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Quantum
  • Quantum
  • Advanced Member Topic Starter
18 November 2024 13:27:43
The heaviest precip at the moment is around eastern anglesy in wales. In even the most progressive model runs, the precip hasn't even reached there yet. Fronts clearly more progressive and/or stronger than expected. I think its a good sign for most people.

2024/2025 Snow days (approx 850hpa temp): Total: 2 days with snow/sleet falling
18/11 (-6), 19/11 (-6)
2023/2024 Snow days (approx 850hpa temp): Total: 8 days with snow/sleet falling
29/11 (-6), 30/11 (-6), 02/12 (-5), 03/12 (-5), 04/12 (-3), 16/01 (-3), 18/01 (-8), 08/02 (-5)
2022/2023 Snow days (approx 850hpa temp): Total: 7 days with snow/sleet falling.
18/12 (-1), 06/03 (-6), 08/03 (-8), 09/03 (-6), 10/03 (-8), 11/03 (-5), 14/03 (-6)
2021/2022 Snow days (approx 850hpa temp): Total: 12 days with snow/sleet falling.
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)
Boardshark
18 November 2024 13:40:43
Which model was closest to the actual present conditions?
449ft Sutton Coldfield, West MIdlands
Quantum
  • Quantum
  • Advanced Member Topic Starter
18 November 2024 14:11:56

Which model was closest to the actual present conditions?

Originally Posted by: Boardshark 


Probably the GFS initialized WRF, which doesn't suprise me actually. Its usually good at getting the position of fronts largelly right.

2024/2025 Snow days (approx 850hpa temp): Total: 2 days with snow/sleet falling
18/11 (-6), 19/11 (-6)
2023/2024 Snow days (approx 850hpa temp): Total: 8 days with snow/sleet falling
29/11 (-6), 30/11 (-6), 02/12 (-5), 03/12 (-5), 04/12 (-3), 16/01 (-3), 18/01 (-8), 08/02 (-5)
2022/2023 Snow days (approx 850hpa temp): Total: 7 days with snow/sleet falling.
18/12 (-1), 06/03 (-6), 08/03 (-8), 09/03 (-6), 10/03 (-8), 11/03 (-5), 14/03 (-6)
2021/2022 Snow days (approx 850hpa temp): Total: 12 days with snow/sleet falling.
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)
roadrunnerajn
18 November 2024 14:18:35
I would say the southern half of the Peak District could well do alright for snow. I imagine it will start as sleety rain below 1000ft but quickly drop to 330ft 100m by late evening. … just what I see looking at the latest modelling.
Germoe, part of the breakaway Celtic Republic.
Quantum
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18 November 2024 14:20:09
Yeh the WRF has it much better than the others:
https://www.meteociel.fr/modeles/wrfnmm.php?ech=3&mode=24&map=330 

AROME, UKV, HIRLAM e.c.t. are not even close. The WRF has most of it right but still about 50-100 miles too far SW.

2024/2025 Snow days (approx 850hpa temp): Total: 2 days with snow/sleet falling
18/11 (-6), 19/11 (-6)
2023/2024 Snow days (approx 850hpa temp): Total: 8 days with snow/sleet falling
29/11 (-6), 30/11 (-6), 02/12 (-5), 03/12 (-5), 04/12 (-3), 16/01 (-3), 18/01 (-8), 08/02 (-5)
2022/2023 Snow days (approx 850hpa temp): Total: 7 days with snow/sleet falling.
18/12 (-1), 06/03 (-6), 08/03 (-8), 09/03 (-6), 10/03 (-8), 11/03 (-5), 14/03 (-6)
2021/2022 Snow days (approx 850hpa temp): Total: 12 days with snow/sleet falling.
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)
nsrobins
18 November 2024 15:07:05
As tiring as it is to read all the ‘north/south’ debate on the various forums, it is a decent essay in the fine detail of the high-res models we have available and a lesson if it needed to be delivered that even the most impressive algorithms will still struggle from time to time with the nuances of the rain/snow situation in the UK.
To be fair, I’d take an old-school screaming easterly any day over this ‘modern’ marginal gunk - nailed on for us far-southerners.
On topic, and the ppn looks to be developing as per a blend of the output and I still expect an area between say Leicester and the M62 corridor to see a covering of snow by the morning.
Neil
Fareham, Hampshire 28m ASL (near estuary)
Stormchaser, Member TORRO
Saint Snow
18 November 2024 15:24:39


To be fair, I’d take an old-school screaming easterly any day over this ‘modern’ marginal gunk - nailed on for us far-southerners.

Originally Posted by: nsrobins 



Another decent essay would be on how different parts of a relatively small country rely on wholly different weather set-ups to get good snow!

I think there'll need to be some elevation to get lying snow - but do reckon the northern extent of the 'snow area' will be around 60-80 miles further north than the M62.

Incidentally, the latest NW radar has snow now falling across Dumfries and Galloway, but the traffic cams show nothing.



