Model Output Discussion - Staying cold into the new year

[johnholmes]

1 minute ago, johnholmes said:

It was this chart, GFS not UK

So just that one chart and GFS for 9 Jan, how reliable who knows but it does, to me, tend to illustrate the possible problems when lows like this do actually materialise. 

[Griff]

Advised caution is duly noted, I can't help but feel as per the last couple of days we're now in a period of model flux and confusion, where various solutions will be offered across the runs. Not wishing to restart old debates about the validity of the various runs, but neither is it time to invest too much stock in FI, good or bad, rather enjoy the ride. 

TLDR I don't think the models know how to factor events in stratosphere yet. 

[Geordiesnow]

3 minutes ago, sheikhy said:

That look beautiful mr frost!!850s of -7 and is that snow showers pushing into eastern areas!!!!looks right side of marginal to me!!

Does not look on the right side of margin too me? 

Lack of significant cold air could be an issue next week I suspect, winds off a warm North Sea, strong winds so plenty of mixing of the air. You need something like the 18Z GFS where it was slacker and slightly colder. From my experiences living in the NE uppers of - 7 with winds off the sea is not cold enough for snow I'm afraid. 

[Methuselah]

18 minutes ago, johnholmes said:

So just that one chart and GFS for 9 Jan, how reliable who knows but it does, to me, tend to illustrate the possible problems when lows like this do actually materialise. 

Some of these charts remind me of the enormous blizzard that came from the south, in February 1969: just enough 'warm' air got into the SE, EA and EMids of England to turn the snow into heavy rain, whilst further north and west blizzards raged for several days?

Edited December 30, 2020 by General Cluster
Doh!

[I remember Atlantic 252]

2 minutes ago, Geordiesnow said:

Does not look on the right side of margin too me? 

Lack of significant cold air could be an issue next week I suspect, winds off a warm North Sea, strong winds so plenty of mixing of the air. You need something like the 18Z GFS where it was slacker and slightly colder. From my experiences living in the NE uppers of - 7 with winds off the sea is not cold enough for snow I'm afraid. 

normally has to be -10, for convective snow

[bluearmy]

1 minute ago, I remember Atlantic 252 said:

normally has to be -10, for convective snow

Given the warm sea temps double digit neg uppers could (as Ed alluded a couple days ago) deliver copious qtys of convective snowfall ......sadly that level of uppers seems unlikely for the time being ......

[Kentish Snowman in Yorks]

1 minute ago, bluearmy said:

Given the warm sea temps double digit neg uppers could (as Ed alluded a couple days ago) deliver copious qtys of convective snowfall ......sadly that level of uppers seems unlikely for the time being ......

Could the warmer than average North Sea temps allow a similar temperature differential at -7 to what it would have been at -10 if the sea temps were colder though?

Or would any convective activity create more of a sleety mess?

[Geordiesnow]

4 minutes ago, I remember Atlantic 252 said:

normally has to be -10, for convective snow

Yeah that's the more safer bet for snow showers(although uppers of - 8 with low thicknesses can deliver) and yet on todays runs, the uppers struggling to get below - 7 and Infact they are forecast to drop down to around - 5 and your not even going to get sleet from that. 

After last night GFS run, disappointing runs this morning and the signal for heights around Greenland has dropped also so reduces the chance of tapping into Arctic air it seems. 

[chris55]

So do we look North or East....

Well the trend today up to day 10 is for a colder easterly to dig in rather than the Greenland high northerly scenario. GFS then goes on to retrogress the high up to Greenland drawing down the North/North easterly. A slower evolution but personally I’m liking the idea. Getting that proper cold air in from the east first.

ECM day 8-9-10 is pretty epic with some decent energy finally undercutting right into Europe triggering the much more meaningful flow of very cold easterly air!

The day 10 ties in with Blues interpretation where by some milder air could be come close to the southern half of the U.K. That’s high risk high reward for a big snowfall on the boundary. But then the high retrogress and pulls in a bitter north easterly so all good.

I’m actually really liking this evolution and it seems realistic, more traditional route to cold.

 

 

Edited December 30, 2020 by chris55

[Ice Day]

3 minutes ago, Griff said:

I meant to add rather than chasing snow events at a couple of days, aren't we usually chasing phantom SSWs at +10 days? 

More reason for optimism than I can ever recall. 

Indeed, this is showing for midday today!!!

[Mr Frost]

15 minutes ago, Geordiesnow said:

Does not look on the right side of margin too me? 

Lack of significant cold air could be an issue next week I suspect, winds off a warm North Sea, strong winds so plenty of mixing of the air. You need something like the 18Z GFS where it was slacker and slightly colder. From my experiences living in the NE uppers of - 7 with winds off the sea is not cold enough for snow I'm afraid. 

 

12 minutes ago, I remember Atlantic 252 said:

normally has to be -10, for convective snow

Not this old chestnut again. 

Parts of Edinburgh got two inches of settling snowfall with 850HPA temperatures of -2 to -4 the other day! @Kirkcaldy Weather already mentioned this I think - from the North Sea! 

Those snow showers even reached the West Coast of Scotland to sea level...from the North Sea! 

There are many more snow parameters than just 850HPA’s as we all know.

Let’s just see what happens rather than writing everything off five days before a potential chart becomes reality - surely as a snow/cold lover you hope for the best rather than always expecting doom/worst outcome!  

Edited December 30, 2020 by Mr Frost

[winterof79]

4 minutes ago, Kentish Snowman in Yorks said:

Could the warmer than average North Sea temps allow a similar temperature differential at -7 to what it would have been at -10 if the sea temps were colder though?

