Model Output Discussion 4th Dec.2013-12z onwards.

[mulzy]

ECM pretty underwhelming to be honest (from a coldie's perspective).  The PFJ actually getting pulled northwards towards the end of the run allowing the Euro High to influence SE parts. Let's see how this fits in with the ensembles.

 

[Gibby]

Good evening. Here is the latest report from me on the midday outputs from GFS, UKMO, GEM, NAVGEM and ECM for today Friday December 13th 2013.

 

All models show a volatile period of weather to come with quickly changing weather from day to day all in association with rapidly deepening depressions moving quickly NE close to NW Scotland and a strong SW wind across the UK with gale and severe gale force winds in the NW at times. There will be some drier spells too, especially across the South as cold fronts clear East tonight and again tomorrow night leaving much of Saturday and Sunday daytime in the SE not too bad. Tuesday too looks an OK day in the South as transitory High pressure runs quickly East across Northern France through the day while the North stays breezy and showery with generally mild conditions for most areas for much of the time as well.

 

GFS shows very windy and unsettled weather across all areas for the remainder of the run with gale and severe gale force winds at times with spells of heavy rain followed by squally and possibly wintry showers before a return to mild and windy weather returns again in oscillating fashion through the Christmas period and beyond.

 

UKMO tonight shows a strong WSW flow later next week with rain and strong winds followed by more showery conditions when it will become a little colder with some snow on Northern hills in the showers.

 

GEM maintains a strong WSW flow too from the end of next week until the end of the run with periods of rain and relatively mild conditions alternating with colder and more showery weather with some potent showers at times falling as snow on higher ground.

 

NAVGEM is little different with very windy weather the biggest feature with heavy rain at times but with some chillier and more showery interludes in between.

 

ECM is less keen on deep Low pressure reaching the South maintaining High pressure over Europe where it remains very mild. Over the UK winds would be strong and SW'ly. There would be spells of rain and strong winds, particularly heavy in the NW but much less so in the South and East where some longer drier spells look possible. Overall milder conditions should outweigh colder interludes which will be more likely to occur in the North.

 

The GFS Ensembles show less range than usual especially for Northern locations where there is the most solid support for spells of wet and very windy weather with Low pressure rattling over or just to the North of the UK. Things are a little more varied in the South where some longer drier spells seem possible at times. Temperatures never look like being particularly low with most members opting for a green Christmas rather than a white one but this doesn't exclude the risk of some snowfall on Northern high ground at times.

 

The Jet Stream shows the flow powering across the Atlantic and the UK for the reliable future. In the latter part of the forecast in the less reliable time frames it shows the flow slipping South of the UK and possibly meaning at least a chance of rather colder conditions developing.

 

In Summary tonight the Jet Stream spawns some major storm systems out to the NW of the UK over the whole output period. How far South the influence of these storm systems come is unclear and it maybe away from the far NW that it will be just windy and wet rather than stormy and wet with some colder spells developing when snowfall could turn up abruptly. ECM shows Low pressure much further NW tonight with High pressure solidly holding firm over Europe steering the worst of the weather out to the NW. The rest of the output is much more determined to bring stormy conditions to all areas at times with some colder polar maritime air capable of delivering some snowfall at times, especially through the Christmas period. Which 1s right is yet to be determined in this very volatile unstable situation synoptically and time alone will tell.

[nick sussex]

After perusing all the model output this evening its a rather depressing outlook for cold; I'm afraid we've been duped again , you know all those crappy commercials with snow falling at Xmas like its a yearly thing!

 

So in terms of tonights model carnage, its like Terminator just wiped out Santa and his little helpers leaving us with broken dreams and dusty sledges! Ok I admit I can go up the mountains here but you know its not quite the same without it snowing in your back garden!

 

Of the big 3 the ECM/GFS very similar upto T240hrs, a few brief colder PM returning flows but really not upto much, perhaps some sleet or snow for the far north helped by some elevation, further south its a case of just rain I'm afraid.

 

The problem really is the misery combo want to reform the PV towards the end and this is not what you want to see, this means the PV after a brief skirmish has just popped a few steroids and now is even less of a mood to leave the scene or disrupt, there is an easy rule for newbies re the PV, a rounded PV is a no go for cold 99/100 even if the models try and bring the cold south with that set up it won't verify, firstly shortwave activity near Iceland will generally cut off the cold flow and that's without taking into account the model bias especially with the GFS to bring the pattern further south.

 

There has to be a trigger to move the PV, so you need to see some ridging into the Arctic and especially low heights lifting out of northern Greenland, a stretching of the PV or to see chunks of it leaving the mothership.

