Model Output - General Discussion

[Northernlights]

I was wondering having looked at some of the predicted charts for the weekend of the 19th /20th December whether they bear any resemblance to the pre Christmas blizard of 1973 in the North of Scotland when the side roads round here had to be opened using a snow blower or is this not so severe looking?. When I mentioned this a couple of years ago Tom SE20 kindly dug out the archived chats and posted them for me to look at.

[Snowaddict]

With Regard To The Easterly:

12Z Ensemble Analysis:

AT T+102 & Onwards...

Perturbation 2, 3, 4, 5, 7, 8, 10, 11, 13, 14, 15, 16, 20...

That's 65% confidence in the Ensembles for a potent (850's of -8 to -13 or -14 showing) easterly across the British Isles @ T+102 and onwards.

Even other perturbations have slightly less cold air or less westward advection, but still opportunities for snowfall.

That's VERY high confidence in a potent easterly from the 12Z GEFS suite..

[TEITS]

May I make a suggestion to prevent any bickering on this thread.

Due to the synoptic pattern at the end of the week there are bound to be cases where a model run might be a downgrade for your region but an upgrade for others.

With this in mind if you feel the latest model run is a downgrade please state whether you're referring to your location or the whole of the UK. This will helps others who might be confused.

[cooling climate]

The gfs still looks like its not going with the euros, that aside the ukmo if you're looking for a sustained colder spell is excellent, any low that heads south from the north is likely to interact with low pressure to the south of the uk , in the ukmo shown over the med, because of this we dont want the low heading south too far west, this happens with the gfs and could lead to a complex feature eventually pushing a milder flow in from the south.

Lets hope the ecm sides with the ukmo here, in these situations theres low margin for error, you want the Scandi trough close to the east but not sitting over the uk.

I think the GFS has back tracked towards the ECM in regards the post 144 mark, but as you say the main difference remaining is the more westerly position of the low from the GFS coming down from the north.

If the UKMO is correct and the ECM 12z backs up this mornings runs then we could well be in for a very prolonged cold spell.

Plenty going on in the near term to be more than happy with.

The runs today are excellent.

Edited December 13, 2009 by cooling climate

[Cloud 10]

Some classic synoptic charts from the ukmo this evening,an easterly followed by a northerly,and looking pretty potent ones as well.

A high octane week of model watching coming up.

[BLAST FROM THE PAST]

Looking at the 12z - It seems to be gearing up for more energy in the southern stream- hence the lower heights to the East & a better flow- however its being VERY VERY progressive on the Greenland jet V the 06z

this will be a better run- but the cold cuts off to soon- due to the abive reason-

Steve

Hi Steve, interesting projection by the 12z GFS, look at deep FI with further LPs to pile in on southerly track. Below were my thoughts I posted back on the 10th. I think it will turn mild for Christmas and i like what the 12z shows because that screams a further reload of cold arctic air flooding in behind any stormy period. I think mild for Christmas becoming increasingly stormy as we approach the New Year and a very wintry January to kick in. If the 00Z ECM verifies then the cold isn't going anywhere even in deep FI.

Post 10 Dec re my thoughts.

One has to look at if the ECM did/has backtracked? Becauuse it was the FI that was changing really, it is only looking like it did a few days ago but in nearer time. My view is that [even the ECM] is showing cold weather but the armaggeddon is wrong. Cold to very cold week to 10 days but mild breaking through...and in time for Christmas. The reason being that the cold signal in my view is just that...a 7-10 day period. I am not convinced this is the real deal yet but a big shot across the boughs......but it may be as it looks like being one of those winters.

This post was made before the ECM jumped spectacularly back on board, and it seems in no mood to shift....that could be significant adn shouldn't be taken lightly.

BFTP

[nick sussex]

I think the GFS has back tracked towards the ECM in regards the post 144 mark, but as you say the main difference remaining is the more westerly position of the low from the GFS coming down from the north.

