Model Output Discussion - 8th December Onwards

[Panayiotis]

Welcome to Netweather too! Dont get too excited when charts show anything positive (in terms of cold) past 120hrs. I personally only look at trends past that, such as where the PV is or where blocks are etc....

[nick sussex]

Yes, who, apart from total newbies to model watching, would seriously think that we are going to get an Atlantic low at anything like 955 mb at this time of year, especially given that it is the GFS which is notorious for over-blowing lows at this range. I would merriy stake my mortgage at 2-1 on us not seeing a low that goes below 960 and bet you at evens on a pressure level quite a lot higher than that - it's just not going to happen.

That poses a question for people more knowledgable than me. If the GFS (admittedly only one run) is sending a hypothetical low with so much energy under the block, given that we know that the low will be weaker than that, does it not follow that an undercut is actually more likely than the models are currently giving us, throwing up a scenario of a channel low giving very heavy snow to S Britain. ie - if we have a low at (guess) 985-990 mb, with less energy than the ludicrous low currently being shown, is that not more likely to be deflected by the low than currently shown?

Or is this just wishful thinking on my part.

Its not wishful thinking its being positive in the face of much recent adversity re the easterly drama!

In terms of the track of the low its not just this but how much cold you have to draw on to turn that rain to snow.

So we don't know at this time what the 850's will be , if you take the GFS at face value then some cold could possibly be pulled in from the east with lowish dew points as the low tracks through the channel.

In terms of the deepness of the low of course a weaker feature would more likely to undercut as there would be less ne pull.

[Nick123]

When are the next model runs, anyone?

[NorthYorksWeather]

When are the next model runs, anyone?

Next run of real interest will be the GFS 00z which starts at 3.30am and finishes 4.45am

[stainesbloke]

The models show increased chances of easterly winds returning after next weekend. The high over Scandinavia/W Russia doesn't want to go anywhere fast...indeed the mild incursion could well drastically change in the next few days. Fascinating stuff, good to see the forum getting back to actual model discussion.

[Panayiotis]

Well i think next weeks cold spell will only be for a couple a days as the models in the last runs have degraded anything wintry after Wednesday. Things can change but looking unlikely as we are nearing the reliable. Earlier on the 06z, showed 3 members going for cold maintaining itself over Britain after Wednesday, now look. (For my location)

http://modeles.meteo...28301&runpara=0

Edited December 9, 2012 by panayiotis

[Snowmad79]

Nice start to the GFS 00z this morning with strong hints of what we said Saturday morning with LP in the Atlantic, Stalling, shearing and break off lows going south under the block possibly. And this showing between 72 - 96hr.Looks like it will make for miles better viewing than most runs yesterday! SErly flow out to 126hr. Game on I think with more twist, turns and maybe backtracks come. Not ramping anything up. Just reiterating that it's NOT game over just yet.

96hr

FI ... 72Hr and don't count your chickens. Block could actually have been under-progged as of late. We shall see.

Edited December 9, 2012 by Snowmad79

[ZONE 51]

GFS - 00z Thickness 500-1000hpa There has been an upgrade on the colder side for next week, the 528dam is quite significantly further west, the deep north Atlantic system is shifted west

18z -

00z -

All charts are 0300hrs next Thurs(+99hrs)

--

The 850s upper temps below -

18z -

00z -

GFS 00z - Atlantic weather holding back towards the end of next week, the cold/very cold further west through next week.

Edited December 9, 2012 by ElectricSnowStorm

[Chris D]

There remains very great uncertainty regarding the pace/timing of the Atlantic system which will come in during Friday. GFS 18z has it much later than the ECM 12z, and this has varied greatly run to run on both models. However, what is certain is the event occuring, and so a relatively short lived "unsettled" spell of weather will occur during the following week or so.

Thereafter, I fully believe the very close Scandinavian block will come into play, and the background factors will take over as the Atlantic backs down again (as it does cycle normally during Winter). So, as others have hinted at, cold weather could well return in time for Christmas. Something to watch, definitely. This has been hinted at by all models.

In the mean time, some bitterly cold weather to come for all this week, with harsh frosts, freezing fog and snow showers (mainly for the E) to become heavy at times. However these should ease by Thursday according to the models.

PS I am deeply saddened by the loss of Ian F tonight, a few on here have really "spoilt it" and because of the apparent cold bias he will not post any more. Deeply disappointing as this is the only insight into what the Met Office thinks...

