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some faraway beach
19 January 2021 10:05:44

It just shows how everything has to be exactly just so on an island with maritime weather. In our case even the feeblest of Greenland highs worked for us because it was so precisely east-centred. A few miles either way, and we would have been moaning that winter is over and we can't get decent snow here any more.

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.
fairweather
19 January 2021 10:11:57


 


 


Given that the "chilly" was initially modelled as "cold" then perhaps mild, chilly, mild, chilly is more likely by the time we get there?


I'm hoping not, this time around but, as we're all seeing, there's still a huge amount of variability from one run to the next beyound around 144hrs.


Originally Posted by: marcus72 


Still? Find me a time when it wasn't thus. Those times are rare.

S.Essex, 42m ASL
backtobasics
19 January 2021 10:36:00


 


Still? Find me a time when it wasn't thus. Those times are rare.


Originally Posted by: fairweather 


I think it is a fair statement, in the summer months when we have large HP cells floating around you can certainly more accurately predict as far as 5 days ahead.  The point is the jet stream is meandering, active and proving hard to model, this is exactly the scenario where models will flap about at that range. 

Rob K
19 January 2021 10:39:22

Still a big disparity between the op GFS and the parallel GFS regarding the extent of any snow in the south over the weekend.


Old GFS has very little:



 


while the parallel gives a good covering for many away from the extreme south coast:



 


The higher resolution of the parallel is noticeable in these ppn maps, but whether the performance will be any better remains to be seen!


 

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
Rob K
19 January 2021 10:43:12

We can actually test the performance much sooner than that. By 42 hours the parallel has a lot of snow in NW England and Wales:



while the main GFS run has next to nothing:



 


I suspect the parallel is overdoing things! None of the high-res models suggest anything like that on Thursday.

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
Brian Gaze
19 January 2021 10:47:13


The higher resolution of the parallel is noticeable in these ppn maps, but whether the performance will be any better remains to be seen!


Originally Posted by: Rob K 


The highest resolution data sets available for both versions are 0.25 degrees. 

Brian Gaze
Berkhamsted
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"I'm not socialist, I know that. I don't believe in sharing my money." - Gary Numan
Heavy Weather 2013
19 January 2021 10:53:55


We can actually test the performance much sooner than that. By 42 hours the parallel has a lot of snow in NW England and Wales:



while the main GFS run has next to nothing:



 


I suspect the parallel is overdoing things! None of the high-res models suggest anything like that on Thursday.


Originally Posted by: Rob K 


Does the iPhone use GFS? I’ve noticed it’s been so poor recently. Some days it’s had snow and then removed them at the 11th hour.

Mark
Beckton, E London
Less than 500m from the end of London City Airport runway.
CField
19 January 2021 10:57:05

I remember that cold snap started with some very heavy dry snow showers on the Friday I was 12 at the time and couldnt concentrate on my lessons looking out the window at the heavy prolonged snow showers accumulating Back on subject more as we head into Feb a similar high could upset the so call return to zonal forcasts predicted and actually produce some winter weather to places that have missed out so far, could be a SW blizzard block ( unlikely on recent form), a slider low or a short term sneaky encroach of colder uppers following a blocked retrogressed trough .


 


Actually Feb 1978 looks like a really weird set-up synoptically. Trevor Harley talks about a Scandi high but in fact by the time of the blizzard on the 19th-20th there was a big Scandi trough and a weird thin ridge of high pressure to its west that somehow managed to act as a block to the Atlantic. Never seen anything quite like it to be honest.



 


Assuming this chart is accurate: https://www.wetterzentrale.de/maps/archive/1978/era/ERA_1_1978021918_1.png


 


Originally Posted by: Rob K 

Favourite snowstorm
Famous channel low
Dec 31st 1978
Hastings East Sussex
Foot of level snow severe drifting
Next day max temp -4 degrees Celsius
Rob K
19 January 2021 11:10:12


 


The highest resolution data sets available for both versions are 0.25 degrees. 


Originally Posted by: Brian Gaze 




Is that so? That's surprising as the Meteociel ppn charts appear much more detailed with the parallel run. Maybe they are interpolating somehow.

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
ballamar
19 January 2021 11:14:55
GFS op run has eastern promise at the end, who knows if Feb will deliver
Rob K
19 January 2021 11:16:49

GFS op run has eastern promise at the end, who knows if Feb will deliver

Originally Posted by: ballamar 


Yes, always the tease at the end to keep us hanging. Would like to see it coming forward 24 hours each day though instead of always being at 384!

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
Brian Gaze
19 January 2021 11:19:55





Is that so? That's surprising as the Meteociel ppn charts appear much more detailed with the parallel run. Maybe they are interpolating somehow.


Originally Posted by: Rob K 


I think the GFS chart you posted was plotted using the low resolution 1.0 degree data sets. It will make the snow and rain areas look bigger.

