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Model Output Discussions 18z 31/01/2016


phil nw.

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Posted
  • Location: Irlam
  • Location: Irlam
38 minutes ago, IPredictASnowStorm said:

waste of snow Really as it is Showing Rain Before it turns to snow  on the  Gfs Charts so It is going to be Wet snow. So it probably wont lye anywhere:angry: 

I would argue though you could be a witness to a rare event. How often do you see a front coming in from the Atlantic going from rain to snow due to colder air digging in from the west? 

Vast majority it is the other way round or cold air comes in from the east and undercuts it.

 

Edited by Weather-history
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Posted
  • Location: blackburn
  • Weather Preferences: heavy snow/ heatwaves
  • Location: blackburn
8 minutes ago, snowangel32 said:

Don't worry we have all made mistakes as we learn, the front at first is expected to be rain but with back edge snow as the colder air mixes in a very unusual set up and one that is to close to call. 12z stays with theme from this morning of sleet and snow Wednesday night into Thursday morning for central England and East Anglia. 

I posted too early...although i still feel a large letdown is imminent for most of us.

 

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

UKMO take on the uppers and precip at +72, seems today we are at least seeing some consistency in the output. What it delivers is a different matter.

 

image.gif

image.gif

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Posted
  • Location: Stroud, Gloucestershire
  • Weather Preferences: Extreme!
  • Location: Stroud, Gloucestershire
15 minutes ago, marksiwnc said:

Is this the will it or won't it snow forum. 

 

Sorry mods but it's annoying now 

People are discussing the output lol, and obviously with some snow potential, that is what is being discussed! Model interpretation is always very individual mind!

And my personal take is that over the last 24 hours the trend has been for the front to stall in situ (and even retreat slightly) and that means the likelihood of the rain turning to snow for some has increased. 

Whether it actually happens or settles is another matter but for now we are heading in the right direction.

GFS 12z pretty consistent with the 00z and 06z, so thats a good thing as the front is still stalling and not barrelling through.

Though ppn intensity will be crucial!! If we get some proper colourful echoes on the radar then snow will no doubt fall, if it's drizzle then it'll be just that.

75-574UK.GIF?15-12

Edited by chris55
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Posted
  • Location: Derbyshire Peak District South Pennines Middleton & Smerrill Tops 305m (1001ft) asl.
  • Location: Derbyshire Peak District South Pennines Middleton & Smerrill Tops 305m (1001ft) asl.

So as ever in these types of set-ups the models are still chopping and changing as to 'where' the snow will fall on Wednesday/Thurday. For newbies expect this to continue over the next few runs, And as i said the other day it could and will more than likely be a nowcast situation. That said its all good fun watching how the models deal with these fine margins leading up to the event.

Here's the GFS 12z take on the snow risk.

a.thumb.png.67c16eb4bb8b4d6edbd33841c5edb.thumb.png.cf906012c0e8c42b30c515ecabf7c.thumb.png.d25093dc6d8700d69373bf3107cc

The GFS also continues to show some cold Pm shots into the run, With nothing mild on the offering..a.thumb.png.abf26111f0c44180c4d40d3b11b2c.thumb.png.7720e236e0a3ce17332d60548827b.thumb.png.ae2ad70ba9de165fb598503447e8

 

Edited by Polar Maritime
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Posted
  • Location: Rotherhithe, 5.8M ASL
  • Location: Rotherhithe, 5.8M ASL

Evaporative cooling will be the critical factor involved for low levels in southern/central England. I notice Arpege rolling out takes the front further *east* some folk will see snow no question about that I would not like to be a weather forecaster. 

image.thumb.png.d638b5ed6d32707add9059c7

Edited by Daniel*
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Posted
  • Location: Eastbourne and Larnaca,Cyprus .
  • Location: Eastbourne and Larnaca,Cyprus .

The models still reluctant to develop any snow ahead of the front but tonights UKMO seems to have increased that chance.

Taking a look at the comparison between the 00hrs T72hrs chart compared to the 12hrs run at T60hrs in terms of 850's, the -6 850 outlined.

ukm2.thumb.gif.03fbf49c7ea08f796438a6f6eukm1.thumb.gif.8323ad6a9d370f5383d3113d6

MeteoFrance have forecast snow for north/ne France late Wednesday into early Thursday. Even with the sea track modification I find it hard to believe that this type of set up won't produce some snow ahead of the front.

