Model Output Discussion - cold spell to end Autumn

[Allseasons-Si]

Guys,come on!!!

this is one run and we will not know the final outcome until much near the time,snow is hard to forecast let alone the models 3-4-5 days out

the northerly looks set of some sorts,granted,what follows ,nobody knows,chill

[Ravelin]

5 minutes ago, Snowy L said:

The 18z for most places will be a few days of dry and cold weather with the odd snow shower folloed by a return to zonal weather. Dont know what is so amazing about that? ECM has been the best today

We have lost the slider and the pattern over the UK completely flattens 3 days after the Northerly starts. I know this stuff is FI but when compared to the ECM the GFS is terrible.

Northerly starts....

3 days later.... 

That is a flat pattern? 

 

[LRD]

7 minutes ago, Winter Hill said:

For one the backedge snow has gone on the 18z 

That in my book is a back track 

Yep, looking at the southerly jet and persistent euro low on the 18z, my first thought was "backtrack". Or, to put it another way... no, it wasn't

[Nick F]

3 minutes ago, knocker said:

A forecast sounding for 12 on the 8th

Steep lapse rates, but if that were over the relatively warmer seas it would look much more unstable! FWIW, Norwegian and North Seas look most primed for instability on GFS, bearing in mind polar lows are convectively driven. Obviously PLs can only be forecast or seen to develop 24hr or less out!

[Snowy L]

1 minute ago, Ravelin said:

Northerly starts....

3 days later.... 

That is a flat pattern? 

 

By Monday the pattern is flat.

[Ice Day]

Well I for one am looking forward to some more 'terrible' runs in the morning!  Nobody knows what's going to happen, but we are as close to a notable UK wide spell of cold weather since 2013.  Maybe things will go in our favour this time, it will eventually so why not now?

Until tomorrow weather geeks.

[snowbob]

11 minutes ago, Winter Hill said:

For one the backedge snow has gone on the 18z 

That in my book is a back track 

Going forward is far better

dont worry about the back edge snow

 

[markw2680]

1 minute ago, Snowy L said:

By Monday the pattern is flat.

That’s like 8 days away ?

[knocker]

4 minutes ago, Nick F said:

Steep lapse rates, but if that were over the relatively warmer seas it would look much more unstable! FWIW, Norwegian and North Seas look most primed for instability on GFS, bearing in mind polar lows are convectively driven. Obviously PLs can only be forecast or seen to develop 24hr or less out!

Indeed I had a shufty at a couple, quite impressive

[steveinsussex]

9 minutes ago, karlos1983 said:

Who cares about back edge snow landing on wet warm ground...... nobody.

troughy snow in frigid air? Everyone. 

Not to mention a PV that’s lost it’s mum, Dad, brothers and sisters at the park and has no money to get the bus home. It’s all good

ps. Yeah I watched it lol

I do; had some of the best falls of snow i can remember as back edge events!

[Derecho]

2 minutes ago, Winter Hill said:

Troll ?? Why because you dont like what you see.. take a look at the 12z the take a look at the 18z.. come back to me and say yep it is just as good are its better.. 

1 no backedge snow...it has gone vanished.

2  no slider.

So tell me again the 18z is better or good like the 12z 

 

 

So 

You are obsessing over tiny features that will vary from run to run. Look how slack the pattern is after T168... this will change from run to run so why dwell on such a volatile pattern?

Lets get a cold northerly and see what happens thereafter.

[Ravelin]

5 minutes ago, Snowy L said:

By Monday the pattern is flat.

Obviously our definitions of flat are at a variance. Even if the above was flat, it doesn't exactly stay that way... 

But then we are really getting beyond the point its worth worrying about. 

[Winter Hill]

1 minute ago, Quicksilver1989 said:

You are obsessing over tiny features that will vary from run to run. Look how slack the pattern is after T168... this will change from run to run so why dwell on such a volatile pattern?

Lets get a cold northerly and see what happens thereafter.

Im just looking at the models.. I would not call the slider a tiny feature.. if it slides then game on

[Allseasons-Si]

The jma was similar to the ecm at 216 with the trough digging that bit further south allowing an easterly feed.

[bluearmy]

5 minutes ago, steveinsussex said:

I do; had some of the best falls of snow i can remember as back edge events!

You have ?  I recall one in the midlands in the late seventies and the thundersnow in 2005 ? 

 

[Mokidugway]

I think tonight's discussion has been well behaved and fun , where all different and have a different take on things 

[karlos1983]

1 hour ago, steveinsussex said:

I do; had some of the best falls of snow i can remember as back edge events!

I was guilty of generalising, but more often than not, back edge doesn’t cut it, those with altitude and latitude will disagree no doubt. 

 

Edited December 3, 2017 by Paul

[bobbydog]

[karlos1983]

4 minutes ago, Winter Hill said:

 

Downgrade yeah ?  ok then 

now remember this is the mean 

more downgrades please if that’s the order 

Edited December 2, 2017 by karlos1983

[LRD]

4 minutes ago, Mokidugway said:

I think tonight's discussion has been well behaved and fun , where all different and have a different take on things 

Yes, that's true but I just can't see a backtrack on the 18z. The general pattern is there. European low pressure. Once that establishes (if it establishes) then the rest is just detail so it's neither backtrack or, er, forwardtrack for me tonight. It might change in the morning of course and I'm worried it will but I'm just commenting on tonight's charts

Edited December 2, 2017 by LRD

[Zakos]

.         

I'm not certain, but given the potency of this cold shot, and the warm seas at this time of year, the temperature contrast  could create disturbances in the airflow,leading to heavier and more widespread snow showers. And these possibly wouldn't be picked up by the models until nearer the event. Some GFS runs I believe have shown widespread snow showers across the UK, however the 18z appears to have a "wishbone effect " to flow, with many inland areas staying dry. Does anyone know what factors can cause a northerly to produce widespread snow showers inland? 

Edited December 2, 2017 by Zakos

[Winter Hill]

1 minute ago, karlos1983 said:

Downgrade yeah ?  ok then 

Was the 18z an upgrade then ? 

Or have 2 features vanished from the 12z 

I'm a coldie but I'm just replying to what I see. 

What is the problem with that ?

 

[Mokidugway]

3 minutes ago, LRD said:

Yes, that's true but I just can't see a backtrack on the 18z. The general pattern is there. European low pressure. Once that establishes (if it establishes) then the rest is just detail so it's neither backtrack or, er, forwardtrack for me tonight. It might change in the morning of course and I'm worried it will but I'm just commenting on tonight's charts

Indeed a  small spanner in the works tonight with luck the new day will bring an upgrade and all will be well 

Edited December 2, 2017 by Mokidugway

[markw2680]

1 minute ago, Winter Hill said:

Was the 18z an upgrade then ? 

Or have 2 features vanished from the 12z 

I'm a coldie but I'm just replying to what I see. 

What is the problem with that ?

 

Tbh I don’t think it’s either it’s just another variation that’s pretty much a week away, details are going to chop and change, pretty sure if it turns out as the 18z suggests then we will be pretty happy

[bluearmy]

4 minutes ago, Winter Hill said:

Was the 18z an upgrade then ? 

Or have 2 features vanished from the 12z 

I'm a coldie but I'm just replying to what I see. 

What is the problem with that ?

 

The rules are that if a couple runs are not as good as the previous continuity it isn't a downgrade. You need around four poorer runs to constitute a downgrade. One better run, however, is an upgrade ?

 

And in all seriousness, we shouldn't really be arguing over gfs op runs more than half a dozen days out .... therein lies madness! , 

Edited December 2, 2017 by bluearmy