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

[I remember Atlantic 252]

It's 22nd November - the tastier charts are still 9/10 days away. That takes us up to 2nd December.

Winter aint really started, so why the distress-type post?

Grab a beer and chill out!

because it still FI and the uncertainty increases

[Zenarcher]

Comparing the ECM 12z run to today's and yesterday,

28th November - Heights to our North not as high as yesterday and a deeper low appears in the Atlantic today,

Yesterday

Today

29th November - Again heights to our North not as strong but still there also high pressure in the Atlantic see's a big change,

Yesterday

Today

30th November - Things pushed further West and the high in the Atlantic links up North,

Yesteday

Today

[IDO]

Last one from me on the 12z model runs; feel like my points are rather laboured today.

We can only comment on the output before us and in the last 24 hours (since the 12z runs yesterday) there has been a TREND by the operational model outputs away from any real cold advecting across the UK. We also now appear to have another shortwave palava on our hands; and this is exactly the reason I urged caution yesterday.

Long term we may see proper cold (low upper air temps & thicknesses) infiltrate the UK but within the next 8-10 days I think it's going to be a real struggle.

I agree. If you look at the GEFS, most of the members, at different times, throughout the run, give it a shot at cold uppers, but they break down, and the model trend appears to be currently an un-sustainable cold upper flow.

http://cdn.nwstatic.co.uk/ensimages/ens.20121122/12/t850London.png

The flatter upstream pattern (US) possibly explains why the mean temp (850s London) is heading towards -1c, after it had cooled to -4c on Dec 1. The individual GFS ensemble members, by T384 have six showing a SW flow (though many from cool origins), twice as many as an Easterly or N'Easterly (3 each):

http://www.meteociel.fr/cartes_obs/gens_panel.php?modele=0&mode=6&ech=384

Still a no entry sign for the Atlantic (end FI) so further reloads are viable and look our best option for snow. Overall a downgrade from yesterday but thankfully not a flip, so cool/cold still the headline; however the first cold shot is trending as a more transient spell. It is also quite possible that even if the pattern remains blocked for 2-3 months we may not see widespread snow till January or later, though there would still be plenty of opportunity for snow showers, for the favoured, in the interim.

[phil nw.]

Regardless of the modelling disagreements it is going to turn colder.

And that really is the sum total that can be drawn from the output! Trying to forecast any snow at this point is impossible as we have no idea where exactly that European troughing will set up, whether shortwaves near Scandi will hinder any cold, whether the Arctic high runs up against the UKMO and its shortwave love-in!

I'd draw a line under this evenings output and hope to see a model convergence tomorrow,

Wise words Nick.All the models continue to show a distorted and sometimes fragmented PV .

All the trends in the ens.means further out and the near time operationals indicate blocking around the N.Atlantic/Greenland area.

That`s the main message to take from the days outputs.

There`s differences in the way the UK/Euro trough is shown going into next week so best not to get looking further ahead for how quickly deeper cold or snow will arrive.

Mean operational hts. tonight are at odds over the wave patterns in week 2.

http://www.meteo.psu...2z/hgtcomp.html

which underlines the difficulties they are having beyond T96hrs.

[Gael_Force]

The ECM site has a map of global data coverage today.

http://www.ecmwf.int/samples/d/inspect/catalog/samplers/banner/data_coverage!synop-ship!12!pop!od!mixed!w_coverage!latest!/

It seems to be very sparse in the region where the weekend storm is developing - might be the reason why modelling from that region appears to be tricky?

[mcweather]

I know this is the model discussion thread but I must admit it gets rather tiresome when people comment and pull to pieces each run as it comes out.

Can I suggest a few things.

Firstly wait until the ensembles for each run have come out before commenting so that you at least have an idea of where the run sits in the suite and also what the ensembles are suggesting which can sometimes be very different to the forecast run.

