General Model Output Discussion

[cold snap]

Looks like we are waiting up for the next GFS round.im so tired.

Will be shocking stuff if GFS does not backtrack then the worry will start to set in.

You know what that low presure i wish it wasnt there at all now.

Edited December 27, 2009 by cold snap

[kold weather]

Possibly OP though just as possible is the GFS is off on one, as all the big models do at times (eg the eCm with the last cold spell)

This just proves IMO once and for all the track of the low we have right now really is KEY to the cold spell, or possible lack of it.

A more northerly LP and the odds of it coming off become much reduced..

However even in FI its a poor run TBH...it WILL have ensemble support BUT is ULTRA progressive...to the point where I'm not even going to be that fussed about it for now!

[TEITS]

Looks like we are going to have to rely on old skool forecasting for this one. This is why I prefer the fax charts because during model uncertainity you need this human touch.

When you think back to forecasting many years ago they didn't obviously have computer models. Some bloke (can't remember name) used to hand draw the charts, take these onto the underground and then present his forecast on BBC TV. I actually think some of this forecasting skill has been lost due to the dependancy of computer models.

At least with the fax charts the Met O forecaster has sat down and viewed far more data than we have available. However more importantly he will be able to see which is more plausible from the vast amount of data.

[Cloud 10]

So this low forms off the Brest Peninsula at 78hrs ambles its way up the Channel heads into the North Sea and at 132hrs decides its bored everyone to death and fills! and then looks like its going to become absorbed by the next Atlantic low! but then decides it wants to keep going all by itself, i mean who writes this rubbish?

Who cares what the rest of run shows its a pile of tosh!

well said!

I have saved the +72 chart from tonights 18z to see how it verifies.

[Snowaddict]

This is simply exceptional..

The 18Z is an absolute shocker, a total write off altogether and flies in the face of every other piece of short, medium and long term guidance that we have at our disposal this evening..

It even erodes the ridge over Greenland by T+192, disposing of a negative AO signal..

It would be extremely unlikely that all of the other guidance is incorrect, almost unheard of at such a short range and would make the recent advisories by the Irish Met and UKMO almost seem like a joke..

I'm quite shocked at the 18Z really.

Are there issues with the initialisation data with GFS or the Euros/GEM and JMA because this has to be in some way related to data being input.. Not necessarily low data but what else could cause these differences at such a short timeframe?

Every other source of guidance goes against the 18Z GFS evolution.

GFS - Global Farsical System - I certainly hope so anyway.

SA

[SMU]

Yes thanks, all we have to do now is find somewhere on the web that publishes that data ( for free) that isn't the GFS, as the GFS runs were shocking

UKMO goes to 72-

Cheers

Steve

[casparjack]

It's very strange to see such a huge change from one model to another and from one run to another. But it has happened before and has come to be the trend setter!

We could well have a trend setting in here.

I agree that's possible as far as a new trend, but my 'gut' feeling is that genuine trends should show up much further out and more often when the other models are less in tune with one another.

..as ever though, it could still verify, but seems an outside bet at the moment.

[davehsug]

Possibly OP though just as possible is the GFS is off on one, as all the big models do at times (eg the eCm with the last cold spell)

This just proves IMO once and for all the track of the low we have right now really is KEY to the cold spell, or possible lack of it.

A more northerly LP and the odds of it coming off become much reduced..

However even in FI its a poor run TBH...it WILL have ensemble support BUT is ULTRA progressive...to the point where I'm not even going to be that fussed about it for now!

Agreed Kold. We end up with a massive Euro high & very mild Southerlies. As far as I know, there is absolutely no teleconnection support fo this type of evolution. Even when mid range forecasts go wrong, they tend to be not so wrong as this. Really really strange. Even with a bad run (synoptically not warm or cold), you can generally point out that it has a general pattern largely correct, just that the pieces haven't quite fallen correctly.

Have to say I fully expected the 18z to fall back in line. That it hasn't is puzzling rather thatn concerning.

[rmc1987]

The GFS does seem to throw up inconsistent outputs from what I can gather on here. Judging by what posters have been posting.

[nick sussex]

Hi Nick. Have you been checking on NOAAs thoughts today? Which model/ensembles have they been going with?

Thanks

Hi Dave

The problem is we're not talking about large scale differences globally but small local detail, the disagreement about the low track is within 72hrs which isn't covered in their medium term discussions, the model prognostic discussions for the USA regions favour different models for different regions and these are the shorter term ones.

http://www.hpc.ncep.noaa.gov/discussions/pmdhmd.html

The medium term liked the gfs 12hrs upstream from Wed to Friday but then said theres alot of disagreements for this weekend coming, though they did highlight the strengthening Greenland block. They did like the gefs/ ecm ensemble means for next weekend and weren't happy with the operationals for the same weekend.

http://www.hpc.ncep.noaa.gov/discussions/pmdepd.html

Really in terms of the longer term pattern its which model they go with for this coming weekend that would be more interesting but as yet they're not favouring any single model.

Edited December 27, 2009 by nick sussex

[Geordiesnow]

BBC24 weather forecast at 2226hrs mentioned snow from Tuesday onwards. This indicates that the MetO are NOT following the GFS model.

They are still using 12Z data remember Yamkin, as i said in my post, the 23:57 forecast will be using the 18Z UKMO data so this is where you will see an upgrade to the graphics and it will be very interesting too see where they put the PPN, this will tell you if the UKMO is starting to trend the low northwards, southwards or stays roughly in the same position.

[bennytes]

this GFS run is one of the most amazing i've seen.

if this is how it all turns out, there'll be an MBE for the fella punching the data in this week, I reckon!

