theweatheroutlook

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Russwirral
29 December 2015 13:11:41
what we really want is to see LPs stalling over the uk... then heading over towards italy. From past experience these setups usually develop in the charts last minute, GFS and ECM always have a preference for LPs to remain in the atlantic or north of the block. I dont think ive ever seen this kind of scenario forecast with any significant advance.

wouldnt be surprised to come back on here later in the week to see this thread has exploded into life...

Weather station:
https://www.wunderground.com/personal-weather-station/dashboard?ID=IWIRRAL24#history 
pdiddy
29 December 2015 13:16:53


 


Yes, a far easier route to cold than a Scandi block which requires everything to fall into place. I don't remember the last time we had a sustained GH. Perhaps it was Dec 2010


 


Originally Posted by: The Beast from the East 


July?


Retron
29 December 2015 13:23:39

Does anyone know what the "bias corrected charts" option is on Meteociel for GEFS?

Originally Posted by: Rob K 


From Meteociel themselves:


"Cartes corrigées du biais/bias corrected :
Les modéles dont GEFS ont souvent un biais pour certains paramètres : par exemple : des températures toujours surrestimées à un endroit et sous-estimées à d'autres. L'idée est d'identifier ces biais en comparant les prévisions passées et la réalité et de les soustraire aux résultats des runs de GEFS. On peut réduire légèrement les erreurs de ce fait. Les impacts sont significatifs principalement à grande échéance pour les basses couches."


Or translated (by myself, not by Google - if you use that you'll probably see something slightly different!)


Bias corrected charts


The GEFS model is often biased in certain parameters, for example temperatures are overestimated on some days and underestimated on others. To identify bias, previous runs are compared to the actual temperatures, then the difference is subtracted from the current GEFS run. This means we can reduce the errors from the model bias by a small amount. The effects of this correction are greatest at the lower layers of the atmosphere.

Leysdown, north Kent
some faraway beach
29 December 2015 13:30:23


 


From Meteociel themselves:


"Cartes corrigées du biais/bias corrected :
Les modéles dont GEFS ont souvent un biais pour certains paramètres : par exemple : des températures toujours surrestimées à un endroit et sous-estimées à d'autres. L'idée est d'identifier ces biais en comparant les prévisions passées et la réalité et de les soustraire aux résultats des runs de GEFS. On peut réduire légèrement les erreurs de ce fait. Les impacts sont significatifs principalement à grande échéance pour les basses couches."


Or translated (by myself, not by Google - if you use that you'll probably see something slightly different!)


Bias corrected charts


The GEFS model is often biased in certain parameters, for example temperatures are overestimated on some days and underestimated on others. To identify bias, previous runs are compared to the actual temperatures, then the difference is subtracted from the current GEFS run. This means we can reduce the errors from the model bias by a small amount. The effects of this correction are greatest at the lower layers of the atmosphere.


Originally Posted by: Retron 


Good translation. Minor correction: un endroit is a location. So line 1 should read for example temperatures are overestimated at some locations and underestimated at others.

2 miles west of Taunton, 32 m asl, where "milder air moving in from the west" becomes SNOWMAGEDDON.
Well, two or three times a decade it does, anyway.
Rob K
29 December 2015 13:45:16

Thanks, I had somehow managed to miss that text at the bottom!

I see Meteociel also has new "probability charts" with various parameters. Most people will probably gravitate towards the snow risk charts, which show the percentage of GEFS runs with snow in map form:

http://www.meteociel.fr/modeles/gefs_cartes.php?ech=180&code=&mode=26&carte=0&proba=1



Yateley, NE Hampshire, 73m asl
"But who wants to be foretold the weather? It is bad enough when it comes, without our having the misery of knowing about it beforehand." — Jerome K. Jerome
Retron
29 December 2015 13:49:42


Good translation. Minor correction: un endroit is a location. So line 1 should read for example temperatures are overestimated at some locations and underestimated at others.


Originally Posted by: some faraway beach 


Aha, I was drawn in by "toujours" and missed the endroit bit. (A bit like being distracted by a mega snow event at T+168 and missing the one at T+24... if only that'd apply to this winter!)


Those new probability charts look pretty good as well and yes, I'd imagine they'll be very popular - thanks for posting that Rob!

