Winter Model Discussion - Cold Hunting -12Z 30/12/12

[PubliusEnigma]

.... And surprisingly the key moments are not in FI. Rather it's around that 120 to 144 time frame. ...

To be honest I cant see any major changes until at least T240

GEM has us basking in potentially milder weather than we have at present ;-

NOGAPS at the end of its run, still generally mild

ECMWF has a a mild flow over the UK, with the UK, placed under a 'warm' high pretty much as we have at present

And the GFS ensembles show a gentle SW flow over the UK.

Even the GFS which goes out further has us in a SW flow...

Which leaves us still searching the elusive pattern change. Bearing in mind the above charts take us out to the middle

of Jan, it's no surprise that the MO, are reluctant to change their long ranger forecast for now.

[chionomaniac]

Hope I'm wrong, but it seems many are pinning too much on the sudden strat warming event forcast and the possible effects it may have.

The chart that you have posted completely contradicts your post!

[Isolated Frost]

Difference between the operationals in the arctic region (tropospherically) is the transported pv segment that travels from Canada into Russia (and then Scandi on the GFS) is based on a meridional polar high- whilst the energy directed eastwards from Baffin Island on the ECM creates an upper trough in which the polar vortex circulates in with, to strengthen the canadian sector vortex-

the GFS/EC stratospheric vortex placements (Hudson Bay or Baffin Island) will be vital in the direction of the upcoming weeks as not only does it affect the polar high circulation, but it significantly alters the shape and dynamics of the tropospheric polar vortex's eastern segment (Siberia or Scandinavia)-

Note the 544 dm over the North Pole and 492 dm nr Novaya Zemlya- and the extensive upper air ridge into Svalbard.. a very conductive set-up

[The Eagle]

To be honest I cant see any major changes until at least T240

Which leaves us still searching the elusive pattern change. Bearing in mind the above charts take us out to the middle

of Jan, it's no surprise that the MO, are reluctant to change their long ranger forecast for now.

That's not what I meant. The changes I am referring to are interim synoptic and jet stream alterations on the way to a colder setup. At 144hrs on the GFS you have to picture what the forecast could be 96 hrs further on. Plunging trough, southerly tracking jet and increasing pressure to the north. I am not talking about the exact weather situation at 144hrs rather the trend.

[Isolated Frost]

Even the GFS which goes out further has us in a SW flow...

Which leaves us still searching the elusive pattern change. Bearing in mind the above charts take us out to the middle

of Jan, it's no surprise that the MO, are reluctant to change their long ranger forecast for now.

Interesting picture of the UK on the 15th, and saying we are searching for the elusive pattern change.

When this on the 13th shows a very cold easterly flow over the UK.

And the 'elusive pattern change' comes in the next 10 days if you look at the hemispherical charts. With warmings down the line that could further interest the situation.

Interesting post PE.

[bluearmy]

we were looking more intently at fi gfs runs to see if there were signs of a trop response to the SSW. nothing more, nothing less. gfs charts low res are still rubbish wrt to any detail. at the very best they have the longwave pattern half right. i'm seeing too much posting on low res gfs as i think some have got the mistaken impression that they are worth analysing. dont bother! be it cold or mild, using low res gfs will only end in tears or more imoportantly, misinformation.

[PubliusEnigma]

Interesting picture of the UK on the 15th, and saying we are searching for the elusive pattern change.

When this on the 13th shows a very cold easterly flow over the UK.

And the 'elusive pattern change' comes in the next 10 days if you look at the hemispherical charts. With warmings down the line that could further interest the situation.

Interesting post PE.

Thanks IF Appreciated. Anyway the HP on the 13th isnt so much a pattern change, as its sunk back over the UK by the following day.

And the fleeting 24 hour easterly is a raging S Westerly two days later..

I would class a pattern change something that alters the synoptic set up for at least 5 days or more. The Temps on the

chart you posted would be around 5 to 7oC across the south and maybe 2 to 3oC in the North. Not really "Very cold

easterly" in the scheme of the things. We really need to see Heights building over Iceland or Scandi with a long fetch out

east or North east. Im not sure how cold the continent is any more as the current milder weather has streamed right the

way east into Northern Europe. With even Stockholm in the range 0oC to +3oC

http://www.bbc.co.uk/weather/2673730

[alexisj9]

In view of Ian F's comments I find the UKMO outlook somewhat underwhelming.

