General Model Output Discussion

[sebastiaan1973]

Hey guys,

Just over the Northsea it is just as exciting as in the UK. Lots of discussion especially about the GFS output, which mean a lot of difference to the Netherlands.

I would like to share with you is that a meteorologist told at www.weerwoord.be something important about GFS. He says (my translation), that there is no biascorrection for the raw NCEP Ensemble, there is a correction for the NCEP but just put in practice for the USA. Besides that he told that in his opinion the GFS ENS gives to little a daily shift (between night and daytimes).

I hope you get your cold and snow!

[aspire27]

http://91.121.94.83/...snh-0-168.png?6

PERFECT Chart for me...

PS not sure where people are getting the southward movement-- must be imagination-

Go to the meteociel Archive & the 00z PPN belt is in exactly the same place at 42 as the 06z is at 36, the same replicates at 78 V 72-

If your in the south forget it & hope for the end of the week - epecially hope that the trough gets far enough SE to allow the intial cold easterly in at around 96-

For those in the risk zone I mentioned yesterday, all the southern counties are probably out of the question with a shift northwards of ~75/100 miles-

It will be interesting what North wales gets still-

S

Out of interest, what do you call south?

[nick sussex]

The very latest from the ukmo 48hrs disagrees with the gfs for the same time at T-48hrs, the ukmo has 0c 850's running from sw Wales to Essex, the gfs has this line about 200 miles further north!

The latest fax chart for tomorrow at 6 am goes with the latest ukmo 48hrs output.

If you apply the general observed bias of the gfs overdoing shortwaves in its output then the way it throws all that energy ne' wards is suspect also. To be honest i just wish the models would agree early on so that we can concentrate on the more medium term which looks very interesting.

Edited December 28, 2009 by nick sussex

[Snowyowl9]

Which models can we trust in the shortterm the new GFS parrallel the first big test.

ECM which is perfect for snow/UKMO which just about keeps the 0c air in here or below.

http://91.121.93.17/pics/Rukm242.gif

http://91.121.93.17/pics/Rukm482.gif

http://91.121.93.17/pics/Rukm722.gif

Fax charts.

Edit:just read your post Nick. :lol:

Edited December 28, 2009 by Snowyowl9

[kold weather]

What there is big disagreements with looking at the ensembles is what the eventual low does around 72-96hrs...the GFs op run holds and holds the low but a fair few of the ensemble members kick it out of the way and like the ECM introduce a E/ENE instead as we get on the northern side of the low.

For now we have enough to keep us preoccupied with before 144hrs, however just keep an eye on the Greenland block lasting a good deal longern then the 06z expects, just like the 0z in many ways...

[Matty M]

The very latest from the ukmo 48hrs disagrees with the gfs for the same time at T-48hrs, the ukmo has 0c 850's running from sw Wales to Essex, the gfs has this line about 200 miles further north!

The latest fax chart for tomorrow at 6 am goes with the latest ukmo 48hrs output.

Nick could you link me to the UKM 6z

I used to be able to get it on a PSU plotting site but it has been discontinued.

Much thanks,

Matt

[nick sussex]

Nick could you link me to the UKM 6z

I used to be able to get it on a PSU plotting site but it has been discontinued.

Much thanks,

Matt

Here you go :lol:

http://www.weatheronline.co.uk/cgi-bin/expertcharts?LANG=en&MENU=0000000000&CONT=ukuk&MODELL=nae&MODELLTYP=1&BASE=200912280000&VAR=prty&HH=48&ARCHIV=0&ZOOM=0&PANEL=0&WMO=

It's actually the ukmo mesoscale model.

Edited December 28, 2009 by nick sussex

[Duane S.]

Nick could you link me to the UKM 6z

I used to be able to get it on a PSU plotting site but it has been discontinued.

Much thanks,

Matt

http://www.weatheronline.co.uk/cgi-bin/expertcharts?LANG=en&CONT=euro&MODELL=nae&MODELLTYP=1&VAR=prec&WMO=&ZOOM=0&PANEL=0&ARCHIV=0&BASE=200912280600%26HH%3D36

[Michael Fishermans Friend]

I have not looked at the models this morning but I take it 'things are still up in the air' as regards to what is happening later this week and the track of this LP with the GFS still going along by itself, I've just got a feeling that nothing will be resolved by the models until a day or so before hand if these strange synoptics keep occuring. It really is quite stressing. :lol:

[Methuselah]

There still this myth that 'back in the good old days,' developing situations similar to this one always resulted if 300ft snowdrifts everywhere from Kent to Cornwall... :lol:

It's simply not true! I remember countless times back then when predicted blizzards either turned-up as rain and sleet or even failed to materialize at all...Unless absolutely bone-chilling air is already established ahead of the system, it's always going to be marginal: snow to rain, rain to snow etc. ect. :lol:

On most occasions it was only after the LP moved away eastwards that NE winds could bring much in the way of snow to the Southeast...Tamara's right: we shouldn't be slitting our wrists over minor North-South oscillations, at this point.