Or would any convective activity create more of a sleety mess?

All academic at this stage but the spine of England and Eastern pennine slopes would get pasted from this set up. Oragraphic snowfall. 

 

[SMU]

Back on the upgrades again

Perfect flow out at 96

[bluearmy]

7 minutes ago, Kentish Snowman in Yorks said:

Could the warmer than average North Sea temps allow a similar temperature differential at -7 to what it would have been at -10 if the sea temps were colder though?

Or would any convective activity create more of a sleety mess?

Assuming you don’t have v low slp (unlikely with an easterly), the difference at -7 would currently create precip but it won’t be snow given the sst’s and the strength of flow required to generate the convection we would be looking for to punch well inland ....

[edo]

 There was an excellent post by @Kirkcaldy Weatherin the previous thread about the weather on the ground from the modelled conditions, uppers of -3 delivered snow off the east 2 days ago in Scotland. Granted there were other factors like the very slack flow but that is the point there are other factors. We all want to see colder uppers but lets not dismiss possibilities solely on sight of 850 temps.

[Battleground Snow]

11 minutes ago, Geordiesnow said:

Yeah that's the more safer bet for snow showers(although uppers of - 8 with low thicknesses can deliver) and yet on todays runs, the uppers struggling to get below - 7 and Infact they are forecast to drop down to around - 5 and your not even going to get sleet from that. 

After last night GFS run, disappointing runs this morning and the signal for heights around Greenland has dropped also so reduces the chance of tapping into Arctic air it seems. 

Uppers already lower in the early stages of the 06z GFS, ironically near Newcastle.

Snow for some showing also

Edited December 30, 2020 by Battleground Snow

[bluearmy]

4 minutes ago, Mr Frost said:

 

Not this old chestnut again. 

Parts of Edinburgh got two inches of settling snowfall with 850HPA temperatures of -2 to -4 the other day! @Kirkcaldy Weather already mentioned this I think - from the North Sea! 

Those snow showers even reached the West Coast of Scotland to sea level...from the North Sea! 

There are many more snow parameters than just 850HPA’s as we all know.

Let’s just see what happens rather than writing everything off five days before a potential chart becomes reality - surely as a snow/cold lover you hope for the best rather than always expecting doom/worst outcome!  

North Sea off the Edinburgh coast is 8c 

off e anglia it was recently 11c (showing 10c now ) 

and when this occurred the other day it was under v low slp which brings the freezing level closer to the surface 

 

[Methuselah]

4 minutes ago, Mr Frost said:

 

Not this old chestnut again. 

Parts of Edinburgh got two inches of settling snowfall with 850HPA temperatures of -2 to -4 the other day! @Kirkcaldy Weather already mentioned this I think - from the North Sea! 

Those snow showers even reached the West Coast of Scotland to sea level...from the North Sea! 

There are many more snow parameters than just 850HPA’s! 

Let’s just see what happens rather than writing everything off five days before a potential chart becomes reality - surely as a snow/cold lover you hope for the best rather than always expecting doom/worst outcome!  

A few Januarys back, we had torrential rain/hail/snow showers (I think one of our Southend-based members even reported thundersnow!) from T850s of a measly -4C... The joys of rules-of-thumb, eh?

[bluearmy]

1 minute ago, edo said:

 There was an excellent post by @Kirkcaldy Weatherin the previous thread about the weather on the ground from the modelled conditions, uppers of -3 delivered snow off the east 2 days ago in Scotland. Granted there were other factors like the very slack flow but that is the point there are other factors. We all want to see colder uppers but lets not dismiss possibilities solely on sight of 850 temps.

For the past five runs, ec op has produced masses of precip over se england in the 7/10 day period from the predicted ene flow. None of the five runs has shown any snowfall (and we know how easy it is for ec op to show snowfall).  Uppers have been as low as -8c on these runs and still nowt!   I’m comfortable that ec op is capable of calculating the factors required better than we are!  As you move north and the sea temps drop I’m sure that you could see snowfall off an onshore flow if the pattern allows. 

[Geordiesnow]

7 minutes ago, Mr Frost said:

 

Not this old chestnut again. 

Parts of Edinburgh got two inches of settling snowfall with 850HPA temperatures of -2 to -4 the other day! @Kirkcaldy Weather already mentioned this I think - from the North Sea! 

Those snow showers even reached the West Coast of Scotland to sea level...from the North Sea! 

There are many more snow parameters than just 850HPA’s as we all know.

Let’s just see what happens rather than writing everything off five days before a potential chart becomes reality - surely as a snow/cold lover you hope for the best rather than always expecting doom/worst outcome!  

Yes from a slack set up, totally different to gale force easterly winds off the north sea. More winds equals more mixing. 

The slacker the easterly, the more chance there is for snowfall away from Eastern coasts. That's the reality. 

[Tim Bland]

GFS slightly colder than previous run so showers into the east are all snow. Uppers -8 / -9 

[Paul]

Just posting this up, to hopefully avoid us going down the same rabbit hole again..

 

[I remember Atlantic 252]

4 minutes ago, Tim Bland said:

GFS slightly colder than previous run so showers into the east are all snow. Uppers -8 / -9 

Aye, better on 06Z

[winterof79]

I'm not buying all this uppers mallarcy 

120z next Monday. Dew points etc from icon and gfs. It will snow inland. 

 

[Battleground Snow]

Very cold here at 150 from GFS,

-10 850mb not far off at this stage

 

Edited December 30, 2020 by Battleground Snow