Brian Gaze
Berkhamsted
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"I'm not socialist, I know that. I don't believe in sharing my money." - Gary Numan
Rob K
19 January 2021 11:40:48


 


I think the GFS chart you posted was plotted using the low resolution 1.0 degree data sets. It will make the snow and rain areas look bigger.


Originally Posted by: Brian Gaze 


The individual areas on the snow depth charts are much smaller and smoother on the parallel, though. On the older GFS they are larger and more blocky, suggesting lower resolution: you can see the individual squares where there are small patches, almost like a mosaic effect. Maybe it's just an artifact of the way they are smoothed but the GFSP snow depth charts certainly give the impression of being much more detailed.

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
Brian Gaze
19 January 2021 11:52:57


 


The individual areas on the snow depth charts are much smaller and smoother on the parallel, though. On the older GFS they are larger and more blocky, suggesting lower resolution: you can see the individual squares where there are small patches, almost like a mosaic effect. Maybe it's just an artifact of the way they are smoothed but the GFSP snow depth charts certainly give the impression of being much more detailed.


Originally Posted by: Rob K 


TBH I think it is an artefact of the data set. It's actually very ease to cheat if you want to make the charts look smoother and more detailed. You can simply regrid the data set to a much higher resolution. It's like a professional foul in football or a trick of the trade depending on how you view it. I don't do that on TWO and the Mciel charts you posted are labelled as 1 degree so they aren't doing it either.  


Edit: If I get bored later this week I'll try and regrid a GFS plot to a very high resolution to illustrate

Brian Gaze
Berkhamsted
TWO Buzz - get the latest news and views 
"I'm not socialist, I know that. I don't believe in sharing my money." - Gary Numan
ballamar
19 January 2021 11:58:36


 


Yes, always the tease at the end to keep us hanging. Would like to see it coming forward 24 hours each day though instead of always being at 384!


Originally Posted by: Rob K 


yes with some good Synoptics in the right place the high over Europe has scuppered as usual

Brian Gaze
19 January 2021 12:04:26


I don't know, but the ones posted from here (the snow depth used above) are clearly labelled as 1 degree. 


http://www.meteociel.fr/modeles/gfse_cartes.php?ech=6&code=0&mode=16


 

Brian Gaze
Berkhamsted
TWO Buzz - get the latest news and views 
"I'm not socialist, I know that. I don't believe in sharing my money." - Gary Numan
JRobinson
19 January 2021 12:30:14

Pert 9


Perturbation 9 please ....... JFF....WNH

Rob K
19 January 2021 12:41:45

The 6Z GEFS is noticeably colder (for London) in the upcoming cool/cold spell, with the mean now dropping to -6C around the 24th and some runs not far off the -10C line.



 


The op run is fairly representative of the mean for much of the run, for once, while the control run is on the mild side.


 


Again, a general dip towards the end of the run, with a few going quite cold (and one proper freeze-up)

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
Rob K
19 January 2021 12:52:54

CFS monthly anomaly charts going for a roughly average Feb but a rather cold March, with heights over Greenland dominant.


Meteociel - Modèle Numérique américain CFS (par mois)


 


The long range CFS model has plenty of eye candy from mid Feb onwards though. Only 654 hours out so probably just about nailed on I would say. 


 


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
JRobinson
19 January 2021 12:56:16


CFS monthly anomaly charts going for a roughly average Feb but a rather cold March, with heights over Greenland dominant.


 


The long range CFS model has plenty of eye candy from mid Feb onwards though. Only 654 hours out so probably just about nailed on I would say. 


 



Originally Posted by: Rob K 


 


Pfff....There’s too much involving winds sourced from the Sahara with that! 

JRobinson
19 January 2021 12:58:58

Ok.... can someone please tell me why I can never post links in any of the forums here?


 


I couldn’t post any links myself. It gets reported as spam.


even now when I quoted another persons post in my reply it got rejected as spam.


only when I removed the link from his post did it get accepted.


many thanks in advance from a forum noob

Gandalf The White
19 January 2021 13:46:39

Deleted - duplicate post

Location: South Cambridgeshire
130 metres ASL
52.0N 0.1E


Gandalf The White
19 January 2021 13:47:16

The latest ECM ensemble run for 10hPa suggests the chance of another wind reversal at the end of the month:


Location: South Cambridgeshire
130 metres ASL
52.0N 0.1E


some faraway beach
19 January 2021 14:31:21


CFS monthly anomaly charts going for a roughly average Feb but a rather cold March, with heights over Greenland dominant.


Meteociel - Modèle Numérique américain CFS (par mois)


 


The long range CFS model has plenty of eye candy from mid Feb onwards though. Only 654 hours out so probably just about nailed on I would say. 


 



Originally Posted by: Rob K 


Wouldn't this be the sort of timescale where we should see the effects of this month's sudden stratospheric warming propagating down to these charts?


I'd always had it in mind that you need to wait 6 weeks to see the effects of a SSW, but this one seems to have been written off after a fortnight for some reason.

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.

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