Please remember that anything after 144 is a possible/ probable trend and not a detailed weather chart.

also its worth taking a holistic approach, so take a look at 8-14 day 500mb charts that John Holmes uses, listen to what those like GP and Chiono

are saying because these guys though not infallible really do know their stuff and then comment on the runs bearing those things in mind.

That way we end up with far less wrist slashing and the like.

I,m a coldie like many on here but have seen enough crappy mild winters in my fifty odd years to be very happy to find us going into December with

the synoptic potential on offer. Winter is never three months of winter armageddon not even 63 or 47 were like that.

Sorry mods Rant over

Edited November 22, 2012 by mcweather

[LomondSnowstorm]

There's been no 'delay' of the cold as such, we've just had markedly different evolutions. Take the 29th November for example using the last 4 ECM 12Z runs:

19th November:

An easterly yes but with uppers just around -2C at lowest and it appeared that it was from that position a few days before the cold could make real inroads.

20th November:

A fairly impressive looking chart but again relatively high uppers with the cold perhaps 48 hours away from the northeast

November 21st:

A more northeasterly tilt to the flow with the cold pool clearly much further west, though still uppers are only around -2Cor -4C in that frame.

22nd November:

Messier with a northerly flow and a more amplified and much further north trough but again with uppers around -2C or -4C.

There has been no postponing here at all, simply a natural failure of the operationals to show consistency outside the reliable timeframe combined with the added confusion of a pattern change. Until we see model agreement it's once again best to stick to the ensembles and the composites as a guide and looking at the models in the context of those rather than considering the most up to date operational run as necessarily the way forward.

[Gibby]

Sorry for the continued lateness of the summary at the moment. I have had a wealth of severe warnings to update as well as forecasting duties on my website. I didn't think running a weather website was so hard and time consuming. Anyway you can always read my report on my website at 19:00 and 08:00 as I always compile it there and paste it into this forum. OK on topic..

Good evening. Here is my take on the 12zs from GFS, UKMO and ECM tonight.

All models show a continuation of the very unstable atmosphere over the UK. The active cold front continues to move down over the remainder of Central and SE England in the coming 12 hours taking some very heavy rain with it. In addition the gales will abate as the rain clears through the evening and night. Tomorrow shows a quieter day with widely spaced isobars making for lighter winds with sunshine and just a scattering of showers. Temperatures will be down on the values of today. On Saturday a new depression is shown to move Northeast towards Southern Britain and bring very heavy rain and strong winds back to much of Britain with further flooding issues likely. Sunday will see an improvement as the Low is shown by all models to track slowly away to the NE or East. Monday will see further Low pressure around over the UK with further rain or showers likely especially in the South.

GFS then shows next week with the Monday low to move across to Germany continuing to deepen with a cold and blustery North or Northeast flow developing with further rain and showers and even some snow on the hills. This cold Easterly flow continues unabated for many days with some settling snow on the higher ground of Northern Britain and still some high rainfall totals possible in the South. In deep FI a 'col' area develops over the UK with the risk of fog and frost increasing as winds fall light away from the far North where a milder Westerly takes hold later.

The GFS Ensembles show a gentle fall in uppers over next week before a slow recovery late in the run. The weather remains quite unsettled for much of the time with further rainfall for many and sleet or snow for the higher ground for a time.

The Jet Stream shows the flow crossing the UK currently and remaining this way for some time. Into next week the flow ridges North through the Atlantic breaking down the flow before it settles running East Southeast to the South of the Uk over france and Northern Spain.

UKMO for midday shows Low pressure towards Southern France and Northern Spain with High pressure near to NW Scotland with a chilly NE flow over the UK. the NW will probably stay dry while Southern and Eastern areas remain at risk of occasional rain.

ECM tonight shows a rather cold Northerly flow with Low pressure close to the East with rain or showers for all with sleet and snow possible over Northern hills. Winds turn easterly late in the run as pressure builds to the NW and NE late in the run. The best weather would be felt in the NW although it will stay rather cold while the South maintains an unsettled feel with the risk of rain maintained in rather cold conditions here too.

