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doctormog
21 December 2022 11:28:22
The ensemble data show better agreement overall now in the short to medium term but the synoptics are such that features like the one on Boxing Day in parts of the south can appear even in "average" conditions.
DEW
  • DEW
  • Advanced Member
21 December 2022 11:36:11

Well the GFS 6z has a Boxing day blizzard for the South. 
https://www.meteociel.fr/modeles/gfs/royaume-uni/precipitations/126h.htm 


https://www.meteociel.fr/modeles/gfs/royaume-uni/hauteur-neige/132h.htm 

Looks like Moomin's house is the sweet spot..😁🌨☃️
 

Originally Posted by: Ally Pally Snowman 



Even more graphically
https://max.nwstatic.co.uk/gfsimages/gfs.20221221/06/132/uksnowrisk.png 
but blink and you've missed it

The 06 z compared to the 00z does seem to separate out the train of LPs somewhat, allowing brief incursions of cold air well southwards - previously these were blocked off by the approach of the next LP
 
War does not determine who is right, only who is left - Bertrand Russell

Chichester 12m asl
Jacee
21 December 2022 11:48:05
In the medium term, the best chance of snow for the south remains post Christmas. I note the 06z eye candy but like the 00z I'm not expecting such a scenario to be well supported in its ensemble suite. It does show the potential for a surpriose or two if the stars align. Naturally, there's a much better chance of snow 23-27th Dec period further north (Scotland + hills of N England).

Thereafter the trend is for more average temperatures, perhaps straying into mild the further south you are towards New Year. Largely unsettled especially further north and west and not especially exciting or inspiring!
Jacee, Hucknall (Notts) 😽 x
moomin75
21 December 2022 12:01:56

...but this is not a forecast thread.

Originally Posted by: Tractor Boy 



I am not going to labour the point, as it's a waste of my time, but analysing models and then saying what you see, is a forecast, and as such, it is relevant to the Model thread.

​​​​​​​But I'm signing out now for a few days and will come back to model watching after Christmas.   
Witney, Oxfordshire
100m ASL
Whiteout
21 December 2022 12:30:04

I am not going to labour the point, as it's a waste of my time, but analysing models and then saying what you see, is a forecast, and as such, it is relevant to the Model thread.

But I'm signing out now for a few days and will come back to model watching after Christmas.   

Originally Posted by: moomin75 



You said that about 3 hours ago lol, do you mean it this time? 😂

​​​​​​​Have a good one.
Home/Work - Dartmoor
240m/785 ft asl
dagspot
21 December 2022 13:04:26
im a bit lost now. Yesterday there was a blizzard for me Fri, (Sun) and Mon.  Now 6dc and ‘mild’   Is everything off or on for simple mind?    #IgnoreAppIcons
Neilston 600ft ASL
doctormog
21 December 2022 13:13:32

im a bit lost now. Yesterday there was a blizzard for me Fri, (Sun) and Mon.  Now 6dc and ‘mild’   Is everything off or on for simple mind?    #IgnoreAppIcons

Originally Posted by: dagspot 



With the risk of being accused of putting a "cold slant" on the reply as you are asking about your locality I would say that snow is possible on both Friday and later on Sunday for your location based on the latest output. Having said that even at this range you could end up with rain or nothing at all.
Gavin D
21 December 2022 13:25:25
Looking at the models and the big freeze that's about to grip millions in the USA and Canada. London is going to be warmer than Orlando, Florida, on Christmas Day!
Jiries
21 December 2022 13:30:12

Looking at the models and the big freeze that's about to grip millions in the USA and Canada. London is going to be warmer than Orlando, Florida, on Christmas Day!

Originally Posted by: Gavin D 



Not sure why Toronto not getting any deep cold? I only see -8C which is nothing new but normally go down to -20 or below but this time now despite the chart touting deep cold over USA which always pass over Canada as well.  
fairweather
21 December 2022 13:38:41

Looking at the models and the big freeze that's about to grip millions in the USA and Canada. London is going to be warmer than Orlando, Florida, on Christmas Day!

Originally Posted by: Gavin D 


Their surprise big freezes seem to happen every winter!
S.Essex, 42m ASL
fairweather
21 December 2022 13:42:24
Not looking forward to the next week or more of wet and windy weather. Stops you doing outside things, is more uncomfortable for me with my constantly watery eyes and just looks thoroughly miserable. Let's hope we get that rarest of things - a decent cold January spell.
S.Essex, 42m ASL
Gusty
21 December 2022 14:23:06

Not sure why Toronto not getting any deep cold? I only see -8C which is nothing new but normally go down to -20 or below but this time now despite the chart touting deep cold over USA which always pass over Canada as well.  

