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Brian Gaze
01 December 2014 18:58:04


The GFS 12z throughout the run shows a set up that we saw all too frequently in the Winters of the 90s and noughties, which resulted in a scarcity of cold/snow in many parts of the UK.


I agree with other posters that once the Azores High pattern sets itself in, it becomes very difficult to dislodge. The ECM in recent days appears more willing than GFS to link the Azores High with growing heights over Greenland but there are still no strong signals across any of the models for this to happen to such a degree to give anything other than a transient Northerly flow.


So not much to please cold/snow lovers in the current output. One thing I would say however is that I'd rather have an Azores High (current signals) rather than a Euro High any day, as with the former there is always a chance of displacement North to give a N/NW outbreak. A Euro High is a disaster as (a) it normally sticks around forever and (b) it just allows the jet stream to plunge over us into Scandi giving us endless periods of wind and rain.    


Originally Posted by: Arbroath 1320 


First class summary IMO.  As I said the other day I think it would be hard to find examples of very cold winters where the Bores high was strong, but it can lead to average conditions with marginal interest. Better than a slug sitting over the Alps.


Brian Gaze
Berkhamsted
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"I'm not socialist, I know that. I don't believe in sharing my money." - Gary Numan
Whether Idle
01 December 2014 19:05:49


 


First class summary IMO.  As I said the other day I think it would be hard to find examples of very cold winters where the Bores high was strong, but it can lead to average conditions with marginal interest. Better than a slug sitting over the Alps.


Originally Posted by: Brian Gaze 


Yes, those  "Berne Winters" daily posts from Dawlish back in 2006-8 about MSLP in Berne being greater than 1016mb still haunt me.


Dover, 5m asl. Half a mile from the south coast.
Quantum
01 December 2014 19:15:54

First major snowfall of the year (potentially)



Now this chart taken at face value may not look overly promising, but it has to be taken in the context of the airmass that is over the UK. This does have a chance (abeilt a small one) of producing a notable snow event in Scotland and perhaps even N england. Previous to this chart an unusually direct westerly imported cold air from canada with rather cold upper air temperatures. Now the upper air temperatures themselves are unremarkable (generally -4C to -6C at the 850hpa level) although barely cold enough to produce some wintry showers in the far west and more generally above 200m or so. However, in the wake of the next depression a ridge could cause cold air to stagnate at the surface, if this happens enough then a warm front pushing into that air could give significant snowfall. Some key factors are:


Strength of the warm front. Perhaps the most important, the weaker the warm front, the less likely snow will fall; this MUST be an ana warm front, a kata warm front will give rain without a doubt. Weak occluded fronts or secondary warm fronts ahead of the main warm front will be extremely counterproductive; this needs to be a clean division between a mild moist, and cold dry airmass. To this end the chart isn't that ideal; the red area gives likely snow coverage, but the front could do with being a little further south, because the tail is just too weak to produce snow, however this could easily be modified closer to the time.


Nature of the airmass the front pushes into. It needs to be both cold and dry for this to work, the more significant the ridging before the warm front incursion, the more likely snow will fall; i.e we need southerly winds, not southwesterly winds in an ideal world. It really is up in the air at the moment, but this is something I will be keeping a close eye on; I think it has the potential to catch a few people out.


 


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.
Polar Low
01 December 2014 19:48:03

Sod any cold weather for now We need that to carry on further North that has the right air mix to be a very nasty Storm for the North indeed!!


http://www.meteociel.fr/modeles/gfse_cartes.php?&ech=138&mode=0


http://www.meteociel.fr/modeles/gfse_cartes.php?&ech=186&mode=0


 


 

Stormchaser
01 December 2014 19:57:34

 


No chart available for the selected hour. Many charts start at 3 hours ahead, so if you have 0 hours selected try stepping forward or selecting a later hour.  No chart available for the selected hour. Many charts start at 3 hours ahead, so if you have 0 hours selected try stepping forward or selecting a later hour.


It makes a nice change to see ECM and GFSP looking fairly similar at 8-9 days range.


A chilly northwesterly, looks cold enough for some snow with elevation, perhaps to low levels overnight. These being in the form of showers in the polar maritime air mass.


