Model Output Discussion: 12Z (02/12/12) And On...

[weather eater]

Fantastic ECM which follows Mr Consistent the GFS. I realise I’m banging on about the GFS its not normally my favourite model but when its starts being this consistent I sit up and take notice.

[Gibby]

Good evening. Here is the latest look at the 12z output from GFS, UKMO and ECM for Sunday November 2nd 2012.

All models show the same pattern of events to take us through the working week. A low pressure trough is moving slowly and erratically East over the UK carrying a band of rain and snow with it over the next 12-18 hours. Following on behind will be a change to NW winds and showers which will then cover the UK until Wednesday with temperatures gradually falling back again later. On Wednesday winds veer North bringing colder weather South with a little rain or sleet falling even in the South as it goes. A ridge then crosses through Wednesday night and Thursday followed by a new area of low pressure developing near iceland and moving SE through thursday with a spell of rain followed by wintry showers to end the week.

GFS then shows the weekend starting with a ridge preceding yet another deep low pressure moving SE over the UK with winds and heavy rain widespread for a while before a return of cold Northerly winds and snow showers to begin the new week. FI tonight is influenced by a complex Low pressure near the Uk relaxing South with time as pressure builds from the North setting up a cold Easterly flow over the Southern half of the UK with the risk of snow very real in the South should FI verify.

The GFS Ensembles show a rather cold outlook with occasional precipitation falling as snow at times. The operational is a colder outlier in the latter stages for a time along with the Control run but many options show some reasonable charts for snow chances.

The Jet Stream shows a pattern of an Eastwards Jet at very southerly latitudes over Europe over the coming week or so. The flow over the Atlantic continues to be ridged before the returning arm settles moving SE to the SW of the UK and on down to the Med.

UKMO for midday on Saturday shows a ridge crossing the Uk from the West with a milder interlude shown. However, the chances are that should the run of carried on the low to the North would slip Southeast with pressure building north behind it and returning cold air South to the UK.

ECM shows Low pressure to the North of Scotland at noon next Saturday with strong Westerly winds and rain sweeping East over the UK to be followed by a return to steadily colder conditions through the following days as winds veer towards the North and later the NE. The Low anchors to the SE late in the run and High pressure links West from Scandinavia to the NW of Britain bringing the likelihood of frequent wintry showers, mostly of sleet and snow especially for the East and SE.

In Summary tonight the mixture of charts persist with variations on a theme the order of the 12zs. That order is for the UK to generally stay on the cold side of normal for the coming two weeks. It also looks like being unsettled at times with the risk of some snow in places with some frost and fog too in the quieter interludes. Little notice should be taken of specifics in FI as specifics can and will change but there is at least a fair chance that many could see at least a little snow within the next few weeks.

[John Cox]

very quiet in here tonight chino steve m and GP where are u ?

thease charts not tickle your fancies ?

I think they have said all they can at this stage.

FI begins at 10th December and any outcome is possible after that . One thing seems certain, the cold theme continues but the extent to where the high positions itself is anyone's guess.

[SLEETY]

very quiet in here tonight chino steve m and GP where are u ?

thease charts not tickle your fancies ?

Obviously not overly impressed with the latest runs I suppose,dont know why as the ecm run is awesome the 2nd best run it has churned out after that 60MPH blizzards chart it showed a few days ago

[phil nw.]

The 12z runs continue with the trend of recent runs in modelling the North Westerly rather cold set up this week and the promise of something colder in week 2.

There are some little differences in the exact track and depth of the low coming down towards the UK towards the end of the week but the overall picture is of the trough gradually weakening as we go towards day10.

The mean outputs have consistently shown pressure rising over the top of the cut off euro trough in week 2 and the ECM op. makes no bones about the eventual outcome by T240hrs with a classic Easterly.

It does look the logical solution as the vortex energy slowly but surely drains away towards the Canadian side.

