General Model Output Discussion Tuesday December 22Nd:

[TEITS]

Huh?????????

Are you viewing the same charts as me?? or are you simply trying to wind people up?

How can the high sink south when there is a low pressure system over Southern France/Northern Spain??

Very well observed and your completely right.

The same applies with the ECM at +168. A HP system will not sink if it has LP underneath. This is why when we look for an E,ly we ideally want LP system in the Med.

[swfc]

I've been meaning to say this for ages but I love your sig. If anyone doubts a model run in the future that is suggesting a very cold spell then they must read your sig. Fair enough its wise to be cautious but your sig shows that at times these very cold model runs go can in our favour.

Classic E,ly about to develop on the 18Z!

http://www.wetterzentrale.de/pics/Rtavn2401.png

Evening teits.Sorry for my ignorance but where do you find an easterley from this set up man.

[Geordiesnow]

The high won't sink but it will reduce the length of any cold spell i would of thought however it's best just to get the cold set up in the reliable timeframe first.

ecm is not that bad and is always subject to change. Plus the GFS 18Z is not that bad, actually the first part of the run could be argued as an upgrade as it sends the colder air further South quicker albeit it does take a time to cover the whole of the UK.

[TEITS]

Evening teits.Sorry for my ignorance but where do you find an easterley from this set up man.

Thats an E,ly.

http://www.wetterzentrale.de/pics/Rtavn2761.png

Well sort of lol.

I thought whilst watching the run that at +240 an E,ly was going to occur in F.I but unfortunately a LP system around Svalbard knackered that one up. :lol:

[SussexmarkyMark]

I'm confused now. I thought the high 'couldn't sink'. Looks like it's doing just that to me with westerlies just north of Scotland

http://www.wzkarten....s/Rtavn2761.png

[swilliam]

Unfortunately the 18GFS has drifted rather more towards the 12 ECM at T+168hrs, with heights falling across Greenland and the HP sinking slowly south. That having been said it's still a very encouraging run towards the end of the high resolution output, with hopefully time for upgrades as the period unfolds.

Yes you are quite right that is is likely to sink. As I pointed out earlier many of the ensemble members on previous runs have shown this scenario so we should not be surprised that the op run has now shown it. The difference between this and getting the greenie high is quite small so we should expect to see some runs showing this at this range. As I also previously showed even when the high sinks - in this case over us, which is what you expect (although the ECM showed an alternative but perhaps less likley outcome) this does not necessarily mean the end of cold prospects. I would only become concerned if the Greenland high scenario does not appear on some of the runs and is not shown by many ensemble members.

Stewart

[TEITS]

As there is a rather negative tone in this thread im going to make one more post on here before I call it a night.

Lets look back at the recent model output prior to our cold spell.

When it comes to following the models we always assume downgrades will occur and the bitterly cold runs remain in F.I. Recently we witnessed a few downgrades prior to our cold spell which is why some members have Ian Browns comments on their sigs. However for a change this short period of downgrades with the ECM failng to develop a Greenland HP was replaced by an upgrade. As we know the upgraded E,ly delivered in many E parts. We then had the following N,ly and some members (won't mention their name!) said the N,ly didn't look strong enough. Well this was shown to be untrue as some of us have experienced further snowfall with many ice days.

Here we are looking at another potential cold spell. Lets have a look at the potential once again from all the models.

http://www.wetterzentrale.de/pics/Rukm1441.gif

http://www.wetterzentrale.de/pics/Recm2161.gif

http://www.wetterzentrale.de/pics/Rtavn1441.png

http://91.121.94.83/modeles/gem/run/gem-0-144.png

http://www.wetterzentrale.de/pics/brack4.gif

This might upgrade or it might downgrade but I tell you what the charts above beat a mild SW,ly. I understand some are cautious by nature and then you have full blown rampers like myself. However I think some are on here just to spoil our fun!!

Edited December 23, 2009 by THE EYE IN THE SKY

[Guest North Sea Snow Convection]

Still very well on course for a reload plunge of the cold air back south taking into account all the modelling tonight.

