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Model Output Discussion - Stormy Period Inbound...


Paul

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Posted
  • Location: portsmouth uk
  • Weather Preferences: extremes
  • Location: portsmouth uk

in broad terms the back end of PTRB 17 on the 12z gefs is a representation of where I think the NH pattern is going. Within two weeks would be a bit quick though.

attachicon.gifimage.jpg

but watch the eye candy expecting more eye candy charts theres with out question a marked change afoot this is now starting to show more wintry heart of winter.

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Posted
  • Location: Brighton (currently)
  • Location: Brighton (currently)

Though storms are rightly the main focus for next week, disruptive snowfall looks sure to happen too. First, Sunday morning - places like Belfast, Edinburgh and Newcastle could be covered:

15011106_0906.gif

Into next week and although the GFS snow charts are notorious for phantom snow events, snow is flying about all over the place on them:

108-779PUK.GIF?09-6

144-779PUK.GIF?09-6

156-779PUK.GIF?09-6

 

I think there is some justification in these charts, as I have rarely seen such a potent PM period coming up - usually 850s from these scenarios are around -4C, which is why we associate them with "high ground" only events - but I'm seeing a lot of -6C / -7C 850s in the days ahead - it could make all the difference. An interesting week ahead.

I am surprised by the first chart to be honest. According to that there will be no lying snow in the Pennines under a cold west/northwesterly flow? How could that be? Plenty of showers are expected in the area and they can't be of rain with uppers in the range of -5 to -7

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Posted
  • Location: Locksbottom, NW Kent 92m asl(310ft)
  • Weather Preferences: Warm summers but not too hot and colder winters with frost and snow
  • Location: Locksbottom, NW Kent 92m asl(310ft)

There is strong support from the GEFS 06z control run for a nationwide cold snap later next week, as per met office update mentioning wintry showers and looking further ahead, reloading cold shots from the north west seems a good bet at this point.

Yes and this type of set up backs up my earlier post where the snow is likely to fall in a NW airflow.Good luck to those who get the snow and send in the pics as and when it happens so those of us in SE and EA can get more depressed lol(sorry off topic)

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Posted
  • Location: Lytchett Matravers - 301 ft ASL
  • Weather Preferences: Snowy Winters, Torrential Storm Summers
  • Location: Lytchett Matravers - 301 ft ASL

There is strong support from the GEFS 06z control run for a nationwide cold snap later next week, as per met office update mentioning wintry showers and looking further ahead, reloading cold shots from the north west seems a good bet at this point.

 

Not that cold though Frosty  :wallbash:

 

gens-21-4-174.pnggens-21-4-204.png

gens-21-4-312.png

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Posted
  • Location: portsmouth uk
  • Weather Preferences: extremes
  • Location: portsmouth uk

Regarding the current output we have the gfs showing a 935mb low for next week. But it does seem as though the ECM isn't intrested at the moment. So I would say possibly the gfs is once again over doing the low pressure system. Now looking at next week we have plenty of -6 to -7 uppers in a cold pm flow which I would suggest will bring some heavy snowfall say North of Birmingham. And regarding the latest ec32 dayer Matt Hugo has stated not much confidence in it after week 2. So all to play for I would say.

i think from what ive seen that the continued push of lower heights futher and futher south east with -7 even -6 air is very much a below average pattern also cold enough for snowfall anywhere in the uk.

 

although birmingham north tends to have more sustained -4 to -6 upper air for a good part of the runs so very snowy and very much stormy and this stormy weather starting to make its way more and more south east.

 

i think its very possible that heights will get a chance to build once the vortex has moved to a different location this possibly around the scandi area.

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Posted
  • Location: Manchester
  • Weather Preferences: Sunny and warm in the Summer, cold and snowy in the winter, simples!
  • Location: Manchester

I am surprised by the first chart to be honest. According to that there will be no lying snow in the Pennines under a cold west/northwesterly flow? How could that be? Plenty of showers are expected in the area and they can't be of rain with uppers in the range of -5 to -7

 

Yes Western facing Pennine areas further South should see temporarary snow accumulations. Snow accumulation maps should be taken with a large dose of salt, they are fairly inaccurate on the whole and local weather knowledge will always trump them.

Even Euro4 which is supposed to be among the best and only goes out to 48h  is rather poor IMO - at least it has been for my area.

