Model Output Discussion 13/11/12 18Z onwards

[January Snowstorm]

I have to say this rubbishing of any particular run is misplaced in my view.

I find them all as good as each other. The 18z used to do some wild erratic things but this has settled down over the last year or so imo.(pbly where it initially got its label 'pub run' from)

If I had to pick one run over the rest in gfs it would be the 12z but only marginally

[johnholmes]

as promised my weekly look at what the 500mb anomaly charts are suggesting for 6-15 days or so down the line.

Is winter on the way or not?

What might the upper air pattern be like by the end of Novembe1.pdf

[Frosty.]

I have to say this rubbishing of any particular run is misplaced in my view.

It's not rubbishing it if the 00z and 12z have the maximum data and the 6z and 18z don't, it's just stating a fact, all the models have flaws but they have improved a lot and continue to improve, we can now more or less believe what the models show a week ahead with some confidence, anyway the reliable timeframe of 1 week shows low pressure to the southwest of iceland controlling our weather until the low begins to fill and pressure rises to the south and east then bring a change in pattern, much as the meto are currently firming up on.

[nick sussex]

Lets hope the GME at 72hrs is a taste of things to come.

Compare its upstream amplification with that shown on the earlier GFS 06 hrs run for the same time:

GME 12hrs

GFS 06hrs

[snowking]

Lets hope the GME at 72hrs is a taste of things to come.

Compare its upstream amplification with that shown on the earlier GFS 06 hrs run for the same time:

GME 12hrs

GFS 06hrs

Nick I think I'm right in saying that's the first time the GME has been rolled out on here this winter...that for me is the first official sign of a winter cold spell

SK

[Ice BIast]

The 12Z looks more amplified than the 6Z.

http://modeles.meteo...fs-0-150.png?12

Edited November 17, 2012 by lce Blast

[January Snowstorm]

At 156hrs the 12z is like chalk and cheese compared to 06zrun

Could be a mighty fine run coming up!

[MKN]

12z definately a massive improvement early on

[bradymk]

Big differences between 6z and 12z, more amplified and some good charts coming closer to a reliable timeframe now. Lets see what FI delivers this time, probably a completely different scenario once again.

[johnholmes]

12z definately a massive improvement early on

quite so but is it correct, or was the 06z more likely to be correct, how does anyone tell?

[Methuselah]

quite so but is it correct, or was the 06z more likely to be correct, how does anyone tell?

Only in hindsight, John...

[bradymk]

quite so but is it correct, or was the 06z more likely to be correct, how does anyone tell?

I think that is a great point John. With so many differences run to run at the moment, which one will be right.

[johnholmes]

I think that is a great point John. With so many differences run to run at the moment, which one will be right.

these quite large changes are precisely why I put the how to follow models with less stress into the Guides and also why I go on about checking, beyond T+144 sometimes, but certainly post T+200 or so, check like with like. Better still get converted to watching the upper level anomaly charts. They are much less fun I suppose but do give a more realistic guidance at these distances. Today I'm at a loose end hence me doing what many on here are doing, 203 on line just now, watching every twist and turn as the 12z GFS runs out.

Over parts of Scandinavia for an example the change between the 06 and 12 is over 30 possibly 40mb-realistic is it heck.

Edited November 17, 2012 by johnholmes

[snowking]

Well its not quite the dreaded B word at the end of FI, but its not far away..

Fortunately given that this is yet ANOTHER scenario painted in recent days, we can continue to see no run to run consistency in FI

As per Nick's thoughts, once again low res really not worth bothering with, and this is exactly what I was talking about when I posted a few weeks ago regarding the correlation statistics out beyond day 6

SK

[Barry12]

I was under the impression that most models were showing a cold blocked scenario, is this not the case anymore?

[Ian Brown]

No consistency in the runs at the moment for next weekend onwards. Uninspiring GFS run on the whole and the ensembles will probably show wide variation beyond T192.

