Model Output Discussion - 28th November - 4th December

[Harsh Climate]

At 162h huge changes on this run from the 06z! Could it be a greeny high trying to develop?? Haha think I may be being over optimistic!

Edited December 3, 2011 by Harsh Climate

[January Snowstorm]

The 12z gfs looks like another labrador's dinner!!

Clueless after 120hrs

Hmm maybe not the ukmo is very similar.

Fridays cold spell has all but disappeared in 6 hours!

Edited December 3, 2011 by January Snowstorm

[ukpaul]

Looks like a chilly 12z, those heights rising towards Greenland paying dividends later in the high res., expect FI will go back to default but you never know!

[Snowstorm1]

Is a greenie high trying to form here :o

[Uncle_Barty]

At 162h huge changes on this run from the 06z! Could it be a greeny high trying to develop?? Haha think I may be being over optimistic!

HC.. probably, as we'd need - IMO - the greeny high needs to be supported by the building of heights there. An upper ridge towards Greenand would be shortlived as it would likely soon be swept aside by the jet with the strong PV in place.

Edited December 3, 2011 by Jim_AFCB

[Harsh Climate]

Is a greenie high trying to form here :o

Looks like it, but with all that cold air flooding out of canada aggainst the high, I can only see it getting flattened.

[Weather Boy]

People are referring to the UKMO but looking at it on netweather it appears to be the run from 28/11 rather than today. Anyone else getting this problem?

Looking at the charts for later in the week, and the consistency not just amongst the models but over time, it seems highly likely that there is a significant cold shot from Thursday (Friday in the south). I'm surprised that people are being quite conservative of the prospects of snowfall in the south. The charts that I am looking at (especially the GFS 12z) seem to be very potent and although I agree that it is marginal and therefore may not be snow, I'd have thought from these charts there is a clear chance of heavy snowfall for the south. Obviously a greater chance the further north you are, but the 528 dam line is there, the uppers are cold and there is pretty potent yet sluggish low pressure.

Gotta be a chance of significant snow countrywide, surely. (Incidentally, the snow potential was mentioned on BBC last night and although he said not widespread, it wasn't suggested that it was likely to be confined to Scotland and northern elevated spots). I think the jury is out almost until we see the precipitation fall, for those of us in the south.

[Snowstorm1]

:o Nearly an easterly on this run its soo close surely surely it can't happen can it? Im not ruling anything out now so much for mild weather for all December...

[Grimsby Snow Lover]

Colder uppers not a million miles away really on this runs FI charts. New trend? We will have to see over the next few days, but still nice to look at non the less.

http://hw.nwstatic.c.../h850t850eu.png

You have to laugh. To finish we have regression of the high to Greenland. I wonder if the AO/NAO are forecast to turn more negative?

http://hw.nwstatic.co.uk/gfsimages/gfs.20111203/12/384/h500slp.png

Edited December 3, 2011 by Grimsby Snow Lover

[Uncle_Barty]

WB.. for much of the south the -5 air only just makes it, and then only for a short time. WE have a couple of shortwaves to come through before then so a lot can change. In any case even -8 air has produced rain rather than snow here.

I would be genuinely shocked if we got any (never mind heavy) snow down here in the next week or two as we rarely get any in a NW'ly..

Edited December 3, 2011 by Jim_AFCB

[ChartViewer]

The 12z gfs looks like another labrador's dinner!!

Clueless after 120hrs

Hmm maybe not the ukmo is very similar.

Fridays cold spell has all but disappeared in 6 hours!

Not sure what model you are looking at.......Interesting though that those who subscribe to the teleconnections dont seem to want colder weather until their beloved teleconnections show it....maybe somethig that should be looked at when mild or cold weather posts are deleted.......Interesting to since the Netweather winter forecast says average to mild in December......Im intrigued x

Look at T84 i think even with a cold stratosphere we can get PM interludes x

Edited December 3, 2011 by ChartViewer

[Weather Boy]

Yes, Jim. Firstly I accept it's marginal. Secondly, I was being a bit on an IMBY when thinking of the south. You're in Bournemouth and I too would be amazed if you saw any significant snow in your location.

However. Friday's flow is not really an NW in my view. Pretty much due north with a little low causing trouble, hence my comment that for inland areas in the southern half of the country (but not below the M4 I'd think) could see some snow in my uneducated opinion. However, in saying could, I acknowledge that it could not happen - it's marginal either way.

[summer blizzard]

Pressure is far too high near the end of the run to produce snow.

That said, the GFS12z is an absolutely brilliant run.

My opinion - Yes Please!!!!

[Aaron]

That looks great. Not really bothered about snow at this time, but would love some air frost.

[Cecil Hogmanay Melchett]

Not overly excited by the longer term tonight 12z has very little support and ukmo looks like a standard toppler to me.