Edited by Mucka
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Posted
  • Location: Peterborough
  • Weather Preferences: Snow and frost in the winter. Hot and sunny, thunderstorms in the summer.
  • Location: Peterborough

Yes Western facing Pennine areas further South should see temporarary snow accumulations. Snow accumulation maps should be taken with a large dose of salt, they are fairly inaccurate on the whole and local weather knowledge will always trump them.

Even Euro4 which is supposed to be among the best and only goes out to 48h  is rather poor IMO - at least it has been for my area.

It would help if there was a scale but here is a snow depth map for Sunday morning (GFS P)

uksnowdepth.png

The freezing level looks poor though (never getting below 300m), but it should be cold enough overnight for temporary accumulations from the heavier showers. The snow will generally melt through the day as 850s and surface temperatures rise to near normal levels during the day as the next front approaches from the west.

Yay for experimental charts :p Conclusion - there should(???) be some accumulations of snow for the usual areas near Irish sea coasts. 

Edited by Captain shortwave
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Posted
  • Location: Brighton (currently)
  • Location: Brighton (currently)

Yes Western facing Pennine areas further South should see temporarary snow accumulations. Snow accumulation maps should be taken with a large dose of salt, they are fairly inaccurate on the whole and local weather knowledge will always trump them.

Even Euro4 which is supposed to be among the best and only goes out to 48h  is rather poor IMO - at least it has been for my area.

Yes, that's true. I usually find that the accumulation chart overdo the snow that's why this chart is even more surprising. I think the one that Captain Shortwave posted looks more realistic.

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Posted
  • Location: Reigate Hill
  • Weather Preferences: Anything
  • Location: Reigate Hill

Yes, that's true. I usually find that the accumulation chart overdo the snow that's why this chart is even more surprising. I think the one that Captain Shortwave posted looks more realistic.

 

Yes it is mainly coastal showers, west and NW:  post-14819-0-95793800-1420818090_thumb.gpost-14819-0-32417000-1420818091_thumb.g

 

The cold front is mainly rain and it decays as it reaches the Midland's>south. In Scotland some backedge snow possible from that front.

 

How much the coastal showers add up to is debatable and they are probably hit and miss.

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Posted
  • Location: West Northants
  • Weather Preferences: Cold Winters, Warm Summers.
  • Location: West Northants

06Z - hope this gets a downgrade TBH

 

T+138 Thursday 15th - was this date an anniversary  - 1991?

 

attachicon.gifh500slp.png

 

Ian

 

Start of the 1st Gulf War?

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Posted
  • Location: Brighton (currently)
  • Location: Brighton (currently)

Yes it is mainly coastal showers, west and NW:  attachicon.gif24-779UK.gifattachicon.gif36-779UK.gif

 

The cold front is mainly rain and it decays as it reaches the Midland's>south. In Scotland some backedge snow possible from that front.

 

How much the coastal showers add up to is debatable and they are probably hit and miss.

That's more realistic. My location does pretty well under a westerly and although not cold enough for accumulations on low ground I expect to see a fair few snow showers by tomorrow night like the GFS suggests. Snow will have no problem settling in elevated areas further east.

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Posted
  • Location: Manchester
  • Weather Preferences: Sunny and warm in the Summer, cold and snowy in the winter, simples!
  • Location: Manchester

It would help if there was a scale but here is a snow depth map for Sunday morning (GFS P)

uksnowdepth.png

The freezing level looks poor though (never getting below 300m), but it should be cold enough overnight for temporary accumulations from the heavier showers. The snow will generally melt through the day as 850s and surface temperatures rise to near normal levels during the day as the next front approaches from the west.

Yay for experimental charts :p Conclusion - there should(???) be some accumulations of snow for the usual areas near Irish sea coasts. 

 

Yes we are getting a bit near regional discussion again here. Any accumulations this weekend will be temporary and require some elevation, I'm fairly sure of that and don't expect to see anything for my area for example though hope to see some snow showers falling.

But, and here is the problem, some surrounding areas not many miles away from me will quite possible see some snow on the ground Sunday morning and these further inland than any snowmap will suggest. I'm not going to run through all the locations as locals will know what to expect in these areas.

