Model Output Discussion 12z 04/12/2012

[Harsh Climate]

Interesting as well, were yet to see one of those great runs with those -10 uppers pushing right through the UK with -15s bearing down into denmark.

For me that is a worrying thing as well, even in the essmbles we are not seeing one of those colossal runs , perhaps all we are going to get is a cold quite dry feed from the continent with no beasterly?

Makes me think that we really could do with a greenland high forming above all else as that would open the gates for reloads which would deliver the goods as the real frigid cold air could then dig in.

Edited December 5, 2012 by Harsh Climate

[Chess01]

Dont no why people are getting wound up about fi . Its called fi for a reason and always changes between each run and lets be honest we have some great scenarios in the reliable time frame

[bradymk]

happy that we now have model agreement for the SW to move South eastwards. GFS 12z another outcome and expect more regarding length/severity of cold but shortwave dropping SE is the main thing initially and the "big" 3 all say now that it heads south eastwards. Like Kold mentioned in an earlier post, if the GFS is overdoing any energy in the atlantic, then this will make a lot of impacts on the rest of the run. This is not from a cold bias but I do think the 12z fi looks slightly implausible and against the trend for vortex shift towards siberia. I do think retrogression is plausible after a possible easterly and this morning NAEFS charts back this up and GP said this morning about retrogression to a GH in the longer term.

[Cheshire Freeze]

Another FI that shows the PV totally mangled and headed East, post Day 10 onwards though...

Can only be a good thing.

Yep, I think we'll start getting some 'weather porn' FIs soon enough

[A Winter's Tale]

Good afternoon. Well what a seasonal period we've experienced since late November and indeed this seasonal start to winter looks like continuing.

Through this evening the snow showers should fade away in some eastern parts of England leaving a very cold and clear evening with a widespread frost. Skies in Ireland should becoming overcast through this evening and overnight as a depression moves in from the west and cloud cover should also increase across Scotland tonight.

There is the chance of some significant snow tonight especially across the high ground in Scotland as the front meets the cold air - there could be some transient snowfall to lower levels in Scotland. Also a very cold night is on the cards, possibly the first -10C of the season tonight, general lows of -3 to 2C.

During Thursday morning there could be some heavy snowfall across parts of Scotland and rainfall extending into Ireland, and pushing eastwards into Wales and northern England where the precipitation could be heavy with some snowfall on high ground. Staing cold and dry in south east.

The band should clear eastwards from Scotland in the afternoon with the precipitation being centred over northern England and Wales, the south east staying dry. In Ireland there could be some patches of light rain whilst showers start to feed into western parts of Scotland and these could be wintry. Maximum temperatures of 1 to 7C.

During Thursday evening, the band of rain should spread into southern parts of England with heavy showers falling in northern parts of England and Wales. Quite cold conditions still in Scotland with a few showers, possibly in southern areas.

Thursday night - the could be some wintry precipitation in places but it's a case of nowcasting regarding any specific details of this. Cold and dry conditions should follow the band of rain as it clears eastwards into the north sea. Possibly a few showers in some areas. Lows of -3 to 4C.

On Friday, temperatures should still be on the cold side with general highs of 2 to 7C. There could be some sunny intervals in western areas whilst there could also be some still close to the north sea coast and there may be the odd snow shower for the Shetland Isles.

Friday night could be yet another cold one, particulary in Scotland, general lows across the British Isles of -3 to 4C. A largely dry night too with some clear spells in places with high pressure to the west influencing the weather conditions.

On Saturday, a warm front should come close to/cross over Scotland increasing the cloud cover and bringing some rain. Further south there could be more in the way of sunshine. Maxima of 2 to 6C.

Saturday night could be a cold one, especially in southern areas, general lows of -3 to 5C. There could still be some spells of rain and overcast skies across Scotland with clearer skies in Ireland and southern England with the influence of high pressure.

On Sunday, yet again it looks like Scotland and parts of Ireland could be overcast with the threat of some rain whilst elsewhere there's a better chance of sunny intervals. However, there is uncertainty at this stage with many factors such as high pressure to the west, low pressure to the east, the specific details will determin the nature of the weather on Sunday and that can't be decided at this stage.

So an interesting, fairly seasonal couple of days coming up. Very interesting period for next week and beyond, there could be some really fascinating synoptics and there's definetly the potential for something spectacular, certainly seasonal so it'll make for fantastic model watching and some enjoyable weather to look forward to during this month. There are many factors that will have a say about the weather in the longer term but the general theme is for blocking - especially to the north east and for cold temperatures - but the nature of the whole period is far from being decided. I hope in the coming days to focus on the outlook into next week and beyond aswell as looking at the weather in the near future. Enjoy the weather and the model watching!

[Zenarcher]

No wonder the UKMO today is much better I've noted the changes over the past 24 hours to it every change is a good step forward,

[Ian Brown]

Im delighted with the UKMO because at least it has woke up and smelt the coffee and realised the SW heads SE, took its bloody time though!

http://www.meteociel...20-21.GIF?05-17

The +144 chart is interesting though because it differs to the GFS and would probably follow on with a Channel LP undercutting the HP to the N.

Yes it looks a little bizarre as if the Atlantic is trying to keep it's foot in the door !