Beyond this, perhaps an period of interest to keep an eye on for the warm air advection (WAA) aligning more N-S or even NNW-SSE:


No chart available for the selected hour. Many charts start at 3 hours ahead, so if you have 0 hours selected try stepping forward or selecting a later hour.  No chart available for the selected hour. Many charts start at 3 hours ahead, so if you have 0 hours selected try stepping forward or selecting a later hour.


GFS just throws energy over the ridge beyond this point but ECM has a hint of negative tilt to the trough (i.e. aligned NW-SE) and the right sort of WAA to encourage a ridge of high pressure NW of the UK, possibly extending east if the trough across the UK continues the southward motion seen from day 9 to day 10.


This does depend on the low off the East. U.S. Coast days 7-8 being far enough west to merge with a trough exiting Canada, which was not being shown this morning. The behaviour of that low has been changing with every run so yet again we are looking for the kind of luck which we have been granted in the past month. GEM's 12z run still has the low coming our way, but tracking quite far south. This means the Atlantic jet flattens out but the trough still aligns in the right way for height rises to occur over Scandinavia.


If we get the luck (hard to bet on that after the run we've been having), we open the door to either another dose of Arctic air from the north - the best we could manage from where GFSP is at day 10 - or some continental cold as the Russia/Scandinavia High extends westward, which ECM seems to be leading toward.


I think the height rises to our east would benefit us most in terms of strat. impacts. Perhaps a source of some comfort that such height rises are the Achilles' Heel of GFS/GFSP.


 


As with the November opportunities, we're still taking about conditions conducive to snow that are more regional than national and persist for at most a few days - nothing like the scale of events seen in December 2009 or 2010. If we ever manage do that this winter, it's not likely to be before week 3 of December at the very earliest, and that's probably pushing it.


Looking at ECM from the NH perspective though, it seems the model is up to it's old teasing ways with regards to continental cold advancing towards the UK - the trough is actually starting to head beneath the continental ridge:



Maybe one day one of these will verify 


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Keep Calm and Forecast On
Phil G
01 December 2014 19:58:08
Scandy high trying to exert it's influence
http://www.wetterzentrale.de/pics/Recm2402.gif 

Would help if that LP over us became a slider low.
Polar Low
01 December 2014 20:04:03

That gfs opp seems to be all over the place in about 6 days as do its members maybe a joey run James


http://www.wetterzentrale.de/pics/MT8_London_ens.png



 


No chart available for the selected hour. Many charts start at 3 hours ahead, so if you have 0 hours selected try stepping forward or selecting a later hour.  No chart available for the selected hour. Many charts start at 3 hours ahead, so if you have 0 hours selected try stepping forward or selecting a later hour.


It makes a nice change to see ECM and GFSP looking fairly similar at 8-9 days range.


A chilly northwesterly, looks cold enough for some snow with elevation, perhaps to low levels overnight. These being in the form of showers in the polar maritime air mass.


Beyond this, perhaps an period of interest to keep an eye on for the warm air advection (WAA) aligning more N-S or even NNW-SSE:


No chart available for the selected hour. Many charts start at 3 hours ahead, so if you have 0 hours selected try stepping forward or selecting a later hour.  No chart available for the selected hour. Many charts start at 3 hours ahead, so if you have 0 hours selected try stepping forward or selecting a later hour.


GFS just throws energy over the ridge beyond this point but ECM has a hint of negative tilt to the trough (i.e. aligned NW-SE) and the right sort of WAA to encourage a ridge of high pressure NW of the UK, possibly extending east if the trough across the UK continues the southward motion seen from day 9 to day 10.


This does depend on the low off the East. U.S. Coast days 7-8 being far enough west to merge with a trough exiting Canada, which was not being shown this morning. The behaviour of that low has been changing with every run so yet again we are looking for the kind of luck which we have been granted in the past month. GEM's 12z run still has the low coming our way, but tracking quite far south. This means the Atlantic jet flattens out but the trough still aligns in the right way for height rises to occur over Scandinavia.


If we get the luck (hard to bet on that after the run we've been having), we open the door to either another dose of Arctic air from the north - the best we could manage from where GFSP is at day 10 - or some continental cold as the Russia/Scandinavia High extends westward, which ECM seems to be leading toward.


I think the height rises to our east would benefit us most in terms of strat. impacts. Perhaps a source of some comfort that such height rises are the Achilles' Heel of GFS/GFSP.