Edited December 9, 2012 by Chris D

[Sawel]

Well well, what's going on with the UKMO at +96 hrs?! Very different to the 12z.

Atlantic not as dominant by 144 hours!!

Edited December 9, 2012 by Sawel

[Snowmad79]

There remains very great uncertainty regarding the pace/timing of the Atlantic system which will come in during Friday. GFS 18z has it much later than the ECM 12z, and this has varied greatly run to run on both models. However, what is certain is the event occuring, and so a relatively short lived "unsettled" spell of weather will occur during the following week or so.

Thereafter, I fully believe the very close Scandinavian block will come into play, and the background factors will take over as the Atlantic winds back down again (as it does cycle normally during Winter). So, as others have hinted at, cold weather could well return in time for Christmas. Something to watch, definitely. This has been hinted at by all models.

In the mean time, some bitterly cold weather to come for all this week, with harsh frosts, freezing fog and snow showers (mainly for the E) to become heavy at times. However these should ease by Thursday according to the models.

PS I am deeply saddened by the loss of Ian F tonight, a few on here have really "spoilt it" and because of the apparent cold bias he will not post any more. Deeply disappointing as this is the only insight into what the Met Office thinks...

To be honest the meto's guidance was more or less putting all its eggs in the SWerly basket (mild, swerly / westerly bias! due to the fact that Atlantic weather is always going to be the odds on favourite), This morning output already re-iterates that this may well not be the case.

And as a side note, I really couldn't care less whether the Atlantic comes crashing in or not. I've lived in the north west long enough to get used to the Wet and Windy weather we often get. I just choose to chase the rarities that snow-fests are. Growing up as a kid in the 80's and early nineties didn't help as I often had winters of 10-15 ft snow drifts and lying snow deeper than my waist line. These were not rare in the 80's and early nighties though. In fact quite regular occurrences, so I think that is why most of us come here during winter. What's the harm in having a happy bias as long as we all remain civil about it ?

Edited December 9, 2012 by Snowmad79

[Swave Snow]

GME shows an easterly setting up within 30 - 36 hrs then goes all blocked Atlantic fizzling against the wall no beast but just huge concrete block deflecting the Atlantic weird but encouraging for those of us with a cold bias

[Zenarcher]

Interesting runs so far today UKMO looks similar to what it did on last nights 00z run and GFS has moved over to agree as well.

UKMO for the 14th

Yesterday

Today

GFS has moved the low in the Atlantic to the south of Greenland exactly where the ECM and UKMO place it so interesting to have it change over to their solution, the GFS does make the Atlantic overall weaker not so much energy going in and a sigh of relief for some after that very strong low on the 18z has gone now. The GFS FI looks blocked and if we start to see a trend here things could get interesting for Christmas time.

[essexweather]

Worth noting on the 00Z GFS that there is a 2-5C difference in 2m temperatures across parts of England and Wales at the end of next week compared to the 18Z from yesterday.

Maybe signs that the block will hold on a bit longer

Edited December 9, 2012 by essexweather

[SMU]

http://www.meteociel...44-21.GIF?09-05

HUM..... I got up early to have a sneak peak at the models -- best chart for around 2 days!!!

Edit the 96 & 120 charts show small systems sliding to the south increasing the risk of snow-

UKMO is very snowy-

S

Edited December 9, 2012 by Steve Murr

[samadamsuk]

could be seeing a refinement on how that strong jet streak will behave - gfs digging a trough currently heading more se/wards than earlier, but each time this happens there's a pumping up of the block and the mean polar front drops south- ukmo promissing as a slow burner, but the ECM is just dumping floods on us and not much else it looks like!

cheers, samos

[SMU]

We have had a significicant change in the GFS & UKMo overnight to a slower system and a stronger signal for trough disruption at a better angle for the UK-

Instead of the South westerly onshore flow we now see a South easterly on SOME runs & the 0c isotherm straddling the SW not making in any inroads-

The overnight turnaround is pretty spectacular & nothing short of the turnaround from the other day when we lost the initial easterly- its almost a double barrelled laugh at us, because not only did things collapse at short notice for the easterly, but now could the thing that was partially driving the collapse of the easterly collapse itself into something more snowy!

