Model Output Discussion - cold spell to end Autumn

[booferking]

I cant build myself to get excited after the weekend cold rain is in the forecast if ecm is close to the mark.

[Britneyfan]

Have a feeling the ECM will be correct, we will end up wetter milder and normal uk winter 

[tight isobar]

Ecm going hammer and tong' trying to flatline...

And is very gfs on its wanting of an' incoming atlantic..

Imo to up and down this 12z...

For any comprehension!!!

...almost a scrappy non beleive of evolution past 96hrs!!!

Certainly one for the bin.

For me anyway!?

Edited December 4, 2017 by tight isobar

[I remember Atlantic 252]

GEFS 4, the best! I know ensembles low res though

[Mapantz]

7 minutes ago, Summer Sun said:

Not bad eh

I'm seem to remember @Nick L saying that he couldn't understand why they were showing all of that snow, as the EC precip model he has access to, showed nothing like those amounts.

[Daniel*]

In experience things tend to correct south and west highly volatile. 

[chris55]

Corrections west nearly always happen with these sliders modelled past day 4/5, wouldn't surprise me one bit if the initial slider ended up missing the UK entirely!!! 

Hopefully not! But the positioning is far from decided. 

Many more runs required before we can have confidence for our little island  

[Frosty.]

10 minutes ago, Summer Sun said:

Wet n windy at D9 maybe a bit of snow for Scotland on the mountains

At least it won't be mild rain..just looking for the positives 

Seriously though there's a lot of water to go under the bridge before then so I would hold fire with the game over comments for now. The  arctic blast is on the way first

 

Edited December 4, 2017 by Frosty.

[iand61]

6 minutes ago, Summer Sun said:

Not bad eh

over a foot of snow IMBY.

personally I can't see anything but a downgrade from there although even a halfway house will do.

[igloo]

2 minutes ago, Mapantz said:

I'm seem to remember @Nick L saying that he couldn't understand why they were showing all of that snow, as the EC precip model he has access to, showed nothing like those amounts.

i have to agree that chart does not correspond with this evenings ecm as the uppers  are simply to high for any type of snow from 144h onwards must be a fault somewhere

[blizzard81]

The big question post day 10 is will there be enough amplification in the mid Atlantic to counteract the inflating north east Canada lobe of pv? The answer to this question will dictate which direction our weather goes in the run up to Christmas. 

[tight isobar]

2 minutes ago, igloo said:

i have to agree that chart does not correspond with this evenings ecm as the uppers  are simply to high for any type of snow from 144h onwards must be a fault somewhere

Further highlighting....

I think the ecm 12z..is bordering ridiculous...

Its a very bipolar run...

"No pun intended".

[damianslaw]

22 hours ago, FiftyShadesofWine said:

 

Sorry can't seem to get rid of the above. Models showing a fair bit of consistency in the reliable, slightly different synoptics on the same theme as we end the weekend and move into next week - i.e. all are showing some form of slider low forming, expect differences in positioning at this range. Such features are notoriously difficult to predict with accuracy, often a case of nowcasting. History shows such features do tend to correct SW than predicted, so I would expect this to happen this time, which will increase the chance of widespread snow following on from the bitter arctic blast on Friday. Cold surface air will be in place and winds will fall light.

Those saying uppers are not cold enough - need to remember in frontal /slider low conditions you don't need uppers in the sub -5 degree range, often just above freezing will do provided winds are light - this prevents mixing of the cold surface air, and more importantly dewpoints remain on the right side.

Most of the epic snowfalls of years gone by have occured in less than cold uppers, indeed the best snowfalls occur in marginal set ups - the boundary between heavy snow and heavy rain is often starkly narrow.

Back to the models - not expecting much change in the overall pattern, but think they will start to latch onto prominent height rises to our NE as we approach the middle of the month.

There is an air of Dec 81 about things at the moment.. (oh dear I've said it now..).

 

[blizzard81]

2 minutes ago, igloo said:

i have to agree that chart does not correspond with this evenings ecm as the uppers  are simply to high for any type of snow from 144h onwards must be a fault somewhere

It's not all about the uppers though. The air over north east Britain will be frigid as the low slides in. 

[Daniel*]

3 minutes ago, iand61 said:

over a foot of snow IMBY.

personally I can't see anything but a downgrade from there although even a halfway house will do.

Yesterday ECM ENS 1st member had widespread depths of a foot and over across Southern England. This is much more desirable.. 

[Frosty.]

I would wait and see what tonight's Ecm 12z ensemble mean shows because the GEFS 12z mean is cold, more cold and then..more cold!