FI is different from the GFS but that is not surprise post High Res, the key timeframes are T120-T144.

[snowking]

It's all down to the modelling of the PV lobe folks, and as GP posted earlier the transition of that to the Siberian side of the pole is going to be the trouble maker in terms of consistency in operational NWP

This is why the best advice for the present time is to stick to ensemble means post 120-144 to check on vortex position (and of course corresponding Scandinavian high positioning)

In the reliable timeframe all we are looking for at present is to see the SW from Iceland head SEwards and clear to our south - after that, we just have to sit back and wait for the models to determine the eventual energy splits, and that may take some days yet

I'm not at all downbeat after the 12z's so far, lets wait for the GEFS, and the ECM (as corresponding mean) later

SK

Edited December 5, 2012 by snowking

[latitude]

Please, people here talking of an beast from the east. I cant see an easterly flow on the GFS, it looks NE then turns to a slack NE flow. Its cold but not a 91 or 87 type event right now.

Oh and its not until tues/weds next week. Thats a long way off in this game!

Edited December 5, 2012 by latitude

[TEITS]

Please, people here talking of an beast from the east. I cant see an easterly flow on the GFS, it looks NE then turns to a slack NE flow. Its cold but not a 91 or 87 type event right now.

Did anyone say it was going to be??

At the moment nobody knows whether it will be a NE/E,ly or even ESE,ly and we won't know the answer for a few days yet. All it looks like at the moment is some kind of cold flow will be coming from an E,ly direction via blocking to our NE.

[PolarWarsaw]

I think a slack flow off the continent is the most likely outcome at the moment-

Favours a very dry and relatively cold feed- but not a snowy one.

Rather annoying that with this 'cold spell' already taking place-most of the above charts referred to rain when any PPN was present-

Annoying- but still good in the early part of the GFS 12z.

[phil nw.]

There will be lot`s of variety to come in the later frames of GFS in particular as the models try to anticipate the movement of the vortex from the Canadian to Siberian side of the Arctic.

Some runs will show some pressure on the block to our north as they try to calculate it`s placement in transition.

Hopefully when it`s resolved we should see the bulk of those blues-low heights-oozing down into E,Europe and then towards the UK.

Edited December 5, 2012 by phil n.warks.

[The PIT]

The mini beast from the east edging closer to the reliable frame but still outside it. So plenty of time for it too modded yet. Deep FI has the Atlantic waking up which it will do eventually regardless. However it's a long time since we've had a prolonged breakdown attempts and they used to be fun. Loads of Snow Rain more snow then more snow then finally rain.

[Ice BIast]

The GEM is really similar to the UKMO at T144.

[CanadaAl]

Even still.. baffles me how quick people are to jump on whether there will be a slack flow, a NE,E or SE. Either way, it's a week away and the outcome is still quite uncertain beyond T+96

[TEITS]

Even still.. baffles me how quick people are to jump on whether there will be a slack flow, a NE,E or SE. Either way, it's a week away and the outcome is still quite uncertain beyond T+96

You know its times like this I wish I had a time machine so I could send all those who complain back to the winters we have all had to endure!

[bobbydog]

apparently, the vortex wants to pay us a visit-

has that ever happened? i'm sure that would get interesting if it took the right track!

[bluearmy]

apparently, the vortex wants to pay us a visit

has that ever happened? i'm sure that would get interesting if it took the right track!

not on that chart bd. not sure what you're seeing other than an atlantic depression

the siberian chunk isnt really moving

Edited December 5, 2012 by bluearmy

[whitespike]

Thanks to A winters tale for a very informed post backed up with charts makes it easier for me to understand what's happening in the immediate future

Top post

[bradymk]

GEFS Ensemble mean very good so far, good agreement with the op at 132 hours

[Rob K]

not on that chart bd. not sure what you're seeing other than an atlantic depression

the siberian chunk isnt really moving

Indeed not on that chart but I seem to recall back in December 2010 we were effectively under a chunk of the PV which dropped down through the North Sea...

http://www.wetterzen...00120101216.gif

http://www.wetterzen...00120101217.gif

http://www.wetterzen...00120101218.gif

The 06Z GFS control run actually did something rather similar in deep FI.

Edited December 5, 2012 by Rob K

[bobbydog]

not on that chart bd. not sure what you're seeing other than an atlantic depression

the siberian chunk isnt really moving

it was the depression i meant BA, its just apparently a chunk of the vortex within quite a large LP system. i just thought it might have quite an effect depending on its track

[weather eater]

GFS 12z, I’ll give it a score of 7, the trend is right the details ok but not as fantastic as this morning's GFS 00z and ECM.

All the building blocks are in place for an easterly of some sort, it’s going to take a few runs before we know how potent that will be. Anybody expecting every run to come out better or as good as the last, knows nothing about model watching, the trend is good, but it really is pointless worrying about the detail, unless you are some sort of model watching masochist, come on admit it I know some of you are.

[Wilxy]

Latest GEFS looks just as good as the last with a strong block moving towards greenland so still some support, overall a good day, so far.

And can see the PV move into E Europe at the end.

Edited December 5, 2012 by TomW

[Cecil Hogmanay Melchett]

Not keen on the ukmo12z i suspect the atlantic is going to break through at 144 with heights building across europe.