Winter Model Discussion 12Z 15/02/13 onwards.

[Tamara]

Gfs short range ensemble http://www.meteociel...=0&type=0&ext=1

Wow

Yes they are rather pleasant aren't they!

[Mucka]

May as well post it I guess.

Edited February 15, 2013 by Mucka

[fergieweather]

My prediction for tomorrow is the UKMO will be further N tomorrow and as a consequence the Met O forecast will be changed from wintry showers to snow showers pushing inland.

errr... It already does. Not sure why you suggest it doesn't (albeit we expect snow grains too, and graupel, so wintry showers a reasoned generic term).

Light snow showers all way from E Coast to W Country by Thurs. No accumulations expected per se from these.... because profiles on N Sea coast show these are exclusively generated from fairly shallow CuSc. However, Exeter note we can't account for focus from convergence at this juncture; i.e. localised accumulations possible through this mechanism

Edited February 16, 2013 by fergieweather

[BlueHedgehog074]

Although it is the pub run, it does have a lot of 'cool' stuff about it for fans of chilly and snowy weather, especially for Southern and Eastern parts. Indeed, the more ideal orientation of the North-East/Scandinavian High pressure cell ensures colder uppers (with even some -10's thrown in) break through to the UK easier than in comparison to the GFS 12Z run...

An example at 144 hours:

GFS 12Z run

This previous run had the magical -10*C upper line just out in the North Sea for next Thursday, rather than over the UK which the GFS 18Z shows for the same time-frame. This seemed to be mostly thanks to the fact the wind direction was a little too South-Easterly over the UK with the high not stretching as far South-West than in does on the GFS 18Z run. As such, delays with the -10*C upper line reaching the East appeared to be caused.

GFS 18Z run

With the Scandinavian high extending slightly further West-South-West on this run for the same period, this seemed to allow more of a direct East/East-North-East flow to establish on the Southern part of the high over the UK. This, I imagine, along with a slightly more substantial upper cold pool out to the East/North-East resulted in the -10*C upper line reaching the UK earlier than it did on the previous run. And also covering a broader area, too.

No doubt, future runs will likely to continue to alter the position and angle of the High Pressure system, thus having an affect on how easily we can obtain those chilly uppers.

It kinda shows that although the 12Z ECMWF was not too brilliant for its very cold uppers, upgrades, just like what happened on the GFS can still occur.

Not particularly great news, however, if you're looking for mild weather, although I have noticed on the last few runs in deep(ish) Fantasy Island, the GFS seems keen to try break down the cold spell with the warmer Atlantic coming back for revenge!

Both the GFS 12Z and GFS 18Z seem eager to bring those South-Westerly winds back with heights to the South-East re-establishing in FI.

I know it's not really best to pay much attention to deep(ish)/deep FI, unless looking for trends (or for entertainment purposes), but I do feel if the GFS continues with this possible trend, then there is that chance this cold spell may struggle to last for more than a week, which, to be fair, is still quite decent for the UK. I suppose we would have to make sure the Scandinavian high does not get pushed too far East or South-East, otherwise the risk of milder Southerly or South-Westerly winds could come to rob all our cold. But having said that, if the High to the North or North-East of us stays stubborn, then we could just possibly stay 'trapped' in this cold, Easterly-like pattern for a long while with perhaps a 1947ish sort of flavour to it. I think we would also have to idealy see some of the heights up North spill into Greenland, which some members, such as Steve, I think have mentioned in the past, to help increase the chances of sustaining a chilly spell. I could be wrong, and I admit I'm not a huge expert on Greenland High Pressure setups, but that would probably be the way we would have to go for cold not to give-up the ghost.

Edited February 16, 2013 by DiagonalRedLine

[fergieweather]

Worth adding that EC EPS snow probs for trace amounts are high everywhere apart from west by Wednesday but very muted signal for even 1mm on E Anglia coast. Anyway, as I always stress, looking at the PPN modelling in raw fields is meaningless unless tallying with forecast profiles. So for example, here's a tephi sample from N Sea coast synthesized by the UKMO-GM. Note limited tops: hence mostly light showers.

[Cal]

errr... It already does. Not sure why you suggest it doesn't (albeit we expect snow grains too, and graupel, so wintry showers a reasoned generic term).

Light snow showers all way from E Coast to W Country by Thurs. No accumulations expected per se from these.... because profiles on N Sea coast show these are exclusively generated from fairly shallow CuSc. However, Exeter note we can't account for focus from convergence at this juncture; i.e. localised accumulations possible through this mechanism

So basically a dryish continental feed, apart from one or two localised areas that may see a slight dusting, however things may get interesting a little later on towards the following weekend with copious amounts of snow encroaching fron the southwest with some places receiving over a mm of snow, emergencey protocols have been put in place, just in case scenario, whereby some areas receive more than 3mm of precipitation, lol (last paragraph made up !)

