Model Output Discussion - 18z - 25th Nov onward

[Zakos]

DO NOT BE TOOK IN BY THE DEFAULT GFS FI

Always has a zonal outlook, goes against every single teleconnection out there, high to our south east ??? Come on get reall gfs, no support long term whatsoever ever . Look forward to the 12z

I totally agree. GFS completely defaulting, goes against all logic and reason.

look how the Arctic high randomly dissapears as soon as the low res starts.Comical. I seriously dont understand why the GFS even goes out to 384 hours.

[Jonan92]

Just wondering if anyone can provide me with a link to the 00z as i was not about early to view be interesting to compare both between 00z & 06z between +90 & +150?

Thanks in advance

http://www.meteociel.fr/modeles/gfse_cartes.php

Choose activer live compare

[bluearmy]

is there a delay? i rather doubt anything you are seeing at the moment would change the thoughts for winter in general. the extended ecm de bilt ens remain cold and wintry. no doubt london will be closer to the less cold air on a ne/sw split so may not be as impressive.

extended naefs remains with high anomoly around s greenland and low anomoly to our south.

[Iceaxecrampon]

Good Grief.. I know the GFS is supposedly renowned for being the most successful at picking up early trends. BUT if this is right

it smacks in the face of the seasoned experts around who have strongly touted a blocked and colder outlook as we

move into the new month. This is as zonal as it gets? What is causing this change to come about. OR is this outlook completely

wrong ?

Yes - a truly disappointing and confusing 06Z on this damned rollercoaster - the cold plunge has gone further east- time for the GFS to make it's mind up as the 30th that even seasoned members were forecasting snowmaggedon is nearing reliability - here's hoping for an upgrade.

Ian

[Polar Maritime]

Still no change, remember its the 06z..

gfs still doesn't know what to make of the blocking, But the firm horse is, it's going to evolve into cold/blocked pattern this week

There is no point in looking at details or breakdowns, until the models have collected themselves and got to grips with the pattern change.

The cold has not even got here yet.

Edited November 26, 2012 by Polar Maritime

[Met4Cast]

I don't think we can say the GFS is just defaulting in this case. The low to the West of Greenland heads Eastwards at T120 - T126, that's not exactly in the outer depths of FI. Whilst the GFS may have a zonal default bias, to say that's all this is, is ludicrous. Explain the ECM, the first model to pick up on this?

I'm not saying we should panic just yet, the UKMO has remained solid and consistent which has to stand for something, but to simply say the GFS is wrong because it looks like its defaulting is ridiculous.

[The Eagle]

Anyone who can't see the subtle change in the short term pre 96hrs on the 6z must be blind. It's clearly gone toward the UKMO but it's not there yet.

[Zakos]

I'm sorry, I must be viewing a totally different 6z to some of you - ignoring timings etc did the Atlantic break through or not on this run?

True, it does break through eventually. But, I ask you,is the pattern at 96 hours better than on the 00z or not?

[Paul]

Is the delay in GP's winter forecast due to doubts how this will pan out?

No

[chionomaniac]

That sounds like your siding with the ukmo ed? The 06z is a much improvement on the 0z , block holds longer this wkend, then the vortex segment/low over the Atlantic looks much weaker and further south.

Not necessarily - more a halfway house that eventually will lead to a suspected block. The GFS shows us a pathway that the complex computer is programmed to work out. I can almost see the smoke coming out of it coping with this set up. I don't think we should look past T+144 presently.

Do I think that the background signals are leading to a more organised vortex? The answer is a resounding no. We are looking at the split vortex transferring to a vortex displaced towards Eurasia eventually.

How we get there is where difficulty arises and no wonder we see different outputs and no consistency. I am wondering whether the recent strat updates to the UKMO model may be beneficial in this scenario though - because it is the transfer of energy in the upper atmosphere that will be driving the tropospheric pattern right now.

Edit The ECM is certainly not a raging positive AO pattern by the end of the run either.

Will look more fully tonight at all teleconnections I think.

Edited November 26, 2012 by chionomaniac

[Troubleatmill]

Just one thing to throw in. How many times have seen the models going for a cold for uk blocked pattern only to drop the idea for a couple of days and then pick it back up again?

[Rollo]

What's forecast ?

His full winter forecast not his pre-season thoughts.

[Iceaxecrampon]

What's forecast ?

Last closed thread - some reliable names on here had the 30th pretty much nailed on looking at last weeks charts and getting worked up into a froth.....

