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Rob K
05 December 2022 07:17:33

The EC has gone full renegade this morning and disrupted the pseudocane energy into France. UK cold/very cold throughout.
 

Originally Posted by: nsrobins 


Yes we are certainly seeing a lot of different t options with that big storm!

The GEFS continues to have wild scatter from as early as next Monday but the trend looks good. 
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
DEW
  • DEW
  • Advanced Member
05 December 2022 08:01:44
Now it's on again - WX temp chart which withdrew the 0C isotherm from W Europe yesterday has reinstated it this morning, patchily in week 1 but in week 2 fully flooded across France and Britain (excepting Eire) . But countries round the Aegean and Black Sea are milder. There's a dry area over France in week 1 and pptn all around (but not much over UK, more in the N Sea); the dry patch moves to Britain in week 2 with again pptn all around - so prospects of widespread heavy snowfall are slim. Maybe coastal showers?

GFS Op - current shallow LP over France with E-lies replaced as dominant feature Thu 8th by LP 1000mb Scandinavia with N-lies for Britain. The very deep LP mid Atlantic Sun 11th 950mb (? - I can't count the isobars) runs out of steam and lies as a trough off Cornwall 1000mb Thu 15th while the Scandinavian LP draws back a bit to the Baltic, but revives for a couple of days with NE-lies back again. Then the action shifts to the N Atlantic, with new LP 995mb Norwegian Sea Tue 20th and HP approaching Britain from the SW. Note an unusually intense HP SE of the Urals developing 1065mb Fri 16th,  and N Siberia under LP instead.

ECM - Similar to GFS to Tue 13th but by Thu 15th the mid Atlantic LP has retained its identity as a centre off Spain, and the Scandinavian LP has moved N and deepened leaving Britain under a weak ridge of HP, looking cold in the E and mild in the W

GEFS - dropping to very cold (6C below norm) with good agreement from ens members until Mon 12th when the agreement breaks up, the mean slowly recovering to norm by Wed 21st, op and control both colder, dry until Sat 10th  (Thu 8th in Scotland) after which small amounts of pptn appearing on random dates in most ens members. Snow row figures generally from 5 in the S to 10 in N England/S Scotland to 15 in N Scotland. though up to 30  in the last over the next few days.
War does not determine who is right, only who is left - Bertrand Russell

Chichester 12m asl
+3
squish
05 December 2022 08:02:51
The ICON/DWD looks potentially snowy for the SE in a weeks time ....

 
D.E.W on Dartmoor. 300m asl
Tim A
05 December 2022 08:04:17

Yep all the models keep the UK cold now until at least day 10 . In fact its looks more like a 2 weeks . Now we just need the snow. Looks like NW England and Midlands could get some Wednesday night. 

Originally Posted by: Ally Pally Snowman 



That band on Thursday morning looks very unreliable,  signal disapeared from MOGREPS and UKV now, still present on GFS in sorts.  THink it will be a Nowcast so there is hope. 

Could be very dry though.  I know we should get the cold in and worry about the snow later,  but it is certaintly plausabile that some areas in the middle of the country will miss out in this setup. 
Tim
NW Leeds
187m asl

 My PWS 
Arbroath 1320
05 December 2022 08:07:25
Looking at the MO as a whole this morning there's consistent agreement for a prolonged cold spell.

Everything is on offer in the mid-term from Northerlies to Easterlies but little sign of any attack from the SW.