If the ECM goes this way then a more positive upbeat mood should ensue today, also the UKMo at 144 sees the shortwave over SE Scandi beginning to turnover allowing high pressure to filter back over the top rather than stay at an angle whereby retrogression can develop-

We are not there yes, however thats a BIG step- we dont need any more big steps on the UKMO- just fine tweaks will do-

SNOW for many...........

Whilst we emphasise the usual disclaimers here are the 18z ensembles for london for reference-

Note the 2 peaks in succession- one for the first wave to move to 0c - then the continued drive east from the atlantic to reach 5c-

Watch for these 2 peaks to be smoothed & taken down sub zero- hopefully could happen over a few runs-

S

Edited December 9, 2012 by Steve Murr

[Swave Snow]

could be seeing a refinement on how that strong jet streak will behave - gfs digging a trough currently heading more se/wards than earlier, but each time this happens there's a pumping up of the block and the mean polar front drops south- ukmo promissing as a slow burner, but the ECM is just dumping floods on us and not much else it looks like!

cheers, samos

The ECM hasn't started yet

[Jupiters Winter]

Model wobble in favour maybe? Interesting change. Worth seeing whether the ensembles are supporting this run. Really signs of hope. The NAM modelling of that low out of east coast is good as over the last two days every run the low has been slowing down by three hours. so in all last two days i would estimate 24 hours slower getting out of east coast with more days in our favour I would guess rather tiny westward shifts of patterns. That ofcourse if the ensembles are seeing this.

[SMU]

A couple of UKMo charts worth noting-

http://www.meteociel.fr/ukmo/run/U60-7.GIF?09-05 t 60- a large pool of -10c 850s just to the east- we are -9

then 72

http://www.meteociel.fr/ukmo/run/U72-594.GIF?09-05

http://www.meteociel.fr/ukmo/run/U72-7.GIF?09-05 Snow for the SE still in -8c air & widely -7 uppers-

then at 96 we draw that continental feed up-

http://www.meteociel.fr/ukmo/runs/2012120900/UW96-21.GIF?09-05

more instabiltiy & possible snow-

well worth watching country file today depening on the ECM & suite + MOGREPS run.

S

[Jupiters Winter]

Nice post- Presumably a late night shift equals great uncertainty (Saturday night shift i can not thumbs up for) Uncertainty -A word to be used frequently. Im guessing a outlier on the ensembles with maybe 3-4 in support of OP at the moment.

A couple of UKMo charts worth noting-

http://www.meteociel.fr/ukmo/run/U60-7.GIF?09-05 t 60- a large pool of -10c 850s just to the east- we are -9

then 72

http://www.meteociel.fr/ukmo/run/U72-594.GIF?09-05

http://www.meteociel.fr/ukmo/run/U72-7.GIF?09-05 Snow for the SE still in -8c air & widely -7 uppers-

then at 96 we draw that continental feed up-

http://www.meteociel.fr/ukmo/runs/2012120900/UW96-21.GIF?09-05

more instabiltiy & possible snow-

well worth watching country file today depening on the ECM & suite + MOGREPS run.

S

[Jupiters Winter]

GFS 00Z Ensembles do suggest a very minor signal in favor with the odd couple of rogue runs prolonging. Otherwise no considerable shift yet. 12's to watch today.

EDIT:ECM T120 = Snow Midlands north.

Edited December 9, 2012 by Jupiters Winter

[Typhoon John]

Ecm 00z looking better at 120 hours.

Low more negatively tilted, pressure higher to the north around iceland, block looking stronger keeping the low a little bit further out West.

Its a small step but exactly the type of thing I suggested we'd see happen.

Look for further small improvements from the 12z runs tonight.

[snow drift]

Haven't posted for a couple of days. It has been difficult to comment because the output has swung so much. The last few runs are looking more "stable" as they get a grip with what is happening in the NH.

Dissapointed where we went from that ECM, got a great screen saver now, to the here and now. Altho I am encouraged by the later frames. 78/79?

Edited December 9, 2012 by snow drift

[Snowmad79]

SNOW for many...........

Whilst we emphasise the usual disclaimers here are the 18z ensembles for london for reference-

Note the 2 peaks in succession- one for the first wave to move to 0c - then the continued drive east from the atlantic to reach 5c-

Watch for these 2 peaks to be smoothed & taken down sub zero- hopefully could happen over a few runs-

S

Those two peaks have "as if by magic!" been SQUASHED. The first peak for the 14th, way below Zero and the second around the 16th just about below 0 now: