Model Output Discussion - The Run In To Christmas

[damianslaw]

I'm posting a lot today, a very reputable mountain forecast (MWIS) website I regularly look at is also stating in longer range outlook - signs of much colder weather for all (mountain regions includes Wales and Peak District) post Christmas. It is often very conservative like the meto forecasts, this is another very encouraging sign for the colder evolutions shown in the models to verify at Christmas.

 

Lets wait and see if the Met also hint at such a scenario - if signals persist I can only say it will be a matter of time probably Friday earliest, Sat latest at it will then be within reliable timeframe.

[Tom Quintavalle]

Having just finished reading the thread and the analysis of this afternoon's output, as was alluded to

earlier, I also saw echoes of Dec.1981, re. the GFS 12z.

As was mentioned further back in the thread, the transition to that bitterly cold Arctic surge

certainly wasn't clear cut either and must of caused a real headache to the METO at the time, with some shortwave drama, as a trawl through the archives will reveal.

In fact the first attempted mid-Atlantic amplification and initial northerly had begun in the last few days of November and as we now know, that failed, the pattern being a little too far east, with a

northerly down the N.Sea and an Atlantic ridge eventually toppling over the UK. Eventually an area of

high pressure close to Spain moved NW into the Atlantic, with a ridge north, and pressure then rose over Greenland. After a few days of delaying shortwaves, located between the southern tip of Greenland and Iceland, an area of low pressure developed on a wave running SE from Iceland, down through the UK and ushered in that severe Arctic outbreak and, as we know, the rest is history. So one could say that from that first initial attempt at a northerly outbreak in late Nov.until that eventual bitter Arctic surge came south on Dec.8th, took around a week and a half.

It should be remembered that even some of our most potent northerly outbreaks, do not always feature an overnight transition to a white Winter wonderland.

Of course to expect a repeat of that cold, wintry spell would be fanciful, to say the least and we

could well have to wait into the New Year for anything wintry but having just seen the ECM ensemble

mean, the portents look good for a wintry spell between Xmas and the New Year.

This kind of synoptic set-up is always fascinating to watch unfold, even if the final result doesn't

deliver a late Xmas present for the UK. It's also a reason why I tend not to get too despondent when a large area of high pressure seems entrenched to the south of the UK, more important to look at the

Northern Hemispheric pattern and what's happening upstream of the UK.

Certainly an exciting and fascinating period of model watching coming up and it could be well into the

weekend before the models have got to grips with the synoptic pattern for the early part of the Xmas

period.

Tom.

Edited December 17, 2014 by TomBR7

[winterof79]

Maybe Ian Ferguson can comment on UKMO on metoceil

Données pour les cartes UKMO entre 6h et 72h partiellement revenues (Z500/T850 de 12h en 12h) mais instable !

Data for 12-72h UKMO charts partially back (Z500/T850 at 12h interval) but instable availability !

Written in red and has the loss of Low pressure system for NE US. Has data for this region been lost or satellite data not reading.

Pre 96z the data is only there for Eurasia.

Has this skewed possible cold spell?

The low pressure cell is only just starting to form by 144z for the n/e conus.

http://modeles.meteociel.fr/modeles/gfs/runs/2014121712/gfsnh-0-144.png?12

 

Cracking set of ensembles around the 25th

http://www.wetterzentrale.de/pics/MT8_Manchester_ens.png

Edited December 17, 2014 by winterof79

[london-snow]

fergieweather, on 17 Dec 2014 - 20:27, said:

Update from Ian FVaried colder NW/northerly types by 28th onwards

Good update from ian if you wouldn't mind posting a link that would be great

I could also see the potential over the past 24 hours more so today of a start n/nw flow but as new year approaches a increasing n/ne flow. (Would post charts explaining but currently unable). This is why i have been even more encouraged to see eastern europe primed to go cold.

Plenty of possibilities but still a while to go

[terrier]

Well now I'm not so sure what model to belive just watched bbc news 24 further outlook and they say cold xmas eve xmas day before milder atlantic air moves in Boxing Day. I'm wondering if there in house models are painting something very different to what we're seeing from the gfs runs. #confused.

[damianslaw]

I'd like to see what charts the Met Office have available as they seem to be different to all the models available for public consumption. Long range forecast just on now, was saying Christmas Eve likely to be coldest day, milder and wet on Boxing Day - none of the models show this..

[texel]

cost ya small fortune and probs will be wrong anyway.

[SMU]

GFS now on board with the ECM solution-  However the track of the atlantic shortwave is key-

 

300 miles south & its jackpot, 300 miles further North & its mild for all-

 

S

[texel]

when do we find out Steve?

[Cheshire Freeze]

I'd like to see what charts the Met Office have available as they seem to be different to all the models available for public consumption. Long range forecast just on now, was saying Christmas Eve likely to be coldest day, milder and wet on Boxing Day - none of the models show this..

Well all of today's NWP & ensemble suites would have to be fairly wrong for that to be the case as most of the modelling shows colder weather attempting to set in on or around Boxing day.

