Model Output Discussion - 18z - 6th December onward

[Snowy Easterlies]

ECM is better than GFS at T144 and T168 but this phrase springs to mind, yet again

http://t0.gstatic.co...yT_8HZwjwysPSop

Edited December 7, 2012 by Snowy Easterlies

[Paul_1978]

The morning's GFS and ECM look ok to me.

The Atlantic tries to make inroads but never really succeeds, and in the end it slides underneath the block anyway, leading to more easterlies.

So, coupled with Ian F's hints about significant snow, and I think the block may well push things back west, then in fact we've got a lot to be upbeat about IMHO.

[Penicuikblizzard]

The GFS picked up a trend in the last few runs and is sticking to it's guns, the model tends to do this more often than not and in recent times has been spot on. This is not a downgrade just merely a change still gonna be very cold but not the snowmagedon that was predicted for Eastern areas over the last few days.

That's why when people have been saying this Easterly is nailed no way not at 120hrs, 120+ hrs in my eyes is FI in these situations!!

[snow drift]

ECM has us under minus 8 air for about 120 hrs. All starting in about T72 to T96 hrs. I will take that. Here is a thought, what if the models are underestimating the strength of the Block?

Edited December 7, 2012 by snow drift

[snow drift]

FI, but atlantic get through and its milder by T216, don't be fooled by those dark blue 500mb charts, anyway blocking is stronger on this ECM but, its still a short term downgrade with those shortwaves ruining that easterly albeit its not as bad as GFS

The block to our NE has gone no where. Come on guys! How bad is this?

[MKN]

ECM has us under minus 8 air for about 120 hrs. All starting in about T72 to T96 hrs. I will take that. Here is a thought, what if the models are underestimating the strength of the Block?

Every chance imo. Once the cold arrives its often here for longer than the models predict at first. I'm expecting yet more up and downgrades over the next few days as clearly when you see big changes in two runs produced 6 hours apart its obvious nothings certain. I imagine the 6z could be quite different again.

[snowking]

FI, but atlantic get through and its milder by T216, don't be fooled by those dark blue 500mb charts, anyway blocking is stronger on this ECM, but its still a short term downgrade with those shortwaves ruining that easterly albeit its not as bad as GFS

http://www.meteociel.fr/modeles/ecmwf/runs/2012120700/ECH1-216.GIF

http://www.meteociel.fr/modeles/ecmwf/runs/2012120700/ECH0-216.GIF

Would you like to point out to me where this 'milder' air is across the UK under a SEly continental flow with sub zero 850 's and low heights?

SK

[ICETAB]

This mornings GEM is worse than GFS in downgrading cold. I think this model has been performing well so one to watch over the next couple of days.

[BARRY]

Can't see anything wrong with these charts, you are going to get downgrades, up to T96 looks fine.

[Snowy Easterlies]

i didn't say the block had gone but the atlantic still crashes through and uppers clearly rise on this run, we can speculate all we like about potential undercutters but i just see the charts of what they actually show and i don't always have faith in just potential,

lets be level headed here, its wrong to say it will be mild by 216 but its also wrong to say that there will certainly be snow from that low, its deep FI

[mountain shadow]

Great charts this morning.

Cold and snow for more eastern areas initially followed by the potential for more widespread significant snow as the Atlantic tries to push in.

Some areas will stay cold throughout.

[IDO]

http://www.meteociel...00/ECH1-216.GIF

http://www.meteociel...00/ECH0-216.GIF

Would you like to point out to me where this 'milder' air is across the UK under a SEly continental flow with sub zero 850 's and low heights?

SK

Milder in relative terms. At T168:

http://www.meteociel...0-192.GIF?07-12

AT T216:

http://www.meteociel...0-216.GIF?07-12

From widespread -8 uppers to mostly 0 to -4c.

Bt T240 positive uppers in the south!

http://www.meteociel...0-240.GIF?07-12

Still feeling cool but clear the real cold is moving back north.

Edited December 7, 2012 by i'm dreaming of...