Leysdown, north Kent
squish
29 December 2015 13:53:14


 


Yes a great run. There are a few GEFS members of a similar vein which drop temps quite markedly from 3rd/4th Jan, and this all hinges on the approaching low at +48/72 being stalled to our west and the scandinavian ridge asserting itself before the next depression arrives- hence allowing the cold air to our east to flood westwards and deflect the subsequent depressions SE.


One to watch on the 12z runs!


 


 

D.E.W on Dartmoor. 300m asl
SJV
29 December 2015 13:57:51


For entertainment only I recommend run #14 on the 06GEFS. Have a look before it changes.
A nationwide whiteout for a week LOL


The parallel isn't too shabby either.


Originally Posted by: nsrobins 


Ooooh....matron  That is a special one.


Certainly heading in the right direction, even if that is one of the colder extremes. Plenty more tantalising charts to come over the coming weeks 


Anything to replace murky mild muck is fine by me, lets see if the 12z is worthy of excited discussion 

nickl
29 December 2015 14:06:33


 


From Meteociel themselves:


"Cartes corrigées du biais/bias corrected :
Les modéles dont GEFS ont souvent un biais pour certains paramètres : par exemple : des températures toujours surrestimées à un endroit et sous-estimées à d'autres. L'idée est d'identifier ces biais en comparant les prévisions passées et la réalité et de les soustraire aux résultats des runs de GEFS. On peut réduire légèrement les erreurs de ce fait. Les impacts sont significatifs principalement à grande échéance pour les basses couches."


Or translated (by myself, not by Google - if you use that you'll probably see something slightly different!)


Bias corrected charts


The GEFS model is often biased in certain parameters, for example temperatures are overestimated on some days and underestimated on others. To identify bias, previous runs are compared to the actual temperatures, then the difference is subtracted from the current GEFS run. This means we can reduce the errors from the model bias by small amount. The effects of this correction are greatest at the lower layers of the atmosphere.


Originally Posted by: Retron 


i am intrigued a little by the bias correction on the new GEFS. surely a model has to be running for a fair period of time to get a handle on where it shows bias'.  in general, I note that the bias corrected anomoly charts are always less promising for cold here. That's just common sense, not bias correction!

some faraway beach
29 December 2015 14:16:04


 


i am intrigued a little by the bias correction on the new GEFS. surely a model has to be running for a fair period of time to get a handle on where it shows bias'.  in general, I note that the bias corrected anomoly charts are always less promising for cold here. That's just common sense, not bias correction!


Originally Posted by: nickl 


They correct for locations where there is a consistent bias, so there presumably has to have been a fair number of runs to determine that.  The key word is toujours ("always").


Les modéles dont GEFS ont souvent un biais pour certains paramètres : par exemple : des températures toujours surrestimées à un endroit et sous-estimées à d'autres.


The models comprising the GEFS often show a bias in certain parameters: e.g. temperatures always being overestimated in one location and underestimated in others.

2 miles west of Taunton, 32 m asl, where "milder air moving in from the west" becomes SNOWMAGEDDON.
Well, two or three times a decade it does, anyway.
JACKO4EVER
29 December 2015 14:27:15


 


Jacko


I'm finding your posts very fair and unbiased of late .........................well done


 


Originally Posted by: Gooner 


I've got too much time on my hands Marcus- plus I have taken to drinking lol


Anyway, I await the later runs with interest, I for one feel we are on the cusp of a tantalizing spell of model output- the cold progged just over the North Sea may well get dragged into the mix over here. I remember similar setups in the 70's and 80's

Andy Woodcock
29 December 2015 15:39:29
MetO finally recognising the potential for colder weather with lowland snow on their latest mid-range outlook. This is a big change from yesterday and clearly reflected in the ECM ENS and I suspect their own.

Longer term forecast remains the same mild and zonal but let's get the cold weather here first and we can see what happens from there, positive feed backs and all that.

Andy
Andy Woodcock
Penrith
Cumbria

Altitude 535 feet

"Why are the British so worried about climate change? Any change to their climate can only be an improvement" John Daley 2001
David M Porter
29 December 2015 15:53:38


 


wasn't there one in the spring of 2013?? It was 2013 that saw all that snow in later February & march or was it 2012... 


 


Originally Posted by: picturesareme 


It's almost certainly 2013 you're thinking of. March 2012 was one of the warmest March's recoded in this country I believe.

