General Model Output Discussion:

[bluearmy]

The GFS is now putting bak the idea of a high pressure forming to our east somewhat further and falling into line with the ECM idea of a upper trough/PV feature down Scandinavia.

The 12z ECM is a stunner for sustained cold, the upper high starts to reform *again* at 240hrs and we would see likely a repeat performance of the previous 7 days modelled, which would then take us upto the 15-20th with sustained cold.

Needless to say the models tonight are certainly an upgrade, the 18z GFS loses the plot somewhat into FI as it creates a huge flabby LP then fires it up, whilst a huge block develops in Scandinavia but a little too our east. Have no doubt that if that set-up arrived into the higher resolution part of the run, that would almost certainly IMO be a cold SE airflow rather then a milder southerly airflow...

Darren, the GFS ops are consistent in their desire for massive blocking to our east in FI. given that the ens NAEFS and cpc show the trough still to our south at this time, do you think we could be looking at a decent easterly for mid jan ??

[Tom Montalbano]

Some similarities now at t120 between the models, although 100 miles or so could make a lot of difference to that low SW of the UK. The latest FAX for t120 has that low a little further NW than ECM. As has been stated, to prolong the cold spell, we need that low to stay south of the UK.

Regards,

Tom.

[kold weather]

Darren, the GFS ops are consistent in their desire for massive blocking to our east in FI. given that the ens NAEFS and cpc show the trough still to our south at this time, do you think we could be looking at a decent easterly for mid jan ??

think we have very conflicting signals at the moment, on the one hand the ECM which wants to bring the PV southwards over Scandinavia whilst the GFS is less keen and quickly shunts the PV westwards as it powers up instead over Canada which causes a chain rection of sorts down the line and promotes blocking further east. If I had to make a punt I think a SE wind is probably the eventual outcome and the GFS is probably onto a decent signal but is WAY too quick in implenting it, indeed the ECM is if anything strengthening the Greenland high once more between 216-240hrs.

Either solution has both its pros and cons but on both sides of the coin I'd have thought a very prolonged spell is probable.

FWIW here is the Paralell run for the 15th December for New Years Eve:

http://91.121.94.83/modeles/gfsp/run/gfs-0-384.png?12

Compare that with the same graphics on the 18z for that day:

http://91.121.94.83/modeles/gfs/run/gfs-0-42.png?18

You really couldn't get more of a total opposite to the pattern that is really going to happen!

[SP1986]

I wonder whether the low GFS minimums are consequentially because the GFS has programmed snow to fall and lie tonight and struggle to melt on those other days. I cannot for the life of me understand why these minimums are being shown (although giving for geographical difference, they will be lower in some places), especially when with a similar pattern to last week temperature are progged much lower.

Surely snow cover may be the factor here, I'm just interested because the minimums over a wide area are unrealistic in my opinion although they're bound to happen locally.

[TEITS]

You are right, the gfs has actually been nearer the mark with what has happened over todays events.

Strongly disagree because at the moment its snowing heavily in Peterborough. If the GFS was right then this wouldn't be the case!

Recently I have become very disappointed with the GFS and for the period between +120 & 240 I shall use the ECM/Ensembles and also the GEM ensemble mean. Before that I shall stick with the fax charts.

[karyo]

Updated t+96 and t+120 fax:

http://cache.netweather.tv/fax/PPVM89.png

http://cache.netweather.tv/fax/PPVO89.png

Low to south of Ireland at t+120 touch further south than UKMO raw - though that far off track will change again on susbsequent runs.

The t+96 chart for Saturday shows a lovely looking low over Scotland with associated troughs that should bring snow in many northern areas as it slowly moves west/southwest. This is in line with the ECM and is a feature that is looking more prominent in the 12z than it did in the 0z.

Karyo

[nick sussex]

The gfs operational run was a mild outlier from the end of next week and the majority of ensemble members keep it colder for London.

Edited December 29, 2009 by nick sussex

[casparjack]

I might have missed a discussion earlier, but what on earth happened today?

I always felt that the FAX charts had the situation nailed with the 528 up into Southern Scotland, but the MetO insisted on giving hysterical warnings of feet of snow for my area, all we had was rain until 3pm then a three hour burst of heavy wet snow, now it's drizzling.

I know this is somewhat off topic, but reluctantly, I am giving the much rubbished GFS (me included) a bit of a pat on the back, I think it called it really well, everything has gone much further North with a more influential warm sector?

Shoot me down if you like!!?

Edited December 29, 2009 by casparjack

[derrylynne]

I have just looked at the latest GFS output and to be honest it does not look credible. Especially in F1. Personally I will bin the pub run - not because I don't like it or it don't fit in with what I want - but because it does not seem to shape up. some of the evolutions for instance just do not seem credible. Be interesting to see what tomorrows run look like....