[LomondSnowstorm]

Even I'm getting annoyed by how far north the low is encroaching - even here the snow showers would be marginal!! Move it 20 miles south and it's exceptional here, and even further south looks good for eastern Scotland, as well as giving frontal snow to one lucky area in the north Midlands/northwest England, but the pub run just looks out of kilter with all the other models. It's a bit silly really, even someone who this outlook potentially benefits hugely can see how ridiculous this run is.

[casparjack]

Looks like we are going to have to rely on old skool forecasting for this one. This is why I prefer the fax charts because during model uncertainity you need this human touch.

When you think back to forecasting many years ago they didn't obviously have computer models. Some bloke (can't remember name) used to hand draw the charts, take these onto the underground and then present his forecast on BBC TV. I actually think some of this forecasting skill has been lost due to the dependancy of computer models.

At least with the fax charts the Met O forecaster has sat down and viewed far more data than we have available. However more importantly he will be able to see which is more plausible from the vast amount of data.

I totally agree with that TEITS, but the current fax charts, albeit quite a long way out for this kind of scenario are showing a very marginal event 'snow-wise' initially in the lower levels of the Midlands to start with.

The simple fact remains that we don't know for sure for another 24 hours - that's part of the fun though isn't it!!

[kold weather]

The 18z shows what happens in the worst case scenario...we get the LP too far north, the cold doesn't even make it in the south, then LP: comes up, a weak brief attempt at a cold push from the east before it all sinks.

Its certainly a possible option, I for one wouldn't rule it out by any means BUT what I will say is the GFS is amazingly progressive, its sooo quick its no doubt as a result of the models bias of being too progressive.

There is very very very little chance the -ve NAO signal is gone by the 216hrs...thats the one part of the run that I refuse to put any creadence into!

[kev238]

The Met Office last Sunday put up a warning for sleet and snow for Monday in a very specific area (Hampshire up to the Wash etc). The GFS didnt show this at all even at 24 hours. It pays to go with the human input when it comes to local scale features.

[Frosty.]

I wonder what Joe B thinks of the GFS 18z run, some fairly colourful language i'm sure. Scotland would still have a wintry week from this set up on the northern side of the low with quite a strong E'ly but FI is just dismal compared to the 12z gfs which was a winter wonderland compared to this load of old tripe. Fingers crossed by the 00z it will have proved to be a bad dream/joke.

[Duane S.]

I was expecting a minor backtrack tonight. Looks like that didn't transpire then!

It does seem that the main reason the LP doesn't play ball on the GFS is because it's deeper which would naturally keep it on a more Northerly track. So is is just a simple case of over-progression from the GFS? Would hardly be the first time.

Edited December 27, 2009 by s4lancia

[Tom Quintavalle]

UK MET latest faxes.

http://www.meteociel.fr/ukmo/fax/fax96s.gif

http://www.meteociel.fr/ukmo/fax/fax120s.gif

Regards,

Tom.

[davehsug]

Hi Dave

The problem is we're not talking about large scale differences globally but small local detail, the disagreement about the low track is within 72hrs which isn't covered in their medium term discussions, the model prognostic discussions for the USA regions favour different models for different regions and these are the shorter term ones.

http://www.hpc.ncep.noaa.gov/discussions/pmdhmd.html

The medium term liked the gfs 12hrs upstream from Wed to Friday but then said theres alot of disagreements for this weekend coming, though they did highlight the strengthening Greenland block. They did like the gefs/ ecm ensemble means for next weekend and weren't happy with the operationals for the same weekend.

http://www.hpc.ncep.noaa.gov/discussions/pmdepd.html

Really in terms of the longer term pattern its which model they go with for this coming weekend that would be more interesting but as yet they're not favouring any single model.

Thanks Nick. I was just thinking that the pattern that GFS ends up with at say t168 though would be so different as to impact on an hemospheric scale? Just a matter of small errors being multiplied etc. I know we're 10,000 miles downstream of the US in a global scale but such large errors in Europe would have to manifest themselves in the US eventually.

Dave

[snowlover2009]

and another gfs run, i would just totally ignore with referance to all the other models almost in total agreement. I have never seen so much trash from gfs when you compare it to the other models. is it me or does from saturday onwards just seem absolutly unbelievable to even happen. i'm sorry but this is my opinion, even in 2 days time it is totally out on its own by bringing the main snow so far north to what some of the models are predicting. this is what i hate about late nights runs from gfs when they just seem to really really off on one, they always leave you on a downer and then you have to wait 6 to 8hrs to see what the other models bring and it gets you worrying. surely something is not right with this model. it is all over the place, even at friday when i flicked back and forth from the 12z to 18z it is totally different. sorry but this is my opinion ignore that run, it cannot even come to agreement with the other models for even tuesdya event, the low looks like a rainfest.

[SMU]

FAX 96-

its totally inline with the ECM- & identical to the PPN distribution I posted earlier-

S

Edited December 27, 2009 by Steve Murr

[Tom D]

Well... GFS is going mad whilst ECM and FAX charts look stunning. What is going on with the GFS!?

[bluearmy]

FAX 96-

S

if you got excited over the T96, i guess you fell over and knocked yourself out when you saw the T120 - otherwise you'd have posted that one aswell !!

[Altostratus]

Yet another GFS run fit for the bin. The programmers of the GFS need to take long hard look at why it has a tendency to be over progressive. It seems utterly incapable of dealing with subtle energy distributions.

The ECM ensembles paint the picture and it is certainly not a mild one.

I simply cannot see all the other models coming in line with the GFS. It simply won’t happen. I have always viewed the GFS with a sceptical eye and the rest of this week, will, hopefully, reinforce this view. I am starting to rate the GEM more highly than the GFS.