Model Output Discussion - 12th December Onward

[TEITS]

GFS 6z takes us into the freezer with maxima of -3 here next monday after a pretty freezing weekend,lol#

Has to be an outlier,surely?

I wouldn't be so sure its an outlier. The combination of a cold airmass, light winds, clear skies, short days, weak sun makes ice days easily achieveable at this time of year.

[SP1986]

I'm not suggesting I'm buying the GFS outlook, but I find the temperature variability from coast to inland quite interesting in the progged frosts, shows the sea is still quite warm at the moment, usually under no wind virtually all of the country sees a good frost. If the scenario painted comes off, there will be harsh frosts in inland areas, but I'm not sure it's going to occur in the first place, as there's alot of chopping a changing that could still result.

[jonnybradley]

I wonder how the models would have handled 1987's storm in the days prior, if todays output was available then?

The GFS track spares us the wind and could give a white bonus.

Looking further afield I see signs that the Atlantic high will try to link with the Siberian high at some point. I think it is the natural pattern evolution and would bring mild southwesterlies before it becomes established. Would the jet then undercut any Scandi high?

chio, weren't you flat dismissing the 2 high meeting up last week. In fact you had some very harsh words to say about somebody that was looking at this as a possible out come. Are we getting there via a different route or has the picture change enough to allow this train of thought?

[No Balls Like Snow Balls]

The 06z progresses to a large Euro High, we could see one of the mildest Xmas/New Year periods on record in the South.

LOL it's been doing that for quite a few runs now, but the op has been one of the mildest members on all these runs too, so it cannot be taken seriously yet. I have just added something else to the list that I cannot take seriously, I wonder what that maybe!!

Edited December 13, 2011 by No balls like Snow Balls

[Bobby]

I wonder if this FAX chart would produce a snow event for those just to the North of the low? Would be fairly close I think.

Edited December 13, 2011 by Barb-

[SP1986]

As I recall in many situations where the Azores High is a player, it often does link up to the Siberian High, even in periods of mild zonality, therefore in my view, nothing can be said about the link between the Azores and Siberian high as much as it's fairly normal occurrence and doesn't really signal anything unless conditions are favourable for southwards (or northwards depending on the scenario) element.

[Thundery wintry showers]

I wonder how the models would have handled 1987's storm in the days prior, if todays output was available then?

The GFS track spares us the wind and could give a white bonus.

Looking further afield I see signs that the Atlantic high will try to link with the Siberian high at some point. I think it is the natural pattern evolution and would bring mild southwesterlies before it becomes established. Would the jet then undercut any Scandi high?

Yes, the current modelling of the low introduces the chance of a marginal frontal sleet/snow event to central and/or southern parts of England, mostly but not exclusively on high ground- evaporative cooling would help to turn rain to snow on the northern flank of any heavy precipitation.

Distribution of shower activity from the subsequent northerly/north-westerly outbreak will depend on wind direction. The GFS 06Z briefly introduces a north/north-easterly which would also give a 24-hour window of sleet and snow showers for NE England, but this is by no means certain. The troughs in the flow should help showers to get further inland at times than we would normally expect in a direct north to north-westerly regime, but even so, inland parts will probably end up predominantly dry.

After that, I don't think we're going to see a resumption of cold zonality and deep Atlantic lows, but there remain a few differing possibilities. The scenario of the Azores High heading across to the south and sucking up very warm, moist south-westerlies is certainly a major possibility. Alternatively high pressure could settle close to Britain giving mild moist weather in Scotland and colder drier weather further south, probably with plentiful sunshine given that the high is set to be preceded by an Arctic outbreak. The coldest runs on the ensembles generally have low pressure slowly sinking down the North Sea and high pressure developing over Scandinavia introducing a sluggish north-easterly regime, though I think this possibility is looking odds against at present.

It does indeed depend largely on the jet- a SW-NE jet would send low pressure into Scandinavia and promote mild SWs, while a NW-SE jet would create more opportunities for stagnant low pressure over Europe and arctic continental airmasses being sent our way from the north and east.

[chionomaniac]

chio, weren't you flat dismissing the 2 high meeting up last week. In fact you had some very harsh words to say about somebody that was looking at this as a possible out come. Are we getting there via a different route or has the picture change enough to allow this train of thought?

It was the direction of meet up that I dismissed cutting through the jetstream. The meet up I suggest will be under the jet stream and we may have to wait a while yet. And the meet up I suggest is unlikely to bear friut immediately because of this.

To continue on this theme we see the heart of the lower stratospheric vortex being forecast now to reside over Eastern Siberia. This is likely somewhat to displace the Siberian high westwards especially if the Greenland vortex has a more westerly position. The only concern here is a residual trough from the arctic towards Europe.

