Model Output Discussion - 30th November onwards

[radiohead]

It's intereting to see on the 12Z GEFS, two distinct clusters pretty much evenly split on the 7th. ~50% go for the shorter, less cold spell (along with the op/control). While ~50% members go for a colder blast & lasting a bit longer.

 

 

 

Will be interesting to see the 18Z....the op could switch sides again.

Edited December 1, 2013 by radiohead

[legritter]

OK ,this evenings outputs are hinting at a slightly shorter period of northerly winds ,but this could easily flip back come tomorrows Model runs .And still the potential there for some surprises come later Thursday .Quite often when high pressure sets up in winter it can meander around and is hard to forecast ,indeed if it comes in slightly later to whats showing on tonights ECM and keeps further North west that could change things for the better from a coldies view .so it still looks like we are in the firing line for an arctic blast ,probably followed by cold temp under high pressure .i am not quite yet buying the possibility of high pressure setting up over the far north west of Europe Scandy high etc ,As some Models are suggesting but i will come on board when all models show this in the more reliable. It certainly is a very exciting time and many of us are going to learn an awfull lot this season ,and thats what we are all here for ,plus the odd freebee ,STella ,cheers all .

[SW Saltire]

A question (I am sorry if this has already been answered and maybe this should be posted in the stratosphere thread but here goes) Do we have any indication as to why this year has had a disconnect between the stratosphere and the troposphere, obviously as chionomatic's fantastic post stated that the two 'dancers' don't mirror one another all of the time but all the stratospheric signals were not very encouraging until 2014 maybe even February whereas we are at least getting some cold in early December. Once again I apologise if this is either in the wrong thread or has been answered, thanks in advance, Andrew

[Frosty.]

If Carlsberg........just BANK P1 GEFS 12Z without any hesitation, it puts us in the freezer and doesn't let us out until later the following week, ice days galore on this peach of a run with a risk of heavy snow for many areas and severe penetrating frosts it goes on and on and on..SENSATIONAL 

Edited December 1, 2013 by Frosty.

[abruzzi spur]

ECM pretty much franks the 48 day cold spell for most,

Rather more optimistic for coldies than some of your posts, Shed?AS

[BLAST FROM THE PAST]

Yes essentially fits in with what Ian F said earlier of an essentially anti-cyclonic pattern with the Atlantic effecting the far NW at times, whether we can avoid some very mild weather on the whole will be dependent on the HP centre not slipping South.

 

Yes, like some of the early 00s winters with potentially a lot of snow for Greece and Turkey.

No, nothing like the 00s, winter has just started and a pattern more probable now than deeper into winter at any time/period?  To get what's likely to come in spite of the current PV etc is pretty good imo

Just to clear that up that I think its a very interesting and good start to the winter season....which is a mere 1 day old

 

BFTP

Edited December 1, 2013 by BLAST FROM THE PAST

[chionomaniac]

A question (I am sorry if this has already been answered and maybe this should be posted in the stratosphere thread but here goes) Do we have any indication as to why this year has had a disconnect between the stratosphere and the troposphere, obviously as chionomatic's fantastic post stated that the two 'dancers' don't mirror one another all of the time but all the stratospheric signals were not very encouraging until 2014 maybe even February whereas we are at least getting some cold in early December. Once again I apologise if this is either in the wrong thread or has been answered, thanks in advance, Andrew

I think that they are dancing happily together presently - the strat is behaving as would be expected per analog years and the tropospheric response measures up quite well too. Wave activity rebounds into the strat every winter and this is no different. CH's excellent post earlier in the thread shows this very well. I suspect that any strong Scandi ridge signal may be slightly over emphasised by the output - but later on in the season I wouldn't.

[SMU]

http://www.meteociel.fr/modeles/ecmwf/runs/2013120112/EDM1-216.GIF?01-0

ECM Mean @ 216 a lot more Scandi blocked than the 00z- Expect more runs to drop after day 12 in the ensemble suite....