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
Snowfairy
18 November 2024 15:37:02
Hoping to see something wintery here in North Notts, Retford.
Caz
  • Caz
  • Advanced Member
18 November 2024 16:06:22

Hoping to see something wintery here in North Notts, Retford.

Originally Posted by: Snowfairy 


Thinking the same here in Warsop.  Although  we visit our daughter in Retford on Tuesdays, so that might prove difficult if we get much. 
Market Warsop, North Nottinghamshire.
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Saint Snow
18 November 2024 16:09:26
Radar shows rain over us right now but it's still dry.



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
scillydave
18 November 2024 16:19:37
Well that's thrown the cat amongst the pigeons a bit. The 12z GEM, GFS and Arome all show a period of snow for Central, South Wales and into parts of the Southwest overnight into Tuesday. 
Interesting times ahead!
Currently living at roughly 65m asl North of Cowbridge in the Vale of Glamorgan.

Formerly of, Birdlip, highest village in the Cotswolds and snow heaven in winter; Hawkinge in Kent - roof of the South downs and Isles of Scilly, paradise in the UK.
Quantum
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  • Advanced Member Topic Starter
18 November 2024 16:53:08

Well that's thrown the cat amongst the pigeons a bit. The 12z GEM, GFS and Arome all show a period of snow for Central, South Wales and into parts of the Southwest overnight into Tuesday. 
Interesting times ahead!

Originally Posted by: scillydave 


And there is another possible system for northern areas on thursday, pretty uncertain times.

2024/2025 Snow days (approx 850hpa temp): Total: 2 days with snow/sleet falling
18/11 (-6), 19/11 (-6)
2023/2024 Snow days (approx 850hpa temp): Total: 8 days with snow/sleet falling
29/11 (-6), 30/11 (-6), 02/12 (-5), 03/12 (-5), 04/12 (-3), 16/01 (-3), 18/01 (-8), 08/02 (-5)
2022/2023 Snow days (approx 850hpa temp): Total: 7 days with snow/sleet falling.
18/12 (-1), 06/03 (-6), 08/03 (-8), 09/03 (-6), 10/03 (-8), 11/03 (-5), 14/03 (-6)
2021/2022 Snow days (approx 850hpa temp): Total: 12 days with snow/sleet falling.
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)
overland
18 November 2024 16:59:49
Snow already being reported in north Staffs.
Mumbles, Swansea. 80m asl
haghir22
18 November 2024 17:02:32
Chucking it down with rain here in Epsom, coming across the Downs earlier and the car thermometer dropped from 8c to 5c really quickly. Here's optimistically hoping for a surprise in the morning, it certainly had 'that feel' but I know very unlikely.
YNWA
Quantum
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  • Advanced Member Topic Starter
18 November 2024 17:17:31
If I'm honest the pattern is much more similar to yesterday morning's UKV than any of today's runs.

2024/2025 Snow days (approx 850hpa temp): Total: 2 days with snow/sleet falling
18/11 (-6), 19/11 (-6)
2023/2024 Snow days (approx 850hpa temp): Total: 8 days with snow/sleet falling
29/11 (-6), 30/11 (-6), 02/12 (-5), 03/12 (-5), 04/12 (-3), 16/01 (-3), 18/01 (-8), 08/02 (-5)
2022/2023 Snow days (approx 850hpa temp): Total: 7 days with snow/sleet falling.
18/12 (-1), 06/03 (-6), 08/03 (-8), 09/03 (-6), 10/03 (-8), 11/03 (-5), 14/03 (-6)
2021/2022 Snow days (approx 850hpa temp): Total: 12 days with snow/sleet falling.
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)
Russwirral
18 November 2024 17:25:39
Heavy sleet here on wirral... big clumpy wet flakes on my windscreen..t emp 3.5*c
Brian Gaze
18 November 2024 17:44:46
I've added snow pellets to the TWO Arome plots after the earlier discussion.

https://www.theweatheroutlook.com/twodata/arome.aspx?run=12&charthour=19&chartname=preciprate&chartregion=uk-region&charttag=Precip%20rate 

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
Quantum
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  • Advanced Member Topic Starter
18 November 2024 17:47:38

I've added snow pellets to the TWO Arome plots after the earlier discussion.

https://www.theweatheroutlook.com/twodata/arome.aspx?run=12&charthour=19&chartname=preciprate&chartregion=uk-region&charttag=Precip%20rate 

UserPostedImage

Originally Posted by: Brian Gaze 


I'm assuming you do a threshold calculation to determine type bins. You could add sleet aswell by creating a bin that must contain 0.3-0.5 rain and 0.3-0.5 snow.

