General Model Output Discussion

[TEITS]

Just to show how much can changein F.I check these ensembles out. Now I saved these a while ago because I had a feeling the model output would change.

Using 10th Jan as an example the mean is now 10C colder!!

http://charts.netweather.tv/ensimages/ens.20100103/12/t850Cambridgeshire.png

[kold weather]

Yep to the two Paul's, I was a bit hasty but I just saw a much flatter upper high and a big low blowing up and rather assumed it would'nt be as good...

As it happens the klow undercuts even better then the ECM does...however I'd think the set-up the GFS 18z suggests is massivly risky...

However is it a stunning run, yeah even though its a big downgrade for my area, still would be pretty snowy!

[nick sussex]

Wouldn't agree with a longer term downgrade at all Darren. I think you're worrying too much about FI in any case and looking for breakdowns that aren't there!

This run is remarkably similar to the ECM with pressure remaining strong to our north and northeast, and undercutting lows going into mainland Europe. Sensational synoptics, and no sign of an end to the cold:

http://www.wzkarten.de/pics/Rtavn2761.html

http://www.wzkarten.de/pics/Rtavn2762.html

Sensational stuff!

I agree totally Paul, i mean its still cold well into FI, even when the very cold uppers disappear, theres loads of surface cold to draw on and most of europe will have snow cover and cold air stagnating at the surface. People have to be realistic here the pattern is still evolving, you can't maintain a non stop supply of -10 upper air, peoples expectatons are just running too high here, if the pattern eventually resets with high edging towards Greenland and trough developing over Scandi then there will be a period with just surface cold to draw on which will still be very cold at the surface. This is western europe not Moosejaw, Canada !, i chose that town because i think it's one of the best town names ever!

[cyclonic happiness]

A really amazing run again, still the chance for alot of snow in places and yes the coldest uppers get pushed away in FI but the surface temps will still be way below normal and the run is COLD the whole way through.

AND look at this jet profile all the way through FI is REALLY way south and flat as a pancake!

http://www.meteociel.fr/modeles/gfse_cartes.php?ech=192&code=0&mode=5&carte=1

Isn't the polar jet where the subtropical jet should be? I'm not an expert but it seems to have displaced it?

[cooling climate]

Excellent run I must admit I was a little confused when I came back on this thread after watching the

run come out and read some of the posts.

Heavy snowfall and then cold for another 7 to 10 days after perhaps, and with the odd top up keeping

a very healthy snowpack, yes I would settle for that.

[kold weather]

One big word of warning though, the set-up at 192hrs is really VERY dodgy, in terms that it could very easily go wrong at that point, just a little more energy going into that low and instead of cutting off a new low it'll ride over the top of the HP, in that solution you'd probably be looking at the end of the cold spell...

As for trying to see breakdowns, I'm not really, just saying how I can see things evolving on the runs, as it happens the 18z is a superb run because the upper low curs off...its the type of evolution seen several times in the severe winters of the past.

Also agree with Nick, don't always expect very cold uppers to be in place, typically the inital thrust of the cold will be very cold in terms of uppers but once established surface cold becomes more important.

I'll be very interested to see what the ensembles suggest...

[johnholmes]

One big word of warning though, the set-up at 192hrs is really VERY dodgy, in terms that it could very easily go wrong at that point, just a little more energy going into that low and instead of cutting off a new low it'll ride over the top of the HP, in that solution you'd probably be looking at the end of the cold spell...

As for trying to see breakdowns, I'm not really, just saying how I can see things evolving on the runs, as it happens the 18z is a superb run because the upper low curs off...its the type of evolution seen several times in the severe winters of the past.

Also agree with Nick, don't always expect very cold uppers to be in place, typically the inital thrust of the cold will be very cold in terms of uppers but once established surface cold becomes more important.

