Model Output Discussion 23/11/2012 18Z onwards

[PubliusEnigma]

http://www.wetterzentrale.de/pics/Rtavn2881.png

GFS 6z seems to want to bring in a milder option with south westerlies and a deep Atlantic Depression to the NW

of Scotland, little more than 10 days out.. Big disagreement between GFS and ECM.

The following chart shows a dartboard Low over scotland with damaging winds, and the jet starting to flatten out

across the atlantic

http://www.wetterzentrale.de/pics/Rtavn3001.png

More output needed to see which of the two will be nearer the mark.

[PubliusEnigma]

I have to say Steve I don't agree that the 06z is the worst performing model but rather than arguing can we put it to the test today.

Right, it has developed the shortwave to our West further and delayed any potential cold and is miles away from what the UKMO is showing.

So let's all hold fire until the 12's come out and (ignoring ECM for the moment) let's see which model backsdown the UKMO or the gfs?

I'm sure if the UKMO proves correct we will all be delighted and jump on the bandwagon that the 06z run is useless!

This afternoon at this time range one will have to backdown

Of course if the gfs does prove to be correct, let's be honest then too and say rather than being useless it actually spotted a trend.

My heart says ukmo will win this, my head knows it wont

Excellent post.. As an aside.. Ive never trusted Polar Anticyclone drifting SSW towards the Far North East Atlantic, to enable a link

up with the Azores High. I seem to recall a number of occasions in winter 2011 where this was progged to happen and the Arctic

or Polar High drifted off on more of an ESE or SE Direction towards the Siberian High, the Azores slowly sunk, ant the Short wave you've

mentioned brought a depression into the western parts of the British Isles and the cold snap melted away. It remained cold around 4 to 6oC

Lets compare the GFS evolution to that of UKMO.. Im sure many will be jumping through hoops if the UKMO keeps its bottle and it comes off.

UKMO imo is the difference between snow in many areas, to the ECM which offers snow in coastal districts in the north, and over high ground

in other areas, and the GFS solution which offers a wintry mix and windier outcome generally.

[bluearmy]

Guys guys, easy!

Remember November 2010, there was alot of chopping and changing all the way till the start of the cold spell. We had eye candy -15c uppers showing at one stage even in T140 with the gfs and then back to -5c in between runs with attempts of the Atlantic pushign back in FI. This was just bound to happen, we see great charts and expect them to keep showing up, but it just doesnt happen like that

was there isaac? i recall the models counted down like clockwork. ok the uppers may have varied as they always will, but the pattern was pretty solid from well into the T200's with variations on a theme and certainly no runs like we are seeing from time to time at the moment, especially gfs ops.

fwiw, the gefs are as varied as ever in fi. the mean only has an east siberian vortex to hang your hat on. the rest of the hemisphere is pretty well up for grabs.

[Liam J]

People should be able to give their humble opinion of what they think the weather will do without being attacked and labeled 'doomsaysers' or 'rampers' or whatever. If you think someone's forecast is wrong then explain why you think so, if someone is just trying to wind people up then ignore it. It'll be much calmer and saner here then.

The 06z GEFS ensemble mean vs the 00z has less cold air over us with it pushed further East.

06z

00z

At +192

Yes, and if we're looking for trends here then this continued back down cannot be totally confined to the bin imo despite the fact it might not be what many people want to see on this forum. The models are there to try and predict the weather (notice I said try) .... they don't control the weather.

[January Snowstorm]

Excellent post.. As an aside.. Ive never trusted Polar Anticyclone drifting SSW towards the Far North East Atlantic, to enable a link

up with the Azores High. I seem to recall a number of occasions in winter 2011 where this was progged to happen and the Arctic

or Polar High drifted off on more of an ESE or SE Direction

Indeed and you could add the previous 10 years to that too.

I often remember Nick Sussex mention the arctic high and how rare a beast it was

It often showed it's face but never it's teeth!

Just to add one huge positve we have today is the Met Office see this cold spell lasting right through December.

For me this is huge, more important than any model!

Edited November 24, 2012 by January Snowstorm

[lorenzo]

Cheer up folks everything will be just fine by the 12z.

The names Bom... James Bom.

