Model Output General Discussion

[SMU]

looks very marginal on tuesday for snow with that low pressure in the south even though it looks better then yesterday western parts actually look better then south eastern later in the run as it turns bk to rain there

If its raining in the Se with that Sharp NW flow then it sure as hell will be raining in the west & SW-

Because of the positioning of the LP- the extreme SW picks up some milder dewpoints...

UKMO out- great to 96- 120 & 144 similar to GFS although the tilt of the southern jet isnt ESE its ENE allowing the Lp to get into the western half of the UK-

much to decide over the next 24-48 hours

The UKMO does however upgrade the snow potential for thurs & frid-

S

Edited December 16, 2009 by Steve Murr

[SMU]

prehelps looked at it wrong does look gd though. i think it will turn bk to rain though by the look of it am i rite

A quite easy one to remember- the SW- if the onshore flow has ent all the way round ireland then yes prob to warm, but if the isoline are curved back through ireland you could be ok-

incidentally the UKMO on WZ is still the 12z yesterday & shows the 00z does reposition the low at 144 further SE-

The key will be it NOT interacting with the low over the Uk- if it does it will get pull northwards-

If it doesnt it has a good chance of going underneath-

Steve

[andy_leics22]

Steve for the first time in my life I am going to say... I hope it doesen't snow next Tuesday!! My auntie is coming over on a flight from Spain for Christmas and i'm getting the coach down to Luton Airport to meet her and then she is renting a car over Christmas and we are driving back up to Leicester with it. So if it's a snowfest it might cause some problems

You know aswell as I do though that the models will no doubt change that completely by next week, I would love to see a snowfest but just not on Tuesday afternoon in Luton haha.

Edited December 16, 2009 by andy_leics22

[snowmadchrisuk]

Steve for the first time in my life I am going to say... I hope it doesen't snow next Tuesday!! My auntie is coming over on a flight from Spain for Christmas and i'm getting the coach down to Luton Airport to meet her and then she is renting a car over Christmas and we are driving back up to Leicester with it. So if it's a snowfest it might cause some problems

You know aswell as I do though that the models will no doubt change that completely by next week, I would love to see a snowfest but just not on Tuesday afternoon in Luton haha.

Good Morning Andy , By Tuesday there might already be problems even if Snow doesn't fall GFS is still looking Cold with Snow until at least Monday. I am surprised more isn't being made of the weekend , Heavy Snow showers are showing all day Saturday over the Midlands and stretching into the South . Sunday has a disturbance coming in from the NW all under -10 850's . Dry and Cold Monday and a bit of a battle from the South Tuesday in Which the cold air looks like it will win out over the Midlands.

Chris

[Iceberg]

I wasn't a big fan of yesterdays models, but this mornings so far are fantastic, As steve mentioned the risk of snow Tues/Wed is increasing next week with GFS a potentially very snowy run, FWIW, UKMETO is a very good run as well as takes the risk of snow further out into next week, the low is a little far west, if we could drag it 50-100 miles east then it would keep the air colder for longer.

The best of this morning so far though are the GFS Ensembles, A significant shift has occured overnight and the chances of the cold lasting upto and even beyond Christmas day have increased. IF we can keep this for the 06Z I would be very happy. There is nothing there that would suggest snow melt during the UK's longest days.

David I agree with you the hook of colder air in the SW being dragged down keeps that area colder than expected and snow would result re Tuesday on the GFS. A northerly develops of the back of it and the colder air is dragged back across the country.

[snowmadchrisuk]

I wasn't a big fan of yesterdays models, but this mornings so far are fantastic, As steve mentioned the risk of snow Tues/Wed is increasing next week with GFS a potentially very snowy run, FWIW, UKMETO is a very good run as well as takes the risk of snow further out into next week, the low is a little far west, if we could drag it 50-100 miles east then it would keep the air colder for longer.

The best of this morning so far though are the GFS Ensembles, A significant shift has occured overnight and the chances of the cold lasting upto and even beyond Christmas day have increased. IF we can keep this for the 06Z I would be very happy. There is nothing there that would suggest snow melt during the UK's longest days.