 

In terms of tonights UKMO and to some degree the JMA as a little support we're not likely to see a miracle even if the UKMO is correct, what we're trying to do here is damage limitation, we know the PV will relocate towards Canada, this will ignite the jet off the eastern seaboard of the USA piling in  a tonne of energy without something to deflect that energy it will just scream across the Atlantic and get diverted ne towards Scandi thereby fuelling high pressure to remain stuck to southern/central Europe.

 

So we need to see some forcing on this, it could be  a lobe of higher pressure extending towards the Arctic from Alaska or something to the ne to help divert the jet onto a more favourable nw/se axis.

 

At the moment the models generally don't want to do this apart from a few GEFS ensembles , some of the lower resolution GFS runs towards the end have done this but to be frank the GFS lower resolution past 240hrs is IMO a waste of space.

 

If we are to mitigate the pattern so in effect we're not looking for a massive NH change but a few tweaks especially to the ne then we would need to see the UKMO be a trend setter, again I have my doubts regarding that operational run, we do have one little straw by means of the strat zonal wind slowing towards the Arctic.

 

Overall then its a race against time to save a more festive weather wise Xmas, don't expect miracles, theres simply no sign of any HLB, but can we squeeze just a bit more interest especially for those folks in the north, maybe, we'll see over the next few runs.

[Frosty.]

Most of the GEFS 12z perturbations are very unsettled with gales and heavy rain at times, and cold enough for hill snow in the north but there are a few here which would bring a white christmas to some parts of the uk if similar charts verified, I would think n.ireland and scotland have a good chance of occasional snow showers with the hills and mountains of scotland at risk of blizzard conditions at times.

[Captain Shortwave]

"The UKMO saves Christmas", sounds like a good name for a film 

Probably the last chance saloon, at least we have a chance.

Edited December 13, 2013 by Captain shortwave

[Froze were the Days]

this  something the coldies  will  love  a white  xmas  day!!!

The biggest ramper on this site...the most +NAO being shown in the foreseeable future and you still come up with some snow!

[bluearmy]

Despite Blue Army's optimism about where the UKMO was leading us ECM brings things back down to earth with a zonal bump

 

 

I really can't see anything decent developing here

 

no optimism, no pessimism - its only algorithms after all.  so much variation in the gefs week 2 that the modelling will keep our interest despite the overall picture looking mobile and predictable.

 

last two ecm extended have drawn the jet back north somewhat compared to the two prior runs. if that trend continues, we will be into 2014 on a zonal train.  conversely, fi naefs is now dropping that mean jet end week 2.

[fergieweather]

"The UKMO saves Christmas", sounds like a good name for a film Probably the last chance saloon, at least we have a chance.

I will advise much later this evening as to whether Ops Centre buy the 12z run or modify it to a cross-model consensus.

[UV-RAY]

I will advise much later this evening as to whether Ops Centre buy the 12z run or modify it to a cross-model consensus.

You'll either be looked upon as Father Christmas or the Grim Reaper, rather you than me.

[Cumulonimbus Tower]

My head says the UKMO is a rogue operational run that will bite the dust by tomorrow, my heart says its nearing Xmas and that slowing of the zonal winds in the strat near the pole will deliver an emergency pressure rise up there to deflect the jet further south and that the UKMO still believes in Santa!

 

Wondering if what the UKMO hints at today is what Steve M was alluding too yesterday when he posted this http://modeles.meteociel.fr/modeles/gfs/runs/2013121212/gfsnh-0-144.png?12

[bobbydog]

After perusing all the model output this evening its a rather depressing outlook for cold; I'm afraid we've been duped again , you know all those crappy commercials with snow falling at Xmas like its a yearly thing!

 

So in terms of tonights model carnage, its like Terminator just wiped out Santa and his little helpers leaving us with broken dreams and dusty sledges! Ok I admit I can go up the mountains here but you know its not quite the same without it snowing in your back garden!

 

Of the big 3 the ECM/GFS very similar upto T240hrs, a few brief colder PM returning flows but really not upto much, perhaps some sleet or snow for the far north helped by some elevation, further south its a case of just rain I'm afraid.

 

The problem really is the misery combo want to reform the PV towards the end and this is not what you want to see, this means the PV after a brief skirmish has just popped a few steroids and now is even less of a mood to leave the scene or disrupt, there is an easy rule for newbies re the PV, a rounded PV is a no go for cold 99/100 even if the models try and bring the cold south with that set up it won't verify, firstly shortwave activity near Iceland will generally cut off the cold flow and that's without taking into account the model bias especially with the GFS to bring the pattern further south.

 

There has to be a trigger to move the PV, so you need to see some ridging into the Arctic and especially low heights lifting out of northern Greenland, a stretching of the PV or to see chunks of it leaving the mothership.