[Chris W]

I haven't time to post charts etc. to back up my view, but I think most would say that over the past couple of weeks or so things have been trending towards a cold end of the month into early December and perhaps for this to continue after that. With the GFS and UKMO model outputs (plus some others) I have seen on average they do seem to be favouring blocking and a north/easterly flow with increasingly cold uppers and lower heights. Indeed this week the Met Office surface pressure charts have shown Atlantic high pressure ridging north to our west as per the GFS this week. Added to this the Met Office comments have gone from 'no strong signal but possibly below average' to 'below average with some wintry showers over hills' to even a little further than that so they seem pretty convinced by their modelling about a cold spell. I guess there is always the threat of westerly lows breaking through blocking, but overall it looks a pretty good overall setup for cold developing and as a cold fan I am pleased at that.

Thanks to all on here for their analysis and interpretation, reading through all of these (however qualitative) does help to form a balanced view of things. I will continue to read with interest.

[Frosty.]

The Gfs 06z offers little comfort for the devastating flooding across the uk, another huge area of torrential rain spreading north today and tonight, only slowly clearing to the northeast by mid afternoon tomorrow and then it's the turn of northern and eastern scotland to get a soaking although the rain becoming less intense by tomorrow afternoon, a small window of fine weather for the south tonight and into tomorrow but that soon gets slammed shut as another area of torrential rain spreads north and east, monday looks very wet in many areas with more flooding, temps also becoming cold away from the southeast early next week, low single digit maxima so on the higher ground it could be turning a touch wintry as colder air begins to dig south, some displaced moderate arctic air spreading south through scotland by midweek with the showers turning wintry up there with night frosts becoming more likely.

[Wadey]

Might be a silly question but I am new to charts how often do they come out ? And which ones come out when ? Cheers

[snowking]

One slight concern of mine at present would be the MJO forecasts:

http://www.cpc.ncep.noaa.gov/products/precip/CWlink/MJO/CLIVAR/clivar_wh.shtml

Many trending towards phases 1/2 now rather than 7/8/1, thought admitedly at a very weak amplitude.

Still this may explain some of the current projected location of troughing across Europe:

http://raleighwx.americanwx.com/MJO/NovemberPhase1500mb.gif

http://raleighwx.americanwx.com/MJO/DecemberPhase1500mb.gif

http://raleighwx.americanwx.com/MJO/NovemberPhase2500mb.gif

http://raleighwx.americanwx.com/MJO/DecemberPhase2500mb.gif

SK

[ISAAC]

was there isaac? i recall the models counted down like clockwork. ok the uppers may have varied as they always will, but the pattern was pretty solid from well into the T200's with variations on a theme and certainly no runs like we are seeing from time to time at the moment, especially gfs ops.

fwiw, the gefs are as varied as ever in fi. the mean only has an east siberian vortex to hang your hat on. the rest of the hemisphere is pretty well up for grabs.

The GFS was showing up slightly different synoptics around in T140-240 once every 2 or 3 runs as expected before nailing it with backing from the other big models but you are right that was more profound overall.

The issue here is it's only been the last 24 hours where we are seeing shift in trend with the ECM and most especially GFS.

[Buzz]

Might be a silly question but I am new to charts how often do they come out ? And which ones come out when ? Cheers

[Weathizard]

Ensembles are poor, very poor in fact but I'll give them the benefit of the doubt and await the 12z which is supposedly more accurate. Hopefully we get some agreement, mild or cold.

[SMU]

Yes, and if we're looking for trends here then this continued back down cannot be totally confined to the bin imo despite the fact it might not be what many people want to see on this forum. The models are there to try and predict the weather (notice I said try) .... they don't control the weather.

Sorry Liam- but its not a level playing field- If you were comparing a run with identical varification stats to another then it would hold weight, however you are comparing the top GFS run V the Worst GFS run-

Hence there is no trend- What your infact seeing is bigger inaccuracy.-

S

Edited November 24, 2012 by Steve Murr

[lorenzo]

Might be a silly question but I am new to charts how often do they come out ? And which ones come out when ? Cheers

Try here Wadey

[Paul]

Ensembles show the issue really - a variety of quite different solutions at 168 hours...

http://www.netweather.tv/index.cgi?action=ensviewer;type=panel;

[phil nw.]