If the UKMO is correct and the ECM 12z backs up this mornings runs then we could well be in for a very prolonged cold spell.

Plenty going on in the near term to be more than happy with.

The runs today are excellent.

I'd say as much as this we have a great chance for an extended colder spell with the ukmo and gem so far, the gfs would likely lead to the cold ending before Xmas, IMO this is actually of more interest than the easterly simply because it could well lock the cold in for a considerable time, for me the ecm is awaited as the most significant model output of recent years.

Of course that doesn't mean we won't see further changes and thats not to say it would verify but we want a good trend and we want the ecm to say absolutely no deal to the gfs.

[dallas]

Latest runs seems to have the cold arrivng quicker for my area, still cant beleive we have great model runs and its only December!

[Thundery wintry showers]

I was wondering having looked at some of the predicted charts for the weekend of the 19th /20th December whether they bear any resemblance to the pre Christmas blizard of 1973 in the North of Scotland when the side roads round here had to be opened using a snow blower or is this not so severe looking?. When I mentioned this a couple of years ago Tom SE20 kindly dug out the archived chats and posted them for me to look at.

There was less of a pronounced Greenland High and the jet was further north, so the coldest air struggled to establish over England & Wales and the mild air swept north to all parts by the 21st. Certainly a snowy-looking spell for Scotland though:

http://www.wetterzentrale.de/archive/ra/1973/Rrea00119731217.gif

http://www.wetterzentrale.de/archive/ra/1973/Rrea00119731218.gif

http://www.wetterzentrale.de/archive/ra/1973/Rrea00119731219.gif

http://www.wetterzentrale.de/archive/ra/1973/Rrea00119731220.gif

http://www.wetterzentrale.de/archive/ra/1973/Rrea00119731221.gif

[Paul]

Hi all, thanks to every one for keeping the off topic stuff to a minimum so far tonight, for those who haven't seen it yet, we have 3 model threads on the go (plus a general chat thread), please have a read of this thread prior to posting so you know which thread your post needs to go into:

http://forum.netweather.tv/topic/58023-winter-topics-please-read/

Don't forget too that the free chart viewer is available here with all the major models available:

http://www.netweather.tv/index.cgi?action=nwdc;sess=

[Frosty.]

A really promising ukmo 12z, an E'ly by T+96 hours across many areas and a potent looking N'ly blasting south by T+144, still time for the wheels to come flying off but it's less likely to fail now. A very wintry GFS 12z with the cold lingering in the north until Boxing Day and never really turning milder across scotland at all, it does become milder in the south but there is lots of uncertaintly as to whether it will become milder at all, the cold blocking might hold on until later, much as the 06z run showed. All attention now switches to the ecm 12z...can it avoid significant downgrades and keep the uk on a collision course with potentially the most severe wintry spell for several years.

Edited December 13, 2009 by Frosty039

[phil nw.]

The gfs still looks like its not going with the euros, that aside the ukmo if you're looking for a sustained colder spell is excellent, any low that heads south from the north is likely to interact with low pressure to the south of the uk , in the ukmo shown over the med, because of this we dont want the low heading south too far west, this happens with the gfs and could lead to a complex feature eventually pushing a milder flow in from the south.

Lets hope the ecm sides with the ukmo here, in these situations theres low margin for error, you want the Scandi trough close to the east but not sitting over the uk.

The gem backs the ukmo at 144hrs, heres the gfs and gem viewed all the way upstream to the USA also see how much further west the low is on the gfs.

GFS

http://moe.met.fsu.e...sure&hour=144hr

GEM

http://moe.met.fsu.e...sure&hour=144hr

Start praying that the ecm sides with the ukmo and gem, we want the gfs to be completely wrong here.

A good post Nick showing the wider view beyond the current focus of the severity of our Easterly.