[yamkin]

I might have missed a discussion earlier, but what on earth happened today?

I always felt that the FAX charts had the situation nailed with the 528 up into Southern Scotland, but the MetO insisted on giving hysterical warnings of feet of snow for my area, all we had was rain until 3pm then a three hour burst of heavy wet snow, now it's drizzling.

I know this is somewhat off topic, but reluctantly, I am giving the much rubbished GFS (me included) a bit of a pat on the back, I think it called it really well, everything has gone much further North with a more influential warm sector?

Shoot me down if you like!!?

It works the other way as well regarding the GFS. Take a look at TEITS's previous post:

Edited December 29, 2009 by yamkin

[casparjack]

Strongly disagree because at the moment its snowing heavily in Peterborough. If the GFS was right then this wouldn't be the case!

Recently I have become very disappointed with the GFS and for the period between +120 & 240 I shall use the ECM/Ensembles and also the GEM ensemble mean. Before that I shall stick with the fax charts.

TEITS, sorry, I normally agree with the majority of what you say, but if you look at my earlier post, GFS was spot on for what has happened here today, MetO warnings of upto 30cms of snow and major disruption, whereas in reality we have had 5cms of wet snow at best that fell in three hours late this afternoon and has all but melted and it's now drizzling...

It works the other way as well. Take a look at TEITS's previous post: http://forum.netweat...ost__p__1681863

Yes it does, the whole event further North and East, just as GFS suggested?

[bluearmy]

TEITS, sorry, I normally agree with the majority of what you say, but if you look at my earlier post, GFS was spot on for what has happened here today, MetO warnings of upto 30cms of snow and major disruption, whereas in reality we have had 5cms of wet snow at best that fell in three hours late this afternoon and has all but melted and it's now drizzling...

casparjack - you're getting various things mixed up. meto warnings are just that - warnings. they have to take into account what might happen as the consequences are possibly quite severe if they do.

GFS was upto 200 miles out with the 0c isotherm - fact. ecm was around 40 miles out.

thats about all you need to take into account.

the precip charts were always a mixed bag with GFS the only detailed model we ge to see wrt snowfall/rainfall projections.

[BLAST FROM THE PAST]

Oh the models have come in line with a certain severe cold/blizzard warning issued the other day? The ECM is on target folks, GEM has been on the ball....good night and prepare...because so many haven't witnessed the winter that is upon us....but it ain't so bad as we have been there many times before. God I'm old

BFTP

[johnholmes]

I wonder whether the low GFS minimums are consequentially because the GFS has programmed snow to fall and lie tonight and struggle to melt on those other days. I cannot for the life of me understand why these minimums are being shown (although giving for geographical difference, they will be lower in some places), especially when with a similar pattern to last week temperature are progged much lower.

Surely snow cover may be the factor here, I'm just interested because the minimums over a wide area are unrealistic in my opinion although they're bound to happen locally.

Stephen I know you have this thing about GFS and its too low min temps.

To make a constructive suggestion-please show the charts you feel are wrong then we can check how far out they were on the relevant morning?

Only that way can you either prove or disprove your repeated comments about it being inaccurate.

I'm not getting at you but as a trained scientist/meteorologist I like to see things done in a scientific manner-my suggestion would enable that to be done?

thanks if you feel able to do this.

casparjack - you're getting various things mixed up. meto warnings are just that - warnings. they have to take into account what might happen as the consequences are possibly quite severe if they do.

GFS was upto 200 miles out with the 0c isotherm - fact. ecm was around 40 miles out.

thats about all you need to take into account.

the precip charts were always a mixed bag with GFS the only detailed model we ge to see wrt snowfall/rainfall projections.

once again we have comments about accuracy with nothing to show whether this is right or wrong.

Again I'm not getting at your Casper-but will any of you that shout foul or its equivalent show charts, warnings, actual data and forecasts etc so we can see how far out they were.

I assume we all want to learn more from our experiences-my suggestion will help us all to learn how good or bad different models are in differing situations.

Please?

[SP1986]

Stephen I know you have this thing about GFS and its too low min temps.

To make a constructive suggestion-please show the charts you feel are wrong then we can check how far out they were on the relevant morning?

Only that way can you either prove or disprove your repeated comments about it being inaccurate.

I'm not getting at you but as a trained scientist/meteorologist I like to see things done in a scientific manner-my suggestion would enable that to be done?

thanks if you feel able to do this.