Meto 5 dayer for Cumbria freezing level dropping to 300m sleet this am and heavy snow on the tops with a nice windchill.

http://www.metoffice.gov.uk/loutdoor/mountainsafety/lakedistrict/lakedistrict_latest_weather.html

[WhiteFox]

The point I was making is that we've had enough consistency for colder weather across the UK that the height anomaly charts have indicated this and the MO have even upgraded their thoughts on cold in their longer range outputs. If we see everything collapse, it's not exactly going to be a minor c*ck up is it?

In the grand scheme of things, yes! The point I'm making is that we've seen this many times before, usually several times each winter and this is followed by "The credibility of x model is shredded, nobody will ever believe it again" (often followed by fourteen exclamation marks).

The point I'm making, which you actually allude to yourself, is that the setup is very fine between the block holding and breaking. If it holds, we get a continuation of cold conditions and if not, we get more mobile Atlantic flows. The difference in the the actual forecasts at the critical point is tiny, but the difference in outcome is huge. I don't think the Met will bin the code and start again if the forecast is incorrect!

I also know that the next time we face such uncertainty, the same debates will be had and whichever model gets the small early forecast wrong will be dubbed as the worst model ever.

The only certainty in model watching is that the hyperbole index will rise towards hitherto unseen levels; the equation is:

HI = f squared x (f squared/root(tx))

Where:

f = Forecast 850s

tx = time period

[Dave Kightley]

Either the UKMO hasn't picked up the new signal yet, OR it's sticking with the cold because that's whats going to happen. We wont know until next week I suppose

To be honest with you i don't even think there is a signal to be picked up before 144 hours anyway. With so much twist and turns upto 144h. Most models are really not that far off to be honest to muck about so much the first place upto as i say 144 hours.. There are differences but no treason why runs should break the block and come up with all sorts of rubbish when the UKMO has been consistent. You could say maybe a signal been picked up but what signal if the runs are changing like disco lights upto 144 and now they look cold.... Why show stupid crap the first place... Either a signal for later next week or drunk!

Edited November 26, 2012 by Dave Kightley

[Iceaxecrampon]

Just one thing to throw in. How many times have seen the models going for a cold for uk blocked pattern only to drop the idea for a couple of days and then pick it back up again?

Rollercoaster................. is the Preston snow shield up and running? - got to love those Pennines and the coast haven't you?

[pyrotech]

Few things today

Firstly the colder conditions were always forecast to start around the 28th November, so its not been kept pushing back

As always the models have fishtailed on the way here.

Looking now at what the 2 main models think the NAO is doing.

Starting with ECM

Now GFS

The AO for GFS

What this tells us is there is a little uncertainty if the NAO will Become positive, but long term its still likely to be negative

AO the same, may be some uncertainty, but longer term the agreement still seems to say negative

The magic word for today and everyday is TREND and the trend is looking good for cold, as always we will not get it easily and the models will struggle.

I would very rarely rule out the ECM output so i think what ukmo says on next run is vital, but what ever happens the trend medium to long term looks very good.

[Weathizard]

Just one thing to throw in. How many times have seen the models going for a cold for uk blocked pattern only to drop the idea for a couple of days and then pick it back up again?

This is true however isn't it practically unheard of for the ECM especially to be wrong at 96-120hrs? Not being negative just realistic, to counter that thought this is such a complex setup that its very, very difficult for a model to predict and the one good thing is the UKMO is sticking to its guns, and is beginning to get support from some smaller models.

Does anyone know if the Fax charts have any human input from proffessional forecasters? I know they have stuck with the UKMO for the last few days so surely the boffins in exeter must think that is the likely outcome? Or is the fax done by computers?

[Mark Neal.]

Personally i think some models are underestimating the block. I can't see energy going straight through as easy as some of the models are showing. Could be a 1/2 way house between UKMO & ECM would be where i would money if i was a betting man!

[Catacol]

Well according to gibby's summary above - The Atlantic looks increasingly likely to dominate with any cold and any significant wintry weather looking unlikely

Rather conflicts with some posts in here I have to say. As an amature and learning, confused is an understatement

Dont look at operational runs - check means. The runs you get on wetter or meteociel are only a single representation of 20 or more parallel runs of the model, and statistically the mean pressure patterns of the full suite of parallel options is the best to look at for trends.

Interestingly it is true that the ECM means last night moved away a bit from polar heights and brought the vortex back together quite quickly, but if you pull up the ecm ensemble mean runs for midnight they have trended back to cold again. Gibby has mentioned the GFS ensembles in his post but not the ecm ones which is a bit odd. GFS ensembles last night were very cold; this morning not quite so much.