What happens to this will dictate whether any attempt at linkage from Atlanti to Scandfinavia will be repelled or not, leaving us back in the zonal flow.

Even if it doesn't happen, again it is more encouraging for January.

Edited December 13, 2011 by chionomaniac

[snowlover2009]

Darn, if only everything was moved a few hundred miles North we'd be in business. Not far from a snowy easterly there.

We don't want to be seeing the holy grail at this stage, hints of easterlies like this is the best we should hope for. If we get a full blown easterly like last year showing in the next run, chances are it will downgrade the intensity. Look at this weeks storm for example. So if these sort of charts continue, then there is every chances they will upgrade etc. Last year, we had hogday charts in FI, only to be watered down. In my experience, the charts need to be watered down first, before they upgrade closer to the timeframe. I mean look at the undercutting low in the next couple of days which starts the cold snap/spell and that only just got handled in the last days or so...

I wonder if this FAX chart would produce a snow event for those just to the North of the low? Would be fairly close I think.

Midlands and north of england would get snow from that I imagine.

[nick sussex]

Quite a shift in the GEFS ensembles with some very interesting looking members but we still haven't had an operational run go with one of these and there is the matter of the ECM, its ensemble suite bar the operational and control run isn't that good.

I think we're approaching a key time period in terms of the run up to Xmas, I think the key is that shortwave, although the ECM develops some interest later its far better to see that energy ejected into Europe much earlier.

[chionomaniac]

It was the direction of meet up that I dismissed cutting through the jetstream. The meet up I suggest will be under the jet stream and we may have to wait a while yet. And the meet up I suggest is unlikely to bear friut immediately because of this.

To continue on this theme we see the heart of the lower stratospheric vortex being forecast now to reside over Eastern Siberia. This is likely somewhat to displace the Siberian high westwards especially if the Greenland vortex has a more westerly position. The only concern here is a residual trough from the arctic towards Europe.

What happens to this will dictate whether any attempt at linkage from Atlanti to Scandfinavia will be repelled or not, leaving us back in the zonal flow.

Even if it doesn't happen, again it is more encouraging for January.

Some people may find the above chart difficult to read so I have modified it slightly to show where I think the major ridges and troughs would be positioned with this type of 100hPa set up. Blue is the lower heights (trough)

c

[kold weather]

06z is VERY close to a very interesting set-up for Saturday/Sunday but just slips a touch too far south. No other model appears to have it though so not something to be too alert of yet.

ECM may look a touch boring but it does probably provide us with a fairly cool set-up in the run-up to Christmas.

[Downburst]

not strictly model related, but there are very beefy snow showers over here, not exactly what one would expect from looking at the model and the -5 isotherm, so lets say the model was 5 days out, one would dismiss snow, yet here we are. I hope you get what I mean

[JCP]

The 06z progresses to a large Euro High, we could see one of the mildest Xmas/New Year periods on record in the South.

Equally so, it could be the coldest Christmas on record, it is way too early to tell.

The ensembles are slowly but surely trending colder around the Christmas period, so I find your confidence staggering.

[jonnybradley]

It was the direction of meet up that I dismissed cutting through the jetstream. The meet up I suggest will be under the jet stream and we may have to wait a while yet. And the meet up I suggest is unlikely to bear friut immediately because of this.

Thanks Chio, I thought that might be the case. Thanks for explaining tho, still try to learn

[Downburst]

06z is VERY close to a very interesting set-up for Saturday/Sunday but just slips a touch too far south. No other model appears to have it though so not something to be too alert of yet.

ECM may look a touch boring but it does probably provide us with a fairly cool set-up in the run-up to Christmas.

Agree entirely, a cold run up to Christmas modelled there and far better for cold if it's cold your after then normal, as its a wet cold so to speak, the worst in my books. If you have a car go up the nearest mountains for a drive and you'll get the snow your after.

[SMU]

As said by Nick a very large swing in the GFS ensembles, not so much cold just jet, but more pressure related to the North & north east of the UK...

Melanie.. Sorry Ian

we could see one of the mildest Xmas/New Year periods on record in the NW

I think you have somesort of balance to the posts- The ECM & now the GFS ensemble suite are changing to see a big ridge plume north over the atlantic- depending on the jet & how fast it shears the high east we could see some very mild temps for xmas in the NW of the UK, but by the same token we could see a similar chart like which has the high further north ( although a similar jet profile- zonal but over 70N) http://176.31.229.228/modeles/gens/run/gens-16-1-240.png?6 where very cold air is being ushered into the uk from the continent- All to play for- please have some balance ......

