Model Output Discussion - January 12th.

[kold weather]

Looks like the NOAA maps follow quite close to the ECM, perhaps a little less agressive with the upper troigh near the UK and same witrh the upper high but the general trend is probably closest to the ECM.

[Geordiesnow]

A few more promising signs from the ECM in particular to break up the PV or at least push it westwards towards Hudson Bay as per what the NOAA report stated yesterday, does not mean its right though or a proper cold spell is on its way but its encouraging too see nonetheless.

In terms of performance wise, then you would have to back the ECM but as per ever you can't rule out what the GFS has been showing fairly consistancy which is keep the PV over Greenland and gradually move any block well to the East. We'll see what the 18Z shows though.

Whatever the doubt, people should not read the charts at face value, its about breaking the PV up and getting proper height rises towards Greenland whichever way possible and work from there so whilst the lack of cold could be a concern as it has been all winter on our side of the Arctic, it doesnt really matter at this stage.

[Tom Montalbano]

A consistent picture from the NOAA maps with troughing over the UK and positive anomaly well to the west:

http://www.cpc.ncep....y/814day.03.gif

The PV located north of Hudson Bay.

This has been the same for several days now, lets hope the GFS operational run does the right thing.

Hi Nick,

That looks pretty close to the 12z ECM mean at t240.

http://www.wetterzentrale.de/pics/Reem2401.gif

Regards,

Tom

[Paul T]

A massive clue to forecasting potentially (very) cold weather arriving to the UK does lie in the ensembles.

Using the GFS's 850's GFS ensembles from early Dec 2010, you can see that they had a mean line that confidently sat at around or below -5oC from DAY 6 ONWARDS.

The current ensembles for London, as posted here below by Mulzy, are starting to hint at this consistent -5 850 temp. This, for me, is a very clear indicator of what is to come. And to think the GFS is the poorest 'cold scenario' model at present!

All will change for the 18z GFS, mark my words; it may even swing from the poorest model, to the best output of the day.

GEFS parallel ensembles much better than previously...

http://www.meteociel...=1&type=0&ext=1

[SMU]

http://www.knmi.nl/e...agse/index.html

Long ECM ensembles paint a SOLID picture with the mean hovering just over Zero-2c after the low passes through SEwards- PERHAPS some of the slightly warmer ones have the low in the channel & the UK just squeezing the cold air-

The LONDON ECm ensembles tonight I suspect the mean to drop to around 3c-

Another rollercoaster day- but are we beginning see a more consistent pattern emerging with Greenland heights on the increase ( yes we want that ridge)!!

Also of good news that noone has chirped up about is the ECM brings a easterly flow in with some very low heights & unstable air- so you can bet there will plenty of deep convection across the North sea!

18 GFS up & running- dont look for the full ECM solution but a trend towards a SE tracking jet at 140 with a bigger wave in amplification at 160 over the NW atlantic-

Hey Nick that NOAA MAP- Im sure you just edit the dates & copy + paste the same image every day!!!

PS the GEFS ensembles are a league better than the GFS ones & inline with the ECM-

S

Edited January 12, 2012 by Steve Murr

[nick sussex]

Even better than the NOAA map, in terms of synoptic detail is this which is made by the duty forecaster and done very much like our UKMO fax charts, this is for the USA and Canada at day 7:

http://www.hpc.ncep.noaa.gov/medr/day7nav.html

Compare that with the ECM:

http://www.meteociel.fr/modeles/ecmwf.php?ech=168&mode=1&map=1&archive=0

GFS:

http://www.meteociel.fr/modeles/gfse_cartes.php?&ech=168&mode=0&carte=1

That map looks very similar to the ECM operational output.

Lets hope thats a good sign!

[SP1986]

I wouldn't be surprised if the 18z leaned a little towards the ECM but not all the way, perhaps incorporating little bits of the ECM and UKMO such as the increase in height over eastern Greenland, I wouldn't expect to see anything like an easterly although the chances are of course heightened. Should be an interesting output, synoptically speaking.

[Jason T]

Hopefully people won't react to much whatever the 18z shows, we know it's unreliability and propensity for going off at tangents.

The 0z runs are much more important.

Why not Ian,The 18z could be the start of the agreement for the GFS, As most of its previous runs became unreliable.

[peterf]

good point,time will tell as always.

[Rocheydub]

Because historically it's the most unreliable run. Bias excluded!

[Catacol]

Hopefully people won't react to much whatever the 18z shows, we know it's unreliability and propensity for going off at tangents.

The 0z runs are much more important.

I thought, according to Steve M, that the 00 GFS verification stats were running in 5th behind the GEM?