I would say that the latest ECM is an upgraded potential for the longer term. Clearly, as time gets nearer the more the models realise that the AO signal and polar field is still very pre-disposed to extensive cross polar ridging. Continuing very emphatic signals for the trough to drop into Scandinavia and for height rises/blocking to become firmly entrenched over Southern Greenland and Iceland. Also the -NAO signal looks to get reinforced once again - all great news to pass the baton into January

Edited December 23, 2009 by North Sea Snow Convection

[nick sussex]

I'm confused now. I thought the high 'couldn't sink'. Looks like it's doing just that to me with westerlies just north of Scotland

http://www.wzkarten....s/Rtavn2761.png

Good grief you're worried about a chart at 276hrs! which incidently would you bring your area some major snow with that small low. The pattern is not set yet and there are still some hurdles to overcome before theres a reload to cold. If a bartlett high appeared within the high resolution part of the output that would be a reason to worry . I'm the moan police! any posters moaning about the current output obviously have been living in Canada for the last 10 years! :smiliz19:

[❄️❄️❄️❄️❄️❄️❄️❄️❄️]

I've been meaning to say this for ages but I love your sig. If anyone doubts a model run in the future that is suggesting a very cold spell then they must read your sig. Fair enough its wise to be cautious but your sig shows that at times these very cold model runs go can in our favour.

Thanks! I don't know how you have been meaning to say that for ages when i only put that quote in earlier today!

Look how mild it could be on Boxing Day. 9C in the South! Maxes below 0 in the Scottish Highlands.

http://charts.netweather.tv/gfsimages/gfs.20091223/18/69/ukmaxtemp.png

[TEITS]

but it was the preferred evolution on the 12ECM and now the GFS 18 has moved into line it shouldn't be dismissed or ignored.

Please tell me where the HP sinks on the ECM.

+168

http://www.wetterzentrale.de/pics/Recm1681.gif

NO

+192.

http://www.wetterzentrale.de/pics/Recm1921.gif

NO

+216.

http://www.wetterzentrale.de/pics/Recm2161.gif

Definately NO.

At +168 on the 18Z the HP doesn't sink which is why at +192 we have a very cold NNE,ly.

At +276 the HP sinks but this isn't the period in question. The period you are referring to is +168 and neither model shows the HP sinking. There is a difference between a HP sinking and not fully retrogressing to Greenland!

[cooling climate]

On the GFS 18z run we see that the block over the pole fails to link up with the block in the Atlantic

because of the vortex around the Greenland, Svalbard area thus we do not get the blocking we saw

on the 12z run.

More runs are obviously required to see how this part of the puzzle resolves itself and this will also

determine whether we see a prolonged cold (very cold) spell or not.

The block could run round the eastern flank of the vortex linking up with the ridge in the Atlantic and

then we would pick up a more n/e airflow.

It does definitely look as though another cold spell is on the cards for Europe and the UK.

[Guest North Sea Snow Convection]

The evolution is simply delayed on the ECM 12z. The GFS will provide a usual heinz 57 of varieties in FI so I am not sure that it is fruitful trying to look for mild breakdowns post t180!

The more reliable trend is identical, the detail from there though will never be the same! I didn't see the 12z's - life and xmas goes on elsewhere. Too much analysis of every output 24/7 is bound to put up varations from one model to another and from one output to another two to four times a day. If you look hard enough and have nothing else to do all day other than watch every single one of these then you can find any variation on a theme you want I am sure to try and make any point you wish

The general theme is for a cold reload - and that signal has grown throughout today.

[mountain shadow]

Basically took the words out of my mouth cooling climate. This was the stark difference between the 12 and 18GFS, which meant the 18 run looked much more in line with the 12 ECM at T+168hrs. Like you I'm not suggesting this evolution is right, the 00 GFS might trend back towards the 12 again, but I'd not be too surprised if the 18GFS does not ultimately prove to be pretty close to the mark.

I see the suicide squad are out after "one bad run". If you look at the Ensembles, their are less cold members in their ans this run has picked one of those.

Since when did the GFS 18Z EVER resolve better than the ECM 12z? Not often I bet.

Leading up to any cold spell you are NEVER going to get full model support at T+168. When doubts in the model output do happen, I look to the likes of Glacier Point for a solution, and you can clearly see what that is likely to be.

