Model Output Discussion - 12th December Onward

[SMU]

nice to see the pub run moving away from that mild xmas already...

so then

Heavy snpow possible in the midlands & west on Thursday night into Friday- with Back edge snow for teh E & SE-

A slider event in offing a couple of days later-

then the GFS getting the jet close to what I think is going to happen..

Heres a teaser this is the GFS chart for the 21st

http://176.31.229.228/modeles/gfs/run/gfsnh-1-192.png?18

the PF straddles the UK - lets see for Xmas how far it goes east or west...

S

S

[January Snowstorm]

As the 18z moves into FI it looks very interesting

[johnholmes]

True John, just trying to highlight that a euro high is not certain in about a weeks time....yet.

I would agree with that

[SMU]

On fridays system the 'cone' of varience is being whittled down from run to run down- yesterday it straddled maybe 400 miles- this evening the trajectory looks to have a 100 mile cone- I would say thats pretty good on a system thats in its infancy ,....

The models are similar tonight- the jet streak at 150 is the key feature of the next 3-5 days of model watching as it almost seals the stamp on xmas...

S

[ukpaul]

As the 18z moves into FI it looks very interesting

If I was a betting man I'd suggest that, whatever GFS has at the end of the high res, it's going to return to something more zonal by the end. Interesting chart watching at the moment anyway, all sorts of options available right down to a few days away.

EDIT: Well, what a surprise, maybe I should be a betting man. That said, with its reputation going before it, there wouldn't exactly be much money in betting at such short odds!

Edited December 13, 2011 by ukpaul

[SP1986]

Sorry Steve but posting that the GFS is backing off a milder Christmas is a bit of a premature thing to say - you cant possibly know that, especially when FI hasn't loaded

Let's not go into premature selective comments, especially with things that don't appear to be happening!

[January Snowstorm]

And the pub run goes close to a beasterly for Christmas

I agree with Steve, game on for Christmas still

[Matty M]

If you look at fridays system the 'cone' of varience is being whittled down from run to run down- yesterday it straddled maybe 400 miles- this evening the trajectory looks to have a 100 mile cone- I would say thats pretty good on a system thats in its infancy ,....

The models are similar tonight- the jet streak at 150 is the key feature of the next 3-5 days of model watching as it almost seals the stamp on xmas...

S

Or has it!!?

I am just saying the prediction for T48hrs from the UKM NAE is very different to the T48hr GFS for example and previous global UKM and looks more dangerous for southern regions of England showing a deeper rapidly developing and more northerly tracking low.

NAE 48hrs

GFS 48hrs

[chionomaniac]

I think anyone showing charts beyond T+24 at the moment is going to see it change on the next run.

If you look at fridays system the 'cone' of varience is being whittled down from run to run down- yesterday it straddled maybe 400 miles- this evening the trajectory looks to have a 100 mile cone- I would say thats pretty good on a system thats in its infancy ,....

The models are similar tonight- the jet streak at 150 is the key feature of the next 3-5 days of model watching as it almost seals the stamp on xmas...

S

I think this depends upon what scale one is looking at the models. If one is looking at surface features then given the last few days then John is right. However if we are looking at 500hPa heights then we do have an idea beyond 24hours.

Edited December 13, 2011 by Paul

[SMU]

http://176.31.229.22...nh-5-192.png?18

All of a sudden on the 18z the jet has gained an amazing amount of amplitude-

certainly not perfect but it highlights that those calling for mild, whilst playing the long game you will always have more success over failure they will actually will be wrong every time the models deliver cold- because if you back the form horse generally it wins- however that doesnt make you a good at forecasting just good at betting the common outcomes-

we cant be REALLY sure of where that jets going for xmas- although its important to explore the common failings of the GFS & models et al & these are-

* not dealing with modality change very well

* Pressure rising fast over Scandi

* amplitude of the jet in the region of 180 into the lower resolution part of the runs...

S

Sorry Steve but posting that the GFS is backing off a milder Christmas is a bit of a premature thing to say - you cant possibly know that, especially when FI hasn't loaded

Let's not go into premature selective comments, especially with things that don't appear to be happening!

Steve- The jet at 180 would suggest that the amplitude of the high is not going to allow an overunning pattern....

Matty- you have just confirmed what I wrote- the variation in track is minimal against your 2 charts- however there is a variation of pressure against the- obviously the deeper low will generally go further north if it does deepen

Edited December 13, 2011 by Steve Murr

[Great Plum]

Heres a teaser this is the GFS chart for the 21st

http://176.31.229.228/modeles/gfs/run/gfsnh-1-192.png?18

the PF straddles the UK - lets see for Xmas how far it goes east or west...

S

S

Just a quick question about this chart... Is it unusual for Iceland to have such warm air (+8?) this time of year?