David I agree with you the hook of colder air in the SW being dragged down keeps that area colder than expected and snow would result re Tuesday on the GFS. A northerly develops of the back of it and the colder air is dragged back across the country.

The Mean on the Ensembles is below -5 for my area now on Christmas day.

im not 100 percent sure the system in the south is gd 4 us generally wouldnt we all prefer the low from the north to go through the uk

The Breakdown has to come sometime , and Systems from the South bumping into the Cold Air , Usually gives the most amount of Snowfall. It is looking more and more likely with strong Ensemble support though that the Cold air is going to win out at the first attempt and this will allow settled Snow to stay on the ground. This is also the best time of year for Snow cover with the sun at it's weekest .

[David-kig]

the gfs esembles are improving in somerset to nt so much as further north but overall looking good

can anyone update me with the ukmo run is it looking like the out come of the gfs

[Lincs Observation]

morning all

that low that comes down for early next week is for me the potential for something good,however it could be the start of the end to. over the past few runs its in no doubt of its intentions to track south to us but on almost every run its given up to me a different scenario. What i mean is ive seen that low sit over the UK or move down then move NW, another run it seems to meet with another Low ect ect, I guess that until we get to at least Fridays/Saturdays run will we see what the out come will be.

In five years on this site i dont think ive seen such a a varied and more excitable period of model watching, the potential on today's runs is fabulous for the snow watchers, and for some who feel Christmas is a drag this year will almost have some Christmas spirit injected into their lives.

LO

[Iceberg]

ECM showing very good, cold, snowy run out to 144Z, very good consistance, UK METO similarly.

All 3 models show a very similar set up at 144, will only minor changes in the position of the LP and how far south the cold air digs. The meto forms the secondary low, but tbh this needs to be within 96hrs to be modelled correctly.

I think all 3 will/would also show the LP coming up from the south, again specifics arn't too important atm.

[nick sussex]

http://www.wetterzentrale.de/pics/Rtavn1801.png

OK WHO BROKE INTO THE GFS_???

What the GFS is asking is nothing short of a miracle- If it came theres no archives I can present that goes up with this-

Run the charts between 144-192 ( Central Southern England away from the coast would have an epic snowstorm)

The GFS is developing a shortwave in the Southern arm of the jet just north of the Azores, because the jet is EXTREMELY surpessed to the south & tilted ESE it runs & develops the shortwave towards portugal before recurving polewards towards France-

THe shortwave then develops more,goes UNDER the UK & up the North sea-

Move the Track of this just 200 miles SE & the WHOLE of the PPN sheild will be snow- with epic totals-

It cannot happen ... can it....

S

Morning Steve

That would be sensational, it sort of reminds me of those big eastern USA snowstorms which we sometimes see running ne up the coast from the southern states, alot of warm air on the eastern flank, huge amounts of energy!

Ecm so far looks very good,at 144hrs IMO an upgrade from last nights, could be an interesting FI.At 168hrs quite a strange looking output with a slack flow, we'll have to wait for the 850's but if we dont see too much mixing out of the cold earlier on then it would likely still be very cold with some low night time temps over the snowfields!

Edited December 16, 2009 by nick sussex

[Iceberg]

Another cold snowny run from ECM, with the snow(particularly in the south(no rain in sight) until Christmas day at least.

The models seem to be pulling away from the atlantic lows moving north enough(or having enough energy) to break into the cold, so the cold with sub 1000 pressure just hangs around, leading to prolonged heavy showers and longer speels of snow.

This is re-inforced by the GFS Ensembles as well.

[Frosty.]