 


As with the November opportunities, we're still taking about conditions conducive to snow that are more regional than national and persist for at most a few days - nothing like the scale of events seen in December 2009 or 2010. If we ever manage do that this winter, it's not likely to be before week 3 of December at the very earliest, and that's probably pushing it.


Looking at ECM from the NH perspective though, it seems the model is up to it's old teasing ways with regards to continental cold advancing towards the UK - the trough is actually starting to head beneath the continental ridge:



Maybe one day one of these will verify 


Originally Posted by: Stormchaser 

Medlock Vale Weather
01 December 2014 20:04:26

30% chance of snow for me on Sunday 


http://modeles.meteociel.fr/modeles/gens/runs/2014120112/graphe6_1000_257_41___.gif


 


Alan in Medlock Valley - Oldham's frost hollow. 103 metres above sea level.
What is a frost hollow? http://www.weatheronline.co.uk/reports/wxfacts/Frost-hollow.htm 
Quantum
01 December 2014 20:10:48

No chart available for the selected hour. Many charts start at 3 hours ahead, so if you have 0 hours selected try stepping forward or selecting a later hour.


The warm front snow really showing up on the Inverness GEFS with all 20 members going for it. I'm really surprised there isn't more interested in this event, warm fronts can really deliver; -5C isotherm in a Nwerly isn't going to unless you have a bit of elevation.


 


 


 


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.
Polar Low
01 December 2014 20:11:47

Dont think ive seen so cold 850,s reach that far west on that jap run


http://www.meteociel.fr/modeles/jma.php?ech=144&mode=0


Medlock Vale Weather
01 December 2014 21:14:18


Dont think ive seen so cold 850,s reach that far west on that jap run


http://www.meteociel.fr/modeles/jma.php?ech=144&mode=0



Originally Posted by: Polar Low 


Indeed PL. Another chart on the JMA run shows even colder air moving into Ireland & other western areas with widely -6 & -7 uppers, some snow no doubt even for low levels I would have thought. Beast from the west??? 


Alan in Medlock Valley - Oldham's frost hollow. 103 metres above sea level.
What is a frost hollow? http://www.weatheronline.co.uk/reports/wxfacts/Frost-hollow.htm 
Brian Gaze
01 December 2014 22:20:08


No chart available for the selected hour. Many charts start at 3 hours ahead, so if you have 0 hours selected try stepping forward or selecting a later hour.


The warm front snow really showing up on the Inverness GEFS with all 20 members going for it. I'm really surprised there isn't more interested in this event, warm fronts can really deliver; -5C isotherm in a Nwerly isn't going to unless you have a bit of elevation.


 


Originally Posted by: Quantum 


The max on the snow row is 23.


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
01 December 2014 22:27:28


 


The max on the snow row is 23.


Originally Posted by: Brian Gaze 


OK my bad, I guess the OP, Control and Pall; but still its fairly impressive, I think even newcastle has about 8. I can't understand why there isn't more interest in this, slack northwesterlies with uppers barely at -5C only deliver for the far north west and the high ground, but warm fronts can be major events; why are people concentrating on the former and not the later even if the former is somewhat more 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.
Polar Low
01 December 2014 22:34:31

As I expected a nasty looking storm on the pub 18z parallel


http://www.meteociel.fr/modeles/gfse_cartes.php?&ech=156&mode=0&runpara=1&carte=1


 

nsrobins
01 December 2014 22:37:06


 


why are people concentrating on the former and not the later even if the former is somewhat more likely? 


Originally Posted by: Quantum 


There is a moderate signal for some wintry ppn on Sunday night at elevation in the North I agree, but it's December! I don't think too many are as enthusiastic about it as you are. Not saying it's a bad thing, but if a few sleety showers on the Cheviots get you this excited I fear you won't last the winter


Neil
Fareham, Hampshire 28m ASL (near estuary)
Stormchaser, Member TORRO
Quantum
01 December 2014 22:43:23


 


There is a moderate signal for some wintry ppn on Sunday night at elevation in the North I agree, but it's December! I don't think too many are as enthusiastic about it as you are. Not saying it's a bad thing, but if a few sleety showers on the Cheviots get you this excited I fear you won't last the winter


Originally Posted by: nsrobins 


But this is the point, it isn't a few sleety showers, I'm not talking about the unstable polar maritime feed, I'm talking about the warm front on monday or tuesday depending on the model. There is the potential, and I admit it is very tenuous at this stage, but it does exist, for significant widespread snow for as much as 12, even 18 hours. Hell if everything goes right Aberdeen could get 20cm; and while I think this is highly unlikely it is possible, and no where short of 400m up is going to see accumulating snow out of the showers before and after.  