[SP1986]

Steve you said and I quote;

"Nice to see that run (the GFS) backing away from the mild xmas already"

so I did read your post, and it hasn't backed away, it's still showing a similar evolution to that shown in the previous 12z and previous days runs which is a ridging (of some form) of the Azores High - there's not even an inclin of an easterly - no matter how close it might come.

I just don't understand why you suggest the model is backing away when it isn't, at least not in graphical form - afterall at that timeframe it's probably not even worth debating what the scenario could turn out to be.

[SMU]

Steve you said and I quote;

"Nice to see that run (the GFS) backing away from the mild xmas already"

so I did read your post, and it hasn't backed away.

I just don't understand why you suggest the model is backing away when it isn't, at least not in graphical form - afterall at that timeframe it's probably not even worth debating what the scenario could turn out to be.

I amended my post- Ignoring the fact the low resolution part of the model is generally poor then if you have a large amplitude wave at 180 where the jet is roaring up towards Svalbard then its unlikely to sink away as fast as the GFS is depicting...

S

[mountain shadow]

Steve you said and I quote;

"Nice to see that run (the GFS) backing away from the mild xmas already"

so I did read your post, and it hasn't backed away.

I just don't understand why you suggest the model is backing away when it isn't, at least not in graphical form - afterall at that timeframe it's probably not even worth debating what the scenario could turn out to be.

The last run shows it mild for xmas DAY, but only just as a cold front pushes south during the big day, indeed the Scottish hills would be seeing snow before the end. Some argueing over nothing sometimes on here.

[Zakos]

Normally I would just say "its only one run"

But, the GFS operational has joined many ensembles in going for a potential scandi high (although it doesnt really affect us in this run)

If more ensembles go with this idea of a scandi this will be very encouraging

[johnholmes]

well the latest Fax charts are out-continuity, a key word for forecasters has been ditched it seems!

There must be an awful lot of waste paper around the main man's desk tonight!

[SMU]

Just a quick question about this chart... Is it unusual for Iceland to have such warm air (+8?) this time of year?

+8c air would probably be around 13 degrees warmer than usual- this is because the storm track is normally south of iceland as opposed to north of it...

S

& before they come out- generally in a situation where a low gets sucked south through Scandi & we get pressure rises to the north of it the GFS ensembles - epsecially the 06 & 18z are SCRAP....

S

[Zakos]

Steve you said and I quote;

"Nice to see that run (the GFS) backing away from the mild xmas already"

so I did read your post, and it hasn't backed away, it's still showing a similar evolution to that shown in the previous 12z and previous days runs which is a ridging (of some form) of the Azores High - there's not even an inclin of an easterly - no matter how close it might come.

I just don't understand why you suggest the model is backing away when it isn't, at least not in graphical form - afterall at that timeframe it's probably not even worth debating what the scenario could turn out to be.

18z-

It has once again delayed the arrival of mild air, and looking at the above charts, It would only take one more upgrade...

[phil nw.]

Quite a cold few days to come on this run,especially around the weekend-early next week period, after the passage of the Thurs/Fri low.

This is showing around S.England on it`s way through bringing cold air behind it.

http://www.wetterzentrale.de/pics/Rtavn542.png

A marginal snow event quite possible there i think,just to the north of the low track.

Still a lot of uncertainty after the weekend as the modelling of the jet is different run to run.

The upper flow modelling still suggests the Azores high will be around next week and a Euro trough to our East.

http://www.meteo.psu.edu/ewall/ECMWF_12z/hgtcomp.html

The amount of buckling in the jet wiil dictate how far North the high will situate so at least we may get some surface cold rather than milder South Westerlys for Xmas.

[SMU]

heres a summary of how pony the GFS is

02nd FEB 2009 ACTUAL

http://www.wetterzentrale.de/archive/ra/2009/Rrea00120090202.gif

All GFS 12z's

9 days away- 204

http://91.121.94.83/modeles/gfs/archives/gfs-2009012412-0-204.png?12

turning the low over but not getting anywhere close

8 days away 192

over running the scandi high

http://91.121.94.83/modeles/gfs/archives/gfs-2009012512-0-192.png?12

7 days away 168

http://91.121.94.83/modeles/gfs/archives/gfs-2009012612-0-168.png?12

GFS wakes up & smells the coffee

6 days away 144

http://91.121.94.83/modeles/gfs/archives/gfs-2009012712-0-144.png?12

Scandi pressure but low moving west gone again-

5 days away-

http://91.121.94.83/modeles/gfs/archives/gfs-2009012812-0-108.png?12

Spot on....