 

S

[SW Saltire]

I think that they are dancing happily together presently - the strat is behaving as would be expected per analog years and the tropospheric response measures up quite well too. Wave activity rebounds into the strat every winter and this is no different. CH's excellent post earlier in the thread shows this very well. I suspect that any strong Scandi ridge signal may be slightly over emphasised by the output - but later on in the season I wouldn't.

Thank you for the reply, I suppose we are a significant way from the Scandi high possibly verifying so it's a waiting game. Your winter prediction have been made crystal clear which is very brave but your confidence I believe is not misplaced. Still, I did think December was predicted to come in above average by quite a few due to background signals becoming more favourable for cold later on, whereas currently it would appear we are going to be at least a bit below average for the first third of the month, with an easterly at least seeming plausible and definitely 'on the table' so to speak, which would take us towards mid month. I am well aware this is only the first of December and a lot can change to those who believe December will be 'zonal' or whatever that is Edited December 1, 2013 by SW Saltire

[Cloud 10]

Latest fax chart for Wednesday has the initial cold front just about to clear Southern England

with the 528 dam line over Northern England with a cold showery flow for Scotland.

 

 

The bitterly cold air at this stage is just south of Iceland.

 

Be interesting to see the 96 and 120 hrs fax charts later to see what the met-office 

make of it all.

 

 

In the longer term,the ECM day 10 ens. anomaly chart showing scandi-high possibilities.

 

[bluearmy]

sorry to have missed the whole evening thus far !  any chance of a westward correction ?  the means say no but the spreads say yes (not surprising) but not a huge amount yes.  as far as the scandi ridge is concerned, i stated this morning that it was a certainty at day 10 and it remains so this evening. the problem we have is our own limpet ridge. at the moment, i cant see a convincing mechanism for removing it quickly. awaiting some guidance from 12z naefs and then subsequently the full ecm ens later.

 

i did note on the post day 10 ecm ens from the 00z that there was a brief zonal period of two/three days before the ridge pushed towards nw europe from n scandi.  is suspect, looking  at the day 10 anomolys on the 12z ecm that this run might be different.

Edited December 1, 2013 by bluearmy

[Gibby]

Good evening. Here is the slightly late report from me on how I see the 12 noon outputs from the big 5 models for this evening Sunday December 1st 2013.

 

All models show a quiet first half of the week as High pressure remains in control for the time being with slack and light winds and largely close to average temperatures. Through the middle of the week weak troughs move South over the UK with the later one bringing a substantial drop in temperature, especially over Northern and Eastern areas where snow showers will become a feature for a time with accumulations here and there. In the South and West though colder the weather will be fine and dry with sunny spells with frost developing overnight.

 

GFS then shows a change to milder conditions soon after the beginning of next week with milder SW winds bringing cloudy and mild conditions with rain at times over the remainder of the run with strong winds at times and the heaviest rain towards the North and West.

 

UKMO closes it's run with fine weather over all areas as High pressure is positioned over Southern Britain. The weather will be cold at the surface with some very sharp frost and fog patches, slow to clear in places. The far NW will become more cloudy and less cold later.

 

GEM shows High pressure slipping away towards Southern Europe through the following week with fresh SW winds developing for all with some rain at times especially in the North and West. It would become milder everywhere.

 

NAVGEM keeps cold and High pressure based weather early next week as High pressure slowly drifts East across the UK. Frost and fog at night would likely be problematical before a Southerly breeze picks up later.

 

ECM tonight shows High pressure sliding over towards Germany towards the middle of next week with milder weather across the North and west though with largely overcast skies. In the South and East a continental feed of air may assist in keeping thing colder, especially overnight if cloud breaks occur when frost and fog is possible. It may be though that it stays rather cloudy and grey.

 

The GFS Ensembles show a colder then milder spell before things return to fairly close to average. There are some colder options shown there, some with a Scandinavian High which could prove interesting in time if it evolves. Rainfall would be limited in the South until later in the run while the NW in particular sees more rainfall than elsewhere.