A very unusual period of Winter weather coming up it seems in terms of longevity. 
​​​
GGTTH
BJBlake
05 December 2022 08:17:57
Old fashioned east coast snow showers will do me just fine...however, the GFS snow rows have changed with each run: The pub run showed the whole country under a blanket. - a la Joe whats-his-names's prediction, someone posted a week ago, so we'll need to get nearer for snow: Best snow falls are often the unexpected ones: In 2010 we had one creep up from Essex into Suffolk, where I lived then, and wow - 4 inches of dusty piste special - delivered to my door. Totally unexpected. We'll see about snow - but the set up is also very unusual and it has taken something special to deliver the cold spell that has potential for snow. The Scandi high delivered rain showers and temperatures of 6- 8 degrees: I cannot believe that back in the 1980s that this set-up would not have already brought showers of snow.
Yes plenty of very interesting twists and turns and tales of the unexpected to come for a good long period: and so well timed for advent.
Brecklands, South Norfolk 28m ASL
Gandalf The White
05 December 2022 08:35:26

Looking at the MO as a whole this morning there's consistent agreement for a prolonged cold spell.

Everything is on offer in the mid-term from Northerlies to Easterlies but little sign of any attack from the SW.

A very unusual period of Winter weather coming up it seems in terms of longevity. 
​​​

Originally Posted by: Arbroath 1320 



UKMO at T+168 has 'that' LP edging in - but probably sliding rather than making much headway.



 
Location: South Cambridgeshire
130 metres ASL
52.0N 0.1E


Tom Oxon
05 December 2022 08:45:45

That band on Thursday morning looks very unreliable,  signal disapeared from MOGREPS and UKV now, still present on GFS in sorts.  THink it will be a Nowcast so there is hope. 

Could be very dry though.  I know we should get the cold in and worry about the snow later,  but it is certaintly plausabile that some areas in the middle of the country will miss out in this setup. 

Originally Posted by: Tim A 



Nowcasting definitely the name of the game.  Although with SSTs still way above average the lake effect on a brisk NE flow is probably being understated by models and forecasters alike 
S Warwickshire countryside, c.375ft asl.
Surrey John
05 December 2022 08:49:28
Cold appears to be consistently modelled

Not much snow, but from memory all the models tend to not pick up minor troughs and disturbances in the airflow more than a day or two out, and so could be light dusting almost anywhere (obviously less in shadow of hills)

 
Bradford on Avon, Wiltshire
35m ASL
Rob K
05 December 2022 09:13:28
Automated output continues to look very underwhelming with MO, BBC and iPhone all going for nothing more than a few days with 2-3C maxima late this week and into the weekend before a warmup to 5-6C with rain showers next week, possibly sleet. 
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
Gusty
05 December 2022 09:36:52
A long cold spell incoming. Notable will be the hard frosts and very low overnight minima.
Snow is on the cards but the devil will be in the detail as to where. Nowhere is immune.
Perception is key and even a light dusting that hangs about for a few days will linger longer in the memory compared to one that doesn't.
 
Steve - Folkestone, Kent
Current conditions from my Davis Vantage Vue
https://www.wunderground.com/dashboard/pws/IFOLKE11 
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Jiries
05 December 2022 09:43:12
I expect to see lot of snow in places due to cold LP over us, very impossible to be wall to wall sunshine and a frost.  in summer same set-up we get flooding from lot of slow moving rains around.   Will see snow here on Thursday since last year snowfall event from Arwen which gve me 8cm depth.

With more models now agreeing for longer subzero spell there should be action to take regarding energy prices that have to be done something about it to allow us to use heating more longer.
Tim A
05 December 2022 09:56:01

I expect to see lot of snow in places due to cold LP over us, very impossible to be wall to wall sunshine and a frost.  in summer same set-up we get flooding from lot of slow moving rains around.   Will see snow here on Thursday since last year snowfall event from Arwen which gve me 8cm depth.

With more models now agreeing for longer subzero spell there should be action to take regarding energy prices that have to be done something about it to allow us to use heating more longer.

