General Model Output Discussion

[Joneseye]

A very interesting 06z GFS post christmas day. Milder air battles its way across England and Wales temporarily, there's even a deep little secondary at one point, but the cold eventually returns in time for new year.

I'll be interested to see the ensembles when they come out as the 00z was among the colder members at that range.

The current synoptics have all the characteristics of the cold v mild battles of winters in the 60s, 70s and early 80s.

From my understanding this is similarly in line with what Blast and RJS have been talking about in their LRF - interesting!

[cooling climate]

The latest GFS run shows a very good possibility of a white Christmas in many areas whether

it be from already lying snow or falling snow on the day itself.

The model is showing ...

528 dam over the country

Surface cold

-3 or lower 850's

Precipitation in some areas

= very seasonal and festive Christmas weather.

[East Herts Snow]

A very interesting 06z GFS post christmas day. Milder air battles its way across England and Wales temporarily, there's even a deep little secondary at one point, but the cold eventually returns in time for new year.

I'll be interested to see the ensembles when they come out as the 00z was among the colder members at that range.

The current synoptics have all the characteristics of the cold v mild battles of winters in the 60s, 70s and early 80s.

As ever with these cold v mild, its an 'all or nothing' deal, where you can end up with just a horrible wet mushy outcome, or a full on snowstorm as what happen mid February 1978.

The current synoptics are pointing to this possible outcome, who knows what will happen, i.e. will mild weather push through straight away, or will the colder dense air hold on for longer and a snowstorm ensues?

Mild will eventually win through, as it always does, just don't know when yet.

Either way as TEITS has stated these current charts are simply amazing and anything could happen!

UK office charts show a little nasty low appear in S Ireland on 24th Dec - this could be very interesting if it moves across S Uk - Major white Xmas for some?????

you hear it here first!

Hi snowingman, have you got a link to this chart?

Cheers

[mushymanrob]

The current synoptics have all the characteristics of the cold v mild battles of winters in the 60s, 70s and early 80s.

indeed this week will be very interesting with a marginal possible big snow event for some.

i agree with teits too, this could be our first white crimbo for 28 years....

[Osbourne One-Nil]

i agree with teits too, this could be our first white crimbo for 28 years....

Or my 5th in the past 12 years. smug.gif

[keithlucky]

UK office charts show a little nasty low appear in S Ireland on 24th Dec - this could be very interesting if it moves across S Uk - Major white Xmas for some?????

you hear it here first!

Nope eye in the sky posted in welsh post 1 hrs ago.

[Frosty.]

The GFS 06z is a wintry run until boxing day, then slowly turning less cold in all but the far north with a spell of snow turning to rain. Away from the far south and west, there is no mild weather on that run and the north remains on the cold side with further snow on hills at least, further on becomes very wintry again with another push from the northeast which was similar on the gfs 00z.

[kold weather]

The models do seem to be in broad agreement with the set-up with high pressure building in Europe, this is all because the low over us ends up too far west and becomes absorbed into a deepening low and promotes a Euro high, its both the worst and the faster way to possibly breakdown from this set-up, but I do think now odds are probably 90% that this happen.

Thats not to say its going to become a dominant feature, some of the ensembles are still progressive and end up taking this low to the east of the UK...we need to keep high pressure near Greenland, as long as there is a weak upper high present then if the low can get to the east os the UK then we will get a colder flow back down.

[Thundery wintry showers]

Looking at the model outputs, once again, we are seeing progressive downgrading of this potential Christmas breakdown as we get nearer the time. Chances of a white Christmas are iffy in the south with many ensembles, plus GFS and UKMO, bringing an area of general precipitation north-eastwards across southern and eastern areas with milder air on its southern flank. They look increasingly favourable from the Midlands northwards, especially for Scotland. There is a chance of snow on Christmas Eve for some which could lead into a white Christmas. For most parts of Scotland and northern England and Northern Ireland, incidentally, it would be the first white Christmas since either 1995 or 2004.

I'm afraid I don't like the bookies' definition of a white Christmas- for me a real white Christmas has to have more than 50% snow cover at some point between 9am and midnight on the big day itself.