[mountain shadow]

i didn't say the block had gone but the atlantic still crashes through and uppers clearly rise on this run, we can speculate all we like about potential undercutters but i just see the charts of what they actually show and i don't always have faith in just potential,

lets be level headed here, its wrong to say it will be mild by 216 but its also wrong to say that there will certainly be snow from that low, its deep FI

If that chart was to occur there would be epic snow.

[Ian Brown]

Well anyone who watched the GFS 18z unfold last night may not be too surprised by this mornings run - the shortwave off the Norwegian coast almost threatened to prevent the HP linking up with the heights around Iceland on that run.

Now on this run the shortwave is that little bit stronger and does prevent the link up, hence the heights are forced to extend South over the UK, so no easterly. Somebody said that easterlies need to come within T72 before they can be 'banked'. We then see a struggle between the Atlantic and the retreating block. GEM supports the initial synoptics from the GFS, and brings the Atlantic in much quicker.

ECM has the shortwave, but makes less of it and the High is able to form to bring an easterly until it then goes down the route of most of the models yesterday by bringing an Atlantic attack from the SW by next weekend.

[snowking]

i just see the charts of what they actually show and i don't always have faith in just potential,

Well that's not really correct is it as I just demonstrated in my previous post.

It's never as clear cut as -6c uppers from the east for snow. I went in to some detail about this a couple of nights ago but when you see the blues on the 500mb charts, that means the corresponding pressure heights are much closer to the surface. Where as usually minus ) 850 's are required to ensure the atmosphere is cold enough from cloud to surface for snow, this is not the case with a shallow flow from a freezing continent.

Anyway, small details in FI at the moment, and that's something I'm sure we can both agree isn't worth the speculation based upon one op run

SK

[snowking]

Milder in relative terms. At T168:

http://www.meteociel...0-192.GIF?07-12

AT T216:

http://www.meteociel...0-216.GIF?07-12

From widespread -8 uppers to mostly 0 to -4c.

Bt T240 positive uppers in the south!

http://www.meteociel...0-240.GIF?07-12

Still feeling cool but clear the real cold is moving back north.

You may wish to see my post below

The uppers from a continental flow make very little difference to conditions at the surface, and as long as they remain sub zero they are conducive of snowfall

Yes landfall of the 0c isotherm @ 240 I will grant you...but it wasn't 240 that was being quoted

SK

[Duane S.]

Model watching is a waste of time we just look at good charts then are let down! Won't be on here until something comes into the 24h charts that is even remotely interesting.

1. How do you know these charts are right?

2. What exactly is so bad about the 00zs?

3. You will post again about model output outside 24 hours. Fact.

Charts looking fine to me still. We have SW activity popping up in the usual area, IF it occurs it could stop any extreme version occuring but we are still looking at a very cold spell of weather, nothing has changed in that respect this morning.

[Craigers]

like people have said, 2010 cold spell had a similar situation where the gfs has been so consistent then dropped the idea out to T96 until it changed back to its consistant runs 2 days after. ECM did this quite a few times during the 2010 event!

wait for the 12z and tonight's charts before expecting more downgrades!

[Snowy Easterlies]

Well that's not really correct is it as I just demonstrated in my previous post.

It's never as clear cut as -6c uppers from the east for snow. I went in to some detail about this a couple of nights ago but when you see the blues on the 500mb charts, that means the corresponding pressure heights are much closer to the surface. Where as usually minus ) 850 's are required to ensure the atmosphere is cold enough from cloud to surface for snow, this is not the case with a shallow flow from a freezing continent.

Anyway, small details in FI at the moment, and that's something I'm sure we can both agree isn't worth the speculation based upon one op run

SK

i don't really want to speculate on "potential" at T216 yet again, nobody knows what will happen then but that chart clearly shows the atlantic winning, and when i said milder i meant too mild for snow i didn't mean milder as in 13c plus the winds are coming from the south at 216 not from germany

i won't be suckered into potential at 216, nobody seems to be talking about the downgrade in the shorter term with the easterly, esp the GFS which removes a lot of the blocking

Edited December 7, 2012 by Snowy Easterlies

[IDO]

You may wish to see my post below

The uppers from a continental flow make very little difference to conditions at the surface, and as long as they remain sub zero they are conducive of snowfall

Yes landfall of the 0c isotherm @ 240 I will grant you...but it wasn't 240 that was being quoted

SK

Yes, I agree, just looking at the pattern not the micro outcome, as snow is almost a law of its own. The trend is for the cold to migrate north and that in turn reduces the chances of snow per se. In any case all in the air. It is clear that we will have no idea till maybe Tuesday next week of how this will unfold and therefore still time for upgrades.

