Model Output Discussion 12z 27/11/2012

[Snowy Easterlies]

of course you have reason to be confident lomand you live in scotland, plus people always say the best runs are the 00z and 12z are you binning this run because its a downgrade from yesterday ?

there is a clear downgrade in the early timeframe, if there was a downgrade at T144 then it might be different

heights fail to make it to Greenland again in FI, this is plausible the GFS does not always go to default im afraid, but thats FI anyway so not worth talking about that

i am no WUM i see the charts at face value, and things look average for our island, forget about what the NH profile looks like, just because there is no raging PV,

lets be honest we haven't seen a belting run for a few days now, is just all "potential" with these supposed sliders

Edited November 28, 2012 by Snowy Easterlies

[Mucka]

UKMO 144 perhaps marginally better than GFS but nothing to suggest we have a strong enough block to disrupt the trough enough and keep us on the cold side.

NOGAPS and GEM also have weaker blocking to our North and East with the pattern slightly further East so based on this mornings output so far a good wintry slider is looking less likely than yesterday and it is back to looking for prospects further down the line. That said it won't be zonal or mild.

Edited November 28, 2012 by Mucka

[summer blizzard]

GFS0z is snow to rain at best for all of the UK but FAX is much more amplified at 120 vs 108.

[scottishandy]

Looking beyond the current cold spell it looks to me like it's all about this odd mid atlantic storm that ECM and GFS have discovered in the last couple of runs. Anyone notice when it first showed up?

Given where it is timescale wise I guess it won't be well modelled yet so we seem to have a choice between it pumping some warm air and heights up north and then east before undercutting it's own block as per ECM 12z.

Or the GFS solution which is not far off at 192.

Unfortunately on this run it doesn't blow up enough of a block so we get a much less severe easterly, but still cool, before the PV ramps up, contrary to most teleconnections and collapse all ridges. Just another variation on a theme.

[Snowy Easterlies]

UKMO poor too unless you live on a hill or scotland, blocking all gone except for a bit around svalbard which has no effect on us anyway

now we wait for the next "potential" spell and go through this all over again zzzzzzzzzzzz

but i give credit to those who still have faith for the next 7 days

however its stays quite chilly but tbh I'd rather it be 13c, than 5c with a nagging, chilly wind won't be pleasant walking around in those annoying conditions, its just a very normal cold spell/snap for early winter

Edited November 28, 2012 by Snowy Easterlies

[Zakos]

UKMO poor too unless you live on a hill or scotland, blocking all gone except for a bit around svalbard which has no effect on us anyway

now we wait for the next "potential" spell and go through this all over again zzzzzzzzzzzz

but i give credit to those who still have faith for the next 7 days

The block is not "gone" at all, we still have 1040mb over the pole.

certainly a step back from the models so far, but I would wager the ECM will show colder conditions, continuing the roller coaster. Even if it doesn't, its irrelevant.

This setup of a slider low, is a very complex, just look at the huge differences on the GFS at 144 hours. The big picture is the same, but the Atlantic low is being moddled completely differently.

If that low dives south eastwards, it will drag frigid air across the UK.

The situation is further complicated by the tropical depression, which appears at around 144 hours just north west of the Azores. This has the potential to make or break the initial cold spell.

[Mucka]

Fairly emphatic no to a snowy slider from the GFS 00z ensembles anyway.

http://modeles.meteo...run=0&runpara=0

Staying cold at the surface though probably, especially to the north with the potential of dragging some cold air back in later.

Maybe ECM can deliver?

Edited November 28, 2012 by Mucka

[Floatylight]

Hi all would it be possible for people making bold statments about the model output to sometimes back up there there thoughts and opinions with some charts possibly outlining what we are looking at?

I love it when peeps circle things!

I am still learning to read the model output charts and this would be helpful.

I have to say making one off statements ,and feeling its suitable for this thread by entering the words,gfs,pv etc.

Is quite frankly putting people off reading in here.

Especially when there are no mods around in the early hours every morning latley.

Many thanks sam x

Edited November 28, 2012 by Floatylight

[Snowy Easterlies]

The block is not "gone" at all, we still have 1040mb over the pole.

certainly a step back from the models so far, but I would wager the ECM will show colder conditions, continuing the roller coaster. Even if it doesn't, its irrelevant.

This setup of a slider low, is a very complex, just look at the huge differences on the GFS at 144 hours. The big picture is the same, but the Atlantic low is being moddled completely differently.

If that low dives south eastwards, it will drag frigid air across the UK.