That's not to say this will happen of course but as of today, that's what modelling is showing.

[John Snow]

It is safe to say that a cold snap or even a severe cold snap is a 99.9% certainty in the Xmas day to new year period, all of the models are in broad agreement bar the finer details so with not a single model out on a limb it will take a miracle for a cold snap not to happen

It is certain to turn cold, it is certain some areas will get snow, it's just a question of how much and where

Exciting times ahead

[SMU]

when do we find out Steve?

 

Well the track were interested in is at about 144 so in 4 days will be pretty clear....

[Met4Cast]

It is safe to say that a cold snap or even a severe cold snap is a 99.9% certainty in the Xmas day to new year period, all of the models are in broad agreement bar the finer details so with not a single model out on a limb it will take a miracle for a cold snap not to happen

It is certain to turn cold, it is certain some areas will get snow, it's just a question of how much and where

Exciting times ahead

No it isn't - I've seen full model support for a cold event dissapear within 72 hours of the event occuring, we're still looking at something that's a week away.

 

Whilst it's encouraging to see continued support, I wouldn't count your chickens just yet

[KyleHenry]

The low pressure cell is only just starting to form by 144z for the n/e conus.

http://modeles.meteociel.fr/modeles/gfs/runs/2014121712/gfsnh-0-144.png?12

 

Cracking set of ensembles around the 25th

http://www.wetterzentrale.de/pics/MT8_Manchester_ens.png

Your absolutely right, ale has skew whiffed my model reading regarding LP in US. Formation is there for 23rd through 24th, what a big part player of the upper stream it is.

It opens the gate for what GFS.ECM are showing for 26th Dec for UK.

[TSNWK]

Well all of today's NWP & ensemble suites would have to be fairly wrong for that to be the case as most of the modelling shows colder weather attempting to set in on or around Boxing day.

That's not to say this will happen of course but as of today, that's what modelling is showing.

Well all of today's NWP & ensemble suites would have to be fairly wrong for that to be the case as most of the modelling shows colder weather attempting to set in on or around Boxing day.

That's not to say this will happen of course but as of today, that's what modelling is showing.

Yes it makes you wonder.. Would it be the glosea model..

[Kentish Snowman in Yorks]

I saw that too re the extended BBC outlook. That forecast of a milder Boxing Day doesn't seem to tally up with this though...

[steveinsussex]

when do we find out Steve?

 

boxing day

[Captain Shortwave]

Well all of today's NWP & ensemble suites would have to be fairly wrong for that to be the case as most of the modelling shows colder weather attempting to set in on or around Boxing day.

That's not to say this will happen of course but as of today, that's what modelling is showing.

Well except this

Though it still looks cold at this point, I'm guessing other models want to place low pressure closer to the UK and introduce milder weather. It could of course be transient anyway if the forecast was specifically focusing on Boxing day.

We are a long way from sorting this in reality. Though surely a colder spell of sorts will do happen.

Edited December 17, 2014 by Captain shortwave

[ItNeverSnowsInWindsor]

I'd like to see what charts the Met Office have available as they seem to be different to all the models available for public consumption. Long range forecast just on now, was saying Christmas Eve likely to be coldest day, milder and wet on Boxing Day - none of the models show this..

Think they must be using the ECM in the forecast which shows milder SW'lys before the low tracks in on Saturday -

 

[Mark Neal.]

Well except this

True, though a solid ECM mean. A lot of water to flow through the bridge yet however.

[festivalking]

No it isn't - I've seen full model support for a cold event dissapear within 72 hours of the event occuring, we're still looking at something that's a week away.

 

Whilst it's encouraging to see continued support, I wouldn't count your chickens just yet

yes December 2011 springs to mind the beast from the east got curtailed at t72. Still scars me does that one.

[Met4Cast]

18z doesn't phase the Scandi low with the low in the Atlantic like the ECM does, so we should be on our way to seeing another good FI here. Heights building into Greenland.

 

[damianslaw]

The forecasted jet profile is for an increasingly southerly path next week - as some say, indeed it would tie in with the BBC outlook and ECM chart in some respects for Boxing Day - a shortlived temporary incursion of milder air for the south but for cold shot from the NW/N hot on its heels. The Met Office and BBC have a strong relationship - the media is itching to know what the weather is likely to be- any inkling of cold wintry weather and they can start putting out silly headlines and speculating on travel chaos.

 

The broadcast today I suspect had Boxing Day firmly on its mind only, as the Christmas period is a very busy time travel wise. Whilst cold wintry weather at Christmas is something many would like to see, from a Met Office, BBC weatherman perspective it is a headache, as they are then under the microscope and no doubt 'very busy' at a time when everyone I suspect just wants to relax, I always get the sense from them that the prospect of a non wintry Christmas results in a major sigh of relief - ah now we can relax because no one cares what the weather is up too - on this occasion though it would be very non-wise at this stage for them to think this..

Edited December 17, 2014 by damianslaw

[The Eagle]

The jet is killing us here.

 

[joggs]

Question to JH.Are the 500mb charts you use showing any change yet?

Thanks in advance.