Model output discussion - cold spell approaching?

[Kasim Awan]

Just now, Battleground Snow said:

Meteociel seem happy about it too.

 

They don't know the half of it.

[Jason M]

2 minutes ago, Allseasons-si said:

They are a complete mess Dan and i wouldn't want to call it which way we are heading,...they look just as bad as my daughter's scribbling when she was two ha ha

which way will we go from here?...

 

The clustering further north would probably be better. Looking through the individual GEFS a lot of them struggle to get the cold south because of the high pressure over Iberia. Most do manage it, even if briefly though. The warmer runs are all generally courtesy of a warm SW due to the fact that the heights in that part of the world refuse to play ball.

Looking at a snapshot of the 12z GEFS at 78 hours its clear we are so damn close to a good easterly its untrue. As always its that last little upgrade to push everything west another 100 miles that is elusive.

[Floatylight]

15 minutes ago, Allseasons-si said:

The 18z ICON is an improvement with the ESP trough that breaks away nicely from the upper Greenland low and because of this we would get more amplification into Greenland

18z 120 v's 12z 126

the front on Wednesday evening is stalling further west too.

18z v's 12z

 

Right over my house in colchester

[chionomaniac]

Great to see 2 ECM runs on the trot showing Greenland blocks. No way is this decided yet, like a good battle with a large fish, we need to see it reel in.  

Normally I am very wary of a displacement SSW in respect of trop blocking responses. Less so this one though, it appears that the Atlantic amplification response is a feedback from Atmospheric feedback from the SSW, which leads to a weak northern polar jet and strengthened southern jet. And the upper strat disruption looks to being continued, rather than a strong reintensification of the vortex. All potentially great news for even longer term prospects.

L

all levels of the strat look weak.

Its been quite a few years since we have seen such an alignment of factors whether or not the atmosphere turns more La Niña. This may not matter a jot now. Still excited about the last third of the month.

[SLEETY]

we  breached the minus 10 and 15 line,now,can we get the minus 20 line breached after the pub run,even Darren Bett may take some notice if that happens.

[TallPaul]

47 minutes ago, Tim Bland said:

Big difference east to west on the ECM for Thursday. 6c in Manchester and 2c in Norwich!

...and a sweltering 10c imby... ?

[chionomaniac]

9 minutes ago, chionomaniac said:

Great to see 2 ECM runs on the trot showing Greenland blocks. No way is this decided yet, like a good battle with a large fish, we need to see it reel in.  

Normally I am very wary of a displacement SSW in respect of trop blocking responses. Less so this one though, it appears that the Atlantic amplification response is a feedback from Atmospheric feedback from the SSW, which leads to a weak northern polar jet and strengthened southern jet. And the upper strat disruption looks to being continued, rather than a strong reintensification of the vortex. All potentially great news for even longer term prospects.

L

all levels of the strat look weak.

Its been quite a few years since we have seen such an alignment of factors whether or not the atmosphere turns more La Niña. This may not matter a jot now. Still excited about the last third of the month.

Just to add this winter we have seen a situation where there has been a disconnect during December between strat and trop, with trop wave patterns dictating the trop patterns.  This has already led to the cold spell that we have experienced. Just as it looks like the trop disconnect is about to wane the feedback from the trop stationary waves has led to a SSW. This SSW is now dictating the state of play for the near future, and the feedback to the trop from this is now assisting the upcoming trop pattern. Add in the continued strat disruption and if we don’t get a significant severe cold spell, then we never will!

Edited January 11, 2021 by chionomaniac

[Methuselah]

2 minutes ago, TallPaul said:

...and a sweltering 10c imby... ?

And with the news that I might, if I'm very, very lucky, see 15 minutes' worth of sleety drizzle, on Thursday, I'll call it a day. G'night all!

[Zak M]

For those curious about what perturbation reached the -17c isotherm line, it's perturbation 22!

