Model output discussion - the beast arrives

[Lynxus]

3 minutes ago, lassie23 said:

Do the models agree that the cold spell vanishes by the weekend

Oh, Absolutely not, ..

Think I was fishing for someone to go " Hey you there! Looks at allllll these other models showing an eastward trend and colder uppers!! GFS too progressive etc etc etc"

Bored of convincing myself

[Weathizard]

What an odd chart, can anyone explain to me why this low pressure barely moves for days on end and won't move eastwards as normal? Is the eastwards reversal that strong it's stopping all energy in the Atlantic in its tracks? Jet?

Edited February 28, 2018 by Weathizard

[Lynxus]

3 minutes ago, Weathizard said:

What an odd chart, can anyone explain to me why this low pressure barely moves for days on end and won't move eastwards as normal? Is the eastwards reversal that strong it's stopping all energy in the Atlantic in its tracks? Jet?

I think the jet being so far south isnt helping it along 

 

[Weathizard]

UKM shows colder air digging back in and fighting back at day 3, much more so compared to the GFS.. pretty large difference at day 3

[nick sussex]

Still no agreement on the low 36 hours out and the UKMO says no to a quick warm up.

More southwards corrections and you can see the battle to remove the cold is going to be a struggle .

The lack of a strong jet near the UK to move the low which hangs around is both a help and hindrance .

The stronger jet is heading off se to Africa .

Because the block has moved a bit too far west a stronger jet might tip things towards a milder outcome , here there’s very little steam in that low and that means it can’t move very far but equally more chance of nearer term more energy heading east as the low comes up against the cold sitting over the UK.

 

Edited February 28, 2018 by nick sussex

[Matthew Gill]

GFS at t216 looks interesting 

[Summer Sun]

t144 from GFS, GEM & UKMO no surprise that all 3 have differing views on the 850's

Taking the -8 line UKMO has it around southern Scotland GFS has it around the north and GEM keeps it north of the mainland

[Matthew Gill]

Would this clasify as a Channel low?

 

[nick sussex]

The UKMO drives more energy eastwards early and this stops milder air getting into Holland and areas further to the east and ne .

This could be crucial because as the next push from the sw moves in the flow back into the UK will still pull in low dew points.

You can clearly see this at T48 hrs note that shortwave energy moving east right into Northern Italy.

Although the GFS does take some energy eastwards  , it’s already lifted more cold out and the boundary is further north .

 

[Derecho]

12z ensembles seem to be firming up on less cold air reaching further north. However quite few of those runs see an east-west temperature contrast with maximums in Wales on Sunday still struggling a fair bit.

Whereas the ensembles seem to be pushing the milder air north it is delicately poised. A run like P3 for example (which keeps the whole weekend and into next week cold) cannot be ruled out yet.

[Tim Bland]

GFS continues the wintry theme with snow opportunities uk wide, even in the far south 

[nick sussex]

3 minutes ago, Quicksilver1989 said:

12z ensembles seem to be firming up on less cold air reaching further north. However quite few of those runs see an east-west temperature contrast with maximums in Wales on Sunday still struggling a fair bit.

Whereas the ensembles seem to be pushing the milder air north it is delicately poised. A run like P3 for example (which keeps the whole weekend and into next week cold) cannot be ruled out yet.

I think the key is some more trough disruption between T72 hrs and T96 hrs.

The GEFS and other ensembles are overall less likely to see this because of the lower resolution and the GFS op bias of too much energy going ne means I’d be more dubious of it.

Lets see what the ECM has to say.

[Derecho]

3 minutes ago, nick sussex said:

I think the key is some more trough disruption between T72 hrs and T96 hrs.

The GEFS and other ensembles are overall less likely to see this because of the lower resolution and the GFS op bias of too much energy going ne means I’d be more dubious of it.

Lets see what the ECM has to say.

Yeah agreed, if we can send a bit more energy east on Friday/saturday the picture could be very different. The 18z GFS  flirted with that scenario last night and I think it could easily come back. It will be interesting to see how accurate the turn north is of storm emma. If it is any further east then forecast that could also have big implications. Given that this is such a slack setup such changes cannot be ruled out just yet.

Edited February 28, 2018 by Quicksilver1989

[nick sussex]

8 minutes ago, Quicksilver1989 said:

Yeah agreed, if we can send a bit more energy east on Friday/saturday the picture could be very different. The 18z GFS  flirted with that scenario last night and I think it could easily come back. It will be interesting to see how accurate the turn north is of storm emma. If it is any further east then forecast that could also have big implications. Given that this is such a slack setup such changes cannot be ruled out just yet.

