Model output discussions pm 31/12/15

[Nick F]

Once the cold air is entrenched mid next week, it's not necessarily bone dry as the 18z demonstrates the potential scenario of a secondary low from the NW to bring a snow event, on this run the south Weds 13/01.

Though there would be usual worry about mild sectors on here with such features, getting the deep cold air far enough south before any such feature is looking increasingly achievable. The max temps mid next week will be a shock in the south given what we got used to in December

 

but it is the day 10 EPS mean that really gives the confidence that this ain't likely to be just a cold snap, the trop PV has well and truly vacated the Arctic and split into 2 -one vortex for N Europe and one for N America, that pattern won't shift too quickly

Edited January 4, 2016 by Nick F

[knocker]

 

7 minutes ago, Nick F said:

Once the cold air is entrenched mid next week, it's not necessarily bone dry as the 18z demonstrates the potential scenario of a secondary low from the NW to bring a snow event, on this run the south Weds 13/01.

Though there would be usual worry about mild sectors on here with such features, getting the deep cold air far enough south before any such feature is looking increasingly achievable. The max temps mid next week will be a shock in the south given what we got used to in December

 

but it the day 10 EPS mean is what really gives the confidence that this ain't likely to be just a cold snap, the trop PV has well and truly vacated the Arctic and split into 2 -one vortex for N Europe and one for N America, that pattern won't shift too quickly

According to tonight's EC32 it shifts it pretty quickly. Of course I'm just spinning it really.

Edited January 4, 2016 by knocker

[Mucka]

Just for the beauty of the synoptic. (not especially cold)

That is such a long fetch Northerly it is almost a Southerly. 

Edited January 4, 2016 by Mucka

[Nick F]

Just now, knocker said:

For even more fu

According to tonight's EC32 it shifts pretty quickly. Of course I'm just spinning it really.

Trust you to put a downer on the cold ramping - you'll be reaching deeper into FI for those mild charts soon

The EC32 has +heights over the pole through most the run with Atlantic ridge re-appearing again though. I guess it's how one interprets it overall.

[Paul_1978]

35 minutes ago, BLAST FROM THE PAST said:

And it still not in the bag by any means yet......but we have movement in the right direction

 

BFTP

Indeed - why do I have the nagging feeling it's all going to fall on its ar$e the closer we get? 

[Mucka]

ECM London ensembles say cold spell on the way! 

Edited January 4, 2016 by Mucka

[knocker]

16 minutes ago, Nick F said:

Trust you to put a downer on the cold ramping - you'll be reaching deeper into FI for those mild charts soon

Wouldn't dream of it I leave that sort of skulduggery to the cold rampers.

[feb1991blizzard]

Just now, Mucka said:

ECM London ensembles say cold spell on the way!

WOW!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!                         WHAT A TURNAROUND.

 

[Nick F]

4 minutes ago, Mucka said:

ECM London ensembles say cold spell on the way! 

A nice tight cluster of members between +5C and -5C even to the end ... so perhaps more than a cold snap.

[feb1991blizzard]

2 minutes ago, Nick F said:

A nice tight cluster of members between +5C and -5C even to the end ... so perhaps more than a cold snap.

What do you reckon though Nick?, should we wait another 24 hours for 2 more ECM suites or will the met office come on board in the middle of the night with their update?.

[snowking]

13 minutes ago, Mucka said:

ECM London ensembles say cold spell on the way! 

Spot the Murr run...

 

SK

[feb1991blizzard]

A good 7 or 8 GEFS members flatlining at between -5 to -10  850hpa temps now, not an absolute classic yet, for that you need the mean to hit -7c and a decent number to flatline between -10 to -15 but a heck of a lot better anyway.

[Nick F]

1 minute ago, feb1991blizzard said:

What do you reckon though Nick?, should we wait another 24 hours for 2 more ECM suites or will the met office come on board in the middle of the night with their update?.

I would be safe and wait another 24 hrs, though northerlies are generally more likely to verify at that range than easterlies, so would say 70 % chance of a northerly, 50% chance of cold air hanging around more than 2-3 days. MetO update tomorrow likely to be more optimistic than just a cold snap.