The situation is further complicated by the tropical depression, which appears at around 144 hours just north west of the Azores. This has the potential to make or break the initial cold spell.

potential doesn't always become reality though, that blocking at the pole is too far north to effect us, our best hope is after T168 when heights start ridging north out of the Atlantic, if the ECM is like the UKMO and GFS you can't say its irrelevant because its cross model agreement on a return to the atlantic, if the ECM does bring that easterly it showed last night forward, or a actual proper slider, then there is reason to be tad more optimistic as the GFS could follow it on future runs, i have seen far better potential than this and nothing has happened, so i see no reason why something snowy is going to happen this time when the charts haven't even shown a widespread snowy scenario for a few days now its just all "potential"

[Zakos]

potential doesn't always become reality though, that blocking at the pole is too far north to effect us, our best hope is after T168 when heights start ridging north out of the Atlantic, if the ECM is like the UKMO and GFS you can't say its irrelevant because its cross model agreement on a return to the atlantic, if the ECM does bring that easterly it showed last night forward, or a actual proper slider, then there is reason to be tad more optimistic as the GFS could follow it on future runs, i have seen far better potential than this and nothing has happened, so i see no reason why something snowy is going to happen this time when the charts haven't even shown a widespread snowy scenario for a few days now its just all "potential"

how can a block possibly be too far north? there is no such thing. If it were on the pacific side then yes. but it is an Arctic high, one which is refusing to budge. Aslong as we have a negative Arctic oscillation, it is only a matter of time before the UK receives a cold spell

It is irrelevant, because it the output could completely change by tonight, as the setup is so complex.

Nope. The models have been predicting a cold spell from the North east for some time now. What is difficult to determine is the arrival of the cold itself, again because of the complex setup.

There is no "atlantic return" look on the gfs 00z, (which i agree is a poor run)

Thats not an Atlantic breakdown. there is high pressure in the Atlantic, which is trying to ridge into Greenland. Given the GFS's tendency to default by overpowering the PV in FI, I suspect heights would in reality rise over Greenland later on.

What we have lost is the initial cold blast from the North east. I believe this is a temporary delay before the real cold sets in.

Dont take it from me,take it from the experts and the teleconnections, which go completely against an Atlantic return.

Edited November 28, 2012 by Zakos

[Great Plum]

Those of you on the overnight runs really need to qualify things...

This is not a bad run; even in London, the mean remains below average throughout...

http://www.netweather.tv/index.cgi?action=charts;type=ens;sess=

Even the op only goes over average for a few hours...

[Snowy Easterlies]

this block is going to be broken down easily so who's to say the next ridge/block won;t do the same ?

a block can be too far north to effect us because you get a slight pressure rise from the south, and those tame heights near the arctic probably won't force the lows far enough south next week, i still think that scotland and the north could end up with snow if a bit of cold upper air gets to them, but i very much doubt the south will

as for GFS FI overpowering lows yes that is true, but it also doesn't mean heights are certain to build into greenland either, this current block was modeled to be a lot stronger than it currently is a few days ago and now it barely gets there before being blasted away

Edited November 28, 2012 by Snowy Easterlies

[bobbydog]

having been woken up at 4am, had a look through the 00z and the first few posts on here..... it's going to be one of those days... again....

[Snowmad79]

this block is going to be broken down easily so who's to say the next ridge/block won;t do the same ?

a block can be too far north to effect us because you get a slight pressure rise from the south, and those tame heights near the arctic probably won't force the lows far enough south next week, i still think that scotland and the north could end up with snow if a bit of cold upper air gets to them, but i very much doubt the south will

as for GFS FI overpowering lows yes that is true, but it also doesn't mean heights are certain to build into greenland, this current block was modeled to be a lot stronger than it currently is a few days ago and now it barely gets there before being blasted away

What block lol. Can we really call what we see a legit block ? High latitude HP just gets rolled over like there is nothing there. Frustrating ? yes maybe but disappointing ? No!. It's not even winter yet.

[IDO]

The pattern, as per yesterday, with the GFS, is to downgrade this weekend's cold snap. Now only the far north have a snow potential and this is reducing run by run. One ECMWF stella run and we all ignore what the ensembles are showing from the GFS (best model at the moment). There is no support for a Scandi high at that time frame. I expect ECMWF to be a lot less wintry this morning. UKMO still at the other extreme but enough said there.

However as far as potential goes, no change. Its a case of looking for a consistency to the ensembles and with the changeable setup this may be T72-T120 so small details difficult to get a hold on.

From the 18z 850s London: http://cdn.nwstatic..../t850London.png and today's 0z: http://www.wetterzen..._London_ens.png

This shows the trend towards a less cold period early next week followed by a dip, rise and dip. Its a quasi cool/cold zonal setup where the Atlantic is never to far away from the south of the UK. This type of chart is now showing up more and I see this as the pattern. These resets may strike lucky and that was what the ECMWF showed on yesterday's 12z, however if this continues to reset then this may be the pattern for a few weeks. Note the mean has risen about 3c from yesterday's 18z. Of course Scotland/N England should get some transient snow. However the 18z and today's 0z show no prolonged cold spell in the next 15 days+ and a continued downgrade from the ensembles.

