theweatheroutlook

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Saint Snow
11 November 2024 17:20:38

Yes there was a story on Toby Young's AGW denying blog site claiming that the Met Office are inventing data. That's not quite true of course, but I think they should be clearer about which sites are actually generating real data and which aren't. The MO site does say that where stations have shut down they use nearby stations to provide the data, but it doesn't seem very transparent.

Back on the charts and 12Z GFS has a bit ore of a diluted/west-based northerly, but comes very close to a Channel blizzard at 300 hours+... doesn't quite undercut enough though and the mild air wins out.

Originally Posted by: Rob K 




As a general set-up, that +120 to +270 period is classic snow potential for MBY... if we were 4-5 weeks further on in the season. Graupel city!


That +300 chart is tantalising on first view, isn't it? That energy was beginning to slide under from +294 and you're willing it to continue and for the low to follow it. Then high pressure ridges up from Africa and it's goodnight, Vienna.


Martin
Home: St Helens (26m asl) Work: Manchester (75m asl)
A TWO addict since 14/12/01
"How can wealth persuade poverty to use its political freedom to keep wealth in power? Here lies the whole art of Conservative politics."
Aneurin Bevan
Chunky Pea
11 November 2024 17:40:16

Fascinating. I hadn't realised that's what they were doing, and at best it seems inept and at worst deceptive - why pretend you have the data when you don't? It gives a leg-up to those sceptics who dismiss the whole tenet of global warming. (I'll still call it that, as that's what's happening!)

Originally Posted by: Retron 


If they are using the now defunct stations data to compare current data with, that cannot be acceptable. The differences between even two closeby stations can be pretty significant. One will not capture the hyperlocal nuances of the other. It isn't possible. 
Current Conditions
https://t.ly/MEYqg 

"You don't have to know anything to have an opinion"
--Roger P, 12/Oct/2022
+1
Retron
11 November 2024 17:43:52
Interesting to see that despite the relatively tepid op run, there are now 4 GEFS members showing -10s for London in the T+180 timeframe... with a 5th member grazing the -10 isotherm.

That's using the tried and tested old Meteociel charts:
https://www.meteociel.fr/cartes_obs/gens_display.php?x=&y=&run=12&ville=Londres&lat=51.5085&lon=-0.12574&runpara=0&type=6&ext=0 

Okay, there are now 30 members (plus the op and control), so not as impressive as it used to be, but even so - it's enough to slightly raise an eyebrow.

The other interesting thing is the rapid cyclogenesis that's possible in the 144-168 timeframe, as shown on the MetO and GEM output. Even though 850s don't seem remarkable, it's the sort of thing that can cause unexpected snowfall to pop up in places on the west and NW side of the low as it pulls away.

At least there's more excitement in the models now than there has been over the past few weeks! 😁
Leysdown, north Kent
+2
ballamar
11 November 2024 18:02:07

Interesting to see that despite the relatively tepid op run, there are now 4 GEFS members showing -10s for London in the T+180 timeframe... with a 5th member grazing the -10 isotherm.

That's using the tried and tested old Meteociel charts:
https://www.meteociel.fr/cartes_obs/gens_display.php?x=&y=&run=12&ville=Londres&lat=51.5085&lon=-0.12574&runpara=0&type=6&ext=0 

Okay, there are now 30 members (plus the op and control), so not as impressive as it used to be, but even so - it's enough to slightly raise an eyebrow.

The other interesting thing is the rapid cyclogenesis that's possible in the 144-168 timeframe, as shown on the MetO and GEM output. Even though 850s don't seem remarkable, it's the sort of thing that can cause unexpected snowfall to pop up in places on the west and NW side of the low as it pulls away.

At least there's more excitement in the models now than there has been over the past few weeks! 😁

Originally Posted by: Retron 


Still a little off an ensemble watch for -10’s !
+1
Retron
11 November 2024 18:10:43

Still a little off an ensemble watch for -10’s !

