Model Output Discussion

[Thundery wintry showers]

Ah, I see what you mean now- but how would the delay of the shortwave reduce the chances of it opening up? I'd have thought that the slower its southward movement, the more likely it would be to open up while over the north- which I agree would scupper the chances of significant snowfalls in the south.

While the GFS has a habit of picking up shortwaves that the UKMO and ECMWF misses out on (I think it's definitely the one area where GFS outperforms the other models) it also has a habit of overcooking them, so I think that it's only an outside bet at this stage.

Personally I think the safest bet for snow lovers, in contrast to yesterday, is this morning's UKMO 00Z run. The logical progression from there takes us to a similar place to where yesterday's 12Z runs took us, and those were exceptionally impressive. A broad north-easterly or easterly flow, bringing the coldest air with it and covering the whole country. The Met Office T+120 FAX chart suggest that the bods at the Met Office are happy to trust their own model.

[andy_leics22]

Ok I apologize to mods if this is not really detailed model dicussion but... From what I have just seen from todays GFS 06z run I would have to say that is the best run YET! I didn't think we would see anything better than what we saw yesterday but that 06z run this morning, that would not look out of place in a 60's, 70's, 80's Easterly spell.

[Cecil Hogmanay Melchett]

Im satisfied with the ouptut but i cant get that ecm run out of my mind.

Still too much scatter in that ecm suite to be overly confident of anything.It has to be said that a good chunk

of those ens dont bring much of a cold spell at all.

12Z should see some consensus at t120 so i'll hope ecm trends cold and the milder members decrease tonight.

Its fine to be discussing where the snow will fall on gfs but ecm shows precious little of the stuff away from

the SE and posibly far NE so with that in mind,most people in the south central and western Britain must

hope from a snow perspective that ecm is barking up the wrong tree here.

All that said at least we have a cold spell coming,snowy(gfs) or dry(ecm) is still far from settled.

[Methuselah]

Lol Pete, we should really add a 1c-2c maybe 3c discrepency on 1962. The climate is warmer- right?

That's why it's so interesting, IMO...I'm not pretending to know what'll happen in any detail, I've had my fingers burned too-many times in the past, for that!

Maybe, just something to keep an eye on?

[kold weather]

The 06Z Ensembles are out and keep the mean 850's below -5 for the entire run from next week onwards(for Wiltshire in central southern England), however there is more uncertainty about what exactly will happen.

More agreement would be nice.

The milder runs are because the low pressure to our SW absorbs the shortwave at just the wrong time which means the flow over the UK switches to a southerly briefly and raises those 850hpa temps ahead of the low.

Given the nature of shortwaves and that jazz, its far too early to make any half decent call in that respect.

[funkymonkey15]

Worth noting that the Op run was one of the milder runs later on, with the parallel run having plenty of support. The mean is still around the -5 mark all the way through.

In this type of setup I don't think the precipitation charts are of too much use. Clearly Eastern areas will do well, but many place inland are likely to see some snow. Risk drops as you move West obviously.

[Cumulonimbus Tower]

Im satisfied with the ouptut but i cant get that ecm run out of my mind.

I know what you mean, it's just like being cheated on by your partner

I have (in a non scientific way) noticed however, that over the last few days the 00ECM has CONCISTENTLY been bucking the trend with some poor output for coldies compared with the other overnighters only to be back on board with it's 12z output. I'm certain a trawl through recent ECM output would demonstrate this. Maybe it's the data fed in or just the econimy 7 they are running it on, but it's there!

[snowmadchrisuk]

Would agree with Ian on this one, re: snowfall.

GEFS ensembles for PPN (taking Deryshire, E. Sussex and Kent) are all very low. One or two members going for 'something' but overall, looking quite dry (btw, op run is, whilst not what I would call an outlier, in general, is rather optimisitc in terms of rainfall).

I think in this situation you need to know your own area , In this setup I know showers will reach my area , Posting 2 charts below . the PPN one is what i think is a rough guide to where I think showers will fall overall . The second chart is the wind , as you can see it is very breezy on the coast and this would ensure snow showers reach the Midlands.

[Yeti]

I think in this situation you need to know your own area , In this setup I know showers will reach my area , Posting 2 charts below . the PPN one is what i think is a rough guide to where I think showers will fall overall . The second chart is the wind , as you can see it is very breezy on the coast and this would ensure snow showers reach the Midlands.

