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

[cold snap]

Suprised nobody mentioned the ukmo at 144 much better if you ask me upgrade there

Edited November 23, 2012 by cold snap

[chionomaniac]

Just seen that the 00Z GFS is at the milder end of the ensembles

from 5th December ( but unfortunately a cold outlier just prior to that) Quite a few othere heading down to the -10C line though!

[Frosty.]

Well just take a look at the GEFS 00z mean, spectacular developments there with a very cold and unsettled further outlook, surely with that synoptical set up we would be looking at heavy snow and sub zero temps, the trend, especially from the gfs 00z op run and the mean is stunning and the uk eventually goes into a very wintry spell with severe frosts and daytime temps struggling to rise above freezing, the longer term gefs mean shows a very wintry further outlook with snow, severe frosts, freezing fog..basically anything wintry and NOTHING MILD, the westward movement of the arctic high is epic.

In the meantime we have more heavy rain and strong winds with flooding chaos for the next few days, indeed the risk of flooding extends well into next week as a slow moving trough sticks close to the southeast but colder and colder air begins to spread south fairly early next week and then it just turns even colder by the end of next week onwards.

PS..just waiting to hear darren bett say there is a freeze on the way wishful thinking

Edited November 23, 2012 by Frosty039

[Timmytour]

Sorry don't no what happened there my post starts from "the thing is "

Hi Shaun...appreciate you clearing that up!

I know there's a lot going against it. Equally I remember a run from back in Nov 12 that pretty much corresponds to what's gone on weather wise today. No science behind it just a gut feeling that GFS will lead the way like I believe it did for the cold spell. That said, I hope I'm wrong and we do get sustained cold.

[TEITS]

Some incredible charts this morning, I reckon Steve M has been tinkering with the GFS because its an absolute snowfest for some locations, including his. Have to say though these models really are struggling as I expected. Whilst N blocking remains consistent the actual details are wildly changing with the ECM being very different to last nights 12Z.

What really impresses me though is just how extensive N blocking is on the model output. Take the ECM for example at +240 because I challenge anyone to find many similiar charts in the past 100yrs for early Dec.

[Tom Jarvis]

can i just say that i have been following this four for the last week and a half. what i have learn in that time is that we need to look at the trend and that models are biast in going back to a milder set up after the cold arrives.

i have a gut feeling that once the cold sets in it will take longer to break down than what the moddels are predicting. let the moddels get to grips with what is happening in the short term and worry about how long the cold will be here next week!!!!!

[Frosty.]

The GFS operational was at the cold end of the ensembles for next weekend, and there still seem to be plenty of options on the table.

What about the GEFS 00Z mean? looks like a very wintry outlook according to that!

[SnowBallz]

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!

Well, we all take different and varying degrees of interest from the models, meteorology and mathematics. My interest is really focused on using regression analysis to determine confidence in a signal. Put simply, it's about interpreting the influence of feedback within a cycle.

My analysis, and therein doubts, around the ECM 32 isn't the fact that it changes - you're stating the obvious there - it's the degree and pace of change which is significant, hence why both John and myself are asking the right question, ie: has this, what may appear significant, paternal change been a recent one, and how established is it as a new trend?

That's not "trying to sound clever" it's about using intelligence to determine confidence within a mid-term forecast. Strong divergence - which is what the ECM 32 relative to its previous solution implies - suggests low confidence in the model.

I'm trying to be as educational as possible, because I think it'll save quite a few people from sleepless nights and early-morning headaches. Models do, and will invariably, chop and change - but instead of reacting to every single peak and trough, it's maybe worth challenging objectively whether there is enough confidence in a solution which offers a widely different proposal.

You are new on this forum, so won't have experienced the swings and roundabouts of the winter season, or the educational, scientific interest which Stewart (GP) and I take. I don't think either of us are so much interested about 'the devil in the detail' which gets churned out, but more the over-arching signals which - ultimately - always govern what then subsequently filters down into low-level output. Focus on those, and the rest takes care of itself.

My personal view - which I've held for 10 days or so - is/was, that cold is absolutely guaranteed to be with us in the next 7-10 days. That view hasn't been influenced or altered by low-level outputs, but more the strong signals which were present some 30 days ago. Those signals have remained consistent, moreoever increasing with confidence and strength.

As we enter the more reliable timeframe, you're going to be exceptional outputs from the intra-day models - and we've all seen that over the last 48hrs. Of course there will be bumps - but, as I'm trying to stress to you, good analysis is about filtering the outliers out from the prevailing trend and - whichever way you wish to cut this cake - this cake is very much cold, and with exceptional potential for a lengthy period of it too. Again, some solutions will suggest longer/shorter - but, again, it's about noticing the underlying trend.