I'll be very interested to see what the ensembles suggest...

see my latest blog for a possible reason it MIGHT happen

[snow raven]

One big word of warning though, the set-up at 192hrs is really VERY dodgy, in terms that it could very easily go wrong at that point, just a little more energy going into that low and instead of cutting off a new low it'll ride over the top of the HP, in that solution you'd probably be looking at the end of the cold spell...

Are you basing that statement on 1 run?

[Liam J]

A really amazing run again, still the chance for alot of snow in places and yes the coldest uppers get pushed away in FI but the surface temps will still be way below normal and the run is COLD the whole way through.

AND look at this jet profile all the way through FI is REALLY way south and flat as a pancake!

http://www.meteociel.fr/modeles/gfse_cartes.php?ech=192&code=0&mode=5&carte=1

Isn't the polar jet where the subtropical jet should be? I'm not an expert but it seems to have displaced it?

sill a good run the 18z gfs, loads of potential for the next 3/4 days for heavy snowfall the event for friday and saturday is way to far away to call yet and not worth getting upset which many people will be, the 00z run could bring back the snow storm..

snow chances will appear at short notice, nowcasting and radar watching aplenty, the first event monday night with the cold front moving down over scotland, through northern england southward, wednesday sees a NE flow quite strong with the low in the north sea with convective showers and bands of snow moving inland..

lets wait until wednesday before people start getting excited/upset at the weekends prospects..

later in the run when we loose the low 850's will the snow risk reduce even with the cold at the surface, but loose the uppers

[kold weather]

I'm only saying it in relation to what the 18z shows SR, its just a warning of what could have come up and why I thought it would downgrade...as it happens though the 192hrs is amazingly close to the 12z ECM as has been mentioned...

Anyway ensembles intially have the high further south but most still bring in a easterly...

Bitterly cold thats for sure!

[PB22]

London ECM 12z ensembles:

http://www.meteogrou...e_forecast.html

Operational pretty much bang on in terms of temperatures, and its cold until mid-month at least. On the lower end of the scale for winds, may suggest many go for a more potent breeze later in the week.

Edited January 3, 2010 by Paul B

[swilliam]

the snowfest at the weekend never makes it out of germany on the ensemble control run.

[snow raven]

I'm only saying it in relation to what the 18z shows SR, its just a warning of what could have come up and why I thought it would downgrade...as it happens though the 192hrs is amazingly close to the 12z ECM as has been mentioned...

Anyway ensembles intially have the high further south but most still bring in a easterly...

Bitterly cold thats for sure!

Thats fair enough Kold. But you are basing those opinions on 1 run - the pub run at that! I'm not saying what the 18z is showing won't happen, but boy oh boy, your posts tonight is seriously enough to make half the SE break out the prozac!

[john w]

Its so interesting picking up on trends.

About 2 days ago now the snow potential for the SE was generally (away from the coasts) not huegly promising. Then...a series of model runs go positive in the precipitation trends and everyone is very excited...me in part guilty for this.

The 18z does pull it east BUT in some respects this was the case 2 days ago, the westward shift was ramped about and noticed and commented on. BUT the more east orientation to be honest was present in the first place.

Still for any case, I think much of London, the SE will see snow this week at some point now and this is an improvement and correction than previously where i thought the front travelling south on Tue/Wed would stall @ midlands or the warm sector would cause rain.

Ridge is further East closer to ireland. the ensembles for pressure are starting to roll on WOL...not sure of neatweathers progress (rolling I guess) so for pressure we will see if the 18z is an outlier...though it is more in accordance with the 12z ECM. One final point to note. The country tracks forecast mentioned the Friday event...for thos who did not see it i-player it and zoom to about 46 minutes. For them to have mentioned this there must at least somewhere be some confidence.

My 100th post I think, so a resolution for the next 100 is to understand more of the maths and teleconnections.

[snow raven]

the snowfest at the weekend never makes it out of germany on the ensemble control run.

Am I not reading that chart right then? What are those lovely blue and green colours covering the SE & EA?