[wellington boot]

So I've been using this breakdown to get myself ready for christmas and be productive without distractions, but the charts have once again become distracting. Can someone tell me though, why are we not just spending all our time staring at this chart in awe?

http://www.wetterzentrale.de/pics/Recm2401.gif

This would be snowstorm of the century for everywhere, provided the atlantic slid along the channel and linked with the raging storm low, and that the raging storm low came close enough to us.

[swilliam]

Please tell me where the HP sinks on the ECM.

+168

http://www.wetterzen...cs/Recm1681.gif

NO

+192.

http://www.wetterzen...cs/Recm1921.gif

NO

+216.

http://www.wetterzen...cs/Recm2161.gif

Definately NO.

At +168 on the 18Z the HP doesn't sink which is why at +192 we have a very cold NNE,ly.

At +276 the HP sinks but this isn't the period in question. The period you are referring to is +168 and neither model shows the HP sinking. There is a difference between a HP sinking and not fully retrogressing to Greenland!

No-one said it did on the ECM but it did and now does on lots of the ensemble members including the control run this time.

We have to consider that this is also a possible outcome - maybe at this stage probable.

The ECM had a rather unusual route to the greenie high by having a relativity low latitude mid Atlantic high which retorgresses and grows northward. Not to say it won't happen though

[Frosty.]

The T+120 fax chart makes the prospect of another cold spell seem more realistic as we are now only 5 days away from the cold arctic air making a comeback southwards, the gfs and ecm will continue to fine tune things over the next few days with some runs being spectacular and others not quite. So, as we say goodbye to this current bitterly cold spell, it only looks like being 4-5 days until we say hello again.

[swilliam]

I see the suicide squad are out after "one bad run". If you look at the Ensembles, their are less cold members in their ans this run has picked one of those.

Since when did the GFS 18Z EVER resolve better than the ECM 12z? Not often I bet.

Leading up to any cold spell you are NEVER going to get full model support at T+168. When doubts in the model output do happen, I look to the likes of Glacier Point for a solution, and you can clearly see what that is likely to be.

No suicides here - we're trying to assess what the most likely evolution is at T168-240 and what is needed to get the Northern blocking over Greenland that most of us would like..

[kold weather]

Basically took the words out of my mouth cooling climate. This was the stark difference between the 12 and 18GFS, which meant the 18 run looked much more in line with the 12 ECM at T+168hrs. Like you I'm not suggesting this evolution is right, the 00 GFS might trend back towards the 12 again, but I'd not be too surprised if the 18GFS does not ultimately prove to be pretty close to the mark.

the 12z ECM has not got anything even close to the PV over Canada which the 18z GFS has by 192hrs, they are light years apart!

Compare the blues and purples over Canada in the 18z run:

http://www.wetterzen...s/Rtavn1921.png

To the ECm:

http://www.wetterzen...cs/Recm1921.gif

Which actually has the upper high nudging into Canada.

What these two charts show in terms of upper patterns are so very different indeed...they are NOT similar in terms of evolution at all, one shows a Mid Atlantic high as the most probable set-up ,the other has a monster Greenland high and a split PV still, big differences!

As for the global set-up, lets just remember we have a southerly jet and a split PV still...those two would argue that the 12z ECM has a much greater chance than normal off pulling off....

Also, lest us forget we just had a record breaking -ve AO spell in December...these will not die off as quickly as the 18z progs, I'd say 90 times out of a hundred such a set-up will last a heck of a lot longer then models will ever forecast...

The 18z is what could happen if we get that 10% that can happen, the ECM is the other 90% of the time...

PS, by the way, IF the 18z GFS was right, the likely set-up would still be for a cold high to form over the UK...there really is IMO little chance of a mild set-up like some of the ensembles try and bring unless we get a RECORD BREAKINGLY fast tranisition from -ve AO to very +ve...lets just say I think there is more chance of a 1740 then a Bartlett high for the first few days of Jan...

Edited December 23, 2009 by kold weather

[AtlanticFlamethrower]

I expect a repeat before the New Year but not counting on any PPN here at least in the first phase since it will have too much of a Northerly aspect.

Also, as koldweather has pointed also out, GFS tends to downgrade the cold projections closer to the event. In this case we might have temperatures raised via encroachment from the West. Right now 850hpa is at -7C for London... that could go down to -4C or -5C.