 

 

 

 

 

Edited by nick sussex
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Posted
  • Location: Whitefield, Manchester @ 100m
  • Location: Whitefield, Manchester @ 100m
1 minute ago, Daniel* said:

Evaporative cooling will be the critical factor involved for low levels in southern/central England. I notice Arpege rolling out takes the front further west some folk will see snow no question about that I would not like to be a weather forecaster. 

image.thumb.png.d638b5ed6d32707add9059c7

That's a straw clutching snapshot! Watch the whole animation to see how little snow is actually forecast to fall out of the sky. Even when it does show snow it is only light. 

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Posted
  • Location: Kirkburton, Huddersfield - 162.5mtrs asl.
  • Weather Preferences: Winter synoptics.Hot summers.
  • Location: Kirkburton, Huddersfield - 162.5mtrs asl.

Euro 4 updating.The +48 is yet to update....the suspense

Here is 42 z

 

C__Data_Users_DefApps_AppData_INTERNETEXPLORER_Temp_Saved Images_16021706_1506.gif

Edited by winterof79
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Posted
  • Location: Kings Norton, West Midlands
  • Weather Preferences: Thunderstorms, Cold & Snowy
  • Location: Kings Norton, West Midlands
6 minutes ago, nick sussex said:

The models still reluctant to develop any snow ahead of the front but tonights UKMO seems to have increased that chance.

Taking a look at the comparison between the 00hrs T72hrs chart compared to the 12hrs run at T60hrs in terms of 850's, the -6 850 outlined.

ukm2.thumb.gif.03fbf49c7ea08f796438a6f6eukm1.thumb.gif.8323ad6a9d370f5383d3113d6

That is a significant difference. Could even bring snow down here to Dull Hull. 

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Posted
  • Location: Eastbourne and Larnaca,Cyprus .
  • Location: Eastbourne and Larnaca,Cyprus .
6 minutes ago, PerfectStorm said:

That is a significant difference. Could even bring snow down here to Dull Hull.

Well that's the UKMO raw output and they do have their other shorter term models. The key really is the behaviour of that shallow low, preferably we want to see this orientate more nw/se this then increases the chance as the flow ahead begins to switch around to the se. The coldest dew points would then be coming in from ne France/Belgium.

Its an unusual set up with cold air to the se and cold air to the nw, often its a case of milder air trying to displace the cold.

Oh I've just noticed your location you'd want the winds to stay more southerly towards Hull so as not to have an onshore flow.

Edited by nick sussex
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Posted
  • Location: Kirkburton, Huddersfield - 162.5mtrs asl.
  • Weather Preferences: Winter synoptics.Hot summers.
  • Location: Kirkburton, Huddersfield - 162.5mtrs asl.

Here's the question.Is the front at 48z fragmenting anyway?

 

C__Data_Users_DefApps_AppData_INTERNETEXPLORER_Temp_Saved Images_16021712_1512.gif

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Posted
  • Location: Kings Norton, West Midlands
  • Weather Preferences: Thunderstorms, Cold & Snowy
  • Location: Kings Norton, West Midlands
4 minutes ago, winterof79 said:

Here's the question.Is the front at 48z fragmenting anyway

It will fragment but it's possible that the band could reinvigorate somewhat as it bumps into the second airmass. Especially where is stalls. 

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Posted
  • Location: Stroud, Gloucestershire
  • Weather Preferences: Extreme!
  • Location: Stroud, Gloucestershire
8 minutes ago, winterof79 said:

Here's the question.Is the front at 48z fragmenting anyway?

 

C__Data_Users_DefApps_AppData_INTERNETEXPLORER_Temp_Saved Images_16021712_1512.gif

The slower the better! 

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Posted
  • Location: Stroud, Gloucestershire
  • Weather Preferences: Extreme!
  • Location: Stroud, Gloucestershire
1 minute ago, Aaki Khan said:

The dew points are not supportive at moment upto the start of band. 

Its Thursday that sees the conditions swing to potential snowfall. The front will no doubt begin as rain for most away from very high ground.