[kold weather]

London ECM 12z ensembles:

http://www.meteogrou...e_forecast.html

Operational pretty much bang on in terms of temperatures, and its cold until mid-month at least. On the lower end of the scale for winds, may suggest many go for a more potent breeze later in the week.

Most also keep it around 0C generally right till the end, the mean is raised by a few very mild runs, exceptional ensembles though thats for sure!

SR, I'm also using the 18z because its VERY close to the upper pattern then ECM on its last 2 runs has been suggesting...saying that IF the PV stays far enough west over Canada then any low pressure heading into the Atlantic will only serve to re-enforce the upper high and help to tilt the winds to a more SE direction, thats what we want if we are to keep the exceptional cold in place.

The pattern on the 18z would probably lead to a severe month (sub 1.5C)

[Sawel]

I wouldn't worry about the 18z, it's hardly the most reliable of runs but the set-up projected is hardly going to favour Ireland, Wales, Northern England, Western England, much of Scotland, the South West or the West Midlands.

Yes todays runs have been a bit disappointing with regards to this easterly "event" for those in the places that you mentioned. Maybe tomorrow the models will show something different but we're around 120 hour territory here- something the models should have a good grip on, especially the ECM as it's been performing well above the other models at +120 hrs this past couple of weeks.

[swilliam]

Am I not reading that chart right then? What are those lovely blue and green colours covering the SE & EA?

Light to moderate ppn totals probably due to showers. The main ppn from the low is centred over most of germany

[damianslaw]

One lesson we all need to learn with the models is that beyond the immediate timeframe i.e. I say only a mere 24 hours at best, they certainly cannot be relied upon to show the realities of detail, only general trends. Compared to the models as shown this time yesterday for this time tomorrow i.e. 48 hours, none appeared to bring in more a N/NW flow, all were showing N/NE flow, look at the FAX charts for tomorrow night, we are now seeing a stronger trough/front develop on a NW flow for tomorrow evening/night, these subtle differences in very short timescales make all the difference to details such as where snow is likely to fall and how much. In an unstable northerly flow as we have now, sudden developments often do occur in the immediate timeframe and troughs and fronts can appear out of nowhere and take different paths to what was generally predicted, unstable northerlies are notorious for bringing such developments - a forecasters headache!

Back to the general trends being shown by all the models and they are all committed to bringing a switch in the flow from the north to the east as we see heights intensify and build over Scandanavia during the course of the week.

For reasons expressed above, I'm not making any judgement on what is being shown towards the end of the week in respect of lower heights over the near continent.

Edited January 3, 2010 by damianslaw

[Bobby]

The massive SE snow storm was a huge outlier on the 12z so it's no surprise it's now gone, was always very unlikely. Still plenty of snow about in the SE though.

[Snowaddict]

18Z GFS Operational was a 850mb Temp outlier almost from the very start for Eastern Ireland:

http://www.meteociel.fr/cartes_obs/gens_display.php?ext=1&x=119&y=26

SA

[Neilsouth]

http://91.121.94.83/modeles/gens/run/gens-11-1-132.png?18

^ Lets hope that doesn't happen , ill go mad

[kold weather]

FWIW the GFS control run shows the other option, with the Atlantic attempting to come back in, probably a big snow event but the less cold air wins out in the end, still not what I'd call mild mind you BUT a far cry from the 18z synoptics.

[johnholmes]

Are you basing that statement on 1 run?

I doubt it from reading KW's posts over the years-a very sound head on young shoulders it seems to me.

As to the 18z KW refers to, he does make the point that, at the end, its not too dissimilar to the EC 12z run and I think he also quotes the 00z run.

In truth EC has done something along these lines over the past 72+ hours, GFS once at the T+240 time frame.

Who knows if they are the correct runs.

What I've done in the last blog posted is to try and explain why they may be showing what they are now and then-no more-as no one professional or amatuer has any idea at that range. possibly one or two may have hunches based on many years experience but nothing more.

[Neilsouth]

Any chance it can be upgraded again and this was just a blip in the water , so to speak?