The only chart I don't like this morning is the ECM 00z T+240 hours, I don't like the way it would probably go by the next frame with the jet further north than gfs at same range. Apart from that the output is brilliant with the gfs 00z extending the arctic spell until almost the end of the year, I missed the 18z last night but gather it was similar to the 00z. To add a bit of northern perspective as everything would seem to be happening in the south only. The north will see just as much wintry weather as the south and scotland looks like being battered this weekend if that arctic sourced low or polar low hits as predicted, blizzards would occur widely and I havent even mentioned the temps yet, sub-zero day and night across much of the uk once we become locked into this freezing spell, I don't think I can remember seeing the jet so far south for such a sustained period as the gfs shows.. the word AWESOME doesn't even do the gfs 00z justice.

Edited December 16, 2009 by Frosty039

[Stu_London]

Nice to see a different and delayed version of the breakdown this morning, with only a couple of ensemble members going for an early return to milder weather.

A good chance that many will see either falling snow for xmas or snow on the ground.

I can understand to an extent the BBC forecast, as the situation next week is only slightly more favourable in terms of uppers than we are seeing today. However, the cold will be embedded by then and I would therefore expect that most will be the right side of marginal

[Frosty.]

Hmmm while i agree with all that the meto update really doesn't reflect what i was seeing in the models.

Rain sleet and snow over high ground this weekend,less cold.

The meto lads clearly dont think this weekend is going to be as cold as the 0z gfs 0z ecm are showing.

I'm very confused by that forecast to be honest.

It doesn't actually say less cold HD, it says continuing cold. The weekend and much if not all of next week look very cold and wintry according to all the latest models and I can't imagine any dramatic downgrades to scupper it, the pattern looks like being prolonged.

[Cecil Hogmanay Melchett]

It doesn't actually say less cold HD, it says continuing cold. The weekend and much if not all of next week look very cold and wintry according to all the latest models and I can't imagine any dramatic downgrades to scupper it, the pattern looks like being prolonged.

Outlook for Friday to Sunday:

Sunny spells, scattered snow showers on Friday, but much of the day dry. Further sunny spells through Saturday and Sunday with rain and sleet showers, snow on hills. Overnight frosts.

Updated: 0330 on Wed 16 Dec 2009

Now i know this is not STRICTLY on topic but does that update reflect the models this morning?

Rain sleet hill snow,if that deosn;t suggest less cold i dont know what does.

[Cecil Hogmanay Melchett]

same here mate, shocking. carol kirkwood showed highs of 4 degrees in the regional cities tomorrow, and i was nothing short of flabbergasted. apparently its turning less cold at the weekend, despite the fact its supposed to get colder if anything. very surprised at the met office. mods move this to the appropriate threads if necessary

Yes the models this morning have us all well within sub 528dam air over the weekend on a cold NW flow with

strong Greenland blocking in force.

One can only conclude we are going to see major modification from the ssts around our country.

IF we get highs of 4 degrees tomorrow in sub -10 air then its a real shame.Those synoptics on offer at this

time of the year with the extremely short days should be offering colder temps than are being shown by the

bbc.

Who do i believe? The models or the BBc?

[TEITS]

same here mate, shocking. carol kirkwood showed highs of 4 degrees in the regional cities tomorrow, and i was nothing short of flabbergasted.

Actually 4C tomorrow is perfectly plausible as it isn't until the evening when we pull in the bitter -10C upper temps, especially further S.

Back to the models and like others have said the ensembles are definately prolonging this cold spell. The mean remains around -5C beyond xmas day.

http://charts.netweather.tv/ensimages/ens.20091216/00/t850Cambridgeshire.png

[snowmadchrisuk]

Actually 4C tomorrow is perfectly plausible as it isn't until the evening when we pull in the bitter -10C upper temps, especially further S.

Back to the models and like others have said the ensembles are definately prolonging this cold spell. The mean remains around -5C beyond xmas day.

http://charts.netweather.tv/ensimages/ens.20091216/00/t850Cambridgeshire.png

Well this is the Chart the 00z produced , I personally don't think we need to be worried about rain Tomorrow.

[Cecil Hogmanay Melchett]

HD, if we only get rain and sleet showers at the weekend from the set-up projected by all the models, it's time to pack it in.

That forecast will change, if the PPN is there it will be sleet and snow away from coastal areas.