And, as for FI? Well - it's FI!

[Yeti]

Like I said earlier remember just before xmas how Luton airport was closed and how some had to abandon their cars due to the heavy snow. Well at 4am on that very day the GFS predicted a lovely sunny, dry day. However the Met O/Fax suggested snowfall.

However in saying this even I think the Fax charts probably have the fronts too far S. Im going for something inbetween the Fax/GFS. You often find with disagreement the answer lies inbetween.

Just add that I have to laugh at the difference between the 0Z/06Z in the medium range. For this period I am definately sticking with the ECM/GEM.

But the FAX is already a "compromise" between the ECM/GEM and UKMO/GFS?

http://www.wetterzentrale.de/pics/Recm721.gif

The ECM doesn't tilt the low and it is further S so even down here sees an easterly. However the FAX have a lot more tilt to them meaning mild air for all of Europe except Britain/Denmark northwards:

http://www.meteociel.fr/ukmo/fax/fax72s.gif

The UKMO raw output and the GFS have this even further N:

http://www.wetterzentrale.de/pics/Rukm721.gif

IMO the FAX is already a compromise if anything leaning more towards the UKMO raw output. (I can't understand why people say it is more like the ECM? They are quite different.)

[Guest North Sea Snow Convection]

The very latest from the ukmo 48hrs disagrees with the gfs for the same time at T-48hrs, the ukmo has 0c 850's running from sw Wales to Essex, the gfs has this line about 200 miles further north!

The latest fax chart for tomorrow at 6 am goes with the latest ukmo 48hrs output.

If you apply the general observed bias of the gfs overdoing shortwaves in its output then the way it throws all that energy ne' wards is suspect also. To be honest i just wish the models would agree early on so that we can concentrate on the more medium term which looks very interesting.

I couldn't agree more nick! The ECM and GEM haven't prevaricated with this low like the GFS and they have been consistent in terms of how this moves away enough to allow in the NE'erly afterwards. The GFS sucks so many in, with its 4x daily fest of shortwave obsession, and as you suggest in terms of a short term feature like this low, it can draw interest away from what looks a potentially very appealing (and much less marginal) medium term.

[Matty M]

Here you go :lol:

http://www.weatheronline.co.uk/cgi-bin/expertcharts?LANG=en&MENU=0000000000&CONT=ukuk&MODELL=nae&MODELLTYP=1&BASE=200912280000&VAR=prty&HH=48&ARCHIV=0&ZOOM=0&PANEL=0&WMO=

It's actually the ukmo mesoscale model.

Intriguing, thanks alot.

[Harsh Climate]

I think if any chart is to be believed it has to be the GFS at the moment

http://www.wetterzentrale.de/pics/Rtavn482.png

This is were it expects the low to be on wednesday and I cant see it being too different as the GFS is usually rock solid in this timeframe. I think it will be precipitation amounts and distribution that may vary 100 miles or so...

http://www.wetterzentrale.de/pics/Rukm481.gif

If you compare the ukmo on the same day, there are some differences but on a whole looks quite similar to me with the precipitation heading into northern england and with that sumwhat milder air to the south..

And lets not forget the ECMWF had an absolute stinker in the run up to this last/current cold spell, whereas the GFS handled it the best. For that reason I would wait for other models to back the ecm before taking this last run or 2 too seriously (ECM).. :lol:

[cold snap]

Just thinking there we could be looking at the 18Z GFS tonight to tell us what the weathers going to like in a few hours.

GFS not going to back down now me thinks something in between GFS and UKMO is my punt

Edited December 28, 2009 by cold snap

[kold weather]

It wouldn't be a disaster if the GFS was correct for my location, may even dry off for a little period if that run was correct.

However the models/ensembles do not agree with the op run placement of the low pressure between 72-96hrs...the op run holds the low over the SE, most ensemble members funnily enough sink the low ESE like the ECM which gives us a colder flow...meanwhile the 0z UKMO agrees with the GFS and in fact really struggles to drag colder air in at all for the south.

Some big uncertainties coming up with this set-up, the low is giving the models massive amounts of headaches!