No mention in the 6 to 15 dayer of anything regarding colder conditions. I would have expected some caveat highlighting at least a small chance of something colder mentioned for the latter part of that outlook.

I think the Met Office are getting excited about the bigger picture, they are watching the whole patern just like us/or me anyway, this could bring cold here or not, it's still imposable to tell. Until they are confident of a cold outcome I wouldn't expect much change in their outlook.

[Isolated Frost]

Thanks IF Appreciated. Anyway the HP on the 13th isnt so much a pattern change, as its sunk back over the UK by the following day.

And the fleeting 24 hour easterly is a raging S Westerly two days later..

I would class a pattern change something that alters the synoptic set up for at least 5 days or more. The Temps on the

chart you posted would be around 5 to 7oC across the south and maybe 2 to 3oC in the North. Not really "Very cold

easterly" in the scheme of the things. We really need to see Heights building over Iceland or Scandi with a long fetch out

east or North east. Im not sure how cold the continent is any more as the current milder weather has streamed right the

way east into Northern Europe. With even Stockholm in the range 0oC to +3oC

http://www.bbc.co.uk/weather/2673730

My note was the pattern change was more hemispherical. And in my opinion, no matter how fleeting it may be, a change from +10c uppers to -10c uppers on UK shores is quite notable.

Indeed the likelyhood is not for anything large scale in the next 10 days, but the wider picture shows huge hemispherical fluctuations this month.

[LomondSnowstorm]

Thanks IF Appreciated. Anyway the HP on the 13th isnt so much a pattern change, as its sunk back over the UK by the following day.

And the fleeting 24 hour easterly is a raging S Westerly two days later..

I would class a pattern change something that alters the synoptic set up for at least 5 days or more. The Temps on the

chart you posted would be around 5 to 7oC across the south and maybe 2 to 3oC in the North. Not really "Very cold

easterly" in the scheme of the things. We really need to see Heights building over Iceland or Scandi with a long fetch out

east or North east. Im not sure how cold the continent is any more as the current milder weather has streamed right the

way east into Northern Europe. With even Stockholm in the range 0oC to +3oC

http://www.bbc.co.uk/weather/2673730

While the next chart does indeed show SWerlies, it's very far from the quite clearly 'raging' zonality of the last few days in terms of the broad synoptic pattern. Whether or not this is felt on the ground is not something anyone can say at the moment, but I'd suggest that going from this:

to this:

is very definitely a pattern change.

I'd ignore the specifics of FI for the moment and even the ensemble mean because both have been changing markedly over the last few days and are likely to again. However, the movement towards a more amplified setup over the last 2 days in the output has been pretty clear, and it is this trend that needs monitoring because there remains a chance that the initial response to the SSW could lead to something more interesting in the medium term.

[SMU]

Afternoon All-

We things have taken an uptick today- which is pleasing to the eye- For most its been incredibly frustrating this winter- for some reason more so than usual- maybe because of the underlying expectation of what it may bring.

There was no coincidence that I posted this chart for reference of ridging yesterday-

http://modeles.meteo...47-1-20-0-0.png

Because that type of ridge & change of wavelength can often support the overall pattern change,- linking up with a polar high.

Taking the strat to one side for a second I can recall at least ONE example everysingle winter where we get the vortex lobe dropping into europe with bitter uppers.

Remember if the train comes the ensembles are warsaw, Berlin ,Debilt, London.- thats how they topple in terms of agreement.

Having been here though every year the crucial memory is that the return of all this coming our way isnt the favourite -as being on the periphery of the atlantic makes it very difficult- even if we have a perfect strat profille.

What does the UK need...?- A window of TIME as long as possilble where the atlantic jet is deflected way north or way south. A one day window of the cold marching west through europe is not enough.-

Anyflow from the east needs to be sustained +48 hours ideally- longer if possible.