I'm actually not convinced that heavy snow showers would reach that far inland under this setup.

http://www.wetterzentrale.de/pics/Rtavn1201.png

The flow isn't really that tight and never has been progged to be; with that in mind the easterlies of yore with heavy snow showers blowing right across the country look quite different to today's output:

http://www.wetterzentrale.de/pics/archive/ra/1991/Rrea00119910208.gif

You're right in that any snow showers would probably make their way to the East Midlands at least, but they will probably become lighter and less potent except nearer the coasts. I'm thinking back to last Feb which had a tighter flow and not many heavy showers made their way to inland Yorkshire (most snow came from troughs, fronts and other disturbances).

Think yourselves lucky though... no lake effect snow around here! And I was in East Anglia less than a week ago - bad luck!

Edited December 10, 2009 by Yeti

[Just Before Dawn]

I think in this situation you need to know your own area , In this setup I know showers will reach my area , Posting 2 charts below . the PPN one is what i think is a rough guide to where I think showers will fall overall . The second chart is the wind , as you can see it is very breezy on the coast and this would ensure snow showers reach the Midlands.

Good point, and it comes down to something I say on here when I can be bothered - these outputs, even in the reliable timeframe are still computer estimates of what may hapen based on the data fed into it at the start of the run.

What makes these outputs 'come alive' is how they are interpreted, and local knowledge is key to this, as well as experience in interpreting these outputs and, yes, past experience. As you say, the synoptics you've highlighted would be OK for Leicestershire, North Cambridgeshire, Parts of Northamptonshire that traditionally do Quite well in E airflows in winter (though a smidge N of East would be even better) and which don't generally have to worry so much about the modifying influence of SSTs - in some respects slightly higher SSTs are good because they can boost convection, which you'll need if the air flow is fairly slack.

Edited December 10, 2009 by Just Before Dawn

[SMU]

Mark these words we have seen a very subtle shift over night in the jet energy distribution around 140- we see a lot more flow moving along the iberinan Peninsula & less energy into the loop jet over scandi- as a result that huge pulse of cold air starts to look a though it may not make it. However on the plus side the jet pushing along the southern flank in a surpressed regime is likely to strenthen the Easterly to start with & begin to elongate the troughs over spain & portugal- Whilst this is a slightly risky pattern as it does bring the 0c isotherm back North it also brings a higher potential for a BIG snow event-

& after all thats what were all here for-

S

NO change from me after the 06Z-

S

[kold weather]

Yep Steve it is a slightly risky situation to have, though on the up side if we can get the LP to our east and south of the UK then it pretty much locks us in another cold easterly/ESE for another few days until the next LP tries to come through...

The GFS runs this morning look closer to the mark then what the runs yesterday showed, as HD said earlier I suspect the shortwave would merge with the Atlantic low and that seems more probable now. Very risky, but probably an even bigger payoff if it comes off, I think regardless Scotland looks very likely to get nailed under any varient of the GFS pattern, the south however is almost as low as 50-50 in such a set-up.

Still thats a while away yet.

[Neilsouth]

Looking worse and worse for the south with just a small blip risk of snow in the east and south east towards sunday/monday , as the week progresses the main focus is towards the north/north east. South east england does not do very well in east,south east winds. As the air has less travel across the sea and more from a dry continent. I'm hopeing the parallel , gfs , ukmo , ecm pushs the main focus towards the south as this would mean all the eastern counties including up north would do well. We need those east/north east winds!

I'm still waiting for fridays charts

[snowmadchrisuk]

I'm actually not convinced that heavy snow showers would reach that far inland under this setup.

http://www.wetterzentrale.de/pics/Rtavn1201.png

The flow isn't really that tight and never has been progged to be; with that in mind the easterlies of yore with heavy snow showers blowing right across the country look quite different to today's output:

http://www.wetterzentrale.de/pics/archive/ra/1991/Rrea00119910208.gif

You're right in that any snow showers would probably make their way to the East Midlands at least, but they will probably become lighter and less potent except nearer the coasts. I'm thinking back to last Feb which had a tighter flow and not many heavy showers made their way to inland Yorkshire (most snow came from troughs, fronts and other disturbances).

Think yourselves lucky though... no lake effect snow around here! And I was in East Anglia less than a week ago - bad luck!

I don't know about Cambridge , but they did here , That event started on Sunday 1st Feb , We had showers all day and a covering by the evening . This then continued into a very Snowy Monday , although I will have to look at the archives to see if a trough was involved on the Monday.

Also trough's could form at short notice on the current setup . Also when looking at the Ensembles they are rainfall rates , i'm not sure what the exact conversion is but I have noticed in past events you need very little PPN showing on the radar to have big snowflakes.

That to me shows showers are possible from late on the 13th . but as ever we will have to wait and see on the day , It depends on the entry point on the coast , some area's can get a covering , other areas can miss out .