Originally Posted by: Jiries 



It can be very dry with cold LP stuck over us.  Second cold spell in Dec 10 was like that here.  Some places will miss out and most of the time it will be clear and sunny. 
6Z GFS makes more of the feature on Thursday which is a positive though. 
Tim
NW Leeds
187m asl

 My PWS 
Whiteout
05 December 2022 10:02:25
Yes, GFS sticks with the featue running N to S on Thursday night.
Home/Work - Dartmoor
240m/785 ft asl
nsrobins
05 December 2022 10:04:38

Nowcasting definitely the name of the game.  Although with SSTs still way above average the lake effect on a brisk NE flow is probably being understated by models and forecasters alike 

Originally Posted by: Tom Oxon 


The 'Lake effect' is a real thing for the UK, and combined with subtle CVZs can deliver impressive local accumulations. It does however need some physics to get going, and it's a multi-blade sword. You need the water to have heat but not so much that it over-warms the airmass passing over it to >0deg. You also need the vertical thermal gradient to utilise the difference between the moister, milder, sea-warmed air near the surface and get it rising into the dry, very cold air aloft but if the milder air doesn't mix out the air mass warms up too much and you get wet snow/sleet.  My own data suggests (given a mostly unidrectional flow of moderate strength, sub zero dps) that the difference between SST and 850T needs to be about 20C. Over the years easterlies leaving the near continent at -3deg 2m and -12deg at 850 have had no problem generating convective snow with ssts around 8C. The current SSTs in the North Sea range 9C to 13C (they have dropped a degree in the last week) so -10 at 850 might do the job if the flow is strong enough, and the airmass is below or close to freezing after the passage (not warmed too much in crossing the sea). It's compicated and why even the highest resolution models have trouble discerning convective coastal snow showers in winter.
It looks like we won't be in streamer/lake effect territory yet with a slack trough over the UK (except the NW maybe) but if an easterlies get going next week it might be a different story.
Neil
Fareham, Hampshire 28m ASL (near estuary)
Stormchaser, Member TORRO
+3
Rob K
05 December 2022 10:16:35

Automated output continues to look very underwhelming with MO, BBC and iPhone all going for nothing more than a few days with 2-3C maxima late this week and into the weekend before a warmup to 5-6C with rain showers next week, possibly sleet. 

Originally Posted by: Rob K 



And the iPhone/IBM model has just updated much colder. Now gives a run of maxima of 2, 1, 2, 2, 2, 1, 0 from Thursday for my location, some 5 or 6 degrees lower than the last update. 
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
UncleAlbert
05 December 2022 10:21:46
Well folks, with what looks likely to be the most wintry December for years coming up and the Met Office going on strike, it is time to put your well honed model analysis skills to good use with your family and friends😀
Jiries
05 December 2022 10:22:53

It can be very dry with cold LP stuck over us.  Second cold spell in Dec 10 was like that here.  Some places will miss out and most of the time it will be clear and sunny. 
6Z GFS makes more of the feature on Thursday which is a positive though. 

Originally Posted by: Tim A 



It been showing snow and cold on Thursday as far as back last week Monday and never been downgraded or pushed back.   Should see more features pop up at short notice.
Joe Bloggs
05 December 2022 10:30:27
Morning all.

Great runs for cold this morning.

With reference to Thursday's feature - beware of assuming all snow. It looks fairly marginal and GFS in particular is picking up dewpoints above freezing for large parts of Northern England which combines with the arrival of the disturbance. Rain rather than snow is absolutely feasible. Obviously - this could well upgrade nearer the time.

UserPostedImage

Manchester City Centre, 31m ASL
White Meadows
05 December 2022 10:33:30

Automated output continues to look very underwhelming with MO, BBC and iPhone all going for nothing more than a few days with 2-3C maxima late this week and into the weekend before a warmup to 5-6C with rain showers next week, possibly sleet. 

Originally Posted by: Rob K 



Really not worth getting hung up on phone apps and mainstream digital forecasts which are often using data 24+hrs behind the wealth of information available, namely via this site. 
In fact, something like an iphone weather app developed in California is the last thing you can take seriously after granny's grebe's migration. 
Tim A
05 December 2022 10:36:06

It been showing snow and cold on Thursday as far as back last week Monday and never been downgraded or pushed back.   Should see more features pop up at short notice.

