Winter Model Discussion 18Z 13/1/13 onwards.

[MattH]

The 00Z and also yesterday's 12Z EC ENS are indeed cold, as I have recently mentioned on twitter. To be honest they are a set of charts which I wish I could share with one and all. The problem is, however, is that particularly into this coming weekend and next week but the trough disruption looks set to take place actually over the UK, which if happens is an absolutely nightmare of a situation to forecast. Ireland could be near average temps, yet its holding near 0C across England, Wales and Scotland with a major snowfall event, as an example.

The ensembles are cold, the mean for Central England never rises above 3C into next week and as I also mentioned on twitter the mean flow according the ensembles is generally E or SE'ly more particularly into next week with a W or SW'ly type at a low risk at the moment, or it is away from say Ireland and SW England.

Obviously I don't have access to MOGREPS, that's behind closed doors at the MO, but without question if there is cross model agreement between these two models/ensembles then confidence would be on the increase for the cold to sustain itself well into next week. For those who like a bet, there are actually 10 members, out of the 51, which produce the 'holy grail' and take the block from the NE across the N of the UK and make it a Greenland high with time.

It's all to play for in my opinion, but as a forecaster and because of the time frames involved with should all be cautious. Clearly this week is cold and we are looking at the 6 to 10 day period here, which of late has been particularly void of any consistency. As ever, I'm simply telling it as it is according to the EC ENS, but going off them the cold is set to stay for most areas...

Have a good week and more importantly for those who like it, actually enjoy the cold weather now that it's here!

Cheers, Matt.

[lord stratus]

So if this undercut was to come off, surely the blizzard it would produce would be something to go in the history books? thats a low of 968 pressure with nice tight isobars.

Possibly or match past snow falls i.e jan 82 South Wales & the south west of England, 60cm+ of level snow with severe drifting. I wouldn't be concerned of the track at the moment as this will not be firmed up until the latter half of the week and probably be corrected southwards. I remember several channel lows in the 80's and in general the northern extent of the snow was around Oxfordshire. Anyway it does look like we are heading towards a snow event (in the south at the moment) between Thursday and Sunday.

My forecast for a big snow event has been between 15th jan to 18th jan so I'll stick my neck out and go for 17th!

[Catacol]

I agree with some on here that UKMO has been handling the very difficult synoptic pattern of this month very well indeed. I too wonder if the upgrade to greater Strat input has put it ahead in the current strat warming scenario.

This chart at 144 for UKMO is a cracker:

You can see the split vortex very well with the energy from the Canadian side flying across the atlantic. Note also the stubburn centre of high pressure in the Iceland area forcing the underut. There is no 168 to see, but I have to assume it shows easterlies on the back of this undercut once again.

For the south of England that HP needs to hold a bit more sway further south. John H has already pointed out the anomaly charts at 10 days showing strong westerlies under a high block. A wonderful cold zonal output with the jet to the south and cold continental air feeding in around the top of the elongated atlantic attack.

I have one fear (especially as a SW resident!) and that is that western areas might possibly see a lot of cold rain rather than snow. I hope I am wrong in this, and that the UK countrywide can see some white diamonds but I see it as a distinct possibility. More long term both GP and RFS see the core of winter on the horizon now, presumably with the Canadian lobe depowering and greater influence from Siberia.

Edited January 14, 2013 by Catacol_Highlander

[chris55]

GFS quite progressive this morning, ECM more like yesterdays UKMO and UKMO is STUNNING once again with a stalling system and bucket loads of snow.

[ChartViewer]

CMA 120....Lovely block holding, southerly tracking jet, cold 850's...

CMA144

Edited January 14, 2013 by ChartViewer

[pages]

Can I ask why some are labelling the latest model runs 'fantastic'? The nw ten day forecast suggests that, in my area at least, temperatures will climb to 5-6c for the weekend. What am I not understanding?

Netweather forecast is based on GFS. Only the gfs showing the Atlantic breaking through

[TEITS]

A better run so far.

Surprised because if ever a GFS run wasn't going to trend towards the UKMO then I would of said the 06Z. Could be a good omen.

[joshuam10]

Love this thread, but one thing that would help is if you can be clear are you interpreting existing models, then show charts or forecasting new outcomes then explain why. Obviously some posters do a fantastic job at this already

[nick sussex]

Possibly for the first time in days we may have the models actually converging on a solution for the end of the week.

The GFS 06hrs run looks to be close to the ECM/UKMO with trough disruption and a shortwave heading se into France.

