Model Output Discussion - 26th December - 1st January

[nick sussex]

NOAA CPC charts look to go with the ECM trend and not the GFS operational runs in their 6-10 and 8-14 day outlooks, the limpet high is likely to edge west with heights lowering in central Europe.

The ECM ensemble mean is close to the operational run with the Russian high in evidence, and troughing over the UK.

It could be better but we have to start somewhere, a few bits to pick out of the NOAA discussions:

THE AO INDEX WHICH RECENTLY

HAS BEEN STRONGLY POSITIVE IS FORECAST TO DECREASE IN MAGNITUDE BUT REMAIN

POSITIVE THROUGH DAY 14.

THE PNA INDEX WHICH RECENTLY HAS BEEN VERY WEAKLY

POSITIVE IS FORECAST TO REMAIN WEAKLY POSITIVE, OR BE CLOSE TO ZERO THROUGH DAY

14.

THE ENSEMBLE MEAN FORECASTS INDICATE VERY LITTLE CHANGE TO THE OVERALL

CIRCULATION DURING WEEK 2 COMPARED TO THAT FORECAST FOR THE 6-10 DAY PERIOD,

ALTHOUGH THE TROUGH FORECAST OVER THE EASTERN CONUS IS FORECAST TO AMPLIFY

SLIGHTLY, WHILE THE RIDGE FORECAST OVER THE WEST DEAMPLIFIES.

We do need that eastern US trough to amplify as this helps draw the limpet high westwards, because of the overall pattern if the PV does weaken and edge westwards then the route to cold really has to come from the east or ne.

So I think the Russian high is now pretty crucial in terms of a possible pattern change, initially this holds troughing over Europe and because it extends nw helps to angle the jet more favourably, the eastern US trough needs to amplify sufficiently pulling the limpet ridge west and north, if the Russian ridge can extend west and help sink troughing near the UK then thats the way to cold, bear in mind that blocking over Greenland often initially comes from an easterly if you have the right background signal to retrogress the pattern.

Theres still a way to go before even thinking of a major change, but certainly we do need to see that troughing in the eastern USA.

Whilst that high sits to the south theres no chance of a pattern change, often the first step is heights dropping in central Europe so this is essential but equally we still need to remove that PV.

So overall a small step forward this evening but thats all for the timebeing.

[Frosty.]

A pigeon step forward then tonight with the NOAA supporting the Ecm/ukmo view of things, so maybe it's going to mean that the gfs is going to be dragged kicking and screaming towards a more amplified upstream pattern although I can't see the gfs just dropping it's jet fueled zonal mayhem, probably more a case of baby steps, or pigeon steps even.

[bluearmy]

The clustering at the end of naefs is strongly in support of a north Atlantic ridge, nudging into se Greenland. That would allow energy over the top but it's better than we currently have and would probably allow northerly attacks as the scandi trough sharpens with the shortwaves.

I note that ECM ens mean T240 clusters blocking over the west of the uk. The two taken together would indicate a block in our vicinity early in the new year, retrogressing slowly west as the scandi trough puts pressure on it, this in turn pushed towards nw Europe by the northwest Russian block getting stronger via the WAA from this scandi trough. quite a lot of supposition there but seems reasonable to me having viewed far too many charts over the Xmas w/end.

[nick sussex]

The clustering at the end of naefs is strongly in support of a north Atlantic ridge, nudging into se Greenland. That would allow energy over the top but it's better than we currently have and would probably allow northerly attacks as the scandi trough sharpens with the shortwaves.

I note that ECM ens mean T240 clusters blocking over the west of the uk. The two taken together would indicate a block in our vicinity early in the new year, retrogressing slowly west as the scandi trough puts pressure on it, this in turn pushed towards nw Europe by the northwest Russian block getting stronger via the WAA from this scandi trough. quite a lot of supposition there but seems reasonable to me having viewed far too many charts over the Xmas w/end.

I think thats a good call, for the timebeing the mid Atlantic ridge, Euro trough, Russian high combo.

As you said energy still running over the top but thats far better than whats currently on offer, the next stage to sledge nirvana depends on the PV finally giving up the ghost.

Thats still up in the air, can we get the trough to sink far enough south and the displaced Azores ridge to hold the Atlantic at bay for long enough to allow the Russian high to back far enough west?

Thats well into the future, lets at least get the amplified troughing in the eastern USA before worrying about that.

[phil nw.]

The clustering at the end of naefs is strongly in support of a north Atlantic ridge, nudging into se Greenland. That would allow energy over the top but it's better than we currently have and would probably allow northerly attacks as the scandi trough sharpens with the shortwaves.