Edited November 28, 2012 by i'm dreaming of...

[Snowy Easterlies]

What block lol. Can we really call what we see a legit block ? High latitude HP just gets rolled over like there is nothing there. Frustrating ? yes maybe but disappointing ? No!. It's not even winter yet.

agree, but im trying not to be too negative as the glass half full brigade are shooting me down

ECM is a clear downgrade from yesterday at T168 as the easterly is gone, but "its just one run" as they say and we should ignore it right ?

Edit the easterly is back at T240 shame its only a half baked one though

Edited November 28, 2012 by Snowy Easterlies

[Matty M]

ECM signals the PV re-forming towards 240hrs.

Overall a big step back from a cold evolution this morning.

Cool yes but our block ppears weaker. Not good runs for coldies.

[snow drift]

ECM signals the PV re-forming towards 240hrs.

Overall a big step back from a cold evolution this morning.

Cool yes but our block ppears weaker. Not good runs for coldies.

This looks full of promise to me. ECM not as bullish as last night, However I would take this so early into the season.

[NL]

An attack from the east/northeast isn't going to happen this week. Yes its going to feel chilly in the north of the UK and a little below in the south but not cold enough for snow except for the higher ground north Pennines and the highlands of 'bonny' Scotland. Looking promising around 5/6th Dec for a renewed attack from a east/Northeasterly direction which has the potential to deliver.

[Duane S.]

but im trying not to be too negative

You must be a barrel of laughs when you're being negative then!

There seems to be a lot of anger seeping out from some members whom I can only imagine were expecting a raging nor easterly with -15 uppers and 30 foot snow drifts up against their shed by now. Potential is the best we can get in this country I'm afraid. Last early winter there was NO potential for a sustained cold period, this year there is, like it or not, living in the UK that's the best it's going to get. But there will always be potential spoilers BUT in setups like these spoilers just knock us back a few days before another opportunity presents itself.

Bottom line is the big picture remains. The vortex is being shreded apart. This weekend things could have gone better for us in the UK but I maintain we are entering a cool/cold/cool/cold setup and any mild will only be shortlived.There will be plenty of opportunities over the next month and we would be very unlucky if a large swathe of us don't see some of the white stuff IMO.

[Snowmad79]

agree, but im trying not to be too negative as the glass half full brigade are shooting me down

ECM is a clear downgrade from yesterday at T168 as the easterly is gone, but "its just one run" as they say and we should ignore it right ?

Edit the easterly is back at T240 shame its only a half baked one though

Now go through the archives (northern hemisphere).. for this time last year including the dates in my signature and look at the profile of PV and the pole in general. Tie in the fact we have a neutral enso winter ahead and you'll see how blessed we really are as we head into the upcoming winter period.

http://www.meteociel.fr/modeles/ecmwf.php?ech=72&mode=1&map=1&type=0&archive=1&mois=11&heure=12&jour=27&annee=2011

[Zakos]

I cant believe some are using charts at 240 hours out to cast doubts on the month ahead. Have you learned nothing from the previous winters?

The "slider" low appears on the ECM once again, although the cold is certainly toned down a notch or two from the previous run.

I really cant see where the second depression can head, apart from taking a south east track.

For those critical of my continued optimism, take a look at these 2 charts: top= ECM bottom =GFS

Both charts depict the same time-frame.

Both have strong heights over the Arctic, a shattered polar vortex, a southerly tracking jet, low heights over Europe, and high pressure in the Atlantic. All very good signs

So just because the charts dont show -15 t850s over the UK doesn't mean we should be pessimistic whatsoever. These "terrible" runs are still a thousand times better than anything on show this time last year.

So please, less of the "cold spell is over" posts, because the reality is the hemispheric pattern is currently very conducive for a prolonged cold spell soon. There is every reason to be optimistic, patience is a virtue.

[Snowy Easterlies]

Now go through the archives (northern hemisphere).. for this time last year including the dates in my signature and look at the profile of PV and the pole in general. Tie in the fact we have a neutral enso winter ahead and you'll see how blessed we really are as we head into the upcoming winter period.

http://www.meteociel...r=27&annee=2011

yes the NH is better this year, but people have been saying that all month and what have we gained from it ? nothing, i think people take too much notice of the NH and don't see whats actually happening on this island

[Paul_1978]

yes the NH is better this year, but people have been saying that all month and what have we gained from it ? nothing, i think people take too much notice of the NH and don't see whats actually happening on this island

Yes but it's not even 1st December, the start of winter. We are still in November!

We have a full three months of winter left yet!

[Jaffusmaximus]

Yes but the models keep throwing out potential, personally I'd prefer at least two months of below average temps with few days of very cold then one week of really below temps. The pure muck of a winter last year broke my fragile little heart!