   

[WINTRY WALES]

3 minutes ago, chionomaniac said:

Just to add this winter we have seen a situation where there has been a disconnect during December between strat and trop, with trop wave patterns dictating the trop patterns.  This has already led to the cold spell that we have experienced. Just as it looks like the trop disconnect is about to wane the feedback from the trop stationary waves has led to a SSW. This SSW is now dictating the state of play for the near future, and the feedback to the trop from this is now assisting the upcoming trop pattern. Add in the continued strat disruption and if we don’t get a significant severe cold spell, then we never will!

Hi chino 

Great update....if all comes together are you anticipating a countrywide severe spell here...or just the northern half that the met are hinting towards??

[Eskimo]

The GFS is bloody off on one again!
 

[Mike Poole]

20 minutes ago, SLEETY said:

we  breached the minus 10 and 15 line,now,can we get the minus 20 line breached after the pub run,even Darren Bett may take some notice if that happens.

In living memory the only time we got the -20 close was this, I think:

March 2018 came close though.  Good chance to beat it this year though, because the synoptics to deliver a bitterly cold NE long draw feed are *possible*. 

Edited January 11, 2021 by Mike Poole

[SnOwFeSt]

Just now, Eskimo said:

The GFS is bloody off on one again!
 

Looks real knife edge stuff doesn't it? I think it will come down to nowcasting. It currently looks the wrong side of marginal, but has been trending in the right direction in very tiny increments!

[damianslaw]

Trends tonight, a more concerted move from all models to strong height development to our NW in a week's time, ECM wasn't showing this yesterday must is today. GFS holding firm. Before we get there, all very messy, we have a colder pulse of air moving down from the north right now, and a much brighter drier day for many tomorrow. Wednesday and Thursday could deliver a notable snow event to some parts - a case of nowcasting. A ridge then moves through before the weekend, calming things down again, before another frontal feature drops in this time on a NW-SE trajectory with possible wintriness, then all eyes to the north and north east.

Gosh there is alot going on, and it isn't the usual atlantic barrage of wind and rain and copious mild.

Most interesting first half to winter in a long long time model watching wise at least!

[sheikhy]

18z snow on saturday again!!

[Kasim Awan]

It's very important that the two shortwaves in the Atlantic don't phase at 120h. This will allow for a more optimal warm air advection and amplification. GFS has a slightly better separation so far.

[Jason M]

Just now, sheikhy said:

18z snow on saturday again!!

Yes. The funny thing is that 850s are around -2 to -4c but with cold air imbedded its just good enough with a gentle undercut  So you get rain with 850s of -8c one week and snow with -2c 850s the next. 

[Allseasons-Si]

7 minutes ago, Zak M said:

For those curious about what perturbation reached the -17c isotherm line, it's perturbation 22!

   

That is a stonker and i would loose my car in that lot

pert 22 and 18...

 

 

[CSC]

what ON EARTH IS GOING ON? Blizzard in south U.K. on SATURDAY? The weather is drunk.

[snowbob]

2 minutes ago, Kasim Awan said:

It's very important that the two shortwaves in the Atlantic don't phase at 120h. This will allow for a more optimal warm air advection and amplification. GFS has a slightly better separation so far.

Isn’t that exactly what @warrenb was saying on the 12z

[Kasim Awan]

Just now, CSC said:

what ON EARTH IS GOING ON? Blizzard in south U.K. on SATURDAY? The weather is drunk.

Lol, we're in a colder than average month mate. We're not used to it but given these temps running 2-3C below normal these surprises could happen. 

[Lampostwatcher]

18z 

Saturday snow event 

[Matt H]

GFS 18z has a widespread snow event across the south at the weekend. Please just be right for once.

 

Edited January 11, 2021 by Frosty Winter

[feb1991blizzard]

6 minutes ago, Kasim Awan said:

It's very important that the two shortwaves in the Atlantic don't phase at 120h. This will allow for a more optimal warm air advection and amplification. GFS has a slightly better separation so far.

It looks like they are going to phase at 150 but not sure it matters by then, the WAA is already in full swing.

[Griff]

Lows phased and gfs backing off yet? 

Edited January 11, 2021 by Griff