Edited December 13, 2011 by Steve Murr

[kold weather]

Some people may find the above chart difficult to read so I have modified it slightly to show where I think the major ridges and troughs would be positioned with this type of 100hPa set up. Blue is the lower heights (trough)

c

I pretty much agree with this, but obviously with that set-up there really doesn't have to be much of a NW extension of that upper high to put the UK under a set-up like we have on the ECM op or some of the GFS ensembles where we have HP aloft over the UK, possibly keeping us quite cool. Small differences in that set-up will make big temperature differences on the ground.

[Zakos]

not strictly model related, but there are very beefy snow showers over here, not exactly what one would expect from looking at the model and the -5 isotherm, so lets say the model was 5 days out, one would dismiss snow, yet here we are. I hope you get what I mean

no snow here (yet!!) but I did get snow on Monday last week when many said there would be none. Just goes to show the -5 isotherm is a guide to where snow is likely NOT a definitive boundary. This Friday particularly is looking very interesting. If the low takes the ideal track, many could see very heavy snowfalls. Imagine last nights heavy rain falling as snow. That's what potentially we could be seeing in the midlands, If something like the 00z GFS occurs.

[Uncle_Barty]

no snow here (yet!!) but I did get snow on Monday last week when many said there would be none. Just goes to show the -5 isotherm is a guide to where snow is likely NOT a definitive boundary. This Friday particularly is looking very interesting. If the low takes the ideal track, many could see very heavy snowfalls. Imagine last nights heavy rain falling as snow. That's what potentially we could be seeing in the midlands, If something like the 00z GFS occurs.

Can you put your location in your profile please?

That way we can put some objectivity to some of your posts.

Thanks.

[BLAST FROM THE PAST]

Well uncertainly in the short-term with the possibility of snow on Thursday night for elevated parts of the Central and Southern Midlands and then later further East. It is highly marginal as the air that it is bumping into is not cold enough and snow would be dependent on how much cold air wrap around there is on the northern flank. A slim chance.

Beyond the brief NWerley that follows the models this morning want to dig the trough into Europe a little which delays the natural toppling, but a delay is all it will be as we have a raging +ve NAO going forward, and if heights do stay relatively low over Europe, that means a Biscay High ridging towards Southern UK and an extended mild period

So Ian now is a Biscay HP and not a Euro HP going forward. Yes the cold ridge blocking the Atlantic is lasting longer than you or models suggested a couple of days ago...expected. I ask again, when will this mild period set in, how long will it last and what sort of synoptic pattern are you going to settle for? Euro HP, Biscay HP, AZH ridgng? Yes Xmas week to New Year is anticipated as a milder period, maybe mildest week of Dec. I really hope so, then the outlook continues and remains nicely on track. Interesting model developments in my eye. If the pattern develops that the HP stays to WSW that eventually brings in less cold even mild air but its poised to bring a pattern change. Way way ahead and we'll look at that down the line next week.

06z does an ECM and sends Fridays LP/shortwave into France then another on next day. What is good to see is that the Atlantic ridge is looking more robust as anticipated lengthening the colder period, [3rd week of Dec].

BFTP

Edited December 13, 2011 by BLAST FROM THE PAST

[Zakos]

Can you put your location in your profile please?

That way we can put some objectivity to some of your posts.

Thanks.

Done! Sorry i have been on my iphone recently and only now have access to a computer.

[Strider]

I think we are definately headed for a period of milder weather from early next week onwards but it's far too early to say how long it's going to last.

The teleconnections were no better at the beginning of Dec, in fact they were probably worse, yet it hasn't really been mild at all.

[BLAST FROM THE PAST]

It was the direction of meet up that I dismissed cutting through the jetstream. The meet up I suggest will be under the jet stream and we may have to wait a while yet. And the meet up I suggest is unlikely to bear friut immediately because of this.

To continue on this theme we see the heart of the lower stratospheric vortex being forecast now to reside over Eastern Siberia. This is likely somewhat to displace the Siberian high westwards especially if the Greenland vortex has a more westerly position. The only concern here is a residual trough from the arctic towards Europe.

What happens to this will dictate whether any attempt at linkage from Atlanti to Scandfinavia will be repelled or not, leaving us back in the zonal flow.

Even if it doesn't happen, again it is more encouraging for January.

Excellent post Chiono, I believe it will fail initially but Jan looks good bet. I also agree that the Siberian/Russian HP will back west and different to my forecast for mid Dec onwards where we look N / NNW for cold....we look east come January.

BFTP

[SMU]

http://www.wetterzentrale.de/pics/MT8_London_ens.png

distinct change in the IOW ensembles-

As said it hinges on the atlantic ridge gaining enough elevation North & the cold air coming along the southern flank-

S