I note that ECM ens mean T240 clusters blocking over the west of the uk. The two taken together would indicate a block in our vicinity early in the new year, retrogressing slowly west as the scandi trough puts pressure on it, this in turn pushed towards nw Europe by the northwest Russian block getting stronger via the WAA from this scandi trough. quite a lot of supposition there but seems reasonable to me having viewed far too many charts over the Xmas w/end.

There`s at last indeed signs of some movement in the further output B.A.

Although GFS not showing as much amplification in it`s 12z run the CPC day8-14 500hPa does pull the Euro heights into the Atlantic with an angled trough into E.Europe

-so the flow trending more north of west as time goes on.A small step for a colder pattern which would become more significaint if we do get more amplification in the pattern upstream, as suggested by the ECM tonight.

[Grimsby Snow Lover]

Hmmm to my untrained eye this looks a lot like the ECM from this morning, only a lot closer. I might be barking up the wrong tree but I see this as a step in the right direction.

http://hw.nwstatic.c...165/npsh500.png GFS 18z

http://hw.nwstatic.c...npsh500.240.png This mornings ECM

Spoke too soon, that high pressure to the south is a pain as by 240+ we could be moving in the direction of colder weather as hights increase over the pole. Instead we are bathed in tropical air with double digit temperatures! Really hope the later stages of the run are a warm outlier like previous runs today.

http://hw.nwstatic.c...264/h500slp.png

At least the jet seems to be moving further south towards to end of the run with a definate weaker PV than we have now at least.

Edited December 26, 2011 by Grimsby Snow Lover

[Frosty.]

If we get back to where we were in terms of a pattern match with early this month, it will be a minor victory. There is a good chance of wintry showers on wed night and thursday across the northern half of the uk, maybe a bit longer in the far northeast and friday also looks a rather cool day with temps only around average so after tomorrow the very mild weather will leave the uk for a little while.

Edited December 26, 2011 by Polar_ Low

[Grimsby Snow Lover]

If we get back to where we were in terms of a pattern match with early this month, it will be a minor victory. There is a good chance of wintry showers tomorrow night and thursday across the northern half of the uk, maybe a bit longer in the far northeast and friday also looks a rather cool day with temps only around average so after tomorrowm the very mild weather will leave the uk for a little while.

I would like to think the 14/15 degrees some places have seen over the past two days will not be repeated until at least the end of March PL.

[Frosty.]

I would like to think the 14/15 degrees some places have seen over the past two days will not be repeated until at least the end of March PL.

I hope so too, temps do look quite a bit lower after tomorrow and the next few days, a bit milder this weekend but then maybe colder again into next week

[JP1972]

Newbie question.

Are we suggesting that the building blocks are beginning to (look like) they are falling in place for a colder set up are we just talking tentative signs that building blocks might be laid?

[West is Best]

Another Bartlett dominated model output from the GFS.

I'm afraid the slug is in charge, and unless there's blocking over Greenland, which there isn't, we're in the Atlantic firing line for the forseeable future.

I remember once about 8 years ago being miffed when Steve Murr said was pointless looking at the outputs and that he would come back in a fortnight because of the Bartlett to our south, absence of blocking to the north-west and zonality into the UK. We're almost in a simlar positon at the moment.

[Grimsby Snow Lover]

Newbie question.

Are we suggesting that the building blocks are beginning to (look like) they are falling in place for a colder set up are we just talking tentative signs that building blocks might be laid?

I would say if the ECM was to be believed then in around 10 days time and beyond a colder set up could occur, but the current signs are only very tentative at best. GFS is currently showing very little signs at the minute. The problem we have is the huge slug of a high pressure currently covering most of southern Europe. Until this is disturbed the gfs will struggle to show any colder outlook. All could change though so keep checking the runs.

Edited December 26, 2011 by Grimsby Snow Lover

[feb1991blizzard]

Newbie question.

Are we suggesting that the building blocks are beginning to (look like) they are falling in place for a colder set up are we just talking tentative signs that building blocks might be laid?

Very tentative signs if your talking about plain model output and thinking in terms of potent cold but the really mild weather of the last 2 days will not last, thats a given.

[SMU]

Another Bartlett dominated model output from the GFS.

I'm afraid the slug is in charge, and unless there's blocking over Greenland, which there isn't, we're in the Atlantic firing line for the forseeable future.

I remember once about 8 years ago being miffed when Steve Murr said was pointless looking at the outputs and that he would come back in a fortnight because of the Bartlett to our south, absence of blocking to the north-west and zonality into the UK. We're almost in a simlar positon at the moment.

8 years ago must have been snow watch lol

Still 10-15 days is the marker in the current outputs- its a slow boat to china....