[John Cox]

"Sleety" states:

"Obviously not overly impressed with the latest runs I suppose,dont know why as the ecm run is awesome the 2nd best run it has churned out after that 60MPH blizzards chart it showed a few days ago"

Yes, It is strange.

GFS seems to be the order of the day generally on the forum.

However here in Ireland our met office seem to generally to use the ECM. Our Met office will not forecast beyond 7 days so I will be listening intently in the coming days. FI is really very exciting from a cold point of view.

Edited December 2, 2012 by John Cox

[damianslaw]

Models very similiar to each other this evening, all show the longwave trough anchoring itself of a NW-SE axis as heights stay high to the north and more importantly to our west which is forcing the jet on a NW-SE tilt scuppering the chances of a westerly airstream developing, indeed the upstream pattern is very conducive for quite a lengthy period of decently below average temperatures.

Next week will be very topsy turvy with rain, sleet and snow, frost, fog, drier sunnier interludes and gales from time to time all in the mix - a colder version of the start to Dec 2011 which saw alot of polar maritime air digging in behind the active weather fronts, this time the polar air will be more pronounced i.e. colder and much more influential.

ECM and GFS are suggesting a possible very cold second week of December as the trough becomes unstuck to our SE and with heights to our NW linking eventually with heights to the NE meaning an easterly/northeasterly flow.

[AWD]

Pretty good agreement with the short term ensembles now, with the mean & Op close to each other;

http://www.knmi.nl/exp/pluim/Data/PLUIM_06260_NWT.png?6767676767

[MR EXTREMES]

i wonder is this setup similar to the 1963 set up?

[bluearmy]

If i get a moment, i'll post the ecm and gefs day 8 means. agreement!! Not too different day 10 although i'll wait for the naefs.

[nick sussex]

Just looking through the ECM ensemble maps and limited support for the UKMO pattern at 144hrs.

I'd say its a margin of 5 to 1 against that but still we can't rule it out completely.

In terms of the GFS/ECM past 144hrs I've seen many of these set ups in the past and often the biggest hurdle is getting any low pressure to head far enough se into the continent .

Shortwave activity near Svalbard can often be a nuisance which stops the ridge to the ne exerting enough forcing on the low.

So we still need to be cautious with getting too excited, so the two main hurdles as I can see are the initial kick start to the change upstream where we still have some uncertainty and getting low pressure to dig right into the continent.

[IDO]

MattHugo81

The ECM ENS between 192hr and 240hr are impressive in terms of northern blocking! All 51 members point towards a cold outcome.

02/12/2012 20:34

Now that is the sort of agreement that we have been hoping for. So the micro changes with the Icelandic Low may be a red herring with regard to long term prospects...just how cold!

Edited December 2, 2012 by i'm dreaming of...

[shotski]

i wonder is this setup similar to the 1963 set up?

In what respect ? but as you say could go down a similar path.

[kold weather]

Good looking ECM ensembles, whilst lacking the severe cold seen on those charts in previous lengthy cold spells, they are decent enough for early December and I have few doubts the extended ensembles will show some runs going through the floor, so to speak.

[nick sussex]

MattHugo81

The ECM ENS between 192hr and 240hr are impressive in terms of northern blocking! All 51 members point towards a cold outcome.

02/12/2012 20:34

Now that is the sort of agreement that we have been hoping for. So the micro changes with the Icelandic Low may be a red herring with regard to long term prospects...just how cold!

I notice Matt H said point towards not are all cold at 240hrs! Good to see though theres a strong trend but it would be better to not go down the UKMO 144 hrs route.

That will try the patience of myself aswell as most people in here, the best route to cold is the quickest with no speed bumps!

[SMU]

Evening All-

Even the UKMO 144 is that bad it does show a flow up the western side of greenland so it still would be ok-

Anyway its been a cracking 24 hours with wintry potential all week especially for the NE, although post that the beast hopefully starts to awaken...

lets see if the pub run has been on the town tonight- as even I would expect an extreme run of some kind....