However I think some are on here just to spoil our fun!!

Not everybody lives in England's snow capital, which can do well out of southerlies, easterlies, northwesterlies and northerlies. Try putting yourself in the shoes of someone who lives in, say, Bristol.

Someone living in Bristol who had complained about the synoptics in the run up to the recent 17th+ Cold spell would have been proved correct. It wasn't any good for them.

If someone in Peterborough is complaining like someone in Bristol you would be justified in the harsh criticism on your own terms.

[stewfox]

The T+120 fax chart makes the prospect of another cold spell seem more realistic as we are now only 5 days away from the cold arctic air making a comeback southwards, the gfs and ecm will continue to fine tune things over the next few days with some runs being spectacular and others not quite. So, as we say goodbye to this current bitterly cold spell, it only looks like being 4-5 days until we say hello again.

A cold spell for the south, Scotland keeps its cold spell till sunday at least ,which is when the BBC suggest it will get milder up there (go figure)

ps its -9c in Edinburgh at present so their wave good bye to the cold is fairly muted

Edited December 24, 2009 by stewfox

[kold weather]

so what your saying is its not worth getting to excited over.

I'm looking through the GFS ensembles and they are *amazingly* proressive with the Arctic pattern, I mean some have a decent +ve AO by 144hrs!!

They are also in general very progressive with developing a powerful Candian vortex.

IMO this is a classic case of the GFS being too progressive with the developing of that Candian vortex...in fact I can't remember ONE Lp that the GFS has not overpowered at some point!

However saying all that its possible we don't end up getting the full works and we could end up with a Mid Atlantic high or maybe a UK high...I'd still suggest for now that for once the Greenland high is the most likely outcome, followed by the UK high, followed by a Mid atlantic high, then zonal+Bartlett are way way way down the list IMO, you need a total 360 reversal for that pattern to come in from what the current global teleconnections show, at least for it to last more then 2-3 days anyway!

[MR EXTREMES]

well somebody spoke of the fax charts but towards the end of the run they look terrible.

apart from the gl high.

[MR EXTREMES]

I'm looking through the GFS ensembles and they are *amazingly* proressive with the Arctic pattern, I mean some have a decent +ve AO by 144hrs!!

They are also in general very progressive with developing a powerful Candian vortex.

IMO this is a classic case of the GFS being too progressive with the developing of that Candian vortex...in fact I can't remember ONE Lp that the GFS has not overpowered at some point!

However saying all that its possible we don't end up getting the full works and we could end up with a Mid Atlantic high or maybe a UK high...I'd still suggest for now that for once the Greenland high is the most likely outcome, followed by the UK high, followed by a Mid atlantic high, then zonal+Bartlett are way way way down the list IMO, you need a total 360 reversal for that pattern to come in from what the current global teleconnections show, at least for it to last more then 2-3 days anyway!

if i remember rightly last winter had alantic high and that proved to be not so bad although not snowy it was cold.

but right now im seeing its difficult to predict anything even with the models help gp is doing very though i must say.

but this year seems to be more unsettled cold as last winter was more settled cold.

i have to say if this winter turns out colder than last then maybe just maybe this could be the turning point in climate change.

[TEITS]

Not everybody lives in England's snow capital, which can do well out of southerlies, easterlies, northwesterlies and northerlies. Try putting yourself in the shoes of someone who lives in, say, Bristol.

Someone living in Bristol who had complained about the synoptics in the run up to the recent 17th+ Cold spell would have been proved correct. It wasn't any good for them.

If someone in Peterborough is complaining like someone in Bristol you would be justified in the harsh criticism on your own terms.

You do actually make a very good point which I shall try and take on board. When I look at the model output I must admit to focussing on my own location rather than looking at all of the UK. I shall certainly make more of an effort in the future.

Back to the models and its time to have a look at the Iceland SLP ensembles like I did last time. This proved to be a worth while exercise prior to our last cold spell.

At the moment its looking quiet good for the period in question with the mean currently standing at 1022mb.

http://charts.netweather.tv/ensimages/ens.20091223/18/prmslReyjavic.png

Edited December 24, 2009 by THE EYE IN THE SKY