[lorenzo]

Hopefully people won't react to much whatever the 18z shows, we know it's unreliability and propensity for going off at tangents.

The 0z runs are much more important.

If the 18z shows a verfied GH or an undercut slider low then I apologise if I go off at tangent. Lake effect snow for the North Sea SM, sounds a lot like Xmas 10.

[Snowmadsam]

If the 18z shows a verfied GH or an undercut slider low then I apologise if I go off at tangent. Lake effect snow for the North Sea SM, sounds a lot like Xmas 10.

How can you tell a verified GH? Hoping for that :lol: fingers crossed for both runs

[Cloud 10]

18z +84hrs,strange triangular shape to the polar vortex.

Lets hope the jet tries a different angle later in the run.

[BLAST FROM THE PAST]

T96, very very subtle difference over Svalbard. 12z has a eastward 'bump' 18z has S to N tramlines. May be nothing at all, but Svalbard is important region and also it changes the shape and angle of approach of the arctic HP.

BFTP

[Rocheydub]

Just saw this BFTP. Interesting, yet insignificant at the moment... Please God the shift gets momentum!!!

[SP1986]

Looking at the GFS development, I think we may see the GFS respond towards the ECM, but not fully perhaps, the setup, perhaps, does seem to be looking like the UKMO/ECM at this stage, just south of the PV. I might well have called that prematurely though, we'll see.

[BLAST FROM THE PAST]

Looking at the GFS development, I think we may see the GFS respond towards the ECM, but not fully perhaps, the setup, perhaps, does seem to be looking like the UKMO/ECM at this stage, just south of the PV. I might well have called that prematurely though, we'll see.

Agreed, T132 looks a tad more like it although very subtle difference, so maybe not but we are close to seeing if it heads towards ECM/UKMO.

Looking at 150 and its a no I reckon.

BFTP

Edited January 12, 2012 by BLAST FROM THE PAST

[damianslaw]

One thing the GFS and ECM both agree on today is the building of heights over the mid atlantic later next week with a propensity for these to build northwards towards Greenland - whilst GFS today may seem to be offering less support for colder weather, in my eyes it is only suggesting a few days of milder atlantic weather and the overall set up is still for a colder evolution later in January it would just take a bit longer for it to verify than ECM is showing.

The 500mb flow forecasts is for an airflow between west and north, not west and south and this has been consistent for many days now, this doesn't support a SW-NE tilting jet with low heights crashing northwestwards into north scandi, what it supports is NW-SE tilting jet with the trough forced on a SE path deep into central europe - we are already seeing this signal now, look how the euro trough is about to get stuck in central/se europe - this is something we haven't seen all winter,

Yes ECM today is showing a superb quick evolution to much colder and very likely snowy weather later next week, whilst I do feel the overall evolution being shown will eventually occur, I think it is being slightly too progressive and we will more likely see a cold shot from the NW first as mid atlantic heights take a bit longer to ridge into south greenland, but by the last week of January they will do and then the floodgates are open for the northeasterly blast as heights over southern greenland are able to link with those heights over NW Russia - which will have been lurking ominously just waiting to say 'hello'.

The building blocks to a much colder period of weather have started at long last I hear some say, but a bit more patience is needed before that colder period arrives - but who knows ECM may be right with their timing.

[davehsug]

It would actually be more typical of the GFS, if it not only moved towards the ECM, but went WAAAAY past it & showed an ice-age. It just always seems to over-react to minor signals. There never seems to be a middle way with the GFS.

[DAVID SNOW]

Agreed, T132 looks a tad more like it although very subtle difference, so maybe not but we are close to seeing if it heads towards ECM/UKMO.

18z starting to map the Arctic high,probably a good run in low res.

[ITSY]

18Z no different to 12Z in the grand schemes of things i feel

[Geordiesnow]

It would actually be more typical of the GFS, if it not only moved towards the ECM, but went WAAAAY past it & showed an ice-age. It just always seems to over-react to minor signals. There never seems to be a middle way with the GFS.

Well its unlikely there be any iceages on this run and even if a cold set up did set up, where is the cold? You can see the differences on the upper air temp maps of the lack of cold on the GFS one and the better(but still fairly poor) ECM one.

GFS sticking to its guns, no reason why it can't be wrong tbh but at least in terms of the Arctic pattern it did at one stage looked like it could break the PV up post 144 hours.

[on the coast]

18z having none of the UKMO or ECM? Interesting watching the morning runs.

[lorenzo]

132 on the 18z for me is the bit where GFS gets confused a complete mess on the eastern side of the migrating PV. After that .. who knows what it will serve up.