If we drag in an easterly on Christmas Day we may well see a thaw near the east coast as the onshore wind could raise temperatures a few degrees above freezing, which is suggested by the UKMO scenario but not so much on the GFS.

Regarding KW's post above there is no certainty over that setup happening- the ECMWF shows it but the UKMO doesn't support it at all, while GFS gives mixed signals on its ensembles. Many model runs pointed to that scenario happening as early as 22/23 December a few days ago and now it has been pushed back so that it stays out at T+168. The most important thing is that for most the cold air looks likely to hang around until Christmas Day, and after a week-long cold spell I think many cold/snow lovers wouldn't begrudge a temporary return to milder weather after the big day. But note "temporary"- I doubt that any such milder weather will hang around for long with all that blocking to the north, check out the northerly in FI of GFS 06Z for example.

[MR EXTREMES]

The models do seem to be in broad agreement with the set-up with high pressure building in Europe, this is all because the low over us ends up too far west and becomes absorbed into a deepening low and promotes a Euro high, its both the worst and the faster way to possibly breakdown from this set-up, but I do think now odds are probably 90% that this happen.

Thats not to say its going to become a dominant feature, some of the ensembles are still progressive and end up taking this low to the east of the UK...we need to keep high pressure near Greenland, as long as there is a weak upper high present then if the low can get to the east os the UK then we will get a colder flow back down.

i dont like the sound of euro high is this the new term for bartlett?

because if it is i know someone who adores the bartlett lol and its not me thats for sure.

i would say 50% of the uk and scotland are likely to see something wintry but futher south no chance,

milder air pushing in as early as tomorrow night maybe tuesday morning.

theres not really a excellent agreement cold will be back and judging by gp post in sw thread it may well be a dissapointing january.

but ive got my fingers crossed and atleast the jet is still pretty south ish.:blink:

[Guest North Sea Snow Convection]

I think that -NAO is going to become a very dominant feature of the weather patterns this winter but our fortunes will depend upon whether this is west or east based. It looks as though this is going to manifest itself initially at least as a west based set-up and hence why the ECM and GEM are indicating a trough to the SW/W and a downstream high developing over Europe.

Unless we can see a signal for renewed heights over Svalbard then the present cold air will get 'lifted out' from the south west with the high pressure to the north west too far away over north western Greenland and eastern Canada.

A reload at some point is quite possible indeed - but a renewed and sustained warming of the stratosphere is one of those ingredients required to assist this. It is a vital one that is missing atm.

Edited December 20, 2009 by North Sea Snow Convection

[azores92]

i dont like the sound of euro high is this the new term for bartlett?

because if it is i know someone who adores the bartlett lol and its not me thats for sure.

i would say 50% of the uk and scotland are likely to see something wintry but futher south no chance,

milder air pushing in as early as tomorrow night maybe tuesday morning.

theres not really a excellent agreement cold will be back and judging by gp post in sw thread it may well be a dissapointing january.

but ive got my fingers crossed and atleast the jet is still pretty south ish.

that post doesnt imply a disappointing january?! it talks about blocking around the iceland area which would give the exact opposite! looks like the cold/cool weather will continue for some time, with temperatures probably slightly above freezing, meaning the snow could slowly thaw in any winter sunshine. towards the end of the week, with that approaching low, it could turn out to be very interesting for some, albeit marginal for a fair few areas.

[MR EXTREMES]

that post doesnt imply a disappointing january?! it talks about blocking around the iceland area which would give the exact opposite! looks like the cold/cool weather will continue for some time, with temperatures probably slightly above freezing, meaning the snow could slowly thaw in any winter sunshine. towards the end of the week, with that approaching low, it could turn out to be very interesting for some, albeit marginal for a fair few areas.

but the sw event is the one thing needed and as has be noted not west based this is also something that has been suggested.

i agree above average is not likely but not really cold enough south of the midlands,

infact id be in the opion of northern england and scotland being the likely areas where :

1 a white christmas could be likely,

2 cold will hang on.

but the rest of the uk being above the marginal for snow event.

but we will see when the models come out later today.

and i do hope somewhere will see a white christmas its something id like to experience myself and i never have, that i can remember anyway lol.