Whilst the operational outputs continue to swing from run to run the 500hPa mean height anomalies shown by NAEF`s and the forecasted CPC patterns continue to look solid.

Temperatures on the Ens. graph continue on the slide.

close to zero by the new month.

The first week in the new setup although colder looks very marginal for widespread lowland snow but the current trend in the height anomalies is to gradually sink that euro trough in week2 which would enable a more direct feed from the east.

[bradymk]

Poor GFS 6z and ensembles however im not worried at all. Solid ECM Ensembles again and height anomalie charts like Phil shows above, a great UKMO, and the UKMO have said that the start of December is going to be "significantly colder than average" gives me alot of encouragement. Looking forward to 12z's

PS Ian on twitter - UKMO go for cold & blocked into at least 10-15d based on MOGREPS-15 & EC Monthly. They say the 'wobbles' typical in this scenario This is why we should not worry at this stage

Edited November 24, 2012 by bradythemole

[Frosty.]

Ensembles are poor

And yesterday they were great...GEFS 00Z mean looked very cold and very blocked out to T+300 hours, in the build up to the freeze of 2010 we had comments like yours as the freeze got closer, it's nothing new.

[Liam J]

Sorry Liam- but its not a level playing field- If you were comparing a run with identical varification stats to another then it would hold weight, however you are comparing the top GFS run V the Worst GFS run-

Hence there is no trend- What your infact seeing is bigger inaccuracy.-

S

Maybe so Steve, but the 6z run more or less followed the 00z wrt the PV & eastwards movement of the Atlantic.

Now if the worst GFS run offered some support to the best GFS daily run then surely it must be worth some thought, the GFS could well be onto something here? Lets wait for the 12z and hope things look completely different.

Edited November 24, 2012 by Liam J

[Weathizard]

Frosty I don't mean it in a negative way just a general comment for people hoping the 6z was a massive outlier, as I've said I still think we'll get a decent cold spell but think people saying 'bin' it ect is daft because you have to consider every run even if you don't like what it shows. Let's just hope the UKMO is right

[snowmadchrisuk]

Massive outlier on pressure in FI , Also Even in the South the Mean stays below 0 throughout the run which tells me there is a Cold spell coming ... I don't know if it's me but the GFS Op always seems to go on one at the Weekends only to look a lot better on Monday , that seems to have been happening for weeks now.

Edited November 24, 2012 by snowmadchrisuk

[AWD]

Massive outlier on pressure in FI

Looks like I will have to forget about this then;

http://cdn.nwstatic.co.uk/gfsimages/gfs.20121124/06/300/h500slp.png

:p

[SMU]

Maybe so Steve, but the 6z run more or less followed the 00z wrt the PV & eastwards movement of the Atlantic.

Now if the worst GFS run offered some support to the best GFS daily run then surely it must be worth some thought, the GFS could well be onto something here? Lets wait for the 12z and hope things look completely different.

HI Liam-

I was answering a similar question posted to me on TWO- around the GFS so I will copy it here-

Its hard to quantify & equate across to the pattern what exactly the deficit in scores means- We are seeing errors at day 7-

However after looking at the same old GFS for the last 8 years then in my mind the failings of the 06z mean.

No amplitude of any highs.

No undercutting patterns recognised.

No retrogression recognised.

Over estimating the speed of the jet.

As a result time & time again past 120- more particular 144 the 06Z GFS taints the pattern toward once of normailty.

You could say it has a 'normality bias!!'- as a result in these conditions the errors that creep in at day 5/6 & 7 will generally have amplified by so much post 192 is useless.

In situations like we have in front of us All it will do is become riddled with errors faster & of a bigger magnitude quicker-

The enembles are tricky, the probably dont have a large bias to do something stupid like the OP, but by the same token do still have the weakness on the patterns I highlighted- as a result they will mute out the signal for cold slowly but surely depsite a large height anomaly in the mid term-

S

Edited November 24, 2012 by Steve Murr

[cold snap]

ok newsflash .

Ive just sent ian fergerson a tweet (@markydub)

ukmo happy enough with a cold block outcome,and that other models are wobbling in these circumstances.

So dont worry.