The models simply can't be run at high enough resolution for this level of detail and anyway in a showery regime they are not that great at picking up where the showers will develop and how far inland they will push and so any accumulation charts will be inaccurate before they start - that and the height (terrain) maps are not accurate enough and local weather effects are not well enough modelled. Always a big problem for my location for any snow forecast to come from a front moving i from the SW against cold air as I've lost count of the times a heavy fall has been forecast and I have seen snizzle if I'm lucky.

Also timing plays a part. Often dawn can be coldest and showrs more wintry early hours than afternoon all things being equal in marginal situations.

 

Just recently my Sister and Brother in law were down and the forecasts they had and their weather apps did not point to a boxing day fall of snow for Sheffield and it was only because they know I'm a weather geek that they took heed of my warning that they would get home to lying snow and and that pennine routes would likely be closed.

This time they will likely be okay because they are not West facing but some heavier showers may penetrate that far east - they shouldn't see lying snow though even with the extra elevation whereas some West facing areas with less altitude may well see lying snow.

 

The Cheshire gap shower effect is well known of course but even now it is very poorly modelled probably due to low res or inaccurate height maps. 

On top of that any subtle shifts in wind direction can make a big dffrence locally to whether we get rain /sleet/snow showers or even stay mainly dry so I am not really criticising the models for being poor, just that ppn rates, accum totals are best treated as a rough guide and not even that if you want to get down to a more local level.

 

Edit.

I should add I am talking about this weekend when mentioning local possible snowfall areas. I hope to see some lying snow at some point next week though it will be here and gone affair if it happens.

Edited by Mucka
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Posted
  • Location: Reigate Hill
  • Weather Preferences: Anything
  • Location: Reigate Hill

Big differences on the GFS op re next Wednesday's storm but still looks like the south will take a battering:

 

post-14819-0-41080000-1420819807_thumb.p post-14819-0-06121700-1420819807_thumb.p

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Posted
  • Location: Reigate Hill
  • Weather Preferences: Anything
  • Location: Reigate Hill

GFS P re the storm at D5-6 could be very stormy south coast:  post-14819-0-86648400-1420820571_thumb.p

 

...and dangerous in the north: post-14819-0-39035100-1420820805_thumb.p

 

The GFS op on the 15th hints at maybe back edge snow from the cold front passing SE: post-14819-0-94692500-1420820683_thumb.p

 

But dies south of the Midlands.

 

 

Edited by i'm dreaming of...
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Posted
  • Location: leicester
  • Location: leicester

Charts continue to look wild ad wintry next week!! Ukmo 144 hour chart looks scary! ! Everything but the kitchen sink on that chart!!! Very stormy! !

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Posted
  • Location: Reigate Hill
  • Weather Preferences: Anything
  • Location: Reigate Hill

Only one run but some very mild uppers moving in at D9+ from GFS op:

 

post-14819-0-68073500-1420821180_thumb.p  post-14819-0-28188000-1420821180_thumb.p

 

D11: post-14819-0-34207500-1420821215_thumb.p  D12: post-14819-0-28878100-1420821282_thumb.p

 

So uncertainty re the cold now and more like the early December pattern showing up.

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Posted
  • Location: Batley, West Yorkshire
  • Weather Preferences: Heat and Snow
  • Location: Batley, West Yorkshire

Only one run but some very mild uppers moving in at D9+ from GFS op:

 

But cold and wintry in the near term for many :)

 

and day 9+ will change on the next run, so plenty to be positive for now.

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Posted
  • Location: Manchester
  • Weather Preferences: Sunny and warm in the Summer, cold and snowy in the winter, simples!
  • Location: Manchester

GEM continues to model a fairly slack trough rather than a storm though it does have some small features zipping across the country.

 

gemnh-0-150.png?12

 

It has been pretty awful so far though and little support which is a shame because FI is reasonable.

 

gemnh-0-192.png?12

Edited by Mucka
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Posted
  • Location: Manchester
  • Weather Preferences: Sunny and warm in the Summer, cold and snowy in the winter, simples!
  • Location: Manchester

I think some living further North in the UK will likely disagree with your last sentence. There could easily be something wintry of note for them over the coming week or so.

 

Yes. I think where there is an obvious North/south divide to the type of weather likely to be experienced we should take care not to make NIMBY posts as though they apply to the whole of England/UK.

Anyway there is growing support for possible widespread snow event across central areas around the 13th within GFS ensembles.

Edited by Mucka
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