[swfc]

very robust 6z at 102 hrs ,upgrade

[southbank]

everyone on the regional threads !! anyway interesting the 6Z at T+90 / T+96 toys with trough disruption and possible undercut , noway like the UKMET or ECM , clearly we are seeing again how the NWP handels the pulses of energy being thrown out by the lobe of PV over Canada , seems as others have said you would expect the Jet to at least be slowed in the atlantic with the PV so displaced and spilt

UK Met 12 z are going to be very interesting alhough for me personally T72 is where i really sit up

[bradymk]

Do we have a little bit of model agreement here?!! haha! GFS moves towards the euros with a big snow event in the west on Friday after trough disruption. Very cold SEly winds

[TEITS]

Very happy with this run so far.

Clearly see the difference in this run because the energy splits at +78 with this going SE and NW. Due to this it allows the block to be further W.

[nick sussex]

That little gap opening up to the north as the shortwave clears into Scandi allows the high to ridge a bit further north.

A very good run so far and bear in mind that the next low will probably be placed further sw with later outputs if the models keep underestimating the block.

[lorenzo]

Joshua when a model run is coming out, like the 06z GFS just now the thread will have shorter posts with commentary on the run as most folk are looking at the model 'live'. You will also find the thread moves much faster..

This will be followed by analysis / scorn / joy / binning / elation / despondency*, thereafter. *delete as applicable.

Don't be put off following the models

[southbank]

T120 .........slider or undercut ??? where will that energy go , at very least the cold seems to be continuing to the weekend at least

[weather eater]

Nothing to suggest that the high level of uncertainty does not remain, therefore synoptic charts beyond 72 hours should be viewed with extreme caution and yes unfortunately that also means the very nice UKMO and GEM ones as well as the GFS. I know its appealing to look for a trend and weigh up the number of models going for one particular evolution over another but frankly; IMO it counts for squat at the moment, no matter how many models are in a more preferable camp. I would say however as a substantial straw to clutch, that the UKMO appears to be handling the modelling of this spell better than most of the other models although the GEM deserves a mention for consistency as well. As I write the GFS 06z does appear to be moving towards the UKMO, still doesn't mean that will be the outcome but good to see all the same. BIt further on and its going to fold like a card tower but as far as I'm concerned at 138hrs thats miles into FI.

Edited January 14, 2013 by weather eater

[swfc]

not at the moment looking like the low will go south east at 126hrs but still an improvement and maybe edging towards the ukmo and ecm.

[Tom Montalbano]

Very happy with this run so far.

http://modeles.meteo...gfs-0-108.png?6

Clearly see the difference in this run because the energy splits at +78 with this going SE and NW. Due to this it allows the block to be further W.

Hi Dave,

as you stated earlier, the best run from a coldies point of view 06z wise for a few days now. John H. often reminds us we should be comparing 06z with 06z, 12z with 12z and so on, rather than consecutive runs, as data criteria is slightly different, run to run.

Regards,

Tom

Edited January 14, 2013 by TomSE20

[Jonan92]

Interesting map of the CMA at t216

Hard to believe

[nick sussex]

Hi Dave,

as you stated earlier, the best run from a coldies point of view 06z wise for a few days now. John H. often reminds us we should be comparing 06z with 06z, 12z with 12z and so on, rather than consecutive runs, as data criteria is slightly different, run to run.

Regards,

Tom

This point is much discussed and may apply at longer range but I don't buy this for output upto 144hrs.

Regardless of the balloon data issue and in this fast moving situation this has 6hrs newer data and with key detail showing as early as T96hrs then you can make comparisons with the rest of todays output.

[Timmytour]

I think the GFS wants to bring the low south but can't quite find the reason yet.

But in preparation for when it does find the reason.it's beginning to bring some very cold uppers down on the eastern side ready to hit us with as soon as it finds the reason for the easterly to make its entrance.

Can't see this being that good a run out from here even further out into FI, but i can see the beginnings of something epic being established for later runs...

Edited January 14, 2013 by Timmytour

[Buzz]

Hang on, this can't be right - people are being POSITIVE about the 06z run? I thought it was usually to be discounted (irrespective of what it was showing) and one for the bin?

[Timmytour]

Interesting map of the CMA at t216

Hard to believe

Wonder if GFS is going to follow this? Maybe the Chinese are leaders......or they've hacked into the Americans data

[TEITS]

Hi Dave,

as you stated earlier, the best run from a coldies point of view 06z wise for a few days now. John H. often reminds us we should be comparing 06z with 06z, 12z with 12z and so on, rather than consecutive runs, as data criteria is slightly different, run to run.

Regards,

Tom

Yes Tom the 06Z in recent days has often been the poorest of the GFS runs. One of the main reasons for this is it seems to have more bias towards moving the overall pattern E. This is something I noted last winter with regards to the bitter E,ly that hit Europe.

At the moment I don't bother viewing the models beyond +144. Seems a trend that the GFS/ECM at +168/+144/+120 are far too keen on removing the block with little undercutting only for them to backtrack at the +96/+72 timeframe. Only the UKMO has consistently suggested the block remains with energy going SE and to some extent the GEM has been the same.