General Model Output Discussion

[Altostratus]

The ECM De Bilt ensembles for the Netherlands show the operational run as being a mild outlier from next Wednesday.

http://www.weerplaza.nl/15daagseverwachting/default_pluim.asp?r=midden

Of course every new trend will always probably start off as some sort of outlier, however for the timebeing it's not well supported. IMO this evening will be important to see whether the models have overreacted to upstream changes, if they have then we're likely to see the jet stream edged further south with the cold hanging on a while longer.

Not too dissimilar to last night’s. The operational has better support from the control run this time though. Still a lot of scatter, so nothing is guaranteed yet. Tne GFS operational was also warmer than it's ensemble mean.

[yamkin]

Rather worryingly the ECM might be an outlier but the control run goes exactly the same way. In these situations you find the ensemble mean will begin to rise should the OP continue with this trend.

As for Sunday and at the moment alot of uncertainity. The UKMO takes the risk much further S and this is shown on the BBC graphics.

Love the GEM to be right this morning.

Looks like the MetO are using their human input after the UKMO backed down on most of the ppn on Sun/Mon.

BBC24 forecast starting to back down from Carol's earlier snow forecasts. Chris Fawkes now showing snow for Saturday night going into Sunday

[NorthNorfolkWeather]

ECM definitely going for the breakdown. I'm sure that many people will be pleased with some warmer weather, but southern counties my end up under much more snow before any thaw sets in. East Coast areas may see rain/sleet if the T144 and following verify.

Scotland on the other hand looks to be keeping an Easterly flow and therefore staying colder than further South.

John Holmes made a comment yesterday about the cold air being difficult to move, so my personal view, taking into account JH's experience, is that this may not bring much warmer weather, we'll need to look a bit further out for another Atlantic attack.

The other point is that the Southern arm of the Jet remains south of the UK apart form a low energy push around T120, and this only gets to the south west, before petering out.

My guess?? A warm up compared to now, but still below average.

Interesting times

Edited January 8, 2010 by NorthNorfolkWeather

[Archie_Lewis]

Graphics on Latest BBC weather showing snow again. Sat night into Sunday.

Expect detail to continue to change on graphics as the BBC always do. that's what they do best.

Back to the models... Could we be in for a channel Low next week? The further SW the Low travels.. The better

[Tom Montalbano]

Morning all,

Always have a routine re. the order I have of looking at models. I tend to look at the smaller models first, then GFS, UKMO, ECM and finally for short/mid term, METO faxes.

I was a bit dismayed on seeing the UKMO/ECM runs after seeing GEM first, which was a corker of a run and has the cold holding on,with a real snowy look about the run esp. for the south.

http://www.wetterzentrale.de/pics/Rgem1321.gif

http://www.wetterzentrale.de/pics/Rgem1441.gif

Just hope the so-called bigger models are being a bit too progressive and we have a throw-back to yesteryear with low pressure attacking from the SW but giving up and retreating over France!

Regards,

Tom.

[TEITS]

Graphics on Latest BBC weather showing snow again. Sat night into Sunday.

Expect detail to continue to change on graphics as the BBC always do. that's what they do best.

Back to the models... Could we be in for a channel Low next week? The further SW the Low travels.. The better

Sorry to ask but how far N did they have these graphics?

Looks like the 06Z has quiet extensive snow for Sunday.

http://www.wetterzentrale.de/pics/Rtavn544.png

I will say though that I find the UKMO precip forecasts often dodgy.

[kumquat]

Does anybody know what time the 06Z NAE is out? 00z shows similar to yesterday's BBC graphics re: Northern extent of main band of ppn on Sunday. http://www.weatheron...EL=0&ZOOM=0

Edited January 8, 2010 by kumquat

[Nick B]

The ECM De Bilt ensembles for the Netherlands show the operational run as being a mild outlier from next Wednesday. http://www.weerplaza...im.asp?r=midden Of course every new trend will always probably start off as some sort of outlier, however for the timebeing it's not well supported. IMO this evening will be important to see whether the models have overreacted to upstream changes, if they have then we're likely to see the jet stream edged further south with the cold hanging on a while longer.

Hmmm. Not actually an outlier I would say, in that it has support from just a few of the members, but it's of course not a run to be welcomed by those wishing to see the very cold pattern extend. However, there is still time for either upgrades to the models, though I feel we are definitely heading towards a lessening of cold in the medium term. It would be fun to see plenty of snow for many areas in the way this is worked out, but this will not really be known until the event itself is almost upon us. There is of course plenty of time and opportunity over the course of the next couple of weeks and into the longer term for the next cold spell to appear over the horizon - as far as I am aware things still hang in the balance for a cold vs mild February? Don't forget, in the past, this type of winter has often lasted well into March... Edited January 8, 2010 by Nick B

[Frosty.]

Stunning GEM 00z this morning with a sustained E'ly blast which briefly gives way to high pressure before a possible reload by T+240 hours, the ECM 00z keeps scotland v.cold next week with bitter SE'ly winds and a risk of snow but a slow rise in temps across the south & west(maybe a snowy breakdown followed by rain & mist/fog + FLOODING RISK) with all areas becoming less cold or milder by T+240, the UKMO 00z shows cold SE'ly winds at T+144 but trending the same way as the ecm so a thaw would set in across southern and western england, wales and ireland but scotland would take longer to warm up but if the gem is right, we all stay v.cold.

[Solar Cycles]

After reading last nights post by GP, I don't think this block is going anywhere fast. Less cold air pushing into the SW, and far West of the country, but the majority of us staying cold/very cold. Snow risk increasing from Wed onwards, away from the above areas!