So whats my thoughts- Well most of its been covered this morning- things have changed to positive outlooks overnight, the PV lobe dropping into europe is excellent because it ensures the maximum cold uppers can be sourced-

We will need more blocking to the west though to get the UK cold unless we get the perfect icelandic wedge to the north of the UK..

cheers

S

Edited January 3, 2013 by Steve Murr

[fergieweather]

I think the Met Office are getting excited about the bigger picture, they are watching the whole patern just like us/or me anyway, this could bring cold here or not, it's still imposable to tell. Until they are confident of a cold outcome I wouldn't expect much change in their outlook.

UPDATE - - They've just made changes and re-issued the briefing - we received these just after 2pm but I have no idea if they've also fed-through to the public website forecast.

The key change is re the 10-15d period. The new guidance from the Deputy Ch. Forecaster talks of some signs of meridional/blocked pattern and colder than average temperatures, but stresses current uncertainty regarding synoptic type by that juncture.

I'm assuming this change in emphasis will also be reflected in the public web 10-15d forecast at some stage soon.

[ITSY]

we were looking more intently at fi gfs runs to see if there were signs of a trop response to the SSW. nothing more, nothing less. gfs charts low res are still rubbish wrt to any detail. at the very best they have the longwave pattern half right. i'm seeing too much posting on low res gfs as i think some have got the mistaken impression that they are worth analysing. dont bother! be it cold or mild, using low res gfs will only end in tears or more imoportantly, misinformation.

I think you have slightly misunderstood the point of people posting various low res charts. They are not to look at and think, this is what will definitely happen, they are for analysing in the context of ensembles throughout the same day, so to see where there could be a possible pattern change. They are essentially for trends and nothing more. But if we are looking for trends to colder weather, that is exactly where we should be looking, and a flick through this mornings ens reflects that.

EDIT: Ian's post above demonstrates the value of looking at low res trends, for an analysis of those trends have prompted the dep. chief forecaster at the met to change their outlook.

Edited January 3, 2013 by ITSY

[Weathizard]

One question I was going to ask earlier but forgot, I understand the control run is started from a slightly different point to the op? But using the same data as the op? Is this correct?

And is there a reason that in recent days the control run has been consistently dishing out good runs compared to the op that has been quite the opposite? (6z aside)

[PubliusEnigma]

... the wider picture shows huge hemispherical fluctuations this month.

This is the crux.. When it comes into the reliable, will it effect our neck of the woods. A lot of talk about SSW although it were the holy grail. Northern blocking in the wrong place

even slightly the wrong place can also bring copious rainfall and poor weather with the jet being pushed south over the UK. We should be careful what we wish for ;o). Our Summer

was ruined in part due to Northern Blocking which kept the Jet too far south. And much of the latter part of November and December Blocking away to our NE caused Atlantic lows

to attack from the SSW bringing copious rainfall and become slow moving..

[Peter H]

The weather Outlook, in their update today, does not share the optomism of some who are posting on this discussion forum:

http://www.theweatheroutlook.com/

There is currently a lot of speculation about the potential for a Sudden Stratospheric Warming (SSW) event to bring much colder weather during the second half of January, and Buzz will be keeping an eye on this with regular updates. The TWO January weather forecast suggests a mixed month, with the coldest weather probably avoiding the UK.

I would tend to agree.

[davacr123]

UPDATE - - They've just made changes and re-issued the briefing - we received these just after 2pm but I have no idea if they've also fed-through to the public website forecast.

The key change is re the 10-15d period. The new guidance from the Deputy Ch. Forecaster talks of some signs of meridional/blocked pattern and colder than average temperatures, but stresses current uncertainty regarding synoptic type by that juncture.

I'm assuming this change in emphasis will also be reflected in the public web 10-15d forecast at some stage soon.

There is greater than average uncertainty through this forecast period, though it looks likely to start with fairly average climatological conditions, meaning the south and east of the UK will see the driest and brightest weather, while the north and west will tend to be more unsettled. However, there could be some rain at times anywhere across the UK. Temperatures will tend to often be close to average for the time of year to begin with. Then, later, there is an increasing risk of more marked changes of weather-type occurring, and the risk of spells of colder than average conditions and wintry weather increases relative to early January.