Originally Posted by: ballamar 


Indeed! There are a few other things I'd need to see before one of those - ice days as a possibility on the ECM ensembles, for example, as well as -10s showing up on the ECM plumes.

https://charts.ecmwf.int/products/opencharts_meteogram?base_time=202411110000&epsgram=classical_15d&lat=51.4333&lon=-1.0&station_name=Reading 

Some of the GEFS members keep the generally cold pattern going for quite some time, and there's at least one with widespread snow moving south across the UK.
Leysdown, north Kent
+1
Jiries
11 November 2024 20:07:57

Interesting to see that despite the relatively tepid op run, there are now 4 GEFS members showing -10s for London in the T+180 timeframe... with a 5th member grazing the -10 isotherm.

That's using the tried and tested old Meteociel charts:
https://www.meteociel.fr/cartes_obs/gens_display.php?x=&y=&run=12&ville=Londres&lat=51.5085&lon=-0.12574&runpara=0&type=6&ext=0 

Okay, there are now 30 members (plus the op and control), so not as impressive as it used to be, but even so - it's enough to slightly raise an eyebrow.

The other interesting thing is the rapid cyclogenesis that's possible in the 144-168 timeframe, as shown on the MetO and GEM output. Even though 850s don't seem remarkable, it's the sort of thing that can cause unexpected snowfall to pop up in places on the west and NW side of the low as it pulls away.

At least there's more excitement in the models now than there has been over the past few weeks! 😁

Originally Posted by: Retron 


One member go down as low as -15C over Nuneaton ensembles while the main line is -6C on 18th November which now ear marked for the coldest air to hit here.  At least some interest about possible out of blue snowfall but mostly happy to see lot of sunshine with it.
squish
11 November 2024 22:21:15
https://modeles16.meteociel.fr/modeles/gfs/runs/2024111118/gfsnh-0-162.png?18 

Enjoy, as we normally spend all winter looking for these kind of charts ( even at +168!)
D.E.W on Dartmoor. 300m asl
Joe Bloggs
11 November 2024 22:25:43

https://modeles16.meteociel.fr/modeles/gfs/runs/2024111118/gfsnh-0-162.png?18

Enjoy, as we normally spend all winter looking for these kind of charts ( even at +168!)

Originally Posted by: squish 


Wow. Fine details aside - that is a truly stunning synoptic setup. 

Manchester City Centre, 31m ASL
White Meadows
11 November 2024 22:41:55
Further shift towards something for coldies this month in the Met text
“Temperatures falling below average and feeling particularly cold in the strong winds”
…along with “significantly colder” as the opening line 
+1
CField
12 November 2024 05:02:20

https://modeles16.meteociel.fr/modeles/gfs/runs/2024111118/gfsnh-0-162.png?18

Enjoy, as we normally spend all winter looking for these kind of charts ( even at +168!)

Originally Posted by: squish 


Wouldn't be suprised to see the SE get a little channel disturbance of this...Tunbridge Wells in firing line again like Dec 2022...
Favourite snowstorm
Famous channel low
Dec 31st 1978
Hastings East Sussex
Foot of level snow severe drifting
Next day max temp -4 degrees Celsius
Brian Gaze
12 November 2024 06:45:56
GFS not without interest this morning.  🌧️🌨️🌧️🌨️🌧️🌨️

UserPostedImage
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
+1
Retron
12 November 2024 06:56:31

GFS not without interest this morning.  🌧️🌨️🌧️🌨️🌧️🌨️

Originally Posted by: Brian Gaze 


Out of interest, is that snow field actual modelled snow, or is it still the old "one flake of sleet in amongst the rain" field? If GFS now has sleet (rain/snow mixed) and pure snow, would it be possible to have the colours changed? Maybe pink as-is for sleet and white/grey for snow?

As for the GFS run, it has 70+ mph gusts here as that low pulls away - with snow over the Downs. Here it'd just be utterly miserable!

It shows the potential of rapid cyclogenesis, though, something which is being flagged up repeatedly of late.

If I had to put money on it, I'd suggest we're likely to see at least one low zipping across or close to the SE, with lots of cold rain and strong winds down here and some snow mostly over higher ground further north and west, perhaps the odd bit making it down to lower levels in e.g. the Midlands and areas west of say Reading.