Ian,

Like steve murr i know i sometimes give you earache but its only because the theory gives me a headache.

Anyway,yes the models are superb for the weekend,i was utterly gobsmacked by that meto update.

Either they know something we dont or they are seriously underplaying things here.

Finally,i agree.If we get highs of 4 or 5 like they seem to be suggesting i might well consider packing it

all in as its the 3rd week in Dec,the days a re very short(weak sun too)we have 528 dam over us and a cold NW wind.

The ONLY thing i can think off is the Irish sea seriously modifying the flow.

Ian?

[LomondSnowstorm]

Cold spell on the mean persisting until the 27th here now - a huge delay in the breakdown from yesterday.

[nick sussex]

I think the reason for that ukmo further outlook is its not a straightforward snow pushing south forecast, if you look at the fax chart for T-84hrs.

http://www.meteociel.fr/modeles/ukmo2.php?ech=84&carte=2000

You've got two triple points here with some milder air to the west of these, so western areas are more prone to a wintry mix with rain, sleet and snow. At this stage the milder sectors wont be modelled accurately so it wont be till 24 hrs out that we can see whats likely to happen. In terms of upper profiles the 850's do rise but then the 500hs drop later as the sourcing of air is the Arctic, there will also be some cold air embedded at the surface.

Just briefly regarding the media forecasts, John Hammond mentioned the weekend on radio 5 live, basically he just said staying cold with the chance of significant snow and likely transport disruption. So hopefully this will allay some of worries of some of the members in here. Personally in these situations i don't follow the media forecasts as we've seen from another thread hysteria breaks out because of the snow blob graphics from the bbc!

Edited December 16, 2009 by nick sussex

[Solar Cycles]

I think the reason for that ukmo further outlook is its not a straightforward snow pushing south forecast, if you look at the fax chart for T-84hrs.

http://www.meteociel.fr/modeles/ukmo2.php?ech=84&carte=2000

You've got two triple points here with some milder air to the west of these, so western areas are more prone to a wintry mix with rain, sleet and snow. At this stage the milder sectors wont be modelled accurately so it wont be till 24 hrs out that we can see whats likely to happen. In terms of upper profiles the 850's do rise but then the 500hs drop later as the sourcing of air is the Arctic, there will also be some cold air embedded at the surface.

Looks like in this part of the world, it will be very marginal for snow. Still like you say, things will change nearer the time!

[Altostratus]

Another morning and another set of very good runs. Despite numerous exciting prospects this week, you can’t help but notice the pattern starting to emerge in the medium to long term. As many of us expected, the cold spell looks to be extended and it is increasingly looking likely that the big day itself will be cold. For the cold spell to extend beyond Christmas, we need the lows to start undercutting into Europe. This will help to maintain us in the trough and help to shunt the ridge further eastwards. Any warm air would then be advected along the flanks of the ridge up into Eastern Europe, away from us. The other thing we don’t really want is for any approaching lows to rapidly deepen and amplify the trough and subsequent ridge. The models look to be moving away from this now, so we are heading in the right direction at least.

Regarding the update from the MetO, they always underplay things until they are absolutely sure. I wouldn’t worry about any BBC forecasts either. Best thing to do now is look out the window.

Edited December 16, 2009 by Altostratus

[kold weather]

Very good models indeed this morning, obviously not a big fan of the GFS since it brings a milder pulse of air up into the SE so the big snow set-up ends up being pretty poor down here...a weaker low would be far better given the way the colder air only just gets over this location in the first place, something more akin to the ECM which would still be cold enough at 168hrs for some decent snowfall.

A big LP is likely to have a far bigger drag from the south. For the north its not really as much an issue but down here it could make a rather huge difference.

Still a nice trend there to see, temps look like staying cold for xmas!

[mezzacyclone]

All round concensus then of the cold period lasting a while?

Interesting for all as to where this Rex Block sets-up?

Basics of the -NAO forecast suggest a white xmas possible so the flutters are back on for Scottish cities at least?