Model Output Discussion - 26Th Dec 21:25-->

[MKN]

gfs 6z not looking any better atm, early stages though

[john mac]

For my area, for snow it looks like this:

GFS op: Horrific

GFS ensembles: OK

ECM: Great

GEM: Great

UKMO: Poor

FAX: OKish

GME: Great

I sure don't know what'll happen.

Thats the beauty of model watching my friend, thats why we do this

[SLEETY]

going to be upgrades all the way

Yes very much,the ecm has already had a massive upgrade,the rest will follow today. Much along my line of thinking,this was always going to see the bitterly cold air to the North East to come flooding back South,with the fronts stalling then being pushed back South. This is so smilair to the end of December 1978,with blizzards in the South followed by sub-zero maxima.

Very poor handling of the output by the models,underestimating the depth of cold which is to come etc,only the gem has its credibility intact,ecm behind the rest,especially meto gfs,hang your heads in shame.

[Barb]

After seeing the 00z op I consoled myself that the 06z couldn't be any worse... I was wrong.

[carinthian]

Just studied all the latest METO data with-in the reliable 72 HOUR time period. Looks like a stalling front moving up against a wedge of much colder air that is already holding firmer than previously expected ( ie) the cold block over Northern Britain. Could see the main low pressure now keep south of the British Isles and main front no further north than Mid-Wales going by the all important 700mb charts at 72 Hours..that seems the trend...

C

[Barb]

I'm really confused about the GFS. It's been all over the place in this cold spell. The only models that have been consistent are the ECM and GEM.

The GFS ensembles though have been decent for the South, but the op has been on the brandy a lot this Christmas i think.

[Yeti]

ECM ensembles remain bitterly cold. Infact the mean is colder than yesterday.

http://www.knmi.nl/exp/pluim/vijftiendaagse/Data/15DAAGSE_06260_NWT.png

I will add that despite being unable to view the ECM +168 upper temps I reckon these would be between -10/-12C. The +168 might not look that cold but trust me it is!

Look at the snowfall chart in the bottom right too. Not often you see that much forecast from so many members!!

[Geordiesnow]

Just studied all the latest METO data with-in the reliable 72 HOUR time period. Looks like a stalling front moving up against a wedge of much colder air that is already holding firmer than previously expected ( ie) the cold block over Northern Britain. Could see the main low pressure now keep south of the British Isles and main front no further north than Mid-Wales going by the all important 700mb charts at 72 Hours..that seems the trend...

C

That post was obviously made before the 06Z which has trended the low again slightly further North in the initial phases.

It seems like we took one step forward and one step back, UKMO has the low further south than it has been on all it's outputs but now the GFS wants to trend it further north!

The difference between the GFS and UKMO for example at 72 hours(66 for the former) shows what a shift either way makes.

[john mac]

I'm really confused about the GFS. It's been all over the place in this cold spell. The only models that have been consistent are the ECM and GEM.

The GFS ensembles though have been decent for the South, but the op has been on the brandy a lot this Christmas i think.

Yeah the models have struggled with this unusual set up also they have had problems with missing data over the christmas period

we should start to see things ironing themselves out over the next 24hrs.

[Rollo]

The GFS continues to fly on the face of the others- I seem to recall at the start of this spell it took a while to come to an agreement,in the meantime keep Nick's prozac close by.

[TEITS]

I'm really confused about the GFS. It's been all over the place in this cold spell. The only models that have been consistent are the ECM and GEM.

The GFS ensembles though have been decent for the South, but the op has been on the brandy a lot this Christmas i think.

There isn't really much support from the other models for the +72 06Z GFS run, even the lesser models disagree.

This doesn't mean the GFS is wrong but I think at this stage nobody can really tell whats going to happen.

[MKN]

There isn't really much support from the other models for the +72 06Z GFS run, even the lesser models disagree.

This doesn't mean the GFS is wrong but I think at this stage nobody can really tell whats going to happen.

I think its going to be a case of +24 untill we have a firm idea exactly where its heading, 1 things for sure though, countrytracks forecast wont be an easy one to do. Lets see where they expect the low to be.