In Summary the weather looks like staying unsettled for the next week to 10 days. The pressure pattern will change with Low pressure transferring to the South or East of the UK with rather colder North or NE winds taking over from the recent mild SW winds. Temperatures will fall to rather cold levels and there will be quite a few days of dull and overcast conditions with rain at times. The risk of snow remains low except for higher ground and with GFS who does show low enough uppers for a time to produce some covering of snow on high ground in the North at times towards the end of next week.

[cooling climate]

In a way I am pleased that the models are showing what they are. By that I mean

how many times have we seen eye popping charts only to get watered down in the

days running up to a cold spell. If we saw the best synoptics now for cold and

snow for later next week they would not be the same in 8 or 9 days time.

The position and orientation of the high pressure would not be the same nor

would the positioning of lows etc.

Looking at the ensemble means,NAEFS etc a cold spell (perhaps prolonged)is

gearing up to start later next week how cold and snowy we just don't known yet.

But I would not mind betting that come the end of the weekend we will all be

very happy with what the models are showing.

[SE Blizzards]

Hi everyone

I am new to all of this. This is my 1st post, so go easy on me.

Firstly i would like to say that i have been viewing this thread for a while now and i find some posts very educational and very enjoyable. I'm only a beginner but learning all the time.

What i don't understand though is some of the negativity on here at the moment. I believe some peoples expectations of cold and snowy weather are far too high at times.

Having a December like the one we had 2 years ago was very very special, but that was a '1 in a 100 year' event, we have to remember that we live in the UK and we would be extremely lucky to see it happen again in our lifetime let alone 2 years after it happened! Maybe because of Dec 2010 that's the reason why the expectations are so high?? I for one absolutely love cold/snowy weather but sometime patience is required, and i guess that's what is going to be required with the upcoming cool/cold spell!

Yes, we all got very excited with yesterdays 'eye candy', but are today's charts really that bad???

You are either 'the glass is half empty' or 'the glass is half full' kind of person and luckily i am the latter of the 2.

Some of today's charts are still ok viewing and the GFS 12z run to me is ok too! Ok, i agree that today's charts are 'not the perfect scenario' but if you cast your mind back 12 months the charts were that bad i found myself hiding behind the sofa in despair and if i could choose between last years charts and this years one's i know which one's i would choose!

So my advice (for what it's worth) is to keep calm! There is lots to play for and lots to look forward too, after all we are still only in November and there are 3 whole months of winter ahead of us. I'm sure there are many twists and turns over the next few days regarding model/chart watching, so let's just have some fun and enjoy the ride of winter 2012/13!

SE Blizzards

[nick sussex]

Wise words Nick.All the models continue to show a distorted and sometimes fragmented PV .

All the trends in the ens.means further out and the near time operationals indicate blocking around the N.Atlantic/Greenland area.

That`s the main message to take from the days outputs.

There`s differences in the way the UK/Euro trough is shown going into next week so best not to get looking further ahead for how quickly deeper cold or snow will arrive.

Mean operational hts. tonight are at odds over the wave patterns in week 2.

http://www.meteo.psu...2z/hgtcomp.html

which underlines the difficulties they are having beyond T96hrs.

At the moment the ECM upstream is classed as an outlier solution within 144hrs, this is looking at the aviation forecasts for some eastern US states.

They expect a more inland system and not the weak feature shown by the ECM operational run. So if we do see this more amplified solution verify then its likely to impact on Europe.

Looking at the UKMO again it looks like one of those shortwaves is ejected from Greenland eastwards and we may well see that Arctic high ridging down afterwards.

I wonder if any of the models have that Arctic high accurately modelled given the lack of observational data in that area, so could be more shortwaves pop up or on the other hand we see them gone in future runs.

Certainly I wouldn't rule out any snow within the next week given the potential in the output but we'll have to wait and see when the model mist clears.