[Cecil Hogmanay Melchett]

Looking worse and worse for the south with just a small blip risk of snow in the east and south east towards sunday/monday , as the week progresses the main focus is towards the north/north east. South east england does not do very well in east,south east winds. As the air has less travel across the sea and more from a dry continent. I'm hopeing the parallel , gfs , ukmo , ecm pushs the main focus towards the south as this would mean all the eastern counties including up north would do well. We need those east/north east winds!

I'm still waiting for fridays charts

I agree Neil BUT ecm is much better for the Eastern half of britain.If that run verified the vast majority would

be bone dry,the high has far more influence.

So,im quite suprised by that meto update,they seem to be siding with Gfs.Interesting.

[kold weather]

Neil, that wouldn't be a bad thing per say, the winds are still coming from the east for a good 24hrs before the wind ever so slightly tilts to the ESE, so that means we get our covering then the colder drier air comes over and stops it from melting, probably would get maxes of -1/2C quite widely here in the SE from that sort of situation thanks to the snow cover and the generally cold air at both the surface and above as well.

[Neilsouth]

Thanks guys , lets hope for the best then for all counties

[SMU]

http://www.wetterzentrale.de/archive/ra/1991/Rrea00119910207.gif

Neil- Feb 1991 had winds just south of East-

I cant believe why people are some down on todays outputs- im very happy- I guess the expectation of that huge ball of cold air arriving had something to do with it-

THe watered down version can be just as good....

S

Edited December 10, 2009 by Steve Murr

[Snowyowl9]

But for the UK hopes, 168 hours IS FI and whether you like or not, it is always possible that change, for better or worst. What i don't like seeing is people saying a cold snowy spell nailed on at 168 hours just because the models agree on it,

3 days away to one of Steve`s Murrs favourite chart set-up with a SVARLBARD HIGH.

http://91.121.93.17/pics/Rtavn841.png

http://www.wetterzentrale.de/archive/ra/1985/Rrea00119850102.gif

[snowmadchrisuk]

Hi Guys and Girls. Been viewing the forum for a while and decided to register. You probably get fed up with these questions but here goes....

I live in Welwyn Garden City, Hertfordshire. What are my chances of seeing some snow next week?

Cheers

Welcome to the Net-weather Forum , I would say your chances would start off low but increase throughout next week , This sort of question is not supposed to be asked in this thread though , but feel free to talk about snow chances as much as you like in this thread here.

Look forwards to reading your posts .

Chris

[cooling climate]

Honestly, how can anyone even dare to complain about a run which has this at T114:

followed by this at T138:

I think people forget how this compares to what we're usually served up. For example, this period last year:

I for one think any griping about current output is churlish at best !!!

I couldn't agree more with you, if these synoptics do not float your boat then some people on

here will never be happy.

I must admit I keep looking at the synoptic runs of the operational and parallel runs (I haven't looked at

the ensembles yet) for t96 onwards and thinking finally after all this time we have real northern

blocking and real heights over Greenland and what these can mean for the UK in wintertime.

Edited December 10, 2009 by cooling climate

[Squigglytay]

Welcome to the Net-weather Forum , I would say your chances would start off low but increase throughout next week , This sort of question is not supposed to be asked in this thread though , but feel free to talk about snow chances as much as you like in this thread here. http://forum.netweat...l-discussion-5/

Look forwards to reading your posts .

Chris

Cheers Chris

Apologies for posting in the wrong thread. Will have a look at that thread now. Heres to a bucket load of snow.

[Methuselah]

Really folks! Some of the doom-and-gloom is really quite surprising... :lol:

As an old fart, I can still recall the run-up to the megablizzard of 1969 (in MK)... For two days' prior to the event, we had to endure a cloudy fresh-to-strong ESE wind with daytime maxima of around +1C and minima around -1C!

Come-on peeps, when was the last time we saw these (potential!) synoptics evolving???

[moses]

Some sensational snow events on the 06Z Parallel Run..

In fact, several feet of snow would fall widely across the country..

In the somewhat more reliable, it looks like rather heavy snow could be falling by late next Tuesday if GFS were correct..

Time for this forecast yet??

A STUNNING 06Z GFS PARALLEL RUN!!!!

For the third time, would someone kindly tell me what a parallel run is?

[SMU]

For the third time, would someone kindly tell me what a parallel run is?

Its been around a while now- its the updated GFS taking over from the current GFS-

It runs around 40 mins after the 12z-

http://www.meteociel.fr/modeles/gfse_cartes.php?ech=6&code=0&mode=0&runpara=1

S