[Snowly does it]

By T120 the GFS 06z block is in better shape and a cold surface SErly with the LPs further south.

At this stage looks like a backtrack to some degree from the 00z, let's see where this goes....

[mushymanrob]

looks like the gfs was correct in suggesting a breakdown by mid week, dispite many saying 'bin it'. it might be a lengthy process but both gfs and ecm now predict mild next week.

[Frosty.]

looks like the gfs was correct in suggesting a breakdown by mid week, dispite many saying 'bin it'. it might be a lengthy process but both gfs and ecm now predict mild next week.

No they don't mushy, a slow trend to less cold in the southern half of the uk but probably a snow event before the thaw begins, the thaw would bring the risk of floods with some areas under 2 foot of snow with much deeper drifts and mist/fog would become widespread, awful slushy messy mushy weather late next week in southern and western areas. Still time for the cold to fight back, like the gem shows.

Edited January 8, 2010 by Frosty039

[NorthernRab]

looks like the gfs was correct in suggesting a breakdown by mid week, dispite many saying 'bin it'. it might be a lengthy process but both gfs and ecm now predict mild next week.

Eh, the GFS certainly doesn't - it has backtracked somewhat from its previous suggestion with high pressure once again building over Greenland and the jet heading south. Less cold yes, but certainly not mild by any stretch of the imagination. Think you're going to have to wait a bit longer for those mild temperatures you desire Rob

[Snowly does it]

06z shows the LP slippin under us and a precarious Easterly flow with marignal uppers during the latter part of next week.

Azores high throwing up what might be a useful ridge?

[chionomaniac]

I am just copying this post that I made in the model thread in order to add a couple of extra charts.

What we are essentially seeing is the polar vortex splitting at around T+200. This is no transient feature and has been modeled for some time. The split extends right up into the middle stratosphere. This is significant suggesting that once the split forms, it will not disappear overnight. The split leaves two main sections of daughter vortices - one over Canada the other over Siberia. Current modeling suggests that the Canadian daughter vortex will be the stronger. Now this is where it gets interesting. The position and strength of these vortices, alongside any reducing residual vortex left elsewhere, will be critical in determining whether or not an Easterly will occur. The models are throwing up differing solutions to height rises between the two vortices. One thing that has been consistent is the suggestion of height rises over Alaska and the Pacific region. What we have to hope for is that we can see similar height rises to out north allowing the jet to undercut and bring us our easterly. With this type of set up we have a good a chance as any.

c

Hopefully update the GFS later

I am going to repost this post made at the start of December because it is equally valid today but with the timeframe being around T+168. Now when I originally posted this it was some 2 weeks later that the first cold spell arrived with a vengeance. That being the case there is the chance that any milder interlude programmed by the models may be brief and followed by a reload of the current winter pattern so far. This may be heavily dependent on the GWO phases and residual vortices positions.

c

[cyclonic happiness]

Latest GFS has the undercutting low alot further south hence delaying the 'breakdown' for a couple of days, maybe it's gonna keep getting pushed back?

Still 50/50 as to whether we get a prpoper breakdown or just a less cold interlude, the overall setup that caused this cold spell is still very much in place.

[The Weather Dragon]

If GFS 06z verifies then we are in for another bitterly cold week with a raw SE Wind - little thaw I would add.

[Frosty.]

06z shows the LP slippin under us and a precarious Easterly flow with marignal uppers during the latter part of next week.

Azores high throwing up what might be a useful ridge?

A bit more like the GEM 00z, I don't think this cold spell will end without a fight and this backtracking is interesting as the mood on here was very glum this morning with the thought of losing all our precious snow.

[snowmadchrisuk]

I'll bank 6z the way it is shown 100% . Bags of potential Snow for alot of people.

[MKN]

The 06z isnt going for any breakdown of any sort really, the surface cold will be here all week, the very cold uppers might not be there but -3/4s with the cold at the surface would be cold enough to support snow if theres any precip around. although mainly it looks like the snow from now til monday that looks like falling wont be going anywhere for another 7days at least. that would mean snow on the ground getting on for 2 weeks which is exceptional for most parts of england.

[TEITS]

Are you mild ramping Rob?

Seriously though, I'm sitting on the fence on this one - uncomfortable at times, yes, but it means that I'm not surprised at the eventual outcome.

I think sitting on the fence is exactly the right attitude at the moment.

Apart from looking at the models im also using past cold winter synoptics as a guide. The return of milder weather has often been a slow drawn out process which on occasion has failed. I really wouldn't be surprised if the model output over the next few days swings between a mild SW,ly and a cold E,ly. However as we enter the latter part of next week it looks to become cold rather than very cold like we have at the moment.

Back to Sundays event and the locations currently favoured to see the heaviest snow is E Anglia/Midlands/Wales. I would put the N extent around Lincs possibly slightly further N.

[Polar Continental]

A colder 06z, with the low undercutting the block further south, so more of an easterly feed, rather than a south easterly. This run supports the 0z Gem which was out on its own keeping the cold easterlies locked. The models will struggle; expect to see many changes over the coming day or so.

[nick sussex]

The model uncertainty continues with the gfs 06hrs run continuing it's backtrack, in typical model fashion it's gone from one of the mildest models yesterday to one of the coldest today.

On a separate note lets hope the wind remains calm and skies remain clear as there is a great chance for Altnaharra in the Highlands to register a record UK low temperature tonight!

[Snowly does it]

And here comes the cavalry at T252 with bitter cold streaming towards Scandi