Lenzie, Glasgow

"Let us not take ourselves too seriously. None of us has a monopoly on wisdom, and we must always be ready to listen and respect other points of view."- Queen Elizabeth II 1926-2022
David M Porter
29 December 2015 15:55:15


Its a poor set-up for cold going forward though Marcus.


Originally Posted by: Shropshire 


Not any more so than the pattern we've had for the past two months!

Lenzie, Glasgow

"Let us not take ourselves too seriously. None of us has a monopoly on wisdom, and we must always be ready to listen and respect other points of view."- Queen Elizabeth II 1926-2022
picturesareme
29 December 2015 15:56:02


 


It's almost certainly 2013 you're thinking of. March 2012 was one of the warmest March's recoded in this country I believe.


Originally Posted by: David M Porter 


time flys by these days so fast I get dates muddled so easily - 2013 it was then 😊

Tractor Boy
29 December 2015 16:04:23

 


Not any more so than the pattern we've had for the past two months!


Originally Posted by: David M Porter 


I think that's understating the output David. We are looking at high latitude height rises and the disappearance of the Euro slug leading to all sorts of colder options of various grades down the line. But hey, I think all on here can see that, including those that say otherwise.

Dave
Farndale, North York Moors
David M Porter
29 December 2015 16:15:04


 


I think that's understating the output David. We are looking at high latitude height rises and the disappearance of the Euro slug leading to all sorts of colder options of various grades down the line. But hey, I think all on here can see that, including those that say otherwise.


Originally Posted by: Tractor Boy 


Indeed, Dave. That is what objective model analysis is all about. It is when people start commenting on what is shown in a way which is clearly intended to wind-up others that problems start.

Lenzie, Glasgow

"Let us not take ourselves too seriously. None of us has a monopoly on wisdom, and we must always be ready to listen and respect other points of view."- Queen Elizabeth II 1926-2022
pdiddy
29 December 2015 16:18:03

This run trying to raise heights towards Greenland; that might be a route to longer cold spell:


Tractor Boy
29 December 2015 16:21:03


 It is when people start commenting on what is not shown in a way which is clearly intended to wind-up others that problems start.


Originally Posted by: David M Porter 


Fixed for you David.  Eyes down for the 12z...


 

Dave
Farndale, North York Moors
doctormog
29 December 2015 16:23:46
Only small changes in thearly stages of the 12z runs with the UKMO looking a bit better than the 12z GFS at the same point (120hr). Both look full of potential down the line.
Aberdeen
Current conditions (personal WS) 
Whether Idle
29 December 2015 16:24:09


This run trying to raise heights towards Greenland; that might be a route to longer cold spell:


 


Originally Posted by: pdiddy 


Interesting at 138hrs the GFS 12z has shifted the slider low southwards compared to 144 on the 6z and raised SLP towards the N of it.  Sadly this is already FI so only noted as a trend item.

Dover, 5m asl. Half a mile from the south coast.
Whether Idle
29 December 2015 16:26:18

Met O 144 delivers one hell of a chart just into FI at 144 Noted only as a trend item, you understand.


I note the retreat S of the Azores High and the rising of pressure towards Iceland


Dover, 5m asl. Half a mile from the south coast.
Solar Cycles
29 December 2015 16:29:31


 


Indeed, Dave. That is what objective model analysis is all about. It is when people start commenting on what is shown in a way which is clearly intended to wind-up others that problems start.


Originally Posted by: David M Porter 

It doesn't bother me Dave as the weather will make a fool of them time and time again, and no agenda ridden nonsense will alter that fact.

David M Porter
29 December 2015 16:30:16


Met O 144 delivers one hell of a chart just into FI at 144 Noted only as a trend item, you understand.



Originally Posted by: Whether Idle 



Lovely Jubby, as Del Boy would say.

Lenzie, Glasgow

"Let us not take ourselves too seriously. None of us has a monopoly on wisdom, and we must always be ready to listen and respect other points of view."- Queen Elizabeth II 1926-2022
Polar Low
29 December 2015 16:32:38

Indeed shes trying her best 


 


 



 


 


 



Met O 144 delivers one hell of a chart just into FI at 144 Noted only as a trend item, you understand.


I note the retreat S of the Azores High and the rising of pressure towards Iceland



Originally Posted by: Whether Idle 

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