2024/2025 Snow days (approx 850hpa temp): Total: 2 days with snow/sleet falling
18/11 (-6), 19/11 (-6)
2023/2024 Snow days (approx 850hpa temp): Total: 8 days with snow/sleet falling
29/11 (-6), 30/11 (-6), 02/12 (-5), 03/12 (-5), 04/12 (-3), 16/01 (-3), 18/01 (-8), 08/02 (-5)
2022/2023 Snow days (approx 850hpa temp): Total: 7 days with snow/sleet falling.
18/12 (-1), 06/03 (-6), 08/03 (-8), 09/03 (-6), 10/03 (-8), 11/03 (-5), 14/03 (-6)
2021/2022 Snow days (approx 850hpa temp): Total: 12 days with snow/sleet falling.
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)
scillydave
18 November 2024 17:59:36

I've added snow pellets to the TWO Arome plots after the earlier discussion.

https://www.theweatheroutlook.com/twodata/arome.aspx?run=12&charthour=19&chartname=preciprate&chartregion=uk-region&charttag=Precip%20rate 

UserPostedImage

Originally Posted by: Brian Gaze 


It's an excellent addition Brian but it totally pooped on my snow party🤣
Currently living at roughly 65m asl North of Cowbridge in the Vale of Glamorgan.

Formerly of, Birdlip, highest village in the Cotswolds and snow heaven in winter; Hawkinge in Kent - roof of the South downs and Isles of Scilly, paradise in the UK.
Retron
18 November 2024 18:05:41

I've added snow pellets to the TWO Arome plots after the earlier discussion.

Originally Posted by: Brian Gaze 


Looks good!

I'm curious, though, as to how it works behind the scenes. Does the model (or any model, for that matter) handle mixed precipitation types? We all know full well, for example, that if graupel's around it tends to be mainly in heavier bursts, and there's often bits of rain and sleet mixed in too. The chart as shown by AROME is thus most unlikely to happen, showing as it does a massive area of graupel, as there would be bound to be rain/sleet mixed in.

Similarly, xcweather does something with the GFS data to enable it to come up with sleet forecasts. I know we discussed the other day about GFS having a snow parameter, and how it gets flagged if it's just sleet, but xc is doing something to differentiate between snow, rain and sleet... almost as if there's a "snow amount" and a "rain amount", and if both are non-zero then it defaults to sleet.

I've not looked at raw GRIB data before, though, so don't know how precipitation is handled. For all I know it could just be an "x mm this period" number, then a "snow" or "graupel" flag on top....
Leysdown, north Kent
dagspot
18 November 2024 18:32:10
Ben Rich giving  damp squib vibe on 630 news..  highest peaks, sleet etc 
Neilston 600ft ASL
Quantum
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  • Advanced Member Topic Starter
18 November 2024 18:43:19

Looks good!

I'm curious, though, as to how it works behind the scenes. Does the model (or any model, for that matter) handle mixed precipitation types? We all know full well, for example, that if graupel's around it tends to be mainly in heavier bursts, and there's often bits of rain and sleet mixed in too. The chart as shown by AROME is thus most unlikely to happen, showing as it does a massive area of graupel, as there would be bound to be rain/sleet mixed in.

Similarly, xcweather does something with the GFS data to enable it to come up with sleet forecasts. I know we discussed the other day about GFS having a snow parameter, and how it gets flagged if it's just sleet, but xc is doing something to differentiate between snow, rain and sleet... almost as if there's a "snow amount" and a "rain amount", and if both are non-zero then it defaults to sleet.

I've not looked at raw GRIB data before, though, so don't know how precipitation is handled. For all I know it could just be an "x mm this period" number, then a "snow" or "graupel" flag on top....

Originally Posted by: Retron 


AROME has I think separate parameters for each precipitation type. If you want to show mixed precip then you can do that by specifying that both the rain and snow parameters are within a specified interval proportion of the total precipitation (which will be the sum of all the precip type parameters).

2024/2025 Snow days (approx 850hpa temp): Total: 2 days with snow/sleet falling
18/11 (-6), 19/11 (-6)
2023/2024 Snow days (approx 850hpa temp): Total: 8 days with snow/sleet falling
29/11 (-6), 30/11 (-6), 02/12 (-5), 03/12 (-5), 04/12 (-3), 16/01 (-3), 18/01 (-8), 08/02 (-5)
2022/2023 Snow days (approx 850hpa temp): Total: 7 days with snow/sleet falling.
18/12 (-1), 06/03 (-6), 08/03 (-8), 09/03 (-6), 10/03 (-8), 11/03 (-5), 14/03 (-6)
2021/2022 Snow days (approx 850hpa temp): Total: 12 days with snow/sleet falling.
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)
Caz
  • Caz
  • Advanced Member
18 November 2024 18:44:27
Sleety snow just started here. My sister 7 miles away near Sutton in Ashfield is reporting big snow flakes there. 
Market Warsop, North Nottinghamshire.
Join the fun and banter of the monthly CET competition.
Rob K
18 November 2024 18:49:50
A good example of how the weather apps can mislead people. Tomorrow shows a max of 11C on my app. But looking smart the hourly readings that maximum comes at 4am (up from 6C now at 7pm!) and by midday it will be just 4 or 5C. 
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
Saint Snow
18 November 2024 19:00:39
Moderate rain here

(Which is what was forecast - want to see it turn sleety within the next hour or so, then hopefully to snow by midnight)

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

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