[peterf]

Worth adding that EC EPS snow probs for trace amounts are high everywhere apart from west by Wednesday but very muted signal for even 1mm on E Anglia coast. Anyway, as I always stress, looking at the PPN modelling in raw fields is meaningless unless tallying with forecast profiles. So for example, here's a tephi sample from N Sea coast synthesized by the UKMO-GM. Note limited tops: hence mostly light showers.

Ian could you put a red dot on that regards Newcastle,just so i can get my bearings.

[fergieweather]

So basically a dryish continental feed, apart from one or two localised areas that may see a slight dusting, however things may get interesting a little later on towards the following weekend with copious amounts of snow encroaching fron the southwest with some places receiving over a mm of snow, emergencey protocols have been put in place, just in case scenario, whereby some areas receive more than 3mm of precipitation, lol (last paragraph made up !)

Yup re first bit.

Second bit clearly open to innumerable aspects of change. We've seen sufficient nuance changes in today's output to highlight due caution in what may transpire by end of week. It could be grim, or equally a non-event. I'm doubtful of real clarity until mid-week in terms of mesoscale outcome, as it has all the hallmarks of a very fluid evolution.

[bluearmy]

to clarify that 'grim' in ian's parlance is nirvana for most of his southwestern brethren on here.

[Panayiotis]

So most models are agreeing with an easterly feed at day 5, with a cold pool heading our way, lets see what the models show:

Above is the GFS,ECM,UKMO,JMA,GEM,NAVGEM,BOM,CPTEC and CFS as you can most show the cold pool (represented by the blue colours coming in from the east) however the CPTEC doesnt show the cold pool coming our way and that is due to the modelling of the high pressure, it has it much more south and east than the other models but i expect that to change as it has been poor like the GFS in this setup.

The best charts at 144hrs for cold is the CFS and NAVGEM as they show the coldest uppers (represented by the deep blue) and they are also good for cold as the cold pool is over us instead of just south of us, like the other models are showing it.

Edited February 16, 2013 by Panayiotis

[fergieweather]

to clarify that 'grim' in ian's parlance is nirvana for most of his southwestern brethren on here.

Ha! Yes, I mean in terms of public forecast parlance. I forget you lot like the notion of chaos ;-)

[bluearmy]

so the best charts for cold are from the worst performing models. at least i wont lose sleep with the anticipation of upgrades in the morning!

[Cal]

Yup re first bit.

Second bit clearly open to innumerable aspects of change. We've seen sufficient nuance changes in today's output to highlight due caution in what may transpire by end of week. It could be grim, or equally a non-event. I'm doubtful of real clarity until mid-week in terms of mesoscale outcome, as it has all the hallmarks of a very fluid evolution.

Yea i think i grasp the jist of it Ian, but what gets me (way of topic Mods) is why they all sit on the fence at Exeter? C'mon where's the 'Characters' nowadays? At least someone have the spark to say this is what i think will happen (cold/mild whatever!!) n put some real excitement into forecasting regardless!

[Cheshire Freeze]

to clarify that 'grim' in ian's parlance is nirvana for most of his southwestern brethren on here.

Was just about to say, I don't think most on here would describe heavy snowfall as grim

I'd say it's about as grim as say, spending a steamy night with Rihanna or Rita Ora......i.e not very........lol!

Edited February 16, 2013 by CreweCold

[Cal]

so the best charts for cold are from the worst performing models. at least i wont lose sleep with the anticipation of upgrades in the morning!

Yes, funny how the GFS has suddenly become the model of choice over the last 48hrs or so

[Cheshire Freeze]

so the best charts for cold are from the worst performing models. at least i wont lose sleep with the anticipation of upgrades in the morning!

The CFS picked out this pattern weeks ago. Well, months ago if you count the first time it picked it out back in October!

[Captain Shortwave]

It seems the metoffice are seeing this as a dry cloudy high event, as per the "attack of the grey cloud symbols" on the bbc for my area. I do hope we can drag that cold unstable air to bring plenty of snow showers to the UK as well as general snow to the south west. But hey go in with the lowest of expectations (a 50% chance of developing rickets ) and maybe things will turn out nicely for us snowmaggendon fans.

Night all and here's to good output tomorrow

Edited February 16, 2013 by Captain shortwave

[lorenzo]

ECM killing it.

Out this evening for some Edinburgh carnage, ECM has simply owned this 240, 216,192,168.

Sat 12z edges nearer.

Its about whether ECM serves another about face right now... Will it...

[Vince Coombes]

Hope the met office and Ian are wrong and we get the severest spell since 2010.lol. Fancy posh words dont cut it with me.

[rory o gorman]

00z gfs is another cracker . strong heights locked in

[Harve]

The 00z GFS is in much the same vein...

[The Eagle]

Excellent output this morning. NOGAPS/UKMO (moving the right direction) and GFS/GEM all excellent.

[Zenarcher]

Very nice runs again from the models this morning.

[SMU]

Morning all

I am happy to see great overnight runs ESP ukmo 120 & 144

I would suggest that should the MOGREPs agree then the cloud tops will be significantly higher bringing a greater risk of heavier snow

S

[goosey007]

Any news on this morning ecm guys.......Surprise to see no comments on it at this crucial stage.......??