[EML Network]

Well after several days where everyone was hoping FI was going to be right "give or take", were all now hoping FI is wrong...and invariably it is ..regardless of what it's showing.

knowing our luck this will be the one time it IS right though :-(

[johnholmes]

Whilst the 12z may be a load of rubbish it has a ring of reality about it. By this I mean the development of the surface ridge from the Azores area moving into Scandinavia is one of the classic ways this happens. Many many moons ago it was used IF certain criteria were there as a means of attempting to predict this kind of development in an empirical way for beyond 48 hours. This was long before the advent of computers. I have no idea if in this case it does conform to those empirical rules but I am just saying the development of the high is realistic if that is the case.

[snowking]

Meanwhile, the 12z UKMO, slightly more amplified and a pretty significant shift westwards of the pattern:

12z: UN120-21.GIF

0z : UN144-21.GIF

SK

Edited November 17, 2012 by snowking

[bradymk]

I do agree with Nick about how the GFS Lower res is really poor at times.

For example, comparing todays 12z to yesterdays 12z

The differences between the two is huge and this happens with nearly every run at the moment, chucking out completely differents scenarios in FI. Like John mentioned in his post, todays FI 12z over Scandinavia has a pressure difference of +40mb over yesterdays at the same time. Forgetting FI, we still have disagreements at the +144 range and until we see agreements at this timeframe, then the uncertainty will continue. Looking at the models over the last few days, I would go for a cooler end to the month/start of December rather than "proper" cold but who knows at the moment. It is all rather exciting with plenty of options still on the table and I still think further down the line may offer something more but that is way too far out at the moment.

Regards,

Matthew

[Snow and storms]

The only useful information all of the models have showed us in the last what 10 days? is that none of them have a clue, every single run is a completely different outcome, might as well have spent the last 10 days watching paint dry because it could probably tell me more about the weather.

Edited November 17, 2012 by Snow and storms

[chris55]

From 168 right through till the end GFS is cool to cold with night-time frosts, cold below average days, and with fog developing widely (possibly freezing fog) And also to note is the high pressure is giving us more of a continental flow rather that one from the Atlantic hence the colder conditions at the surface.

Overall for me personally this is a nice end of Autumn pattern and beats mild Atlantic weather any day. Also with all this high pressure around and a meridional jet the chance for some cold snow bearing conditions to appear are higher.

[nick sussex]

A more amplified GFS run but the limpet trough still refuses to disrupt and split in time, then the lower resolution takes over and manages to undercut the ridge with a positively tilted trough!

The UKMO is a little better at 144hrs with a bit more amplification, it looks like we'll see a phasing of two lows off the eastern USA and its the amplification of this troughing that will determine how much of a ridge is pushed ahead.

Time for our first shortwave drama of the winter season, its looking like we will need to see the trough split far enough west and a shortwave to be ejected se'wards.

So its over to the ECM to deliver and do the right thing!

[Zenarcher]

I have been saving the GFS ensemble charts for the past week to pick up trends (you can view them on NW here http://www.netweathe...ensviewer;sess=), the mean pressure all the time is much higher towards the final week of November, this is a good sign but it all depends on what type of set up it is and for now that's too far off to tell.

The models at the moment to me are struggling a lot, we are seeing big changes and disagreements amongst other models in a time frame where they usually don't happen. The low pressure system which is due to arrive late on Sunday which you can read more about here http://forum.netweat...20#entry2406124 took the models a bit of time to catch onto as well and we saw big disagreements at a shorter than normal time range.

Edited November 17, 2012 by weathermaster

[bradymk]

Well after several days where everyone was hoping FI was going to be right "give or take", were all now hoping FI is wrong...and invariably it is ..regardless of what it's showing.

knowing our luck this will be the one time it IS right though :-(

Its called a Rex block i believe and It would still bring some very cold days and nights just the upper air temperatures are too warm for any snow. Still wouldn't mind this, especially over what we have at the moment but if it is snow your after, then this set up is no good. However like you say it is likely to be wrong anyway.