The GEM,UKMO, whilst promising for extending the cold spell we want the 00z ECM to validate for perfection i think.

http://www.meteociel.fr/modeles/ecmwf/run/ECH1-168.GIF?13-12

Great position of the Vortex over Scandi. and with jet well South.

Model viewing is so enticing at the minute Nick,like reading a good thriller,you can`t stop looking.

[MKN]

For those people mentioning polar lows, they cant be forecast far in advance, normally inside 36hours. http://en.wikipedia.org/wiki/Polar_low To say we have one due next week means your either a very good forcaster or need to read up on them.

[snowmadchrisuk]

Latest runs seems to have the cold arrivng quicker for my area, still cant beleive we have great model runs and its only December!

The 12z is a massive upgrade for Tuesday in the Midlands, Net weather forecasts have a max of 0 , heavy ppn 525 dam and the little icons actually forecast snow. Wednesday is showing as an ice day with temps below freezing all day . Very impressed with the short term potential .

Chris

Edited December 13, 2009 by snowmadchrisuk

[nick sussex]

A good post Nick showing the wider view beyond the current focus of the severity of our Easterly.

The GEM,UKMO, whilst promising for extending the cold spell we want the 00z ECM to validate for perfection i think.

http://www.meteociel.fr/modeles/ecmwf/run/ECH1-168.GIF?13-12

Great position of the Vortex over Scandi. and with jet well South.

Model viewing is so enticing at the minute Nick,like reading a good thriller,you can`t stop looking.

Thanks Phil

I agree but it's just too nerve shredding! Unfortunately i won't be around for the ecm 12hrs so will have to catch up with this later, i don't want to overplay the significance of the ecm tonight but this is a great chance for the UK to get something not seen for years, especially also as it's coming at the right time and not the end of winter where recent colder spells have occured.

Of course regardless of what the ecm does the next model thriller is just developing and there are likely to be more changes over the coming days.

[Duane S.]

I posted last night with my thoughts from inside info from a good friend and exactly what he said so far has come true. I am not to sure as off why a few was slating the ECM this morning and favouring the GFS. The ECM sorted the flip episode 3 days ago and has remained constant ever since while the GFS up until three days ago was consistent they both swapped places by the looks off things i did get information passed on to me saying the GFS will come in line by possibly tonight's pub run if not tomorrow and looking at the two GFS runs today they seem to be edging closer and closer with the ECM. Plenty to be ecstatic over i know i am.

This is good point. The ECMWF, in my opinion (and some others), had some sort of particular issue the other day which led it produce those two awful runs. Other than that, on the whole, it has been its normal consistent self.

Great METO charts once more (seriously Neil South, you need to spend longer viewing the charts before commenting I think).

GFS heading a tad more towars the Euros again after the 06z earlier on.

I expect to see the ECM follow on with another good (but probably not quite as) as the 00z this morning.

All good folks, all good.

[snowmadchrisuk]

Thanks Phil

I agree but it's just too nerve shredding! Unfortunately i won't be around for the ecm 12hrs so will have to catch up with this later, i don't want to overplay the significance of the ecm tonight but this is a great chance for the UK to get something not seen for years, especially also as it's coming at the right time and not the end of winter where recent colder spells have occured.

Of course regardless of what the ecm does the next model thriller is just developing and there are likely to be more changes over the coming days.

Nick the MJO looks like it is heading back to phase 4 . Is this likely to be a problem in having a sustained cold spell ?

Chris

[phil nw.]

'the classic possible a few days ago' ? I'm not sure about that, the models are firming up on the easterly and details of trough disruption etc.. will not be known closer to the time.

As for the general situation, the Greenland High could challenge the record 1060mb set in Dec 1981. I wouldn't be too concerned about the GFS plunging the trough to far West, it did this on many runs prior to the Feb event this year and it didn't happen.

Any breakdown is dependent on the jet behaviour over the US and how the AO signal goes, but for once we have the cold in the short to medium term and the milder weather in FI !