Originally Posted by: Jiries 



Core of the cold is to the south of Toronto. Nothing sinister or untowards going on. 

https://www.ventusky.com/?p=41.9;-91.1;4&l=temperature-850hpa&t=20221223/1500 


 
Steve - Folkestone, Kent
Current conditions from my Davis Vantage Vue
https://www.wunderground.com/dashboard/pws/IFOLKE11 
Join Kent Weather on Facebook.
https://www.facebook.com/stevewall69/ 



Snow Hoper
21 December 2022 14:24:48

Their surprise big freezes seem to happen every winter!

Originally Posted by: fairweather 



Yeah, and they fill up FB posts with "another dose of GW last night" when referencing the huge dumps of snow🙄

Can see some opportunities for transitional stuff at times on the models especially the further north you go, but on the whole, all rather underwhelming from an outlook point of view. Just hope they over play things, as having the PV set up in its usual place, is the last thing we need.
Going to war over religion is like killing each other to see who has the better imaginary friend.


Home : Thorndon, Suffolk.
Gandalf The White
21 December 2022 14:33:41

Not sure why Toronto not getting any deep cold? I only see -8C which is nothing new but normally go down to -20 or below but this time now despite the chart touting deep cold over USA which always pass over Canada as well.  

Originally Posted by: Jiries 



-20c in Toronto in December is actually very rare Jiries.  
Location: South Cambridgeshire
130 metres ASL
52.0N 0.1E


Retron
21 December 2022 15:41:46

Their surprise big freezes seem to happen every winter!

Originally Posted by: fairweather 


When I was on holiday in Alaska a few years ago, it was mentioned (by the sled dog guide, one of those outdoorsy types) that the lower 48 keep seeing these record cold blasts and as such that which not must be spoken about is regarded as a bit of a hoax. Meanwhile up in Alaska, it's been getting warmer and warmer, leading to "drunk forests" as the permafrost melts. They're not impressed one iota with it all!

I also note that whenever the lower 48 gets one of these cold blasts, it invariably fires up the jet and leads to Atlantic mush. (A few decades ago, i.e. 90s and earlier, the extra Atlantic energy generated by those US plunges sometimes went so far south that it "pumped up" blocking to our north, but as the jet has migrated northwards over time (and heights over Europe have risen as a consequence), that's much less common these days).

Still, I suppose it keeps the heating bills down. Now that the cold is a distant memory down here, it means just a few hours of heating a day!

As for the models, all I can say is that from my point of view they're showing mild conditions for the majority of us (e.g. Reading EPS ), but there remains a small chance, circa 10%, of cold conditions returning by the end of the year.

Further north, it's more interesting. Inverness , for example, looks likely to see a spell of very cold weather over and just after Christmas, with ice days likely.

It remains to be seen exactly where the jet, and hence the dividing line ends up being, but it's undeniable it's trended northwards these past few days. However, as long as it's nearby cold cannot be completely ruled out... as Doc said yesterday, my old catchphrase - of "as ever, more runs are needed" - is just as applicable today! 😄
Leysdown, north Kent
LeedsLad123
21 December 2022 15:54:10

Their surprise big freezes seem to happen every winter!

Originally Posted by: fairweather 


Well it’s a huge continental landmass, and cold Arctic air flooding south has no obstacles - no mountain ranges  going from west to east to keep the cold air north, no big body of water to moderate it. It’s just a straight path all the way down to Florida.

The US Deep South probably gets colder in winter than anywhere else in the world at the same latitude. Memphis in Tennessee fell to -21C in February last year - that’s further south than Malaga in Spain. 
Whitkirk, Leeds - 85m ASL.
Brian Gaze
21 December 2022 15:57:07



I also note that whenever the lower 48 gets one of these cold blasts, it invariably fires up the jet and leads to Atlantic mush. (A few decades ago, i.e. 90s and earlier, the extra Atlantic energy generated by those US plunges sometimes went so far south that it "pumped up" blocking to our north, but as the jet has migrated northwards over time (and heights over Europe have risen as a consequence), that's much less common these days).

Originally Posted by: Retron 



You've hit the nail on the head IMO. I've made the same point a number of times in recent years and it is essentially what Paul Bartlett was talking about a couple of decades ago. Look at the reanalysis charts from winters in the 1960s and often heights were much lower over Europe.
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
21 December 2022 16:10:38
Even the ICON has a window of opportunity in some NW quarters for a short period over the festive window.
Mark
Beckton, E London
Less than 500m from the end of London City Airport runway.
Brian Gaze
21 December 2022 16:13:07
GFS 12z is showing the possibility of a technical white Boxing Day in the far south west of England.