[feb1991blizzard]

1 minute ago, Nick F said:

I would be safe and wait another 24 hrs, though northerlies are generally more likely to verify at that range than easterlies, so would say 70 % chance of a northerly, 50% chance of cold air hanging around more than 2-3 days. MetO update tomorrow likely to be more optimistic than just a cold snap.

Yes agree, with that, I think they wont do anything in  the night update though, they will wait until the 0z's, I like to see more GEFS members support before finally climbing on board, particularly as there isn't overwhelming teleconnective / strat support yet but its looking a heck of a lot better though - thanks for your views.

[Mark Neal.]

Judah Cohen latest thoughts as cold spell begins to show in models for our part of the world..

http://www.aer.com/science-research/climate-weather/arctic-oscillation

[Bullseye]

Can I ask why the PV is split into two yet going by data we are experiencing strongest PV since 1970, is this down to the MJO and wave 2 activity  (which according to few tweets is coming to an end) which is showing the cold potential? Thanks.

[Swave Snow]

6 hours ago, feb1991blizzard said:

 

 

 

Let's see what happens 

 

On another note if you look at the evolving satellite loops the push from the east looks much stronger and expanding all the time. But I've see that type of thing before for it to squash out as the Atlantic rolls in

Edited January 5, 2016 by ajpoolshark
removed off topic quote

[Mucka]

MetO mention a possibility of a "brief" cold interlude but hopefully they will revise that, especially as their own model looks like setting up for a cold spell to me or maybe they prefer GFS which of course is not as promising for cold lovers.  (144 comparison)

GEM with a huge Atlantic block in contrast with GFS which is pretty awful for coldies  out to day 10

Edited January 5, 2016 by Mucka

[Abyss]

The Gfs stalls the low over us for days even as the HP in the Atlantic edges east toward us it's static for quite some time.  I'm a novice at reading charts but it seems strange how it lingers for so long as there is no block to the East. Is there any merit to what I said and please enlighten me if I'm missing something. Thanks

[Mucka]

19 minutes ago, -Bomber- said:

The Gfs stalls the low over us for days even as the HP in the Atlantic edges east toward us it's static for quite some time.  I'm a novice at reading charts but it seems strange how it lingers for so long as there is no block to the East. Is there any merit to what I said and please enlighten me if I'm missing something. Thanks

I will try my best. First it is useful to view charts in NH view as this is very intuitive way to learn and see how pressure patterns develop and low pressure interacts with high pressure.

It is just the way GFS models the trough. We need a deep trough to the East of the block to aid the WAA. Think of the ridge as being squeezed between to areas of low pressure like toothpaste in a tube .

The reason GFS doesn't build a decent ridge is because of a flatter upstream pattern which could be thought of as just squeezing the top of the tube and then wiping the top away (which is the energy moving over the ridge flattening it out) instead of squeezing from the bottom.

Check these jetstream charts for 168h coming off the US East coast, the first is GEM and the 2nd GFS. Note how GEM is digging Southeast while GFS is flatter.

and again 192.

Edited January 5, 2016 by Mucka

[Abyss]

Thanks Mucka. Great explanation especially at this hour.

[Mucka]

20 minutes ago, -Bomber- said:

Thanks Mucka. Great explanation especially at this hour.

Thanks and you're welcome. A bit of a clumsy analogy and I'm sure someone else could do a better job but you are stuck with me at this ungodly hour. 

GFS ensembles a real dogs dinner. Hard to take anything GFS is churning out on face value at the moment though it would be fair to say it favours a faster flatter pattern than what would we (coldies) like overall.

London(ish) ensembles

Clearly a long way from being as convincing as last nights ECM.

It will be interesting to see if ECM wavers this morning or it just just looks at GFS a bit like this...

Edited January 5, 2016 by Mucka

[Ali1977]

Very dissapointing GFS, if the ECM goes the same way this place is going to be depressing this morning...

[northwestsnow]

Well gfs has put a bit of a dampner on proceedings !!

UKMO looks more amplifies at 144 so i'll not concern myself too much with gfs at the moment.

[Mucka]

ECM 144 not great (for Atlantic ridge), more GFS than UMO upstream but with better orientated trough for cold. comparisons, UKMO, ECM, GFS

 

 

Edited January 5, 2016 by Mucka