 

In terms of tonights UKMO and to some degree the JMA as a little support we're not likely to see a miracle even if the UKMO is correct, what we're trying to do here is damage limitation, we know the PV will relocate towards Canada, this will ignite the jet off the eastern seaboard of the USA piling in  a tonne of energy without something to deflect that energy it will just scream across the Atlantic and get diverted ne towards Scandi thereby fuelling high pressure to remain stuck to southern/central Europe.

 

So we need to see some forcing on this, it could be  a lobe of higher pressure extending towards the Arctic from Alaska or something to the ne to help divert the jet onto a more favourable nw/se axis.

 

At the moment the models generally don't want to do this apart from a few GEFS ensembles , some of the lower resolution GFS runs towards the end have done this but to be frank the GFS lower resolution past 240hrs is IMO a waste of space.

 

If we are to mitigate the pattern so in effect we're not looking for a massive NH change but a few tweaks especially to the ne then we would need to see the UKMO be a trend setter, again I have my doubts regarding that operational run, we do have one little straw by means of the strat zonal wind slowing towards the Arctic.

 

Overall then its a race against time to save a more festive weather wise Xmas, don't expect miracles, theres simply no sign of any HLB, but can we squeeze just a bit more interest especially for those folks in the north, maybe, we'll see over the next few runs.

 

hi nick, you say we need the UKMO to be a trendsetter, yet there is very little difference between the UKMO and the GFS at T120-

 

UKMO-

 

GFS-

 

 

the PV may not be in the ideal place there but its certainly not "rounded".

 

also, in the relatively short time i have been model watching, i don't recall the GFS modelling -5 uppers over such a large swathe of the country, from a NW, PM flow, so far into FI.

such as this-

 

[Rickstar]

I will advise much later this evening as to whether Ops Centre buy the 12z run or modify it to a cross-model consensus.

awwhhh what a tease!!!!

[Iceberg]

Still far too much diversity in model output and especially ENS output tonight from T144 onward to believe in any kind of solution for Christmas or beyond.

The only certainty is that a shed load of energy enters the atlantic and that we have some very disturbed weather from it (a GFS ENS has pressure for one low down to 918mb). Quite a few runs shows some kind of deep low crossing the UK particularly around christmas eve to the 27th, with some starting the fun and games from wed/thur next week onwards. An outside chance the lows bring down enough cold air for a shot of PM airmass over christmas.

As to pattern changes, until we get a steering on the almost record breaking energy entering the atlantic nobody has a clue tbh.

[nick sussex]

hi nick, you say we need the UKMO to be a trendsetter, yet there is very little difference between the UKMO and the GFS at T120-

 

UKMO-

 

GFS-

 

 

the PV may not be in the ideal place there but its certainly not "rounded".

 

also, in the relatively short time i have been model watching, i don't recall the GFS modelling -5 uppers over such a large swathe of the country, from a NW, PM flow, so far into FI.

such as this-

 

There is quite an important difference between the GFS and UKMO concerning heights to the ne. In terms of the rounded PV perhaps I should use the one blob analogy, indeed the pattern as a whole is not as bad as some I've seen but still really isn't good. We still seem to be seeing these small areas of higher pressure appearing towards the pole and that's probably due to that strat zonal wind slowing. We need to see something cut off the energy from diving ne towards Scandi, it makes a lot of differences to going forward if some of that energy disrupts away to the se.

 

The problem isn't so much the T144hrs charts because they at least have some interest, the problem is that the PV becomes more unfavourable for cold as the ECM/GFS head towards the T240hrs mark.

Edited December 13, 2013 by nick sussex

[Paul_1978]

BOM following the GEM with the black hole @240hrs!

I have it say I've never actually seen a LP system at 0z with such a large centre - these things don't happen do they?

[bobbydog]

There is quite an important difference between the GFS and UKMO concerning heights to the ne. In terms of the rounded PV perhaps I should use the one blob analogy, indeed the pattern as a whole is not as bad as some I've seen but still really isn't good. We still seem to be seeing these small areas of higher pressure appearing towards the pole and that's probably due to that strat zonal wind slowing. We need to see something cut off the energy from diving ne towards Scandi, it makes a lot of differences to going forward if some of that energy disrupts away to the se.

 

The problem isn't so much the T144hrs charts because they at least have some interest, the problem is that the PV becomes more unfavourable for cold as the ECM/GFS head towards the T240hrs mark.

 

maybe i'm just being optimistic but "the blob" does seem to be more 'off centre' than usual when it is planted over greenland, allowing height rises elsewhere over the northern hemisphere. there may not, on the face of it, be the weather we 'coldies' crave showing in the short term (i.e. the range of the models) but this seemingly strong vortex seems 'unbalanced'. question is, will it lead to more prolonged cold, further down the line?

 

time will tell.....