This mornings' models do not surprise me in the least - as they are on-cue with the underlying trend, and serve to highlight outlier solutions which popped up 24hrs ago. Those are the ones which can be easily dismissed and no sleep lost over. Expect further 'upgrading' as we transit through the next 48hrs and the pattern falls further and further within the reliable timeframe.

I hope you've found that helpful, and happy model watching

Edited November 23, 2012 by chionomaniac
Removed personal assumption

[EML Network]

The only thing that worries me about the GFS is that the model consistently wants to make this a short lived cold snap, 3 - 4 days at best, before pushing the default button.

The ECM, however, consistently wants to point us towards a possibly longer spell of colder weather, and the UKMO keeps falling off the fence and getting back on it again.

does anyone have a link to the JMA model ?

[SnowBallz]

can i just say that i have been following this four for the last week and a half. what i have learn in that time is that we need to look at the trend and that models are biast in going back to a milder set up after the cold arrives.

i have a gut feeling that once the cold sets in it will take longer to break down than what the moddels are predicting. let the moddels get to grips with what is happening in the short term and worry about how long the cold will be here next week!!!!!

In a nutshell, bang on target Tom.

And yes, once cold is established, there is a virtuous cycle which can prolong it and often you need either a lot of energy or a high latitude change to displace it.

Good post Tom, you're picked things up quicky.

[Methuselah]

I wouldn't say it's been at all 'consistent' EML. On the contrary, it's flipped and flopped from one extreme to the other...The equations used in the computer simulations are chaotic in nature...

[TEITS]

The only thing that worries me about the GFS is that the model consistently wants to make this a short lived cold snap, 3 - 4 days at best, before pushing the default button.

The ECM, however, consistently wants to point us towards a possibly longer spell of colder weather, and the UKMO keeps falling off the fence and getting back on it again.

does anyone have a link to the JMA model ?

http://www.meteociel.fr/modeles/jma.php

[Snowy Easterlies]

How good is the CFS ? lets hope this won't happen

[Gibby]

Apologies for anyone trying to log into my site today. I have a server upgrade underway to cope with more traffic. should be back working soon.

Good morning. Here is the report of the 00zs from GFS, UKMO,GEM and ECM for today Friday November 23rd 2012.

All models show a continued spell of very disturbed weather over the UK lasting well into next week. A day of respite is shown today as the active cold front of yetaerday takes the last of the rain away from the SE. A slack SW flow will ensure a mostly dry and bright day for many with a quiet and cold night tonight with a frost in the North. Tomorrow sees cloud quickly invade from the South as Low pressure travels North from Biscay bringing strong winds and heavy rain back to the South. It will be less mild than recently. This Low then is shown to transfer slowly NE on Sunday taking it's disruptive wind and rain away with it before a new Low moves in towards the SW on Monday bringing yet more wind and heavy rain.

GFS then shows next week to be dominated by Low pressure having transferred to the SE of Britain with an increasingly cold and unsettled NE flow blowing down over the UK. There will be rain at times with snow developing over the hills with time. By the weekend the cold intensifies somewhat as colder air is filtered SW from Scandinavia. With Low pressure still close to the SE more of the rain will turn to snow for a while. Later in FI winds fall light and the cold pool becomes cut-off just to the East as High pressure to the South encourages winds to back into the South or SW with milder air moving across the UK from the West with wind and rain extending to all areas later.

The GFS Ensembles show a colder spell is on the way. The operational was a cold outlier in the middle of the run before becoming a mild outlier at the end. There are plenty of cold options though on offer, sufficiently cold enough for the unsettled conditions to permit snow in places later next week. The overall picture remains a more modest cold spell though with rather cold weather with rain and sleet tempering somewhat towards the end of the run.

The Jet Stream shows the flow travelling East across Southern Britain for several more days before the flow ridges North through the Atlantic with the returning arm travelling South to the West of Britain and then East across Southern areas of Europe later next week.

UKMO for midnight on Thursday shows High pressure stretching from the Arctic to the South of Iceland with Low pressure over the Med with a cold NE flow strengthening over the UK. There would be wintry showers or perhaps some longer periods of rain or sleet, these chiefly towards the SE.

GEM shows a different picture as a weak Northerly flow at the same time point gives way to yet another very deep depression moving in from the West with gales and heavy rain extending to all areas later before the cold weather eventually arrives on a cold Northerly at day 10.

ECM shows a complex pattern later in it's run with a rather cold North or NNW flow with rain or wintry showers at times before things turn more definitively chilly late in the run as winds turn to the East with further rain or sleet at times, especially in the South.