Originally Posted by: Jiries 



Morning Joe,
Hopefully the timing of the band/ landing onto frozen ground should give a bit of an advantage to Northern England.  If indeed the band does exist and doesn't fragment too much. 
As we know from Nov 28th last year, very difficult to forecast these things in advanced. 
Tim
NW Leeds
187m asl

 My PWS 
+1
Quantum
05 December 2022 10:38:09
Think the story could be cold rather than snow.
The temperatures that could come out of this cold spell could truly be exceptional, especially given any modest snow cover. -20C by night in Scotland and widespread ice days are highly likely.
 
2023/2024 Snow days (approx 850hpa temp):
29/11 (-6), 30/11 (-6), 02/12 (-5), 03/12 (-5), 04/12 (-3), 16/01 (-3), 18/01 (-8), 08/02 (-5)

Total: 8 days with snow/sleet falling.

2022/2023 Snow days (approx 850hpa temp):

18/12 (-1), 06/03 (-6), 08/03 (-8), 09/03 (-6), 10/03 (-8), 11/03 (-5), 14/03 (-6)

Total: 7 days with snow/sleet falling.

2021/2022 Snow days (approx 850hpa temp):

26/11 (-5), 27/11 (-7), 28/11 (-6), 02/12 (-6), 06/01 (-5), 07/01 (-6), 06/02 (-5), 19/02 (-5), 24/02 (-7), 30/03 (-7), 31/03 (-8), 01/04 (-8)
Total: 12 days with snow/sleet falling.
+1
Joe Bloggs
05 December 2022 10:43:05

Morning Joe,
Hopefully the timing of the band/ landing onto frozen ground should give a bit of an advantage to Northern England.  If indeed the band does exist and doesn't fragment too much. 
As we know from Nov 28th last year, very difficult to forecast these things in advanced. 

Originally Posted by: Tim A 


Yes absolutely right and there was nothing marginal about Nov 28th. 

In these scenarios though, positive dewpoints are never a good sign. I actually think we are primed to see the precipitation but just have my doubts it'll be 100% snow. It could be GFS have them a degree or two too high. EURO4 is still the best model for features like this (if it still exists).. 

Manchester City Centre, 31m ASL
Quantum
05 December 2022 10:48:48
UserPostedImage


UserPostedImage
UserPostedImage




The all time UK record of -27.2C has happened 3 times in Scotland (all shown above). Notice the synoptics are near identical, and that there will be synoptics like the above appearing on multiple occasions. All we need is some decent snow cover (and this is N scotland so that shouldn't be hard). Imagine if 2022 saw both the hottest temperature and coldest temperature ever recorded?
 
2023/2024 Snow days (approx 850hpa temp):
29/11 (-6), 30/11 (-6), 02/12 (-5), 03/12 (-5), 04/12 (-3), 16/01 (-3), 18/01 (-8), 08/02 (-5)

Total: 8 days with snow/sleet falling.

2022/2023 Snow days (approx 850hpa temp):

18/12 (-1), 06/03 (-6), 08/03 (-8), 09/03 (-6), 10/03 (-8), 11/03 (-5), 14/03 (-6)

Total: 7 days with snow/sleet falling.

2021/2022 Snow days (approx 850hpa temp):

26/11 (-5), 27/11 (-7), 28/11 (-6), 02/12 (-6), 06/01 (-5), 07/01 (-6), 06/02 (-5), 19/02 (-5), 24/02 (-7), 30/03 (-7), 31/03 (-8), 01/04 (-8)
Total: 12 days with snow/sleet falling.
Brian Gaze
05 December 2022 10:50:42
GFS 06z shows quite a lengthy cold period with a breakdown starting around 16/12. I still think that's the period which needs watching closely.

UserPostedImage
Brian Gaze
Berkhamsted
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