[LomondSnowstorm]

I have it say I've never actually seen a LP system at 0z with such a large centre - these things don't happen do they?

 

Sylvain could correct me if I'm wrong but I believe that it's some kind of flaw with the data which means that air pressure below 950mb isn't showing up for those models on meteociel.

Wetter has it at 935mb:

I was mentioning on the regional thread the similarity of this synoptic setup to January 1993, which was a generally mild month and probably not all that notable for the south but included what I believe was the deepest Atlantic low pressure recorded in modern history, the Braer storm, which brought the most almighty blizzard to central Scotland, with upper air temperatures no lower than -6C and a similarly dominant Polar Vortex:

I can certainly see some similarities between the above and this from GFS in FI:

Of course Nick is right about shortwave scuppers occuring frequently etc. but for Scotland, Northern Ireland and northwest England these aren't necessarily the worst setups in the world if you're looking for snow.

Edited December 13, 2013 by LomondSnowstorm

[Frosty.]

Tonight's Ecm 12z ensemble mean reinforces the very unsettled and windy outlook, it's even more bullish about the intensity of the unsettled spell than the op run, yes it actually strengthens the grip which low pressure (s) look like having on the uk weather during the coming weeks and it will be cold enough at times for wintry ppn, especially on higher ground and further north but I would not rule out the risk of sleet or wet snow from anywhere between next week and the new year, again this evening, the signal appears to be stronger for a blast of colder zonality to coincide with christmas week or perhaps something even colder from the arctic. For those of us who like action packed weather, this is your dream realized, for those who were hoping for benign mild stagnation, you may have a long wait...how things have changed in the last 5-7 days, now it's a completely different outlook..to me it looks like this unsettled spell will continue well into the new year before gradually running out of steam, maybe then we will see height rises around greenland or scandinavia.

Edited December 13, 2013 by Frosty.

[bradymk]

I will advise much later this evening as to whether Ops Centre buy the 12z run or modify it to a cross-model consensus.

Thanks Ian! I would expect unless MOGREPS supports the UKMO-GM, that it will be modified towards ECM-GFS as it has no model support at the moment (as far as we can see). Interesting though. 

[bobbydog]

Sylvain could correct me if I'm wrong but I believe that it's some kind of flaw with the data which means that air pressure below 950mb isn't showing up for those models on meteociel.

Wetter has it at 935mb:

I was mentioning on the regional thread the similarity of this synoptic setup to January 1993, which was a generally mild month and probably not all that notable for the south but included what I believe was the deepest Atlantic low pressure recorded in modern history, the Braer storm, which brought the most almighty blizzard to central Scotland, with upper air temperatures no lower than -6C and a similarly dominant Polar Vortex:

I can certainly see some similarities between the above and this from GFS in FI:

Of course Nick is right about shortwave scuppers occuring frequently etc. but for Scotland, Northern Ireland and northwest England these aren't necessarily the worst setups in the world if you're looking for snow.

 

 

that would be a nasty storm if it hit scotland.

 

 

 

YOU CAN TAKE OUR LIVES... BUT YOU'LL NEVER TAKE OUR PATIO FURNITURE!!

[Frosty.]

Bit of a cliff hanger.Reminds me of waiting to see who shot J.R !

Yes I thought it would be CLIFF barnes.. :-) Edited December 13, 2013 by Frosty.

[East_England_Stormchaser91]

What concerns me, is that low on the end of ECM exiting E Canada. That looks as if it could under go extremely rapid cyclogenesis over the Atlantic and end up right over us!! I see worrying times ahead with such an extremely disturbed pattern heading in our vicinity. 

GFS also showing a nasty storm that will affect much of the UK in the semi-reliable timeframe too 

Edited December 13, 2013 by East_England_Stormchaser91

[Rocheydub]

As long as this poisoned dwarf doesn't shoot through that evil looking low pressure cell, we'll all survive…. Enough of the Dallas analogies! 

 

It's clear from the outputs that there is a change to a more mobile set up, but no Atlantic slow down, so no sustained cold so far. I took a few days away from the models, and was pleasantly surprised to see a more "seasonal" output… Especially better than the 'Bartlettesque' (I really hate that term, either a Bartlett or it's not!)... I never really felt we'd be looking at a white 25th, but I still am hopeful of some cold PM air, which I enjoy also. Anything is better than the 15 degrees we had here yesterday, that's just pants at this time of year!

 

So enjoy the weather, whatever it does!

[Cloud 10]

Lets see what the 18z does with that developing LP heading towards us at 108 hrs.

 

 

 

This looks like being the theme in the run up to christmas,with the UK in the 

firing line.

 

 

edit..

 

138 hrs...

 

Edited December 13, 2013 by Cloud 10

[weirpig]

wow the gfs really cranks up that atlantic low