If we are going to get some momentum towards decent heights to the NE that will deliver cold then it will be in the next 48-72 hours on the GFS-

I seem to remember the same conversations on here with the same people 6 years ago..]

http://www.wetterzentrale.de/archive/ra/2005/Rrea00120051226.gif

S

[Costa Del Fal]

Just ploughing through the ensemble charts, it is very divided over whether Precip affects England/Wales or stays over France. Very 50/50 it seems right now on that. ECM keeping pretty much all precip over France meaning a possible dry Thursday night for most. But a pretty much equal number of members showing snow potential for Central England and on the back edge as it clears SE.

[damianslaw]

heres a summary of how pony the GFS is

02nd FEB 2009 ACTUAL

http://www.wetterzen...00120090202.gif

All GFS 12z's

9 days away- 204

http://91.121.94.83/...12-0-204.png?12

turning the low over but not getting anywhere close

8 days away 192

over running the scandi high

http://91.121.94.83/...12-0-192.png?12

7 days away 168

http://91.121.94.83/...12-0-168.png?12

GFS wakes up & smells the coffee

6 days away 144

http://91.121.94.83/...12-0-144.png?12

Scandi pressure but low moving west gone again-

5 days away-

http://91.121.94.83/...12-0-108.png?12

Spot on....

If we are going to get some momentum towards decent heights to the NE that will deliver cold then it will be in the next 48-72 hours on the GFS-

I seem to remember the same conversations on here with the same people 6 years ago..]

http://www.wetterzen...00120051226.gif

S

The last chart is good evidence of a strong PV over greenland not necessarily resulting a in a mild rainfest for us - its a very plausible set up in the 'longer term'....

[Roger J Smith]

Well, what a conundrum ...

Have pity on both the models and the forecasters, despite all the advances and the billions of dollars invested, we are basically doing a D-Day forecast for Friday as Thursday looms before us.

I am not one who believes that short waves push the upper flow around, it is definitely the reverse of that, but that doesn't change the significance of watching the short wave now around 25W approaching Ireland tomorrow morning. If that should become moderately intense and if it takes on a slightly northward curve with time, then (to use inaccurate teleological language) it could "pull in" the looming Bermuda low about the way the UKMO model was showing a day or two back, if not quite all the way back to the superstorm that never was, as shown about a week ago (I don't think there's now any chance of that, but could not rule out a 950 mb low in the central North Sea as an outcome).

Clearly it is self-evident that the further north this manages to fight, the stronger it will be in its warm sector and frontal zone. A track into northern France will be just a moderate storm for France, but a track into south Wales and on to Lincs would be a major storm for southern England. The further north it tracks, the faster it will intensify and deepen.

I think the prudent forecast at the moment is to assume a track along the south coast and to mention something like a 30% chance of a stronger storm extending further north, as well as a 30% chance of a weaker storm largely avoiding the UK altogether.

With the 8-hour time difference, I will be watching this fairly continuously from now to at least 1200h GMT, so if I sense any big shifts aside from model output shifts, I will post again; no posts from me and no model shifts would add up to more certainty in my subjective estimation on model consensus. Right now, after their prodigious spanking for last Friday's naughtiness, the models must re-earn our trust and respect (only kidding, they are wonderful, can't live without them). Somewhere in between, really.

Love-hate relationship with these models, lately.

[snowlover2009]

heres a summary of how pony the GFS is

02nd FEB 2009 ACTUAL

http://www.wetterzen...00120090202.gif

All GFS 12z's

9 days away- 204

http://91.121.94.83/...12-0-204.png?12

turning the low over but not getting anywhere close

8 days away 192

over running the scandi high

http://91.121.94.83/...12-0-192.png?12

7 days away 168

http://91.121.94.83/...12-0-168.png?12

GFS wakes up & smells the coffee

6 days away 144

http://91.121.94.83/...12-0-144.png?12

Scandi pressure but low moving west gone again-

5 days away-

http://91.121.94.83/...12-0-108.png?12

Spot on....

If we are going to get some momentum towards decent heights to the NE that will deliver cold then it will be in the next 48-72 hours on the GFS-

I seem to remember the same conversations on here with the same people 6 years ago..]

http://www.wetterzen...00120051226.gif

S

Excellent post and isn't it also a coincidence (and we have seen this millions of times) that as soon as high res starts, everything get modelled very differently and the block collapses etc. Everything there is spot on and if anything a scandi high will properly develop in the next couple of days as we get closer to the time frame and the heights at the end of low res move closer to the time frame.

[Bobby]

Just ploughing through the ensemble charts, it is very divided over whether Precip affects England/Wales or stays over France. Very 50/50 it seems right now on that. ECM keeping pretty much all precip over France meaning a possible dry Thursday night for most. But a pretty much equal number of members showing snow potential for Central England and on the back edge as it clears SE.

As MattyM mentioned the NAE has a deeper more northerly low with heavy rain heading well into central Britain. Strong winds too.

What a nightmare this low is proving to be to forecast.