[NorthernRab]

While it's all doom and gloom on here, the 12z GFS, like the 6z before, forecasts some very good snowfall for much of Scotland.

850hPa temperatures eventually head down towards the -10'C here too.

[Frosty.]

Although tonight's Ecm 12z op is a pale shadow of last night's epic run, it still shows a colder outlook and by T+240 it would be cold everywhere, the Gfs 12z op run is much more promising in my opinion with eventually a NEly blast from scandinavia slowly spreading south to all areas followed by a Nly blast at the end of FI, really good retrogression and superb height rises towards the nw with a completely blocked atlantic, the only direction the depressions could attack from is either the northeast or the south. The most important aspect is the trend which points to a pattern we haven't seen for a long time, the weather coming at us from northeast europe instead of the azores, really wonderful northern blocking but for now, it's northern britain which looks favoured for any snow but that could easily change with the placement of the european trough still not nailed, but if I had a choice tonight I would plump for the gfs 12z op run evolution which shows a prolonged cold/very cold further outlook along the lines of the extended meto update today with reload arctic outbreaks through december, there really isn't much to moan about trend wise, it's going to turn much colder than it is now

[phil nw.]

Welcome to the forum SE Blizzards.

A good first post.

[mcweather]

Welcome to the forum SE Blizzards.

A good first post.

I would very much like to second that S E Blizzards. Welcome to Net weather.

[Matty M]

The ECM Ensemble mean in the medium-long term is nothing short of excellant.

144hrs

192hrs

240hrs

[Paul_1978]

Look at the GFS 12z at T192.

When was the last time you saw such a long stretch of easterlies, from Mid Europe to the Azores region?

The pressure patterns are very much in reverse compared to what we are used to.

I am personally very pleased with the last few days output.

Lets just say "it makes a change"! (to raging south westerlies).

Edited November 22, 2012 by Paul_1978

[SMU]

this 850s argument runs on and on can fergie weather.john holmes or steve answer this correctly in pure english

many thanks

The answer isnt definitive im afraid- theres a lot of people in the thread plucking numbers from thin air.- of which labelling them as -X in a Northerly = snow is misleading to others-

There is a definate ability within continental air to sustain higher thicknesses to support snow- However thats not the end of it-

People cannot just correlate -6 =Snow in Northerly.

You need to consider the following-

Wind direction

Length of time cold has been embedded

Dewpoints & wet bulb-

Lapse rates

Type of PPN- convective or frontal

PPN intensity

Time of Day

So lets just get the cold in & then think about it.

As for the runs all 3 big guns- if you treat them like the traditional top 3 then they are ALL different at 144,

The GFS has No shortwave over svalbard linking the arctic & Atlantic ridge-

http://modeles.meteo...nh-0-144.png?12 so does the NOGAPS

http://www.meteociel.fr/ukmo/runs/2012112212/UN144-21.GIF?22-18

UKMO is not bad- a bit slower & will be a day behind the GFS with the cold spreading across Northern Europe- although at 168 I would suggest that that small circular shortwave close to svalbard will have been shunted south by a long way-

so 168 & 192 sees a strong march west of the cold.

ECM- disapointing again, although again i cast my mind back to 2012 when ECM had some really shonky runs for example-

1st Feb 2012 ACTUAL

http://modeles.meteociel.fr/modeles/reana/2012/archivesnh-2012-2-1-0-0.png

22nd run 192

http://www.meteociel.fr/modeles/ecmwf/archives/2012012212/ECH1-192.GIF?12

23rd run 168

http://www.meteociel.fr/modeles/ecmwf/archives/2012012312/ECH1-168.GIF?12

24th run 144

http://www.meteociel.fr/modeles/ecmwf/archives/2012012412/ECH1-144.GIF?12

Only when we got down to 120 the next day was it correct

So the ECm can come vulnerable as well-

Tonight at 144-

http://www.meteociel.fr/modeles/ecmwf/runs/2012112212/ECH1-144.GIF?22-0

The angle tilt of that single shortwave over Northern russia stops ANY real westward progression of the deep cold-

