomolys seem the only reasonable tool.

[johnholmes]

Latest update of the ECM 32 day control:

Big change from the previous update, this time rather than signalling raging zonality, it builds in a big scandinavian HP at around +400 mark to repel any attempt from the atlantic to get back in, LP from the atlantic undercuts the block and i'll leave you to guess what that leads too

For the remainder of the run its much the same, blocking transferring between our NW and NE, repeated undercutting scenarios (including one showing on xmas eve) and generally cold

So from the control run its a case of a continuation of prevalent northern blocking in our part of the world, over to Matt in the morning to see what the full ensemble suite shows

SK

hi SK

Can I ask over the last 4 runs what has the overall pattern been. I realise that its over a 4 week period so the forecast period changes but I'm just curious to know what the overall pattern has been from it?

Is it switching from one to the other type, or is it more consistent with one than the other?

thanks if you can reply to that-j

[lorenzo]

2 random charts roughly 365 days apart.

This years pub run

Last years pub run

Zero complaints from me about anything, any of the models, are churning out at the moment.

(apart from the ECM going all strange this evening at 192)

[LomondSnowstorm]

2 random charts roughly 365 days apart.

This years pub run

Last years pub run

Zero complaints from me about anything, any of the models, are churning out at the moment.

(apart from the ECM going all strange this evening at 192)

While I agree with the sentiment, you can't deny that early December last year was a very enjoyable period of weather watching: a staggeringly strong PV, cool-cold zonality with some low ground snowfall and Hurricane Bawbag to boot.

But of course I'd much rather have these synoptics too.

[snowking]

hi SK

Can I ask over the last 4 runs what has the overall pattern been. I realise that its over a 4 week period so the forecast period changes but I'm just curious to know what the overall pattern has been from it?

Is it switching from one to the other type, or is it more consistent with one than the other?

thanks if you can reply to that-j

Hi John,

Bearing in mind im only viewing the one run of a 51 member ensemble suite, its been pretty changeable to say the least.

The previous trend for the period beyond the impending cool down in the next couple of weeks had been for a trough to drop down the north sea, and that was as far as the run went, though to me it looked likely that this would lead to a reload of the cold pattern with some WAA eventually up to the west of the UK and a rebuild of heights up to the NW.

The last run (from tuesday) instead replaced this with a return to zonality as the HP to our north sunk slowly to the south of the UK.

This run looks to go back towards dropping that trough south, but it drops it well to the west of the UK, with WAA sent NEwards towards scandi (this goes around the UK to the NW incidentally) and helps heights to develop there, and I must say its an almighty high (1060mb at peak).

But yes certainly the control run has moved around a fair bit in its longer term outlook in the last few runs. Im sure there has been more consistency from the ensemble mean, but I know the last run of that suggested something more zonal in the longer term, so it will be interesting to see if theres any support from the ensemble mean for scandinavian height rises

SK

[pyrotech]

Hi alk.

Can someone verify this.

The low out in Atlantic which is due saturday appears to have sporned a new low infront of it currently just off the North of spain coast. This not shown on any model that i can see. Due to the current situation can someone take a look se if true and any signifigance as in track it likely to take as i look at it feel it would get to southern uk late friday ahead of main low. im using the current estimated pressure chart and sat image. Both can be seen on the floodwarn radar page. Have the models missed this and whats likely outcome. Or is it just too late and im seeing ghost lows.

I am in work viewing on mobile phone. Can also tell you high volume pumps have been sent to midlands and boats. 12 HVPs. And 8 boats i believe as a proactive. Just in case scenario. I believe this to be first time at such levels and clearly shows how serious situation is.

Next surface pressure chart now out feature changed to a 1012 high. Sorry guys and gals thought i had spotted something new. Goog night all

Edited November 23, 2012 by pyrotech

[Zenarcher]

While I agree with the sentiment, you can't deny that early December last year was a very enjoyable period of weather watching: a staggeringly strong PV, cool-cold zonality with some low ground snowfall and Hurricane Bawbag to boot.

But of course I'd much rather have these synoptics too.

It was a very interesting time of weather I remember the storm gave me 72mph average wind speed got gusts over 90mph that day as well.

I remember taking a screenshot of the forecast for my location that morning never seen anything like it,

[chris55]

p18 has got the pattern nailed.

http://modeles.meteo...18-1-174.png?18

http://modeles.meteo...18-0-174.png?18

Edited November 23, 2012 by chris55

[SnowBallz]

Latest update of the ECM 32 day control:

Big change from the previous update, this time rather than signalling raging zonality, it builds in a big scandinavian HP at around +400 mark to repel any attempt from the atlantic to get back in, LP from the atlantic undercuts the block and i'll leave you to guess what that leads too

For the remainder of the run its much the same, blocking transferring between our NW and NE, repeated undercutting scenarios (including one showing on xmas eve) and generally cold

So from the control run its a case of a continuation of prevalent northern blocking in our part of the world, over to Matt in the morning to see what the full ensemble suite shows

SK

Hmm. To be honest, to see such a swing in what is widely regarded as a respectable MT model, is alarming. I don't think that's positive at all, more that it implies it to be unreliable.

Whatever way you interpret it, that's a huge divergence in probabilistic determination. Don't get me wrong, I'm as keen as anyone to 'get the cold' and see it in the models - but, as a mathematician and scholar of algorithms, such variance worries me.

John asks the right question: is this switch sudden, subtle change or is it flip-flopping? There's more to be learnt about the probability of model forecasts by how they react to changing variables over time, not-so-much the intra-runs.

I think sometimes it's really worth taking a step back and, instead of jumping all over the latest output, assess with an objective mindset whether what you're seeing gives you confidence, or a lack of? For me, flip-flopping - like this - predicates poor confidence in the underlying deterministic calculations.

I recall writing more at length on a similar theme last winter, re: short, mid and long range modelling. Not for wanting to regurgitate, but the ECM 32 is not filling me with much confidence at all.

[Barry12]

Hmm. To be honest, to see such a swing in what is widely regarded as a respectable MT model, is alarming. I don't think that's positive at all, more that it implies it to be unreliable.

Whatever way you interpret it, that's a huge divergence in probabilistic determination. Don't get me wrong, I'm as keen as anyone to 'get the cold' and see it in the models - but, as a mathematician and scholar of algorithms, such variance worries me.

John asks the right question: is this switch sudden, subtle change or is it flip-flopping? There's more to be learnt about the probability of model forecasts by how they react to changing variables over time, not-so-much the intra-runs.

I think sometimes it's really worth taking a step back and, instead of jumping all over the latest output, assess with an objective mindset whether what you're seeing gives you confidence, or a lack of? For me, flip-flopping - like this - predicates poor confidence in the underlying deterministic calculations.

I recall writing more at length on a similar theme last winter, re: short, mid and long range modelling. Not for wanting to regurgitate, but the ECM 32 is not filling me with much confidence at all.

I think your putting to much thought and analysis into this..the models change all the time, they are never always consistent. None of the models especially one that goes out to 32 days will be accurate and will change all the time due to the long time period.

'divergence in probabilistic determination' - are you trying to sound clever!

Edited November 23, 2012 by Barry95

[Jupiters Winter]

GFS 00Z is Spectacular again upto T192 so far with nothing of the atlantic influences.......

[summer blizzard]

GFS0z out now and it brings in the cold by day 6, has -10C by day 8 and is generally colder and drier than previous runs.