Model Output Discussion 12z 04/12/2012

[chris55]

It isn't Chris because the energy is going North, milder air would get ahead of the PPN. You would need an Atlantic attack to be negatively tilted or at worst vertical to get widespread frontal snow.

Anyway, hopefully academic and not happening !

Yes Ian, that's my whole point, at day 10 these things are open to change, a tilt here or there, or a more favourable jet could change the conditions for our little patch.

[SnowObsessor90]

Perhaps those now deleted comments posted in strat thread the other day about the PV winding up putting us in a more zonal flow from mid month onwards shouldn't be totally dismissed after all, just a thought.......

[OldMetMan]

The models continue to tantalise us with the prospect of cold easterlies, and each day brings yet more variations on that theme.

Two things in particular are getting my attention today:

First, the position of both polar and sub-tropical jets across the Atlantic is pretty far south, with a particularly strong one across the Mediterranean - indicative of cyclonic activity continuing in the area:

The jet over Canada/USA is showing signs of strengthening in association with a broad upper low across Canada and seems likely to push NE eventually. Meanwhile, the LP that nearly became a sub-tropical LP is not playing much of a role in the current synoptic development, but according to some of the models, seems likely to be followed by a 2nd one, pushing NW.

Second, the models are showing very high pressure developing over N Russia - common enough this time of year - but the cooling in that part of the world is continuing apace (judging by the way the Russians were caught out by very heavy snow over the weekend, when they are supposedly well geared up to deal with, so it must be unusual).

So, as I see it, it could play out two ways - one, the HP will extend SW and W towards us with LP to our W pushing a upper ridge towards Greenland or two, HP will build W all the way to Greenland with LP activity well to the S of it's normal track.

We have seen this scenario before many times, but for it to stick, I think we need to see more noticeable signs of strong blocking developing which is only slight at the moment - but there nevertheless. Personally, I think the risk of easterlies in the next 2 weeks is high - mostly because the jet is far south - but we'll see how the models vary in the next few days.

[cooling climate]

Well that run did not pan out the way I thought it would. Probably just a operational

wobble.

The little details and orientation of the high still to be decided but a Scandi high and

a east,northeasterly airflow in about 6-8 days time is all but nailed now I think

[Lee Smith]

Iin the extended range we have a nice signature for mean jet flow displaced well to the south allowing stable blocking structures to take root.

Spreads at day 14 show little variability on a flat trajectory around the Med.

GEFS H5 mean height anomaly depicting a retrogressive signal:

Note in the last one the anomaly over the Arctic showing good agreement on shifting of the core pv towards Siberian sector.

is that good news stewart that the polar vortex is going to siberia

[Duane S.]

Should we trust the GEFS Ensembles? Of course we shouldn't. Should we sit up and listen when the 12z produces a set like that? Yes we should.

That said I'm not going to totally dismiss the ECM, it goes against the grain but stranger things have happened. I suspect it is showing the worst case scenio

[BARRY]

I dont post on here very much just read all the interseting comments. , but I came across this chart ..it shows high pressure to the east bringing a south easterly air flow, a long way off but the set up is there, what would this airflow bring just before christmass

I keep reading F1.. can you please explain what this means

It's FI not F1, it means fantasy island

[nick sussex]

Nick

wasn't there an exceptional cold pool at that locale that formed this SW?

BFTP

Yes you can see that here!

Now that is cold.

Regarding the ECM, the CPS sitting there does have a large bearing on the following output so if that shortwave at least clears even a couple of hundred miles further south this would alter the angle of Atlantic attack.

For the timebeing the ECM post 168hrs is meeting an untimely end in my model output shredder.

Due to being a SSO Suspicious Synoptic Outcome!

I seem to be suffering from an overdose of acronyms this evening!

Edited December 4, 2012 by nick sussex

[Frosty.]

Perhaps those now deleted comments posted in strat thread the other day about the PV winding up putting us in a more zonal flow from mid month onwards shouldn't be totally dismissed after all, just a thought.......

NOOOOOOO don't say that, Ii had just erased the mild zonal FI 6z and now it's back again

To be honest, if we don't get a cold blocked outlook after all this hype, it will be the biggest let down since that easterly the gfs showed for a solid week and then imploded it, I think it was christmas/new year 2005/6.

Edited December 4, 2012 by Frosty039

[Country Boy]

Formula One Gaz - car racing.