S

[stratty]

Something to go to bed with This is the end of run 12 from the ensembles and shows what snowies are wishing for with regards the manipulation of the high pressures that we are hoping to appear! night all :smilz38:

[Grimsby Snow Lover]

The colder theme on the ensembles has improved again on the 18z run with more runs going towards -10 towards the end. Also good to see that the warm barrlet high mid run was a bit of a warm outlier.

http://hw.nwstatic.co.uk/ensimages/ens.20111226/18/t850Lincolnshire.png

[feb1991blizzard]

For any newbie on here, this is an example of how any evolution to proper cold with big snow potential may happen, Ensemble number 12 of the 18z GEFS suite,

http://www.meteociel...&mode=0&carte=0

Note the yellow colours (high heights), ridging up into greenland, acting as a block, stopping any LP systems from the west reaching the UK.

EDIT : beaten to it.

Edited December 27, 2011 by feb1991blizzard

[Iceni]

Another Bartlett dominated model output from the GFS.

I'm afraid the slug is in charge, and unless there's blocking over Greenland, which there isn't, we're in the Atlantic firing line for the forseeable future.

I remember once about 8 years ago being miffed when Steve Murr said was pointless looking at the outputs and that he would come back in a fortnight because of the Bartlett to our south, absence of blocking to the north-west and zonality into the UK. We're almost in a simlar positon at the moment.

Me too. I'm going to give up if the high's still around after 12th Night (6th January). You win some (last two winters) you lose some…

[davehsug]

Is your link to the wrong ensemble member? I fail to see any yellow any further North than a line approximating to central Ireland/Northern England. AND, as I have mentioned before, unless the jet goes towards the North Pole, any ridge from the Azores high is not going to last. The Azores high can NOT ridge across the jet, it can only get as far north as any buckling might allow.

[shedhead]

Another Bartlett dominated model output from the GFS.

I'm afraid the slug is in charge, and unless there's blocking over Greenland, which there isn't, we're in the Atlantic firing line for the forseeable future.

I remember once about 8 years ago being miffed when Steve Murr said was pointless looking at the outputs and that he would come back in a fortnight because of the Bartlett to our south, absence of blocking to the north-west and zonality into the UK. We're almost in a simlar positon at the moment.

Agreed - whether ECM is right or not remains open to question, but what cannot be argued in any way is how abysmal the 18z GFS is for cold. Once again it suggests 12-14c maxima are possible through the first week of January due to a fetch from SW of the Azores and even at T+384hrs double digit temps would be very likely across much of England and Wales IF it were to verify. OK it's unlikely to do so, but lets not forget that recently several members posted T+384hrs charts when they showed a cold Northely and suggested they might represent the start of the pattern change.

Edited December 27, 2011 by shedhead

[feb1991blizzard]

Is your link to the wrong ensemble member? I fail to see any yellow any further North than a line approximating to central Ireland/Northern England. AND, as I have mentioned before, unless the jet goes towards the North Pole, any ridge from the Azores high is not going to last. The Azores high can NOT ridge across the jet, it can only get as far north as any buckling might allow.

I agree with your last point but it depends what you mean by 'last', to my mind that member just shows how an initial ridge can create a REASONABLY sustained block, as a cold fan i have to ask myself, is that what i call potent cold?, and if you look at the uppers profile that is over a weeks worth of snow potential, i know people may think i am a cold ramper but anything lasting weeks and weeks like last december is extremely unlikely, i am realistic and would you take that now, fair enough its not an omega or a textbook greeny but surely what wintry PPN potential it delivers is what matters.

[Great Plum]

Interesting ensembles this morning...

http://www.netweather.tv/index.cgi?action=charts;type=ens;sess=

Whilst from the 7th Jan, the ensemble mean dips with a number of ensembles approaching -10 in extreme FI, the operational is again having none of it and is very mild towards the end...

[KTtom]

It may come to nothing in terms of effecting our weather, but the trend over the last 3 ECM runs is to shift the whole pattern further west and increase the block to the north east, not a bad chart for potential at +144 this morning.

We even get a cut off low heading south east undercutting the block at +168

A very interesting chart at +216 as a ridge heads to Greenland and the block to the north east continues...one of those runs you hoped would go out further, for eye candy if nothing else.

....and for fun at +240 the PV is in tatters!

Edited December 27, 2011 by KTtom

[IDO]

Well the latest GFS is an outlier but can anyone explain why GFS continue to use their mildest run please? The ensembles are trending down in temperature so not all bad and if the outlook was a jigsaw puzzle, we would have the corners sorted; still some work to be done but the pieces should start showing the picture soon; a seasonal offering I proffer.

"When I no longer thrill to the first snow of the season, I'll know I'm growing old."

[Beasterly]

GFS 00Z looks a major outlier. It is the mildest of the runs. Take a look at the GFS mean dropping to -5 at the end of the run with most trending downwards towards the end of the run. So a pattern change looking more confident this morning.

Edited December 27, 2011 by BreezeInTheEast