John I never have and dont claim to have the science to back this up and besides it's difficult to prove/disprove with hard science anyway but I say through my experience I've learnt that the GFS has not got the best base for widespread minimas, or if not the case they often are progged in the wrong place. I'm just surprised that's after last week where similar temperatures were forecast for the west of the country but never came off, and then these occurred in the east, I'm not criticising the actual outputs I'm just wondering why the GFS is misplacing these temperature consistently, especially in cold spells.

In the first part of our cold spell, there was numerous predictions of -5C to -7C in my area, and generally areas close by, this never came to fruition, however over time, the eastern parts including your location saw temperatures of -4 to -6C.

Therefore I'm not saying those temperature are wrong but I was just pondering whether they were to do with perhaps lying snowfall as I don't think the upper air temperature for example are conducive, unless were expecting inversions?

[kold weather]

I wonder whether the low GFS minimums are consequentially because the GFS has programmed snow to fall and lie tonight and struggle to melt on those other days. I cannot for the life of me understand why these minimums are being shown (although giving for geographical difference, they will be lower in some places), especially when with a similar pattern to last week temperature are progged much lower.

Surely snow cover may be the factor here, I'm just interested because the minimums over a wide area are unrealistic in my opinion although they're bound to happen locally.

You said exactly the same thing last time round though Stephen, and the mins progged were widely hit even by areas without snow cover, indeed at times they were a little on the high side!)

-4/5/6s are easily obtainable in the flow we are progged to have inland and away from the far east, we have sub -5C 850hpa temps, a slack flow that isn't that mosit either and relative high pressure aloft for a time, I see no reason why it would be wrong!

Heck we hit those with temps at 2-5C at 850hpa in a high pressure set-up many a time, no reason why in a far colder flow it shouldn't happen again.

ps, Stephen, if you look back thorugh the records you'll see many many central areas got every bit as low as the GFS was progging...I'm guessing the min issue is something mainly reserved for those right by the coasts, I've noticed a similar thing down here at times right near the east coast but a little further to the NW and temps easily match and often exceed the GFS progs.

Edited December 30, 2009 by kold weather

[TEITS]

TEITS, sorry, I normally agree with the majority of what you say, but if you look at my earlier post, GFS was spot on for what has happened here today, MetO warnings of upto 30cms of snow and major disruption, whereas in reality we have had 5cms of wet snow at best that fell in three hours late this afternoon and has all but melted and it's now drizzling...

Yes it does, the whole event further North and East, just as GFS suggested?

If you don't mind me saying but your location missing out on the snowfall and the GFS are two entirely different things.

A fair assumption is the LP was nowhere near as far N as the GFS previously suggested but probably slightly further N than the ECM suggested. As for your snowfall, to be fair to the Met O predicting snowfall in marginal situations is a nightmare to forecast. I remember an occasion when heavy rain fell all evening in Peterborough and yet 5miles to my E they had 7 inches of lying snow!

I must admit some of the warnings from the Met O did seem a bit OTT especially with regards to snow depths. However suppose the Met O didn't put out any warnings and you had 8 inches of snow! The met O would of been panned by the media/general public. I feel sorry for them at times because they can't win either way.

[casparjack]

casparjack - you're getting various things mixed up. meto warnings are just that - warnings. they have to take into account what might happen as the consequences are possibly quite severe if they do.

GFS was upto 200 miles out with the 0c isotherm - fact. ecm was around 40 miles out.

thats about all you need to take into account.

the precip charts were always a mixed bag with GFS the only detailed model we ge to see wrt snowfall/rainfall projections.

I accept that a warning is exactly that, however a 'panic stations' MetO renewed detailing upto 25cms of disruptive snow issued at 13.56 for my area when it was already clear from synoptic conditions monitored at my station and radar that it just wasn't going to happen has to draw a question or two...

The wrong area to debate this, but you did respond, sorry.

Edited December 30, 2009 by casparjack

[J10]

You said exactly the same thing last time round though Stephen, and the mins progged were widely hit even by areas without snow cover, indeed at times they were a little on the high side!)

-4/5/6s are easily obtainable in the flow we are progged to have inland and away from the far east, we have sub -5C 850hpa temps, a slack flow that isn't that mosit either and relative high pressure aloft for a time, I see no reason why it would be wrong!

Heck we hit those with temps at 2-5C at 850hpa in a high pressure set-up many a time, no reason why in a far colder flow it shouldn't happen again.

ps, Stephen, if you look back thorugh the records you'll see many many central areas got every bit as low as the GFS was progging...I'm guessing the min issue is something mainly reserved for those right by the coasts, I've noticed a similar thing down here at times right near the east coast but a little further to the NW and temps easily match and often exceed the GFS progs.