Definitely something to keep an eye on, anyway.
Leysdown, north Kent
+1
nsrobins
12 November 2024 07:31:21
Although the ‘interesting’ blizzard scenario the GFS DET seems to be keen on this morning has as much chance of verifying as my youngest daughter has of putting her phone down for more than three minutes, it does highlight the potential - as Darren has hinted at - of rapid cyclogenesis given the cold uppers (strong NW flow), warm surface layer (anomalous high SST along 50N) and jet exit region combo. 
If pieces fall together there is a raised chance of a significant event as per GfS 00Z run.
Neil
Fareham, Hampshire 28m ASL (near estuary)
Stormchaser, Member TORRO
+3
DEW
  • DEW
  • Advanced Member
12 November 2024 07:38:30
WX temp charts - cold weather firming up over C Europe as the area of freezing weather over N Russia extends its influence. In week 1, freezing for small patches of mountainous areas as far S as the Balkans; in week 2 noticeably colder also across N Europe including Britain, with Scandinavia and Scotland also set for a freeze. Week 1, some pptn for N Atlantic including Britain, bits and pieces elsewhere; in week 2 really heay rain fro N Spain, France, Italy, the low countries and Britain on the fringe of this is also damp.

GFS Op - HP hangs on over or just W of Britain to Fri 15th, but by Sunday the large LP over Scandinavia is projecting N-lies across Britain, and this N-ly stream spawns a set of cold and stormy LPs running from the W or SW; Mon 18th 980mb N Sea, Tue 19th 975 mb S Ireland (this rapidly traverses England), Thu 21st 965mb Devon running up the Channel. There is then a shift as Atlantic rather than Scandinavian LP controls British weather; trough 995mb Brittany Sun 24th runs up the west coast followed by another Tue 26th closer in before HP begins to reassert itself 1040b Biscay Thu 28th. 

BBC (Meteo Group) weather shows the breakdown at the end of this week as a flabbier affair; cold from the north, certainly, but spread over a larger area without the storms offered by GFS.

ECM - agrees with GFS to Mon 18th but the LP by then in the N Sea 990mb stays around S Norway and contents itself with extending troughs to Ireland 1005mb Wed 20th, N France 995mb Thu 21st and back to W Scotland 1000mb Fri 22nd. Still definitely cold but not nearly as stormy.

GEM - favours the cold and stormy outlook after Mon 18th ; 970 mb Devon Wed 20th moving rapidly to N Sea dragging a second local LP 990mb W Scotland behind it

GEFS - a big dip in temp to 6 or 7 C below by Mon 18th, colder than shown yesterday and with better (though not perfect) ens agreement. Temps stay low for a week, op and control amongst the lowest, enough milder runs to drag the mean back to norm by Sun 25th while op & control stay on the cold side. Rain starts 17th Nov, heavy and persistent in the S, moderate amounts for Scotland and the N. Snow row figures widely in the 20s for Scotland, even a few reaching 5 or 6/33 on the south coast, so snow likely on high ground anywhere.
War does not determine who is right, only who is left - Bertrand Russell

Chichester 12m asl
+4
Retron
12 November 2024 07:42:44
Wow.

Who fancies widespread deep snow next Monday followed by several widespread ice days?

If you do, PTB26 has what you want...

https://www.meteociel.fr/modeles/gefs_cartes.php?code=26&ech=144&mode=0&carte=0&ext=0 

Of course it's a humongous outlier, one of the biggest I've ever seen - but the fact that it's at only 144 shows what happens if you roll five sixes....

EDIT: The funny thing is synoptically it's actually rather similar to many of the other runs / members, it just runs the trigger low further south. It shows what can happen if you get snow on the ground, it seems GEFS now has enough layers to model the effects of a cold boundary layer well. (We all know, for example, that once you have snow on the ground you no longer need to look for such low 850s / thicknesses for further snow).

One thing's for sure - we've now more excitement to look forward to than in the previous few months combined! Silly season is upon us, folks, buckle up and enjoy the ride! 😁
Leysdown, north Kent
+5
Brian Gaze
12 November 2024 08:09:13

Out of interest, is that snow field actual modelled snow, or is it still the old "one flake of sleet in amongst the rain" field? If GFS now has sleet (rain/snow mixed) and pure snow, would it be possible to have the colours changed? Maybe pink as-is for sleet and white/grey for snow?

Originally Posted by: Retron 



1) It hasn't changed

2) It is a categorical variable, so it doesn't provide the amount

I've taken a look through the variables available and there isn't anything to replace it that I can see. Therefore, I think you'll basically find it to be the same wherever you view GFS precipitation type forecast charts.