No, in all seriousness FI means fantasy island. Charts that can look amazing, but will never actually materialise.

Ha..Ha..thanks...F1, thats a chart to get the hart racing then.

Fantasy Island, ...Funny that is the dream I have every night.

Thanks again...

[snowking]

It might be worth remembering that the ECM often has an Eastern bias, in 2010 it placed everything too far East, given the background signals for blocking I'd expect to see the pattern corrected Westwards placing the UK under the cold air and pushing the Atlantic back.

The 12z GFS Ensembles have gone COLD

Dan

I'm at work at the moment on a phone so I can't look myself

Are you able to find the archive charts to support that? I posted some yesterday evening regarding a very similar eastern bias for last feb...if you can find another example then we are starting to build a bit of a warchest and it could be useful going forward to find any such bias in particular scenarios (ie easterlies)

Cheers

SK

[GoonerGregg77]

NOOOOOOO don't say that, Ii had just erased the mild zonal FI 6z and now it's back again

To be honest, if we don't get a cold blocked outlook after all this hype, it will be the biggest let down since that easterly the gfs showed for a solid week and then imploded it, I think it was christmas/new year 2005.

Remember that 'Let down' well, if indeed I am right from 2005, it was around that time anytime. From what I remember, didn't we have a slack easterly flow for a good few weeks, and ended up with endless dry days whilst countries like Germany was hammered with snow? I also remember a roof of a school caving in from it all! Was so dissapointing.

[chris55]

NOOOOOOO don't say that, Ii had just erased the mild zonal FI 6z and now it's back again

To be honest, if we don't get a cold blocked outlook after all this hype, it will be the biggest let down since that easterly the gfs showed for a solid week and then imploded it, I think it was christmas/new year 2005.

No it wont, it's all conjecture to be honest, forecasting beyond day 5 is not an exact science, if we move to a mild pattern then so be it.

A conjecture is a proposition that is unproven, all model output and professional opinion is unproven when it comes to weather forecasting, it's the very essence of model watching.

If my car is stolen, then I would feel let down by that, as I know 100% that I own it. We don't know anything is 100% in weather terms.

Edited December 4, 2012 by chris55

[Frosty.]

Remember that 'Let down' well, if indeed I am right from 2005, it was around that time anytime. From what I remember, didn't we have a slack easterly flow for a good few weeks, and ended up with endless dry days whilst countries like Germany was hammered with snow? I also remember a roof of a school caving in from it all! Was so dissapointing.

Yes Gregg that's what we ended up with after the gfs was showing january 1987 type riches, it went down like a lead balloon. The trend to a cold blocked outlook is still intact but the models are just showing different routes to get there, at some point they will have to merge if this is really going to happen but the golden potential is still beyond T+168 which is a dodgy timeframe to pin much hope on.

[Mark Bayley]

I wouldn't worry to much about the longer range ECM. The mean ensembles from earlier today would cast some doubt on the extent of the PV that it ramps up over on the western side of the arctic.

http://www.meteociel...H1-240.GIF?04-0

Strong support for heights to the north east extending towards Greenland

And below average 850mb temps

Edited December 4, 2012 by Mark Bayley

[Frosty.]

No it wont, it's all conjecture to be honest, forecasting beyond day 5 is not an exact science, if we move to a mild pattern then so be it.

A conjecture is a proposition that is unproven, all model output and professional opinion is unproven when it comes to weather forecasting, it's the very essence of model watching.

If my car is stolen, then I would feel let down by that, as I know 100% that I own it. We don't know anything is 100% in weather terms.

true, the weather will do what it wants, not what we want. Model runs have no feelings for our feelings.

[karlos1983]

Liking this chart from JMA, more tonight please from GFS to put a bit of confidence back into Forum, then hopefully the UKMO can also get more in line.

http://www.meteociel.fr/modeles/jma.php?ech=192&mode=1

[Gibby]

Good evening. Here is the evening report on the 12z outputs from GFS, UKMO, GEM and ECM for tonight Tuesday December 4th 2012.