[Scandinavian High.]

Lots more runs to come it is not a done deal yet. With the lows coming in to uk so I would not get down beat. End of week and in to weekend there is snow in the forecast and it is not just for the north..

Edited December 4, 2017 by abbie123

[Froze were the Days]

The low pressure which is crossing the north west of UK in a few days time is far deeper and further north than what the GFS and ECM were showing last week, how many runs did we see with that low pressure cutting through the country as a weaker feature only to deepen in situ as it moved into the North Sea (GFS markedly out)...makes you wonder if the GFS has got this wrong regarding the slider lows (too far south) and there after...

Edited December 4, 2017 by Froze were the Days

[jvenge]

9 minutes ago, igloo said:

i have to agree that chart does not correspond with this evenings ecm as the uppers  are simply to high for any type of snow from 144h onwards must be a fault somewhere

Checked the regional and global surface. Looks right.

Just keep in mind thats accumuated (fallen) over the time period and it doesnt mean it fell as fluffy white snow and at that depth or that it stuck around.

Thats before we get to looking at precipitation at T144, let alone snow...

[Chesil View]

1 minute ago, damianslaw said:

Sorry can't seem to get rid of the above. Models showing a fair bit of consistency in the reliable, slightly different synoptics on the same theme as we end the weekend and move into next week - i.e. all are showing some form of slider low forming, expect differences in positioning at this range. Such features are notoriously difficult to predict with accuracy, often a case of nowcasting. History shows such features do tend to correct SW than predicted, so I would expect this to happen this time, which will increase the chance of widespread snow following on from the bitter arctic blast on Friday. Cold surface air will be in place and winds will fall light.

Those saying uppers are not cold enough - need to remember in frontal /slider low conditions you don't need uppers in the sub -5 degree range, often just above freezing will do provided winds are light - this prevents mixing of the cold surface air, and more importantly dewpoints remain on the right side.

Most of the epic snowfalls of years gone by have occured in less than cold uppers, indeed the best snowfalls occur in marginal set ups - the boundary between heavy snow and heavy rain is often starkly narrow.

Back to the models - not expecting much change in the overall pattern, but think they will start to latch onto prominent height rises to our NE as we approach the middle of the month.

There is an air of Dec 81 about things at the moment.. (oh dear I've said it now..).

 

Two things to note from the 12z ECM. Firstly the slider has corrected southwest slightly and as other have noted this is often seen with sliders. From  40 years experience

of monitoring synoptic developments I would expect further corrections over the coming runs as the slider moves into the more reliable time frame.

Secondly as Damians Law states in his post above please can we get past this rubbish about uppers having to be between minus 5 and minus 10 for every case of snowfall.

If you want an example of just how much snow you can get from much higher uppers then google the great southwest Blizzard of February 1978 look at the pictures of the twenty foot drifts and take on board the fact that this colossal fall came with uppers of just minus 2

[tinybill]

http://www.meteociel.fr/modeles/gfse_cartes.php?mode=2&ech=204

looking deep in to f1 all i can say is  all eyes  on friday could we be geting  a white one  for  the  big  day  !!!

[Mokidugway]

It's all getting a bit pornographic and I'm no cold chaser 

[PLANET THANET]

2 minutes ago, Mokidugway said:

It's all getting a bit pornographic and I'm no cold chaser 

as long as it doesnt go t*ts up

Edited December 4, 2017 by PLANET THANET

[Spah1]

9 minutes ago, tinybill said:

http://www.meteociel.fr/modeles/gfse_cartes.php?mode=2&ech=204

looking deep in to f1 all i can say is  all eyes  on friday could we be geting  a white one  for  the  big  day  !!!

IT’S FI NOT F1 aaahhhh!

Edited December 4, 2017 by Spah1

[A.J]

6 minutes ago, ShortWaveHell said:

As I’m new on here .. can someone exilain a certain ecm output that made someone called Ian Brown say ‘wtf’ ? 

It’s mentioned a lot on here , id like to know WTF it’s all about ? Pretty please 

probably best to pm another member or contact the site team......

 

for questions about snow...will it?...won't it?.....what parameters need to be in place etc etc....I highly recommend reading the following NW link from John Holmes (for those who don't know or are new to the forum, John was a met office forecaster IIRC, and was senior forecaster here on NW for several years - he knows his stuff)

also to add, the NW Knowledge center is a great place to learn about all things model related, indeed all things meteorology

https://www.netweather.tv/forum/forum/5-the-netweather-guides/