Model Output Discussion - Tuesday 20:25 -->

[cold snap]

Not to state the obvious one thing is surely nailed now with the models that we are in for

Some sort of cool or very cold snap.

PPN not sure

[PersianPaladin]

18z shows how easily the upper-atmospheric conditions can result in the UK being stuck under an uneventful col; with the CAA out of reach. The situation created by too much energy amplified southward in the southern arm of the jet with the bifurcated pattern looking to stall an elongated area of upper-level divergence west of Spain in the Atlantic. Granted, it is GOOD that the northward amplified arm of the jet remains weak, but it all comes down to the most optimum ratios.

Meanwhile, the shape of the ridging into Greenland is not quite what we want.

Still; there is room for change.

Edited December 8, 2009 by PersianPaladin

[Tim Bland]

When does the parallel run become the main GFS run?

Others may correct me but I thought it was starting tommorow?

[LomondSnowstorm]

Parellel run looking much better. This update to the GFS model seems to be very consistent.

http://91.121.94.83/...fs-0-168.png?18

dammit beat me to it!

It shows a decent easterly for southern parts before bringing the low pressure down from the northeast, and behind it very cold air in FI. As JH says we must try to compare like-for-like model outputs i.e. this run to last night's 18Z, while a lot of the other models have upgraded from yesterday. Just hope the GEFS stays cold, though the pattern displayed on the 18Z is not that bad, it just never really allows to cold air near us. If the 00Z is similar though, I doubt anyone on here would be that optimistic.

LS

[Guest North Sea Snow Convection]

Parellel run looking much better. This update to the GFS model seems to be very consistent.

http://91.121.94.83/...fs-0-168.png?18

Atm the most important thing is to see HP to the north and low pressure to the south. Assuming that basic theme holds, then the details will follow. Worrying about whether it is a drizzly easterly or a cold snowy convective easterly (the latter I hope ) is pointless atm because so much in terms of detail is going to change

Edited December 8, 2009 by North Sea Snow Convection

[nick sussex]

I totally agree nick

Details at this stage are less important. The overall pattern getting locked into shutting the atlantic out (and shortwaves) is.

To my mind and eye, the northern blocking is getting stronger and stronger. We haven't seen charts like this for a very long time

Hi Tamara

Yes theres too much worry about detail which is likely to change many times. I remember many moons ago some great charts that showed almost -20 upper air getting close to the uk, each run changed this with one time northern areas getting the coldest , then the south, much debate about the 850's then the whole thing imploded! Theres no point of dreaming about the snow and the sledging and perhaps the odd day off work if you don't get past the first hurdle. For the timebeing for me the only thing that matters is events upto 144hrs.Once we have agreement from all the models then we can see whats in store, given so many previous let downs each run that goes by without major calamity is a big success!The things to concentrate on for me and not being too simplistic is this, block to the north, elongated atlantic trough running north/south over eastern us and canada, low pressure to the south extending into the med, as the gfs 18hrs still has this then great.

Edited December 8, 2009 by nick sussex

[snowmadchrisuk]

Others may correct me but I thought it was starting tommorow?

It's the 15th .

[The Eagle]

The P run is better but once again struggling to get the really cold air west before 180hrs despite a pretty brisk Easterly. That's two runs now that show the shortwave East of GL spoiling it somewhat on the GFS. I hope there is not a 3rd! Nite.

[on the coast]

The 18z shows a classic if cold can escape the uk then it will

Two GFS runs the same now. Please dont let the others follow. Still away to go i suppose.

[Tim Bland]

It's the 15th .

Are they adding anything to the Parallel run to make it more reliable or simply swapping the parralel to become the main output?

[Guest North Sea Snow Convection]

Yes quite right. We're getting completely spoilt at the moment. Such strong N blocking is so rare, just getting it in place is one major hurdle that if completed could then set us up for just about ANYTHING!

Exactly right. Lets wake up to this - a week ago people would have been in apoplexy about a drizzly easterly!

[yamkin]

Oh dear what an awfull run The final kick in the goolies is +14c for Christmas eve with the anticyclonic gloom just a bad memory! Lets hope to wake up to better charts or the 1st dissapointment of the winter may have just happened

GFS 18Z is not that bad. Looks like you have gone past the 144h marker and gone for a conclusion. ECM & UKMO are impressive tonight.

[kold weather]

Paralell shows another solution yet again, the shortwave goes the route that we see in the 18z op but a new shortwave develops further east and allows the cold air to be dragged back westwards.

As PP said, this shows how we can have an amazing block and southerrly jet and still end up in weather thats pretty bland and not even 'that' cold overall.

[January Snowstorm]

The P run is better but once again struggling to get the really cold air west before 180hrs despite a pretty brisk Easterly. That's two runs now that show the shortwave East of GL spoiling it somewhat on the GFS. I hope there is not a 3rd! Nite.

I remember last year a lake freezing over in Cork from an Easterly with uppers around zero

Do we really need cold uppers with an Easterly?? Imo we don't as dew points will be low anyway

[Lewis]

Atm the most important thing is to see HP to the north and low pressure to the south. Assuming that basic theme holds, then the details will follow. Worrying about whether it is a drizzly easterly or a cold snowy convective easterly (the latter I hope ) is pointless atm because so much in terms of detail is going to change

Agreed

To be honest the 18z brings the colder air in much quicker, and obviously the uppers are generally -5 to -6 at best.

Forget about this chart, it might be the worst for snow lovers etc, but in modeling terms it's a very good run, as it will bring a different pattern of weather to our shores.