Personally, I always take a look at the accompanying snow depth charts from the GFS  / GEFS, because they can ameliorate the issue to a degree. So you get something like this:

UserPostedImage


From GEFS 00Z you get this for Berkhamsted:

UserPostedImage


Both of the above are generated using snow depth variables in the data sets rather than being derived from them. That said, IMO the GFS / GEFS badly overestimate snow depths, at least for the UK. I'm not sure if that's because they over forecast the amount of precipitation or if other factors such as compression and melting in marginal conditions are the main issue. There is a variable which gives the total amount of water that would be produced if all the accumulated snow on the ground were melted that could help with that, but I don't have the time to delve into it.  
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
+1
Retron
12 November 2024 08:18:34

1) It hasn't changed

2) It is a categorical variable, so it doesn't provide the amount...

That said, IMO the GFS / GEFS badly overestimate snow depths, at least for the UK


Thank you for the detailed info! 👍

It's disappointing in a way that GFS doesn't provide finer differentiation of rain, rain/snow mixed and pure snow, but it's not too surprising - that, along with the snow depth overestimation, stems (IMO) from a model designed mainly for the continental climate which North America enjoys. They seem to have less (British style) sleet out there, and I guess that more often than not when the "snow" element is triggered it'll be snow rather than sleety, slushy stuff.

The Canadian GEM suffers in a similar way with its snow depth estimations too. I suspect in both cases they're assuming dry powder snow ratios (again, reasonable considering that'll be the main type of snow out there) rather than the sopping wet slushy stuff we tend to get.

All in all it just means we'll have to continue taking GFS' snow charts with a very large dose of salt!
Leysdown, north Kent
Jiries
12 November 2024 09:56:24

GFS not without interest this morning.  🌧️🌨️🌧️🌨️🌧️🌨️

UserPostedImage

Originally Posted by: Brian Gaze 


Would be nice for us here with lot of snow and at least something interesting and more sunshine in between and glad no HP over us next week, don't want any HP anymore after the recent HP brought 2 weeks of gloom.  Still some HP again this week but not over us more to the west so keep gloom out.
idj20
12 November 2024 10:32:37
Dunno about the wintry aspect, there are some stormy looking runs for this time next week. Still plenty of room for changes/downgrades but wouldn't surprise me if it does verify come nearer the moment. 
Folkestone Harbour. 
ballamar
12 November 2024 11:22:40
Love the channel low on the 6z op run, whatever happens will be more interesting weather. Probably fairly windy at times!
Retron
12 November 2024 12:55:13
The 6z GEFS once again produces a member with widespread ice days, and again in around a week's time. Just goes to show what's possible if that trigger low is south enough!

https://www.meteociel.fr/modeles/gefs_cartes.php?code=1&ech=168&mode=0&carte=0&ext=0 
Leysdown, north Kent
+1
CField
12 November 2024 13:05:06
Liking the end runs of the 6z,  ...the sleeping volcano the artic high   cold air to the east and WAA from the azores trying to link up....it won't verify but we need different nuances in the set up to prevent this cold snap being winters only kerfuffle and a trend to a colder than average winter
Favourite snowstorm
Famous channel low
Dec 31st 1978
Hastings East Sussex
Foot of level snow severe drifting
Next day max temp -4 degrees Celsius
+1
The Dub Version
12 November 2024 13:28:53
Nothing out of ordinary.
Possibly coldish down south 7c, maybe a frost, Gosh.

Up north some sleet, snow on hills. Normal service of previous years.
Berkshire
The Beast from the East
12 November 2024 13:39:55

Dunno about the wintry aspect, there are some stormy looking runs for this time next week. Still plenty of room for changes/downgrades but wouldn't surprise me if it does verify come nearer the moment. 

Originally Posted by: idj20 


Yes, that storm looks concerning after such a long period of benign weather. Hopefully it stays up north
"We have some alternative facts for you"
Kelly-Ann Conway - special adviser to the President
ballamar
12 November 2024 13:41:50

Nothing out of ordinary.
Possibly coldish down south 7c, maybe a frost, Gosh.

Up north some sleet, snow on hills. Normal service of previous years.

Originally Posted by: The Dub Version 


Might be worth looking back through the models rather than just stating your thought. Potential for some very cold Synoptics for time of year 

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