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.
Polar Low
01 December 2014 22:46:46

Perhaps a bit less than 200m but a small window Q


Freezing level GFS Su 07.12.2014 18 GMT


Q quote=Quantum;647994]


First major snowfall of the year (potentially)



Now this chart taken at face value may not look overly promising, but it has to be taken in the context of the airmass that is over the UK. This does have a chance (abeilt a small one) of producing a notable snow event in Scotland and perhaps even N england. Previous to this chart an unusually direct westerly imported cold air from canada with rather cold upper air temperatures. Now the upper air temperatures themselves are unremarkable (generally -4C to -6C at the 850hpa level) although barely cold enough to produce some wintry showers in the far west and more generally above 200m or so. However, in the wake of the next depression a ridge could cause cold air to stagnate at the surface, if this happens enough then a warm front pushing into that air could give significant snowfall. Some key factors are:


Strength of the warm front. Perhaps the most important, the weaker the warm front, the less likely snow will fall; this MUST be an ana warm front, a kata warm front will give rain without a doubt. Weak occluded fronts or secondary warm fronts ahead of the main warm front will be extremely counterproductive; this needs to be a clean division between a mild moist, and cold dry airmass. To this end the chart isn't that ideal; the red area gives likely snow coverage, but the front could do with being a little further south, because the tail is just too weak to produce snow, however this could easily be modified closer to the time.


Nature of the airmass the front pushes into. It needs to be both cold and dry for this to work, the more significant the ridging before the warm front incursion, the more likely snow will fall; i.e we need southerly winds, not southwesterly winds in an ideal world. It really is up in the air at the moment, but this is something I will be keeping a close eye on; I think it has the potential to catch a few people out.


 


Brian Gaze
01 December 2014 22:51:41

The GFSP storm looks ridiculous:



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
Quantum
01 December 2014 22:52:26

I mean different models are handling this low very differently, so it is very difficult to make a call; but I am amazed people don't seem to be seeing the potential. The JMA and ECM in particular are very promising, a slight modification of the system south could give some non-trivial snow event for Scotland; and not just to higher ground. The JMA and GEM both occlude the warm front as it moves through, so these models give the prospect of some very persistent snow, hence the possibility of a 12+ hour event. The GFS and Navgem go for a much more tightly bound, juvenile system which if tracking slightly further south than it is at the moment could give a spell of heavy snow on its northern edge. 


And the models seem to be upgrading the strength of this front, be it warm or occluded, the stronger the front the more likely this delivers. 


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
01 December 2014 22:54:59

More worrying than the threat of wintry precipitation:



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
Polar Low
01 December 2014 22:56:58

indeed Brian 


 



More worrying than the threat of wintry precipitation:



Originally Posted by: Brian Gaze 

Quantum
01 December 2014 22:57:40

Modele GFS - Carte prévisions


GFS para actually has the frontal snow right into Northern England, and it is probably underestimating the potential here; given that the ECM/GEM/JMA all are far more favourable. 


 


EDIT: nevermind, this is just the showery garbage before the LP. 


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.
Matty H
01 December 2014 22:57:58


 


There is a moderate signal for some wintry ppn on Sunday night at elevation in the North I agree, but it's December! I don't think too many are as enthusiastic about it as you are. 


Originally Posted by: nsrobins 


Basically, The Doc is going to chew you to pieces and then spit you out! 


Polar Low
01 December 2014 23:01:22

Nav starts to see it now


 


Quantum
01 December 2014 23:01:51

 


Appologies for that embarrasing mistake. This is the real deal:



The frontal system is really quite obvious, the cold front trails in the south atlantic, whereas the warm front gives snow on its leading edge for scotland. If this system were somewhat further south and perhaps bigger (think of a hybrid between the GFS, ECM,JMA and GEM solutions) then there is very large potential for widespread snow in scotland and perhaps the extreme north of England. 


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.

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