In Summary a cold spell is on the way. Things will not be desperately cold but it will feel quite wintry. With Low pressure in close proximity for much of the time and winds from a North or NE quarter the question is will any precipitation be of snow. The answer is there will definitely be some snow on the higher ground at times but the lower ground will probably see just rain or sleet. However, having said that with uppers marginal a shift by a degree or two downwards could make all the difference to what develops at the surface. More runs needed over the coming days but a period of sustained cold does look well and truly possible this morning.

[Tim Bland]

Jma here... http://www.meteociel.fr/modeles/jma.php?ech=192&mode=1&nh=0&archive=0

Looking good!

[snowking]

Well, we all take different and varying degrees of interest from the models, meteorology and mathematics. My interest is really focused on using regression analysis to determine confidence in a signal. Put simply, it's about interpreting the influence of feedback within a cycle.

My analysis, and therein doubts, around the ECM 32 isn't the fact that it changes - you're stating the obvious there - it's the degree and pace of change which is significant, hence why both John and myself are asking the right question, ie: has this, what may appear significant, paternal change been a recent one, and how established is it as a new trend?

That's not "trying to sound clever" it's about using intelligence to determine confidence within a mid-term forecast. Strong divergence - which is what the ECM 32 relative to its previous solution implies - suggests low confidence in the model.

I'm trying to be as educational as possible, because I think it'll save quite a few people from sleepless nights and early-morning headaches. Models do, and will invariably, chop and change - but instead of reacting to every single peak and trough, it's maybe worth challenging objectively whether there is enough confidence in a solution which offers a widely different proposal.

SB

For what it's worth I completely agree and I very much hope that I was not giving the impression that this one run of the ecm32 was definitely going to happen

As I explained in the reply to John, it is very much changeable, and to be honest that's expected when I only get to see the control run of a 51 run ensemble suite - obviously similar to just using the GFS det. out to 384

However, as barely anyone has access to such charts, I feel it's helpful to put the information out there into the public domain for all to see

Kind regards

SK

Edited November 23, 2012 by chionomaniac
to keep in line with previous edit

[AWD]

Jma here... http://www.meteociel.fr/modeles/jma.php?ech=192&mode=1&nh=0&archive=0

Looking good!

That be yesterday's run. Hasn't updated today yet.

[Paul_1978]

How good is the CFS ? lets hope this won't happen

The Met Office don't pay a blind bit of attention to it.

The models they tend to use are their own, ECM, and have much respect for JMA. They say GFS good up to 8 days but not worth the paper it's written on after that.

As such, they're the models I pay the most attention to.

Edited November 23, 2012 by Paul_1978

[weather eater]

We can see from this morning runs why it’s best to not pay that much attention to FI charts as the disagreement between the ECM and the GFS is well before 144hrs, On a personal level I’d go for the ECM, it takes longer to get cold (my mother in law will get back to Kent, hooray) but it’s much better for long term prospects, the GFS is more of a quick fix before falling apart (real danger that the mother in law gets stuck here, not so good).

Edited November 23, 2012 by weather eater

[snowking]

Well both ensemble means pretty consistent at 240

GFS:

ECM:

Subtle differences with the atlantic ridging, with the ECM looking a little more secure with its Greenland heights.

And up at the dizzying heights of 850mB:

Both bringing the -4c line across most of the UK (bearing in mind that from the looks of the fact we are headed into the cold, the 'rogue' ensemble runs are diluting that somewhat), with a huge surge of even colder 850's just to our NE

Again, no complaints here about the current offerings

SK

[bluearmy]

Ecm ens and naefs both dropping the uppers late next week. definitely an upgrade on the 00z suites. The ecm london ens shoud be interesting after 11am

[chris55]

Ecm ens and naefs both dropping the uppers late next week. definitely an upgrade on the 00z suites. The ecm london ens shoud be interesting after 11am

Yes Nick averaging close to the -5 line (around London)

http://modeles.meteociel.fr/modeles/gens/naefs/graphe_ens3.php?mode=0&x=311&y=143&run=0&runpara=

[Duane S.]

Another set of runs and another set of incredible charts.

As for the shortwave drama around Greenland, to my eyes it is highly plausible scenario. Some energy is bound be left around there and it may be enough to stop full on ridging, initially, but there after it won't have a chance. This is one of those rare instances setting up when we would have to be VERY unlucky not to cop a decent cold spell out of it.

[Summer Sun]

The next 10 days is going to see things turn colder and for some parts of Europe very cold

Scotland looks like been the driest place over the next 10 days with 25% to 50% of the average rainfall for the period

[VillagePlank]

Have to keep things in perspective guys,

The GEFS control and the operational are clearly cold outliers; the form money is still on 850hPa's being around -5C. I don't think this will be well resolved until at least Sunday based on the spread of temperatures begin -11C to +4C - a whopping 15degsC just 8 days from now.

We're not facing "The Day after Tomorrow" just yet

Edited November 23, 2012 by Boar Wrinklestorm