Yes Ian the Scandi trough`s positioning far enough East is what we need as Nick S. posted earlier,that`s if we are looking for an extension of the cold.

As suggested ECM has the better outlook at present.Here 00z mean height comp.

http://www.meteo.psu...0z/hgtcomp.html

Looking closely it can be seen the trough digs further South on the ECM and more likely to hold back any warm air approaching from the South West further on.

Edited December 13, 2009 by phil n.warks.

[BLAST FROM THE PAST]

Looking at posts as I've trying to catch up it looks as though the UKMO wobbled a bit as regards to depth of cold etc but I have to say the 12z is a stormer of a run.....bitterly cold for sure along with the ECM. With these two agreeing it is IMO significant BUT 7-10 days is along time ahead and GFS could verify...but that is really neither here nor there. What is important is the synoptic pattern despite El Nino which leads to the to its effect being controlled by cyclical patterns IMO. I think folk must be sitting up now and looking at this readiness for southerly jet pattern to take hold, as it has been showing its hand for 3 years now....and lots more to come. So serious cold blast.....we await you. Joe B is a happy man it seems!

BFTP

[Paul]

Reminder - model chat / mood thread for the more emotive, light hearted model discussion - just moved a number of posts in there..

[Snowyowl9]

Heres a good link I kept which I didn`t know I had, looks like the Iceland site -10upper air coming in anyway with a strong east/NE flow.

http://en.vedur.is/weather/forecasts/atlantic/#eg=temp&type=temp

Link doesn`t seem to work but is typed in properly as double checked,it`s also the 12z run.

Edit it does work.

Edited December 13, 2009 by Snowyowl9

[Duane S.]

I think folk must be sitting up now and looking at this readiness for southerly jet pattern to take hold, as it has been showing its hand for 3 years now....and lots more to come. So serious cold blast.....we await you. Joe B is a happy man it seems!

BFTP

At the risk of this going O/T can I just say I totally agree with that. Unfortunately one of the lynch pins of this 'christmas pudding' was that the PFJ would be heading further North than average. This has simply not been the case over the past few years (no blip), it is the absolute ease at which the jet over the past few years heads down towards Spain and below that has totally discredited the theory.

Here's comes the ECM, don't less us down now...

ps: Love what has been done to those two words above although it is a bit of an insult to Xmas puddings

Edited December 13, 2009 by s4lancia

[bluearmy]

ecm 12z is about 700 miles east of the 00z. bad news in the short term but should hold the atlantic back for longer - you dont think it might sink the block SE ala NOGAPS from a few days ago ??

[high ground birmingham]

I think something of note has been missed in the obsession to see if the easterly has 'upgraded' or 'downgraded' later in the week. If people have a look, the GFS 12z has upgraded the short term snow potential which is within the next 48 hours- as early as tomorrow night:

Having a look at the situation, we have an area of precipitation tommorow night moving off the North Sea, from the NE. It will probably start off as rain with 850s around -2 to -3. As the night goes on however we have an undercut of -5C 850s on the eastern side of the precipitation. Together with lowering DPs and temps on the eastern side, this will begin to turn to sleet and then snow by about 4-5am. This will then be pushed west by the strengthening easterly wind through Tues am.

In all the precipitation according to GFS 12z will turn readily to snow and thus there is the possibility of getting an 1-2 inch covering of snow throughout the Midlands, the south and east of Wales and into Central Southern England.

It is something to watch and it will be intriguing to see if it is still on the 18z. BUT what it does show us is that precipitation amounts can 'upgrade' closer to the event with new opportunities for snowfall simply springing up. So please do not get worried if the GFS is showing a lack of precipitation in the easterly because this will be firmed up much closer to the time within T24-T48.

Kind Regards, Mark

[bluearmy]

GFS trended to ecm through runs 06z and 12z. if ecm trends towards the centre ground, it should nt be a shock. i think posters should refer to the facts and not what they think they've seen thru the day.