[Yeti]

Btw for some reason I've just been reminded of this chart:

http://www.wetterzentrale.de/pics/archive/ra/2009/Rrea00120090210.gif

This was the only other time I remember such disagreement at close range - the ECM had the track of that low further N than actually occurred and the GFS turned out to be (almost) right in all its insistence. In fact the ECM ended up being by far the weakest model and I feel we may be making the error of relying on it too much at short range (it is not designed for this purpose).

The GFS/UKMO may not be as wrong as most of us would like. Personally I'm dreading the GFS being right as the weather would be truly revolting here!

[Harsh Climate]

The front will have difficulty progressing much further, despite the outcomes of the GFS,

Yes youd certainly fancy those areas to get the heaviest precipitation leading up to the front stalling, then some lucky area whether it be north midlands or northern england should get pasted.

I just cant see it staying all snow for wales/ west midlands during the whole event. Id fancy it to turn sleety or to rain as wednesday progresses with milder air from the south filtering through. Maybe the damage will have allready been done though, before that happens if they get 10cm of snow the warning will have been justified. I just think its further north though were some real intense accumulation could build up and STAY..

[Snowstorm1]

Im confused now people are saying ECM/UKMO and all the other models v GFS and other people saying UKMO/GFS v Ecm and all the other models im confused!

[nick sussex]

I think if any chart is to be believed it has to be the GFS at the moment

http://www.wetterzentrale.de/pics/Rtavn482.png

This is were it expects the low to be on wednesday and I cant see it being too different as the GFS is usually rock solid in this timeframe. I think it will be precipitation amounts and distribution that may vary 100 miles or so...

http://www.wetterzentrale.de/pics/Rukm481.gif

If you compare the ukmo on the same day, there are some differences but on a whole looks quite similar to me with the precipitation heading into northern england and with that sumwhat milder air to the south..

And lets not forget the ECMWF had an absolute stinker in the run up to this last/current cold spell, whereas the GFS handled it the best. For that reason I would wait for other models to back the ecm before taking this last run or 2 too seriously (ECM)..

I have to disagree here, you have to take a models bias into consideration, notice that feature that the gfs had near Norway in its earlier output which the ecm filled quickly, yes another case of the gfs overblowing these features,the ecm in all the time i've been viewing it has only had to do one major backtrack within the 96hrs timeframe, the gfs numerous, i'm sorry but the verification stats say it all, the gfs is in 4rth place behind the ecm, ukmo,and gem. The gfs even allowing for its early disagreement has caved in to the ecm regarding the undercutting low later because yes you guessed it, it modelled the feature near Norway incorrectly by overblowing it!

I could understand this obsession by many members in following the gfs if it was the best global model but it isn't, all models do go through the odd bad patch but the gfs has many more of these than the ecm.

[kold weather]

On the other hand Yeti the GFS did a poor job with the Feb 07 set-up and thats IMO the closest set-up we've had to this in the internet age with regards to the evolution of the low pressure system and the troughing of the low.

I remember the GFS kept driving the precip into N.England/Scotland whilst the UKMO/ECM kept holding the fronts further south and in truth the GFS proved to be vastly too progressive with the frontal system pushing northwards,in fact I think it was only after the second front finally came through did the first front reach further north a full 24-30hrs later then was progged...I suspect something similar will occur here.

[Weather-history]

Well the Met Office have updated their advisories and they are still not going the GFS route

[bluearmy]

just to put the record straight, the only model that got the shortwave right at the beginning of the current/last cold spell was the ecm which deepened it as it ran from denmark to the low countries. meto was close behind but failed to deepen it enough and GFS wasnt accurate even the day before.

some models are right on occasions and some are wrong. my take on the midterm is that the southeasterly off a cold continent as shown in the 06z and, more importantly the ens mean is the current favourite. (it should be noted that the 2m temps for the ens mean show de bilt to be mean below 0c for a week or so - not dissimilar to ecm ens). again, our island nation is not as fortunate and whilst will benefit from convective precip, must walk the snow/sleet tightrope along with it.

i expect the meto 15 dayer will look similar to yesterday with a cold next week and the theat of an incursion from the sw.

anyone notice how similar the ecm 00z evolution is to the last cold spell. it was right to drop the trough in that time. repeating patterns ayone??

[grab my graupel]

Morning everyone

Could I ask that we use the Cold Weather Discussion/Media threads for discussing the Meto/BBC forecast etc. please?

If not, the Model thread can go off topic very quickly

Thank you

[kold weather]

Ensembles confirm the idea that the GFS is too progressive in breaking down the cold set-up, quite a few hold onto a cold surface set-up right through to the end of the run. Given the ECM ensembles are generally cold the whole way through as well...I suspect there is not going to be any quick way out despite what the GFS 06z suggests.