Certainly GFS temps around the coasts are too high in winter, especially for night time temps, it seldom has temps of below freezing for here, even when actual temps end up being as low as -5c.

As an example for the morning of 22nd December a minimum temp of 0c was forecasted, and the actual temp was -4.5c and for the morning of 23rd December a minimum temp of 2c was forecasted, and the actual temp was -2.5c.

[casparjack]

If you don't mind me saying but your location missing out on the snowfall and the GFS are two entirely different things.

A fair assumption is the LP was nowhere near as far N as the GFS previously suggested but probably slightly further N than the ECM suggested. As for your snowfall, to be fair to the Met O predicting snowfall in marginal situations is a nightmare to forecast. I remember an occasion when heavy rain fell all evening in Peterborough and yet 5miles to my E they had 7 inches of lying snow!

I must admit some of the warnings from the Met O did seem a bit OTT especially with regards to snow depths. However suppose the Met O didn't put out any warnings and you had 8 inches of snow! The met O would of been panned by the media/general public. I feel sorry for them at times because they can't win either way.

As ever yes, but I think we could all see it was going to be a marginal based on the lack of initial cold air.

A classic 70s/80s, you never quite know, as you say the next one could easily be the other way round.

I for one am sitting pretty having told all my mates (many farmers) to ignore the MetO warnings as I felt they were over the top, but still disappointed as I would have quite liked to look out now on 25cms of blowing snow, rather than wet grass with a few patches of melting slush...

[Duane S.]

I looked at that quick & thought - those are crap Ao ensembles- then realised they have changed the scale!!!!!!!

World record -AO is -7 in December 1976...

Might I add- dec 09 is going to go down as a RECORD breaking -AO month-- lowest in History-

& Iceberg- This thread is for the model discussion, I am discussing what the ECM is showing- I know its probably an wrong / outlier- same as if my Nan was a bloke she would be my grandad-

However I stand by that post- the MAX / Mins would be very similar to what I projected given THAT set up-

Steve

Steve, I did exactly the same!! My heart sunk when I saw that the actuals hadn't ended up subbing -4 then realised they had changed the scale to match!!! That in itself is incredible! :lol: :o And to top that some of the ensembles hint at breaking even the -6 barrier. Drains the brain a bit getting this into context!

Edited December 30, 2009 by s4lancia

[casparjack]

...anyway, looking ahead, I see the latest FAX has the rubbish moving SE more quickly, which must be a good sign?

528 a good 100-150 miles further south than on the previous run...

[cj114]

Snow seems to be down to nowcasting for the next few days. However the cold we are seeing seems rather low, esp if no Snow is on the ground to lower the temps.

Having lived through the 70's and 80's we did have very low temps but Snow was always laying when we did!

Interesting times ahead methinks.

Am still hopeful that New Years eve will be rain, being "Jolly" and ice just does not go together in my opinion and experience. i.e 1978 doing a great Torville and Dean outside a pub in 6" heels. I got a round of applause for that.

These days I would just break my leg. lol

Will watch the next few runs with interest, nothing is set in stone, we live in a Bermuda Triangle of weather in this Country.

Lucky us.

[rmc1987]

Oh the models have come in line with a certain severe cold/blizzard warning issued the other day? The ECM is on target folks, GEM has been on the ball....good night and prepare...because so many haven't witnessed the winter that is upon us....but it ain't so bad as we have been there many times before. God I'm old

BFTP

I assume this 'event' isn't going to hit this part of country? It seems rather quiet in here! What is expected from these charts?

[Hairy Celt]

John I never have and dont claim to have the science to back this up and besides it's difficult to prove/disprove with hard science anyway but I say through my experience I've learnt that the GFS has not got the best base for widespread minimas, or if not the case they often are progged in the wrong place. I'm just surprised that's after last week where similar temperatures were forecast for the west of the country but never came off, and then these occurred in the east, I'm not criticising the actual outputs I'm just wondering why the GFS is misplacing these temperature consistently, especially in cold spells.

In the first part of our cold spell, there was numerous predictions of -5C to -7C in my area, and generally areas close by, this never came to fruition, however over time, the eastern parts including your location saw temperatures of -4 to -6C.

Therefore I'm not saying those temperature are wrong but I was just pondering whether they were to do with perhaps lying snowfall as I don't think the upper air temperature for example are conducive, unless were expecting inversions?

GFS generated temperatures are rarely accurate for my location unless the weather is really settled. Recently (the last 3 days) I have had max -1C and min -4C but GFS temps have invariably been too low. In my case the error is largely down to me being so close to the sea (<100m) but there are some spectacular local variations that GFS can never deal with - eg the next village 1 mile west from here sometimes sees temps 10 degrees lower, occasionally 15 degrees lower.