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Posted
  • Location: Kirkburton, Huddersfield - 162.5mtrs asl.
  • Weather Preferences: Winter synoptics.Hot summers.
  • Location: Kirkburton, Huddersfield - 162.5mtrs asl.
3 minutes ago, PerfectStorm said:

It will fragment but it's possible that the band could reinvigorate somewhat as it bumps into the second airmass. Especially where is stalls. 

Yes and the million dollar question is where?

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Posted
  • Location: Kings Norton, West Midlands
  • Weather Preferences: Thunderstorms, Cold & Snowy
  • Location: Kings Norton, West Midlands
9 minutes ago, nick sussex said:

Oh I've just noticed your location you'd want the winds to stay more southerly towards Hull so as not to have an onshore flow.

As you can imagine, it's very hard to get snow here, and have only seen settling snow once in the 3 years I have been studying at Hull. The North Sea and most likely the estuary don't help at all. I'm not expecting any settling snow, however I'm optimistic for falling snow as the lower dew points set in towards the beginning of the night.  

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Posted
  • Location: Drayton, Portsmouth
  • Location: Drayton, Portsmouth
7 minutes ago, winterof79 said:

Here's the question.Is the front at 48z fragmenting anyway?

 

C__Data_Users_DefApps_AppData_INTERNETEXPLORER_Temp_Saved Images_16021712_1512.gif

Do you know, you're absolutely right - perhaps the biggest variable of all is the intensity of the front. Those sorts of things can vary so much even within T36. Stalling fronts tend to fizzle out in situ. 

But interesting, most models keep this front going until Friday morning. So conceivably, if the front stalls over you in a "snow zone" and it keeps going, could there be inches and inches of white?? Perhaps the peaks of Salisbury plain could see 6 inches or more if current modelling is right, as some suggest snow in this place for 24 hours!

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Posted
  • Location: Kings Norton, West Midlands
  • Weather Preferences: Thunderstorms, Cold & Snowy
  • Location: Kings Norton, West Midlands
1 minute ago, Man With Beard said:

Do you know, you're absolutely right - perhaps the biggest variable of all is the intensity of the front. Those sorts of things can vary so much even within T36. Stalling fronts tend to fizzle out in situ. 

But interesting, most models keep this front going until Friday morning. So conceivably, if the front stalls over you in a "snow zone" and it keeps going, could there be inches and inches of white?? Perhaps the peaks of Salisbury plain could see 6 inches or more if current modelling is right, as some suggest snow in this place for 24 hours!

The only snag is that any reinvigoration (for lack of a better word) on the stalling front doesn't look strong, and precip accumulation looks, at best, 0.5-2mm per hour according to the models. Then you have to deal with an already wet ground. 

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Posted
  • Location: Eastbourne and Larnaca,Cyprus .
  • Location: Eastbourne and Larnaca,Cyprus .

T60hrs fax chart, I'm still very surprised the UKMO aren't mentioning snow ahead of the front, you can see the comparison between that and the earlier one to T72hrs.

fax60s.thumb.gif.1c47b24132d2c8a3df05ca2fax72s.thumb.gif.df29e6c13d02ee8d01afb23

 

Edited by nick sussex
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Posted
  • Location: Wildwood, Stafford 104m asl
  • Weather Preferences: obviously snow!
  • Location: Wildwood, Stafford 104m asl

airpressure.png

This looks to be where cold air ahead of front mixed out, to me this looks SW'ly Atlantic air, surely with that it cannot start as snow, but just what it looks, I'm no expert but surely need the air on more negative SSE angle

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Posted
  • Location: Drayton, Portsmouth
  • Location: Drayton, Portsmouth
11 minutes ago, PerfectStorm said:

The only snag is that any reinvigoration (for lack of a better word) on the stalling front doesn't look strong, and precip accumulation looks, at best, 0.5-2mm per hour according to the models. Then you have to deal with an already wet ground. 

Yes I get that, and you're probably right, it could end up as a day of light flakes for some without much settling (and nothing for those west/east of the front). But - hypothetically - what if we do have a situation where the front is just a little more active and stalls for a long time? 2mm per hour x 24 hours equals 48mm! These sorts of things can and do happen! I picked Salisbury Plain as much of it goes above 200 metres asl. Just exploring the possibilities - goodness me, if I didn't I wouldn't have survived so long this winter! ;)

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