The overall message here for you as a new learner is that the models are picking up on the overall trend for high lat blocking and cold weather, but are having one hell of a job resolving what is going to happen in the short term with the low pressure system strengthening over Nova Scotia. If that system fires through due east then it will upset the cold pattern for a day or two, but not for the long term ("game over") posts which some on here like to throw out. The only thing that would bring back the zonal express of west to east from here would be a strong reformation of the vortex. All the background signals are against that happening, so whether the nova scotia low upsets things a bit and brings westerlies in for 24 - 48 hours it will be only a blip in a trend towards blocked and cold. To get to the trends run the mean ensembles for several days - that gives you the picture and will help you ignore the odd operational run that goes astray, or even the odd ensemble run that moves away from the general direction. Only get concerned about a change of pattern if 2 or 3 ensemble means start to go the same way: that might mean something. As it stands at the moment this has not happened - at least for the long term. I posted the 5 day cfs mean chart earlier - here is the slightly longer range one - there is nothing remotely zonal or mild on the horizon from this up to date mean analysis. In fact this is reverse zonality at its best!

Edited November 26, 2012 by Catacol_Highlander

[Thundery wintry showers]

Yesterday's runs saw the UKMO and to a lesser extent GFS painting a snowy-looking picture and the ECMWF going for a breakdown into early December with a northern arm of the jet developing and lows heading across to the north of Scotland. It seems that the ECMWF and GFS have switched around- the ECM does show the Atlantic temporarily making inroads but the jet always remains titled NW-SE, while the GFS has a full-on breakdown. These sort of model switch-arounds cause a lot of forecasting headaches and the length of this cold wintry spell is still up in the air, though with a considerable amount of evidence to suggest that the GFS is being too progressive.

The UKMO operational runs have been remarkably consistent up until now and this morning's T+144 output shows a pretty snowy-looking east to north-easterly flow with some of the coldest air getting down from the NE, but most of the other cold runs tend to favour a northerly with shortwaves out in the North Sea. The northerly type could still be quite snowy if the troughs in the North Sea help to generate more organised precipitation, but a "wishbone effect" is more likely when precipitation is generated mainly from cold air flowing over the comparatively warm North Sea.

Meanwhile some relief coming up for the flooded areas as it appears that the persistent/frontal type rain will clear out of the way tomorrow leaving brighter weather and some showers, increasingly of a wintry nature, in the east of the country. It is probable that showers will be mostly of sleet and rain tomorrow, maybe sleet and wet snow in the north on Wednesday, before generally turning cold enough for snow at low levels by Thursday, but again watch out for the wishbone effect with winds likely to be from the north, rather than the north east as shown on the UKMO operational runs.

[Jaffusmaximus]

If I were to build a model I would have it programmed to favour allowing lows to smash through any blocking as that would be a typical scenario. The only way to prevent my system constantly breaking through a high would be to keep pumping data into it until it gets to grips with a change in norm. So then the question is how much data is needed or how much closer to the projected time of a cold snap would be required. So in the next few runs either all models will have to align or we will just have to wait till Thursdays runs.

[Southender]

As far as I can see the 6z GFS has made a subtle movement towards the UKMO in the 5 day range. With regards to the energy strength and track coming out of the NF/Lab region. That is a positive surely? Everything else it goes on to show is immaterial in my book. Complete guess work. Until this time frame is nailed anything past this weekend is not even worth talking about.

Edited November 26, 2012 by Shrimper

[Methuselah]

If I were to build a model I would have it programmed to favour allowing lows to smash through any blocking as that would be a typical scenario. The only way to prevent my system constantly breaking through a high would be to keep pumping data into it until it gets to grips with a change in norm. So then the question is how much data is needed or how much closer to the projected time of a cold snap would be required. So in the next few runs either all models will have to align or we will just have to wait till Thursdays runs.

Welcome to netweather, maximus!

[london-snow]

Just comparing the over nights and the 06z it seems to me the more stronger that low pressure is the more likely it is to head N-NW and put us favorably towards the cold. The less weaker the more likely it is to head E-NE and we dont get that cold.

Now although i am still learning as i go along thanks to the more experienced. Surely the stronger the low pressure the more likely that block is to be broken and the weaker the low pressure the more likely that the block will hold. At the moment all i am seeing roles reversed which makes me scratch my head or think i am totally wrong .COM