 

The Jet Stream shows the flow turning Se across the UK and North Sea later next week before another change occurs and for the first time tonight this season the flow is shown to blow well South of the UK in Week 2 as pressure possibly builds to the NE.

 

In Summary tonight the weather is set to turn colder later this week, albeit briefly. Some sleet or snow showers should be likely in the North and East with fewer showers in the West closest to High pressure moving in from the West. Thereafter the most popular solution looks to be for High pressure to be sliding away South or SE with milder SW winds developing but there is a lot of mileage over the coming days of this week for this pattern to change as it looks no means certain that this is how things will evolve.

[MKN]

http://www.meteociel.fr/modeles/ecmwf/runs/2013120112/EDM1-216.GIF?01-0ECM Mean @ 216 a lot more Scandi blocked than the 00z- Expect more runs to drop after day 12 in the ensemble suite.... S

Are you trying to suggest that's a good chart Steve? I respect your opinion but that to me looks a million miles away from anything that resembles cold for the UK. Hopefully I'm missing something here as I would love to be proven wrong

[nick sussex]

More easterly options showing on tonights ECM ensembles for Holland:

 

http://www.weerplaza.nl/15daagseverwachting/?r=midden&type=eps_pluim

 

Some very low dew points shown there down to -15c, difficult though to tell whether this is an inversion type scenario, earlier the ECM operational run is at the top end of the main cluster.

 

The wind direction shows quite a scatter but again more east/ne/se wind flows than this mornings run. I think we have to sit tight for a few days and see how the models develop that troughing in the Atlantic because this is quite crucial in helping the high ridge ne.

 

In terms of the UK in terms of how long any cold lasts that depends on what sort of flow is picked up, theres quite a difference at this time of year between a southerly and se flow from that high, it could remain cold at the surface well past the point that the models lift out the cold uppers.

[shotski]

Are you trying to suggest that's a good chart Steve? I respect your opinion but that to me looks a million miles away from anything that resembles cold for the UK. Hopefully I'm missing something here as I would love to be proven wrong

 

I think maybe steve can see that HLB could be just around the corner.

Not a million miles away from this chart.

You can't make a cake without cracking a few eggs.

[Frosty.]

Tonight's ECM 12z ensemble mean shows a strengthening arctic flow blasting down across the uk by late thursday once the trigger low has done it's job, and the bitter spell then persists throughout friday, friday night and into saturday am and then the n'ly flow weakens with a ridge of high pressure building into the uk but bitterly cold and frosty weather next weekend once the snow showers die out on eastern coasts. I think there is potential for disruptive snow across parts of the uk during thursday and friday, the far north of the uk turns arctic during thursday am with snow showers packing in thick and fast from the north and N'ly winds rising to gale or severe gale force in the far north which would whip the snow up into deep drifts by thurs night and throughout friday/overnight.

 

Once the band of rain with back-edge snow clears south through the midweek period, snow showers will then spread south to remaining areas and as the arctic air digs in, frosts will become widespread and sharp..super start to winter is only 4 days away, let's hope for longevity in the cold spell upgrades, something like P1 GEFS 12z would be awesome but just to carry on cold and blocked with no thaw would be nice and the ecm mean shows a continental drift with anticyclonic weather locking in towards the end of the run with surface cold bringing widespread frosts and max temps struggling in low single digits celsius, perhaps the only area of the uk to see temps recover would be northwest scotland as the high just pulls away from there allowing a sw'ly flow to brush around the nw corner of the BI. Let's hope the EC32 day is still indicating further cold and wintry weather in the run up and during the festive period. 

Edited December 1, 2013 by Frosty.