The ECM ensembles from this morning show there’s still a cluster with more trough disruption.

We’re not looking for big changes , small incremental changes between runs will do fine .

The mission is cold extension and snow retention ! 

And then to increase chances for further snow , but crucial to get that trough disruption.

Whatever happens for some parts of the UK this cold spell has been exceptional perhaps not in terms of duration but  the depth of cold in terms of uppers might never be seen again this late in the season for many years to come.

Edited February 28, 2018 by nick sussex

[Matthew Gill]

8 minutes ago, Quicksilver1989 said:

Yeah agreed, if we can send a bit more energy east on Friday/saturday the picture could be very different. The 18z GFS  flirted with that scenario last night and I think it could easily come back. It will be interesting to see how accurate the turn north is of storm emma. If it is any further east then forecast that could also have big implications. Given that this is such a slack setup such changes cannot be ruled out just yet.

Still learning here. Are you saying ideally we need storm emma to go slightly east?

[Derecho]

3 minutes ago, Matthew Gill said:

Still learning here. Are you saying ideally we need storm emma to go slightly east?

I think it would push the milder air whipped up by Emma east and perhaps it wouldn't phase with the low to the SW of it leading to better trough disruption. (seems to show some sort of Fujiwara effect which helps it move back west)

A long shot though, it seems unlikely unfortunately but there's still a chance of something like last nights 18z GFS if it doesn't.

Edited February 28, 2018 by Quicksilver1989

[nick sussex]

Looking at the fax chart the UKMO have modified their raw output , they’ve deepened the low to the sw at T48 hrs.

It looks incredibly complex, a chance some places could see snow a short spell of freezing rain and then back to snow . That would be extremely dangerous.

Edited February 28, 2018 by nick sussex

[nick sussex]

Good grief it’s utter chaos !

No agreement at T48 hrs and the ECM throws a curve ball at T72hrs! 

[Derecho]

34 minutes ago, nick sussex said:

The ECM ensembles from this morning show there’s still a cluster with more trough disruption.

We’re not looking for big changes , small incremental changes between runs will do fine .

The mission is cold extension and snow retention ! 

And then to increase chances for further snow , but crucial to get that trough disruption.

Whatever happens for some parts of the UK this cold spell has been exceptional perhaps not in terms of duration but  the depth of cold in terms of uppers might never be seen again this late in the season for many years to come.

ECM shows some trough disruption... and the -10C line is still over the Humber midday saturday.

[mulzy]

ECM day 3 - still very cold across most of the UK.  How will that channel low move?  Snow across the south on Saturday - goodness me!

[Snowmusic]

 Can you elaborate on the curve ball? I’m on tenterhooks!! (Ps love reading your posts...thank you )

[Derecho]

Sunday looks very cold on this chart, especially by night with the slack pressure pattern and deep snow over some areas. Now if that low to our west keeps out of our trouble, we could well end up under cold NE'lies (not to the same extent as this week but still).

Kinda reminds me of March 2013 later on in the month when models kept going for a breakdown only for the cold air to win out. Different angle of attack but it seems like a genuine possibility still.

Edited February 28, 2018 by Quicksilver1989

[nick sussex]

Just now, Snowmusic said:

 Can you elaborate on the curve ball? I’m on tenterhooks!! (Ps love reading your posts...thank you )

You’re welcome thanks. 

It ejects a shortwave east at T72 hrs , the GFS and UKMO don’t do this .

And because of this you end up with another snow event for parts of the UK,  by T96 hrs the shortwave has moved ene into Holland.

Astonishing turnaround ! 

 

[That ECM]

1 minute ago, nick sussex said:

You’re welcome thanks. 

It ejects a shortwave east at T72 hrs , the GFS and UKMO don’t do this .

And because of this you end up with another snow event for parts of the UK,  by T96 hrs the shortwave has moved ene into Holland.

Astonishing turnaround ! 

 

That's what gfs control did this morning nick.

[A.J]

3 minutes ago, nick sussex said:

You’re welcome thanks. 

It ejects a shortwave east at T72 hrs , the GFS and UKMO don’t do this .

And because of this you end up with another snow event for parts of the UK,  by T96 hrs the shortwave has moved ene into Holland.

Astonishing turnaround ! 

 

cheers Nick, a good spot by you, but yes indeed, secondary LP born out of disruption....Serves the parent LP right, mess the models around and you get disruptive kids! 

Edited February 28, 2018 by ajpoolshark