Luckily at 240 when are seeing signs of another go at building the greenland high.

in Summary a difficult call tonight-

I would say the GFS + NOGAPS are a tad fast & the ECM looks incorrect with the tilt & allignment of that shortwave- so

I will stick with the UKMO which is slower but looks good-

S

Edited November 22, 2012 by Steve Murr

[snowking]

Not as much difference as I was expecting between the GFS and ECM ensemble means at 240:

Subtle differences between the ridging in the atlantic and also the angle of the trough, but actually fairly good agreement.

As Nick said earlier, despite the potential shortwave drama incoming (perhaps it should be called Shortwave Shore, the new soap opera for the winter), there is no change in the fact that we are entering a phase of significant cool down.

For those of you chasing specifics at this range, the 850's:

From the point of view there will be milder members 'diluting' this, i'm pretty impressed with that actually

SK

[andymusic]

few more encouraging Joe B tweets folks

Just like Nov 2010, heavy rains preceded the turn to colder over Nw Europe... Rains into UK now

Is the UK and NW europe ready for a start to the winter season that will rival 2010. We will find out soon enough

Santa also wanted me to let you know that n hemisphere snowcover is above normal and that the sled will be used more than normal this year

[Buzz]

I know this is the model discussion thread but I must admit it gets rather tiresome when people comment and pull to pieces each run as it comes out.

Can I suggest a few things.

Firstly wait until the ensembles for each run have come out before commenting so that you at least have an idea of where the run sits in the suite and also what the ensembles are suggesting which can sometimes be very different to the forecast run.

Please remember that anything after 144 is a possible/ probable trend and not a detailed weather chart.

also its worth taking a holistic approach, so take a look at 8-14 day 500mb charts that John Holmes uses, listen to what those like GP and Chiono

are saying because these guys though not infallible really do know their stuff and then comment on the runs bearing those things in mind.

That way we end up with far less wrist slashing and the like.

I,m a coldie like many on here but have seen enough crappy mild winters in my fifty odd years to be very happy to find us going into December with

the synoptic potential on offer. Winter is never three months of winter armageddon not even 63 or 47 were like that.

Sorry mods Rant over

Agreed. I rarely post here but this has to be said:

I find the model threads incredibly tiresome during the winter months, but i still read them for the few good, unbiased and informative posts that crop up - even when the models are showing some great synoptics there are always a number of people who will whine and gripe like a bunch of grizzling babies and pick holes in every single run. No doubt some are trolling, some are ignorant (in which case, don't comment!) and some are simply incredibly negative people who will NEVER be satisfied ("the snow is only 12 inches deep - wahhh!", "The temperature is only going down to -10C tonight - wahhh", "It's only going to be cold for a week - wahhh". Etc.

This grizzling by a relatively small number of people completely ruins the model threads.

Enough said.

Edited November 22, 2012 by Buzz

[SLEETY]

Exactly... Is this cold spell going to be prolonged or a short lived cold snap;which even if it is their is still plenty of time for further cold spells

The thing that excites me is what happens in december do we keep this cold or go back to zonal

[Liam J]

ECM ensemble mean @ T240, not sure I like the look of the low heights north of Svalbard plus the Arctic high is now sitting over Siberia.

Edited November 22, 2012 by Liam J

[SMU]

POST updated prev page

S

[Duane S.]

We need to get it before we can keep it

Are you actually going to contrbute to the model thread or are we to expect a continuation of doom and gloom one-liners based on days when the model op runs are not as good as the previous day? Just wondering.

I think the ECM the other day lulled people into thinking we would all be buried under 15 feet of snow by the the first week of December, it was too progressive. The pattern change is underway, it may take a while but it will get there. Cold weather is coming, snow too but if you and certain others are going to base their expectations on a period akin to December 2010 and anythig less is rubbish then you are more likely than not going to be disappointed.