On met office that was updated today

[bluearmy]

I think you have slightly misunderstood the point of people posting various low res charts. They are not to look at and think, this is what will definitely happen, they are for analysing in the context of ensembles throughout the same day, so to see where there could be a possible pattern change. They are essentially for trends and nothing more. But if we are looking for trends to colder weather, that is exactly where we should be looking, and a flick through this mornings ens reflects that.

ITSY, i know exactly the reason why i made my post and i was not misunderstanding anyone. we are on the cusp of a pattern change to much colder weather and some of the more experienced on here have recently been referencing deep fi gfs op output which is not something we'd normally do. its important that the less experienced and newcomers are aware that low res gfs is close to 'chocolate teapot' status. we have also seen a trend to posting individual ens members to illustrate that deep cold still exists in the nwp. hopefully, that too, can be dispensed with as we see ens means that are worth posting instead.

fwiw, the catalyst for me posting was someone using a deep fi gfs frame which reverted to a mobile flow in order to question the earlier colder frame tht had already been posted. the worst way to use low res deep fi gfs in the current situation.

[-uksnow-]

The weather Outlook, in their update today, does not share the optomism of some who are posting on this discussion forum:

http://www.theweatheroutlook.com/

I would tend to agree.

Without slating Brian, its got to be said he is a fairly sit on the fence type forecaster who also doesnt pay alot of attention to strat happenings. Often his forecasts often more accurate but this imo is because he is often last to make a call on something giving a higher chance of it being right. So one to add to the mix, but i would trust fergie and the MO far more than him..

[bluearmy]

The weather Outlook, in their update today, does not share the optomism of some who are posting on this discussion forum:

http://www.theweatheroutlook.com/

I would tend to agree.

i would be astonished if it wasnt right peter. try and think of a cold scenario where the uk would be the coldest place in europe. meanwhile, brian has a decent track record in LRF. can you enlighten us as to why you think he's right apart from the obvious one i made

[Paul]

Latest from Michael Fish - he looks ahead to the upcoming week and also talks about the prospects of something colder into January - revealing too that he is a coldie (with a love of very loud shirts)

[BLAST FROM THE PAST]

Well as mentioned a rapid improvement on the models. Dates of development on GFS look about righ to me too, Just to spice up things, why have I zoned in on 16-22. Well its where I expect block to be in place before then, a bit like the following

It looks rightish to me and I am very pleased with what I'm seeing. There is potential for some extreme weather 16-22 and some incredible low temps to head our way......will it get to us?. We're up and running folks, harnesses on.

BFTP

Edited January 3, 2013 by BLAST FROM THE PAST

[UV-RAY]

i would be astonished if it wasnt right peter. try and think of a cold scenario where the uk would be the coldest place in europe. meanwhile, brian has a decent track record in LRF. can you enlighten us as to why you think he's right apart from the obvious one i made

Brian Gaze states that he will be keeping an eye on developments, which most of us will be doing. The January forecast is the one he made at the end of November. Edited January 3, 2013 by Sceptical Inquirer

[mountain shadow]

The weather Outlook, in their update today, does not share the optomism of some who are posting on this discussion forum:

http://www.theweatheroutlook.com/

I would tend to agree.

99% of us would also agree as missing out is the norm for the British Isles.

What we have is something to offer us hope. Nothing more, nothing less.

[johnholmes]

T think this needs repeating and probably at regular intervals as the amateurs question why there is no mention in their 6-15 day outlook!

fergieweather, on 03 January 2013 - 01:10 , said:

Just to re-stress a key point, as some might have overlooked it, judging by certain frustrated posts! UKMO emphasizes again (in new 6-15d briefing) how potential cold/blocked outcome from incipient SSW remains v possible but crucially how this may not be manifested within their current 10-15d forecast period. So - as others have also tried to stress - NOTHING in any NWP output in further reaches of MR should be taken with even moderate confidence! We are entering a truly fascinating & potentially rewarding period for this thread.. but it'll take time! I'm hoping to hear tomorrow how the good folk at Hadley Centre are assessing fortunes from this SSW.