[Iceaxecrampon]

Pressure is far too high near the end of the run to produce snow.

That said, the GFS12z is an absolutely brilliant run.

My opinion - Yes Please!!!!

Yes the LP comes straight from Iceland but like you say not enough of a low for decent ppn.

[Dorsetbred]

WB.. for much of the south the -5 air only just makes it, and then only for a short time. WE have a couple of shortwaves to come through before then so a lot can change. In any case even -8 air has produced rain rather than snow here.

I would be genuinely shocked if we got any (never mind heavy) snow down here in the next week or two as we rarely get any in a NW'ly..

Also needs the overall temperature to drop,as we are still warm down here, well into double figure today.

As you say even -8 air has produced rain, and a NW just aint a good direction for us central southerners by any means. Current MO really has some rainfall for us, which in it's own right is welcomed.

Edited December 3, 2011 by Dorsetbred

[shedhead]

With the main models chopping and changing like the wind, there's probably no better time to remind folk that chasing ever nuance across every run of every model is both pointless and untimately soul destroying, especially if looking for cold. We keep hearing this has changed that has changed every 6hrs, but in reality nothing much has changed overall. A mixed week ahead, cold in the north for much of the time, then a spell of high pressure followed by a flattening pattern around mid month.

Edited December 3, 2011 by shedhead

[weathe20]

Got to say that is most encouraging charts ive seen this winter from the 12z

The 12z gfs looks like another labrador's dinner!!

Clueless after 120hrs

Hmm maybe not the ukmo is very similar.

Fridays cold spell has all but disappeared in 6 hours!

have a look from 141 into FI............????

With the main models chopping and changing like the wind, there's probably no better time to remind folk that chasing ever nuance across every run of every model is both pointless and untimately soul destroying, especially if looking for cold. We keep hearing this has changed that has changed every 6hrs, but in reality nothing much has changed overall. A mixed week ahead, cold in the north for much of the time, then a spell of high pressure followed by a flattening pattern around mid month.

Theres no flattening on the last run? Which 12z did you just look at?

Edited December 3, 2011 by weathe20

[johnholmes]

do'nt mean to be rude but surely f1 is 24 hours out no modelnis able to predict any more than that.as regards to next weeks northly it will just weaken and be downgraded over the next couple of days .would not be suprised to see it as a 12 hour event for the highlands only.-5 air will never get any where near the south.these predictions are based on previous data from past similar set ups.hope this post is okay hate to get a slap on the wrist for my first posting

apologies for me having a go at your punctuation and it being your first post-wrong of me.

To your comments

No the models do not base their predictions on previous data. They are based on all available data for the time the model starts, in this case 12z, from all over the world, land, sea, surface, upper air etc etc. The models then compute for each 'spot' location, on a world basis, usually 60km or less out to T+180 I think!, correct that if its wrong someone-please, the grid length increases for the later stages simply due to time constraints.

The laws of physics are used, especially thermodynamics, solved by extremely complex mathematics.

Past history has no part in the model forecasts other than as the model has been developed any tendencies not to deal with some weather patterns are 'fixed' to ensure a more realistic solution.

sorry mods its not about the 12z output but as I cannot pm the poster yet he deserves an explanation.

[cyclonic happiness]

I must say I almost spat out my tea whaen I saw the evolution of the 12z, especially FI!!

We've been so used to seeing the default, zonal south westerlies, that to see all that blocking and an (almost) easterly, sent a shiver down my spine.

I hope it's a new trend that is being picked up on, but I suppose as ever, more runs needed!

Can't wait for the 18z! Although it will probably bouce us all back into reality

[nick sussex]

Regarding the GFS 12hrs run well it's not as outlandish as people might think.

A Euro high is a possibility and you can get an easterly with a cold stratosphere, I've seen many easterlies with a deep PV as long as this is held further west towards western Greenland.

The trend was for higher pressure to try and move in from the sw but this just takes it much further north than might be expected.

The odds still favour the high unable to get that far north but it's been a strange week in the models.

[Uncle_Barty]

Very good agreement on the ensembles down here to the 7th.. but op is among the coldest members 10th onwards.

[shedhead]

Got to say that is most encouraging charts ive seen this winter from the 12z

have a look from 141 into FI............????

Theres no flattening on the last run? Which 12z did you just look at?

That is the whole point of my post. Look at the big picture, not the swings and roundabouts produced by every run.

[weathe20]

That is the whole point of my post. Look at the big picture, not the swings and roundabouts produced by every run.

Fair enough. But the typical zonal, zonal, zonal of late is gradually changing to more 'encouraging' outputs from the models. The bigger picture as you say has been changing in models...towards more colder scenarios.

Edited December 3, 2011 by weathe20