[benb]

Right can I ask what is actually being shown on this mornings models in real terms without imbyism? I am reading these posts from this morning and where one post says looks great the other says downgrade then another says not too bad then another says another downgrade.......from what I can see or read there's hasn't been a major downgrade I was expecting sw'erly winds and +10 temps after some of these posts!

The forecasts this morning show a very cold week next week, probable minus double figure frosts at night followed by possibility of widespread frontal snow event from Friday onwards... although much of that is speculative at this stage.

[snow drift]

i don't really want to speculate on "potential" at T216 yet again, nobody knows what will happen then but that chart clearly shows the atlantic winning, and when i said milder i meant too mild for snow i didn't mean milder as in 13c

i won't be suckered into potential at 216, nobody seems to be talking about the downgrade in the shorter term with the easterly, esp the GFS which removes a lot of the blocking

IB has. As he says, it is to do with ste SW coming out of Norway. This was only picked up by the output in the last 12 hours. It may still be there in 12 hours time but would you bet against it being gone?

[Iceberg]

Have to admit I've been pretty disappointed wrt some of the comments on here won't say which ones but it was an effort at times to read through some posts that were only really interested in wind ups. Hope the mods can do something about it.

Precip only at 72hrs and below general patterns from 72-144 and only general trends backed up with ens and cross model support t144 and beyond.

Quite why some expected the exact tightness of the isobars on a model run 5 days away to stay the same is beyond me, but they are probably the people who counted the thickness of the snow that they would bring.

Good agreement on the start of the easterly still.

Some differences re the sw and the ability of the low to move westwards, but to counter this a strong high in the reliable medium range.

Generally too model agreement that the cold is still in place to t200 or so and still agreement on the chance of a snowy break down.

As things get more and more into the t72 region I am sure they will change and more chances for snow et will crop up in the cold to very cold air.

Remember its at this time free t72 to t120 that gfs in particular likes to discover a new shortwave/trough and over play it, before down playing it agin in later runs.

[Snowy Easterlies]

IB has. As he says, it is to do with ste SW coming out of Norway. This was only picked up by the output in the last 12 hours. It may still be there in 12 hours time but would you bet against it being gone?

i have no idea and won't answer that question, but i want to hear from a level headed poster and not from the blind faith brigade because even though i sound negative the clear fact is the GFS in particular is a downgrade in the shorter term and mid term with the blocking and easterly, i refuse to talk about next weekend and beyond now, im only interested in early to mid next week's easterly if there will be one

the ECM and UKMO give some sort of easterly but even they have toned it down a little, anyway best wait for more runs before i get too downbeat but im not getting my hopes up

Edited December 7, 2012 by Snowy Easterlies

[80sWeather]

Have to admit I've been pretty disappointed wrt some of the comments on here won't say which ones but it was an effort at times to read through some posts that were only really interested in wind ups. Hope the mods can do something about it.

Precip only at 72hrs and below general patterns from 72-144 and only general trends backed up with ens and cross model support t144 and beyond.

Quite why some expected the exact tightness of the isobars on a model run 5 days away to stay the same is beyond me, but they are probably the people who counted the thickness of the snow that they would bring.

Good agreement on the start of the easterly still.

Some differences re the sw and the ability of the low to move westwards, but to counter this a strong high in the reliable medium range.

Generally too model agreement that the cold is still in place to t200 or so and still agreement on the chance of a snowy break down.

As things get more and more into the t72 region I am sure they will change and more chances for snow et will crop up in the cold to very cold air.

Remember its at this time free t72 to t120 that gfs in particular likes to discover a new shortwave/trough and over play it, before down playing it agin in later runs.

Best post of the day so far,just what we needed to hear.

Get the cold 1st,the snow will come.