[A.J]

Are you trying to suggest that's a good chart Steve? I respect your opinion but that to me looks a million miles away from anything that resembles cold for the UK. Hopefully I'm missing something here as I would love to be proven wrong

Hi ST, from what I can see with my admittedly untrained eye is heights building into Scandinavia at T216 and T240, with troughing in the mid-atlantic allowing a LP to form, this low could well be the trigger low to slip south eastwards where heights are not quite so robust et voila, lower heights to our south, blocking to our NE and the result would be an easterly......providing of course if it verifies.....more runs needed as ever but the building blocks are there to see to my eyes

 

(I might be completely barking up the wrong tree of course, still learning!)

Edited December 1, 2013 by ajpoolshark

[The Enforcer]

Are you trying to suggest that's a good chart Steve? I respect your opinion but that to me looks a million miles away from anything that resembles cold for the UK. Hopefully I'm missing something here as I would love to be proven wrong

Either way, at T+216, even for the ECM, there's limited chance of it verifying, so not one to lose much sleep over.

[Biggin]

because the next low is moving over the top of our high.

but we shall see at t192

Please post some charts please

[Gaz1985]

JMA still going for a short lived cold snap

 

 

 

Turning milder.....with high pressure settling to the south of us

 

 

 

[chionomaniac]

Anyone spot the big shift in the NAEFS 11-15 day anomalies between the 00Z and 12Z runs?

 

00Z

 

 

12Z

 

 

Even the cumulative anomaly charts are jumping around - these should be the most dampened of the lot without such interrun variance. Big reduction in the strength of the Scandi anomaly. Doesn't mean that it is anywhere near correct though.

Edited December 1, 2013 by chionomaniac

[Jason M]

Are you trying to suggest that's a good chart Steve? I respect your opinion but that to me looks a million miles away from anything that resembles cold for the UK. Hopefully I'm missing something here as I would love to be proven wrong

 

Your not missing anything. In isolation that would be a poor chart. the 'mean' chart though represents a combination of all the ensembles and I think Steve is saying that the relatively high pressure over Scandinavia illustrates quite a few of the ensembles are going with a Scandi High. Of course another way of looking at it is that even more of them are still going for a high to set up to our SE.  

 

I'm not a fan of using these personally as they are very misleading IMHO (except of course if all the ensembles agree and it would then be pointless anyway). Some people post charts highlighting the geographical areas where the output has the highest / lowest confidence and these are more helpful.

 

As we stand tonight there is the possibility of a full on easterly in say 10 days time or thereabouts although it remains an outside chance at present (but the signal has been gaining strength). That really is the underlying message.

 

Jason

[SMU]

Anyone spot the big shift in the NAEFS 11-15 day anomalies between the 00Z and 12Z runs?

 

00Z

 

00znaefsCumulative500mbHeightAnomalyNH360.gif

 

12Z

 

12znaefsCumulative500mbHeightAnomalyNH360.gif

 

Even the cumulative anomaly charts are jumping around - these should be the most dampened of the lot without such interrun variance. Big reduction in the strength of the Scandi anomaly. Doesn't mean that it is anywhere near correct though.

 

Eastward bias my friend-  .....

 

So before any one else thinks I make it up- whos got the link to the NCEP model bias page-

 

S

Edited December 1, 2013 by Steve Murr

[bluearmy]

Anyone spot the big shift in the NAEFS 11-15 day anomalies between the 00Z and 12Z runs?

00Z

00znaefsCumulative500mbHeightAnomalyNH360.gif

12Z

12znaefsCumulative500mbHeightAnomalyNH360.gif

Even the cumulative anomaly charts are jumping around - these should be the most dampened of the lot without such interrun variance. Big reduction in the strength of the Scandi anomaly. Doesn't mean that it is anywhere near correct though.

Was just about to post that ed (distracted by athletico beating barca) - thats the naefs swinging back and forth (point taken steve and i'll look out for that on the 12z. in future when block building to our east though it isnt something ive noticed in previous winters).

Soon be able to assess ecm full ens. They have been fairly consistent on that scandi height rise and judging by the dutch graphs, they look like continuing thus.

Edited December 1, 2013 by bluearmy

[lorenzo]

http://www.hpc.ncep.noaa.gov/mdlbias/index.html