All models continue to show an agreed pattern to the course of events between now and Monday. An occlusion moving steadily South over the UK will bring a mix of rain, sleet and hill snow overnight, reaching Southern England by morning. Following on behind a slack North flow will push the occlusion away South tomorrow morning and give many areas a dry cold end to the day with some snow showers near Eastern coasts as a ridge of High pressure brings a very cold night with a severe frost tomorrow night. On Thursday Low pressure will slip SE over Scotland and down the North Sea towards the SE on Friday. Rain and hill snow spreads SE through all areas on Thursday followed by a cold and windy day on Friday with rain and sleet clearing South to leave snow showers for many Northern and Eastern areas through Friday. The weekend then sees High pressure building rapidly from the West bringing cold, crisp weather with frosty nights with some increase of cloud over the extreme West and North later as the High pulls away slowly SE.

GFS then shows the early part of next week with the UK under slack and relatively high pressure. The weather would be relatively dry with frost and fog by night, chiefly in the South. Through the week the trend is for progressively colder air to drift West from Europe with dry conditions still with broken cloud and some weak wiintry sunshine, especially in the West. Later in the week the breeze increases with a bitter feel and the trend for some wintry showers of sleet and snow or snow grains increases towards the East and South. A breakdown is shown in the latter part of FI with a messy transition of snow and sleet followed by rain and much milder conditions pushing up from the South.

The GFS Ensembles show good prospects for cold lovers this evening with uppers well below the long term mean throughout over the UK. Some very cold members are being shown tonight with -10C breached by several members later on. With very few mild options shown it is a big step back from the somewhat disapponting sets we were seeing earlier. There is some precipitation about too at times with no doubt some of that falling as snow in places.

The Jet Stream shows that the UK lies as the target for the South-eastwards moving flow for some considerable time as it moves down to Southern Europe where it continues East. later next week it ridge High over the Atlantic and crosses East to the North of the UK before turning SW from Scandinavia to the UK and South to Spain.

UKMO for Midday on Monday shows High pressure over Northern France with slack Low pressure over Scandinavia, moving SE slowly. Fine and dry weather would be likely for many with cloud and drizzle to the far West and NW. It would be rather cold in the South with some frost and fog at night.

ECM shows not such a pretty picture for those wanting snow but shows a messy transition from rather cold and dry conditions early next week into what would be a rapid change into a cold Easterly flow were it not for a stubborn small but significant Low cell near Denmark preventing a quick link from the UK High to the Northern European High. Nevertheless, it does show a dveloping and cold SE flow towards the end of its run before the cold is thwarted by a large and powerful depression out to the NW pushing warmer Atlantic winds in towards Southern and Western Britain.

In Summary things have taken an upturn for cold lovers this evening. GFS has returned to its former opinions of bringing a cold East flow into the UK in a week or so. However, as always there is a fly in the ointment in the shape of ECM tonight where it refuses to show the Low to the East slipping SE which in turn prevents the vital feed from the East to the UK. Consequently the Atlantic power horse looks very active late in its run and will attempt at least to break the block down around the UK with the usual messy mix of snow and rain. We will need to see where this solution lies in the ensembles later with the GFS ones very favourable tonight. So the period of fascinating model watching continues with many more instalments of upgrades and downgrades to be endured over the days to come.

[Tomj211093]

Can we please stop looking into Fi and have some news about this thirsday and Friday!!!! Snowfall wise

Edited December 4, 2012 by Tomj211093

[SouthPennine88]

Look at the above post, Tom.

Edited December 4, 2012 by SouthPennine88

[karlos1983]

Can we please stop looking into Fi and have some news about this thirsday and Friday!!!! Snowfall wise

This is the model discussion? The models go all the way to FI, they shall therefore be discussed.

[Stuie]

The Jet Stream shows that the UK lies as the target for the South-eastwards moving flow for some considerable time as it moves down to Southern Europe where it continues East. later next week it ridge High over the Atlantic and crosses East to the North of the UK before turning SW from Scandinavia to the UK and South to Spain.

Hmm to me, with all my knowledge (sarcasm), this will introduce "warmer" air than we are having currently?

[BLAST FROM THE PAST]

Hmm to me, with all my knowledge (sarcasm), this will introduce "warmer" air than we are having currently?

No, Gibby is describing a cold pattern

BFTP

[Ice BIast]

Well the ECM ENS mean at T168 looks a bit better than the operational - a bit further west.

Edited December 4, 2012 by lce Blast

[Stuie]

No, Gibby is describing a cold pattern

BFTP

Ah ok. Always thought being under the JS meant warmer but I suppose with all other aspects that is not true. Thanks mate.