S

[Catacol]

Intially no we won't see a GH. However if the E,ly does occur then in my opinion from mid month onwards we could see the block over Scandi transferring W towards Greenland as the PV backs further W.

I don't wish to ramp but we could be on the cusp of something very special developing here!!

Yes - agreed. Op runs today are favouring LP splitting the 2 ridges discussed before for much longer than was modelled a few days ago, but still the final evolution is heights over scandy or perhaps more close to Iceland as TEITS states here if the mid atlantic ridge is dominant.

I must admit to being a little disappointed today, because I had thought the evolution to this might actually accelerate and occur more quickly, but in fact the scenario has defaulted to the usual "the models say it will happen on Monday so it'll probably arrive about Friday" setup. Chio referred to this earlier very accurately and wisely. It is interesting how this seems to be a consistent flaw in modelling - a pattern is picked up and the models push it through too fast.

However... shoving my timing error to one side for a moment we still have a setup that leads to an easterly with deep low pressure over Europe. If ice and snow is what you like this is ideal. Not much change therefore from what was modelled yesterday. Those jumping up and down in irritation at a single UKMO run at 144h need to go and sit in a bucket of ice for a bit - I dont know how many times it has been pointed out that it is pointless to get frustrated by a single run. Look at the excellent ensembles today, and listen to IanF who quite clearly stated a MetO firming up on an easterly with attacks from the SW. Strat signals still good and getting better.

[nick sussex]

Evening All-

Even the UKMO 144 is that bad it does show a flow up the western side of greenland so it still would be ok-

Anyway its been a cracking 24 hours with wintry potential all week especially for the NE, although post that the beast hopefully starts to awaken...

lets see if the pub run has been on the town tonight- as even I would expect an extreme run of some kind....

S

I'm not saying the UKMO is bad, it still might get there but once you've seen the ECM it sort of feels a bit underwhelming.

And rather get over the first hurdle quick than have the whole saga drawn out even more. And since when did you become the eternal optimist?

[ITSY]

18Z gives a snow event wednesday morning for Scotland, NE and Central Northern England..

[phil nw.]

The 12z ECM and NAEF`s mean heights show the Euro low heights seem less keen to sink away from the UK by T240hrs.

http://www.meteociel...H1-240.GIF?02-0

http://176.31.229.22...-1-0-240.png?12

the low complex around the south east of the uk only slowly filling.

so maybe the ECM Op. was somewhat progressive with that relatively rapid evolution to an Easterly.

The mean uppers of around -4C for middle England at T240 are still cold but not yet suggesting any deeper cold arriving from the east by then.

http://www.meteociel...H0-240.GIF?02-0

The overall polar modelling wrt to Greenland energy weakening and heights rising to our north hasn`t changed and it does look like it`s a matter of time before our current rather cold setup evolves to something even colder.

Edited December 2, 2012 by phil n.warks.

[ITSY]

Ha, you have to say the marginality is decreasing throughout these events. Form 18Z alone:

Tonight is 50/50 for most away from Scotland

Wednesday seems more nailed in terms of PPN type whilst..

Thursday's front has snow on its leading edge and backward edge.

Then let the games begin...

[bluearmy]

naefs day 8 and ecm day 8

naefs day 10 and ecm day 10

looks pretty good to me

[Timmytour]

That low in the UK on thursday is punching its way through to Germany on the gfs 18z.....in earlier runs it's centre was struggling to get over the Irish Sea

[Grimsby Snow Lover]

Well out to Friday and the GFS 18z is pretty much the same as the previous run with quite a few snow opportunities for many this week. Temperatures after tomorrow look low single figures for most with the 528 dam line never too far away from the whole of the UK. Im really pleased with consistency up to now.

[nick sussex]

Great stuff by the GFS 18hrs run so far with no support for the UKMO.

Also more oval shape to the low than the football of the 12hrs run, looks very good for the ne and wonderful for the Scottish ski industry.

Edited December 2, 2012 by nick sussex