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

Thats the re-load point on that chart. The jet will be further south, there is a reason there's such bold predictions for deeply negative AO, the northern blocking will be more pronounced.

Another benefit is that nothing changes drastically in the stratosphere according to GP, so theres no reason the PV should reform as suggested in the 18z. I suspect the 18z will be one of the warmer ensemble members, the parallel looking much better.

Lewis

[bluearmy]

the parallel is quite a similar evolution to the ecm. imagine that we were a week ahead of now - we'd be saying: fantastic cross model agreement out to t240

[cooling climate]

The ECM and the UKMO look almost identical with the 12z and 18z GFS operational runs cutting off

the link to the heights further north because of its obsession with shortwaves.

The ECM 0z operational was the same but it now looks to have ditched this idea and is siding with

the rock solid UKMO.

I can see credit being given to the Euro models with the GFS backtracking so to speak to a more east

northeasterly pattern tomorrow, but for me the GFS picked this much colder pattern up way before

the Euro models.

[Cloud 10]

Meteociel - Cartes du modèle numérique GFS pour l'Europe

Yet another snowfest on the parallel run,the sooner it takes over the better.

The vast majority of the gefs ensembles have a colder flow over us at +144.

Edited December 8, 2009 by Cloud 10

[ChartViewer]

Paralell shows another solution yet again, the shortwave goes the route that we see in the 18z op but a new shortwave develops further east and allows the cold air to be dragged back westwards.

As PP said, this shows how we can have an amazing block and southerrly jet and still end up in weather thats pretty bland and not even 'that' cold overall.

Kold,

The building blocks are in place. We have just seen stunning ECM....UKMO good....This is supposed

to be the pub run (why i dont know) and as you quite rightly said....Details will change nearer

the time buts lets enjoy synoptics not seen for a while?

GP already said HP centred over Iceland West Greenland......But not sure how cold the air we pull down will be

from Russia for cold snow/colder wintry mix scenario, but to have this in Mid December I

think everyone should be excited by this. The HP position and energy curve drive what happens next to the colder air, but to me this

has been best 2 weeks of Model watching in December for ages!

ps - I notice the experts mentioning another warming event soon...More

blocking in Mid Jan anyone!

Edited December 8, 2009 by ChartViewer

[Snowyowl9]

I remember last year a lake freezing over in Cork from an Easterly with uppers around zero

Do we really need cold uppers with an Easterly?? Imo we don't as dew points will be low anyway

That was probably an E/SE-ly with a sinker high,very cold surface air last year.

A NE-ly not so god for that IMO not here anyway unless theres cold uppers aswell but we`ll see what comes of this.

http://91.121.93.17/pics/Rtavn1082.png

[cold snap]

GFS 18Z is not that bad. Looks like you have gone past the 144h marker and gone for a conclusion. ECM & UKMO are impressive tonight.

IF the 18Z is to be believed it would be upsetting,I mean this,Around Christmas Everybody to the East of

the U.K would have good coverage of Snow ,we would miss out.

UKMO and ECM dont want this to happen,today we can take GREAT bits out off all models how often could you say that

[damianslaw]

Further increasing signs this evening that we are about to see a period of sustained settled and at least below average temperatures, how low they will go is open to debate but certainly below average with plenty of frost and fog about - the fog will suppress temperatures this weekend I feel from what are currently being forecast. In many parts I don't expect the fog to suddenly disperse into low cloud, this is mid december if there is ever a time for fog to hold its grip it is now.

Longer term some strong signals that some real cold will dawn on us - the major players being a combined deeply negative NA0 and A0 - once you have this you are almost set up for a sustained cold even severe cold spell, the jet has nowhere to go but deep south.

So yes no real cold or snow in the reliable timeframe, but the upstream signals as we head into next week look very conducive indeed for some proper cold and hopefully snow. Some real seasonal weather - couldn't ask for more from the models today if you are wanting cold and snow.

[patneve]

GFS did pick the new cold trend up before the European models (about a week ago i think?)! BUT i really can't see why people are so GFS addicted! GFS always goes on its romantic sagas before eventually agreeing with the European models - its happened many times before. I believe that in the timeframe we're looking at the European models are much more trustworthy in picking up trends (GFS beating them in longer range F1 trends though).

Good Night and snowy dreams to all.

[nick sussex]

Kold,

The building blocks are in place. We have just seen stunning ECM....UKMO good....This is supposed

to be the pub run (why i dont know) and as you quite rightly said....Details will change nearer

the time buts lets enjoy synoptics not seen for a while?

GP already said HP centred over Iceland West Greenland......But not sure how cold the air we pull down will be

from Russia will be for cold snow/colder wintry mix scenario but to have this in Mid December I

think everyone should be excited by this.HP position and energy drive what happens next but to me this

has been best 2 weeks of Model watching in December for ages!

I totally agree CV

Perhaps someone should put up a few archives from many of the recent mild dross winters with a bartlett and sw/ne tracking jet! The current model output is just really very rare, lets just hope the end result makes this rather draining model rollercoaster worthwhile.

[kold weather]

The enembles still ging for the older style of shortwave direction, and in turn look pretty good overall...still can't ignore the fact that the op runs have higher resolutin and will deal better with short term shortwaves better.

Once again, it is very nice looking at very good northern blocking in December, but its all rather useless if it doesn't actually give much in the way of cold conditions, practically you may as well just keep a cold high over the UK for all the good such good synoptics give to the UK on the 18z.