(hmm dont think its on)

Edited December 27, 2009 by SnowTornado

[Barb]

ECM @ Tuesday night

Blizzards down to M4

GFS @ Tuesday night

Blizzards only for N England/Scotland

Also here's GEM, further south again. Huge disagreement at this range:

Edited December 27, 2009 by Barb

[Geordiesnow]

The GFS is really aggressive in progressing the Low up the Irish Sea, if it carries on going there won't be a cold snap or spell !

Yes there will be however it seems like on this run, the only real cold air will be in Scotland but a cold snap/spell is still there on this run but the mildness has been shifted further North(again).

The cold does finally get widespread on this run but it's not a run i like too see coming off. To be fair, UKMO has been predicting a fairly similar set up in it's output recently and people dismissed it. I don't think they should now, there is every chance of the low being too far North and filling over us reducing the length of any coldness.

[Osbourne One-Nil]

Huge disagreement at this range

Is a 200 mile difference 72 hours away really a huge disagreement?

[nick sussex]

You'd think as we neared the important timeframe there would be more agreement! very confusing if you're in the UK and want to know whether you need a shovel or umbrella. What i would say though is that at least the gfs 06hrs is not making such an issue of that ridge of high pressure that edged north from Spain, also the nuisance feature near Norway heads more south. So it's a dodgy start followed by an improving trend later,however there are likely to be alot more changes across the board.

[The PIT]

Is a 200 mile difference 72 hours away really a huge disagreement?

It is if you're in a small country and the differance effects a lot of people.

UKMo fax chart shows the whole country in cool air at t120. FI land otherwsie before thta slightly marginal.

[john mac]

Unless there is other model support later for the way the GFS develops the Low early on, then it's safe to say the GFS is struggling and you can forget the rest of the run after about T48 !

I totally agree with you ian, as we have said many times already on this thread there are going to be changes on each run as to what track the low takes.

Some further northn some furthur south, either way this is going to boil down to a nowcast, 100-200miles is a very small diffrence in the track but makes a massive difference as to where the snows going to fall

[Lewis]

Is a 200 mile difference 72 hours away really a huge disagreement?

I back the GFS, it has easily been the most consistent run and we are coming into reliable time frame, the GFS has been showing this Northwards shift since yesterday morning, if you have 1 run that shows is it, then the other run does not, then it does again, you could say theres a chance it's wrong, but with it being rather consistent showing this, i back the GFS.

Lewos

[East Herts Snow]

Is a 200 mile difference 72 hours away really a huge disagreement?

On planet Earth, maybe just a 0.01% variability, for the UK about 20%!

[Guest]

The GFS is really aggressive in progressing the Low up the Irish Sea, if it carries on going there won't be a cold snap or spell !

GFS also shoves it back down the Irish Sea fairly quickly too, a bit of a yo-yo-low.

[Barb]

Well GEM shows blizzards down to the South coast while GFS has snow only for N. England/Scotland. Pretty big difference at just 3 days out I think.

[Duane S.]

You'd think as we neared the important timeframe there would be more agreement! very confusing if you're in the UK and want to know whether you need a shovel or umbrella. What i would say though is that at least the gfs 06hrs is not making such an issue of that ridge of high pressure that edged north from Spain, also the nuisance feature near Norway heads more south. So it's a dodgy start followed by an improving trend later,however there are likely to be alot more changes across the board.

Hi Nick.

Yep that's how I see it. A better GFS run up to the mid term than the 00z in terms of a prolonged long spell. Although I must say the spoiler could well be an advancing ridge from the south, a trend that has been rearing it's ugly head recently. We need to see that Northern blocking not get too far North.

[carinthian]

Unless there is other model support later for the way the GFS develops the Low early on, then it's safe to say the GFS is struggling and you can forget the rest of the run after about T48 !

Yes Ian , I agree. Even at 36 HOURS, looks to progressive. The UKMO latest trend is opposite to this run and I know who I would back with-in the 72 hour time frame.

C

[nick sussex]

The problem here regarding the initial low isnt so much the track but what it does with the system, throwing off little shortwaves and filling. Here it's a fine balancing act with the Greenland high, as this strengthens and ridges se the low finally edges away.