UserPostedImage
Brian Gaze
Berkhamsted
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"I'm not socialist, I know that. I don't believe in sharing my money." - Gary Numan
doctormog
21 December 2022 16:19:35
It’s unfortunate from a White Christmas perspective that the milder interlude coincides with Christmas Day for most parts and that the chance of at least a “technical” white day is just before or after the 25th in places. The BBC forecast this morning suggested that the colder air may move south just in time to give a White Christmas to northernmost parts. I’m not entirely convinced but we will see. Perhaps for the NW Highlands and Western Isles (as shown by the 12z GFS op run).
Brian Gaze
21 December 2022 16:26:29

We have a similar debate here every year. 😀 This could turn out to be a mild winter which produced one period of severe wintry weather - The Troll of Trondheim - but it is far too early to draw conclusions. In recent days I have read comments about "experts" elsewhere who are explaining why another very cold spell in the near future is "nailed on". As usual the predictions turn out to be more miss than hit because the blunt truth is that the best way of looking into the future, albeit not a very reliable one, is to study the data spewed out by a few of the models.

The NCEP  / ECMWF / UK Met suites are more than enough unless people are bored and trying to fill in time. Needless to say there will be comments about the model data jumping around, but if people didn't hang on to every run it would be make life a lot easier. In my update on 13/12 I suggested the chance of a nationwide cold spell returning during 20/12 to 26/12 was approximately 25%. In the days which followed that number would have fluctuated, but I'm confident that when averaged out over a period of days it would not have approached 50%. 

Just my take. 🙄 The Met Office update today will be worth a read but my guess is they will angle it in a less wintry direction on the whole than the current forecast.   

Originally Posted by: Brian Gaze 



Completely wrong.
Brian Gaze
Berkhamsted
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"I'm not socialist, I know that. I don't believe in sharing my money." - Gary Numan
Ally Pally Snowman
21 December 2022 16:31:13

Completely wrong.

Originally Posted by: Brian Gaze 



Indeed fairly wintry update from the Met office.  Wonder what they're seeing?
Bishop's Stortford 85m ASL.
doctormog
21 December 2022 16:39:29

Completely wrong.

Originally Posted by: Brian Gaze 



I would guess they are seeing, in the medium term, quite an anticyclonic outlook leading to colder conditions rather than a wintry blast as such? Prior to that a more unsettled spell with average temperatures bringing in brief passing risks of wintry weather in some locations. Charts like this would back up such a scenario (brief passing wintry risk in places): https://www.wetterzentrale.de/maps/GFSOPEU12_186_1.png  
Retron
21 December 2022 16:44:15

Indeed fairly wintry update from the Met office.  Wonder what they're seeing?

Originally Posted by: Ally Pally Snowman 


This might give a hint - I didn't know these charts existed until just now, I think they're new.

They're the 42-day ECM ensembles in meteogram form. Note that these are different to the more usual type, in that they show anomalies rather than absolute temperatures. This is for Reading, but pretty much anywhere is available by typing it in.

They show a signal for a cold first week of January and again for the second half of January. Nothing especially strong, but looking at the box-and-whisker charts it's around a 70% chance of colder-than-normal conditions at the beginning of Jan and around 65% at the end of the month... enough to be noted, I guess!

https://charts.ecmwf.int/products/opencharts_extended_meteogram?base_time=202212190000&lat=51.4333&lon=-1.0&station_name=Reading 

EDIT: And if you look up Inverness, for example, you'll see it barely struggles to average before dropping again. Looks like the mild/cold boundary will continue to be close to or over the UK, if ECM is correct anyway!

 
Leysdown, north Kent
Ally Pally Snowman
21 December 2022 16:47:41

This might give a hint - I didn't know these charts existed until just now, I think they're new.

They're the 42-day ECM ensembles in meteogram form. Note that these are different to the more usual type, in that they show anomalies rather than absolute temperatures. This is for Reading, but pretty much anywhere is available by typing it in.

They show a signal for a cold first week of January and again for the second half of January. Nothing especially strong, but looking at the box-and-whisker charts it's around a 70% chance of colder-than-normal conditions at the beginning of Jan and around 65% at the end of the month... enough to be noted, I guess!

https://charts.ecmwf.int/products/opencharts_extended_meteogram?base_time=202212190000&lat=51.4333&lon=-1.0&station_name=Reading 

EDIT: And if you look up Inverness, for example, you'll see it barely struggles to average before dropping again. Looks like the mild/cold boundary will continue to be close to or over the UK, if ECM is correct anyway!

 

Originally Posted by: Retron 



Very interesting.  A little more hope than usual perhaps. 
 
Bishop's Stortford 85m ASL.

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