[azores92]

but the sw event is the one thing needed and as has be noted not west based this is also something that has been suggested.

i agree above average is not likely but not really cold enough south of the midlands,

infact id be in the opion of northern england and scotland being the likely areas where :

1 a white christmas could be likely,

2 cold will hang on.

but the rest of the uk being above the marginal for snow event.

but we will see when the models come out later today.

and i do hope somewhere will see a white christmas its something id like to experience myself and i never have, that i can remember anyway lol.

its not essential though is it? im sure there are other ways of getting height rises to our north somehow, perhaps starting with a surface high, which could be cold and give seasonal weather.

[Barb]

06z ensembles are actually quite good - below 0c 850's for the whole period for the South and op was on the mild side with quite a few much colder runs. A big scatter occurs as early as Christmas in places so plenty of uncertainty. Hints though of the cold not quite leaving?

Edited December 20, 2009 by Barb

[stewfox]

The models suggest as the low moves up (or skirts the South East) within T24 , snow could fall (away from the coasts) in land, say reading to kent.

Interesting even the BBC were not sure how far north it could get.

Anyway let you lot get back to T144 or FI

[oldsnowywizard]

sorry mods not sure where to post this as there is no uk general radar watch thread (that i could find!)

if you look at this

sat image

you will notice a few things..

1. that is almost an eye on the low over scotland.

2. the low over scotland is heading SW slowly.. as it does the bank of precip is heading slowly further south and then its picks up on the westerly wind...

comment.. with the low heading up from the SW and the low from the north heading SW there seems to be be a slight chance that the two areas of precip could meet somewhere over the UK?...?

[nick sussex]

Where is everyone? Chances of a White Xmas grow for especially eastern areas with the gfs almost hinting at sinking the Atlantic low under increasing heights to the ne! I'm shocked at the lack of interest regarding an excellent gfs 12hrs run which is trending towards the ukmo 00hrs run, maybe everyones bored of snow and cold now!

Edited December 20, 2009 by nick sussex

[Optimus Prime]

Dead as a dodo this thread. Very interesting for the 'festive' period some snow for the east and increasing heights to the NE. Cold upto Christmas with a -20c somewhere in Scotland.

Still long way off though.

Edited December 20, 2009 by Optimus Prime

[stewfox]

Where is everyone? Chances of a White Xmas grow for especially eastern areas with the gfs almost hinting at sinking the Atlantic low under increasing heights to the ne! I'm shocked at the lack of interest regarding an excellent gfs 12hrs run which is trending towards the ukmo 00hrs run, maybe everyones bored of snow and cold now!

I dont see the JH or SM or any real big hitters with a details model watch summary on here last few days

The tech thread has remained empty which is a pity.

Yes I like the gfs 12hrs run but would like a trained eye to comment

[conor123]

Where is everyone? Chances of a White Xmas grow for especially eastern areas with the gfs almost hinting at sinking the Atlantic low under increasing heights to the ne! I'm shocked at the lack of interest regarding an excellent gfs 12hrs run which is trending towards the ukmo 00hrs run, maybe everyones bored of snow and cold now!

[/quote

It's probably mainly us Midlanders who have had nothing viewing it, 12z would bring sleety rain christmas eve here, thats about as wintry as it gets in the 'reliable timeframe'.

http://www.wetterzentrale.de/pics/Rtavn2042.png

We;d stop moaning however if this came off.

Edited December 20, 2009 by conor123

[SteveB]

So is the south still likely to be cold for Christmas?

[Guest North Sea Snow Convection]

The GFS is encouraging - some of us have not had much of a snow fix at all so it is interesting to see this scenario for xmas time (not that it would make much difference in terms of my own appetite for snow if I had snow up to my window ledge!)

It does look a bit like the recent UKMO, but the ECM to date doesn't want to know and is insisting on bringing in yukky mild swerlies. But lets hope the GFS is onto something to at least keep the weather cold down here, even if snow might be asking too much around xmas!

[mountain shadow]

Forget about breakdowns, what about reloads with a vengence

http://91.121.93.17/pics/Rtavn1681.png

Stunning potential in that chart.

[BARRY]

So is the south still likely to be cold for Christmas?

No about 4c is as good as it gets.