Model Output Discussion - Into February

[nick sussex]

Quite an unusual set up if of course it verifies!

We have the high over Europe and some colder air heading west along its southern flank .

Still uncertainty as to how much of that gets nw into the UK as the flow turns more se .  

The models are also toying with some PM air trying to head se between day 5 and 6.

 

[Mike Poole]

This second burst of WAA has piqued my interest, shown here on GEM at T192:

Piggy backing on the initial height rises towards scandi, this is one to watch perhaps.  Options there (possibly including last night’s pub run!)

[Johnp]

14 minutes ago, Gowon said:

 

The GEM gives us some snow next Thursday/Friday

GEM is now looking more ‘GFS-like’ than GFS which is ironic. 

[alexisj9]

9 minutes ago, Johnp said:

GEM is now looking more ‘GFS-like’ than GFS which is ironic. 

Doesn't surprise me, tbh. I'm not sure the fat lady has sung yet on the high. Was expecting the low to be modelled stronger today cause of how mild today has been. Put more of a temp difference in, so it being stronger and making the high higher makes sense.

[feb1991blizzard]

25 minutes ago, Mike Poole said:

This second burst of WAA has piqued my interest, shown here on GEM at T192:

Piggy backing on the initial height rises towards scandi, this is one to watch perhaps.  Options there (possibly including last night’s pub run!)

Its on the GFS as well, several bursts of WAA roughly aligned with the 0 degree longitude.

[RhHh]

34 minutes ago, Gowon said:

 

The GEM gives us some snow next Thursday/Friday

How is that possible under high pressure?

[SLEETY]

6 hours ago, Spah1 said:

There was no disappointment. The 2 main models never showed anything from the East

UKMO had us in mild West winds start of next week, so it also was miles out, gfs wasn't far out in the end 

[Gowon]

1 minute ago, RhHh said:

How is that possible under high pressure?

From the low which moves north from the south 

Edited February 3, 2023 by Gowon

[Ali1977]

Obliterated 

[Cuban Zebra]

I think this weekend is going to be interesting model watching, it seems primed for a good old GFS picks up something, drops it again then roars back in a t 48-72!!!!

[snowking]

Always worth remembering when monitoring the stratosphere that temperature is just one element of what we're looking to shift.

When looking at heights too:

Not quite obliterated, but a huge Wave 1 pushes the vortex off of it's usual axis across to the Siberian sector and gives it a very good stretching too.

Battered and bruised at this stage, and we can also see from looking at the wind charts that a technical SSW has taken place (and a pretty significant one at that):

All in all very good signs again - vortex moved completely off-axis in a useful direction at 10mb at least and zonal wind speeds significantly reduced (and in fact here reversed).

 

However as always trying to figure out how this translates to conditions in the troposphere is a fun game for the coming weeks.

Edited February 3, 2023 by snowking

[bluearmy]

15 minutes ago, RhHh said:

How is that possible under high pressure?

Upper cold pool 

[Chesil View]

The blocking appearing in the latter stages of the 12z Gfs seems more in line with what one might expect timing wise with regards to suggested strat developments going forward. This past weeks gfs shenanigans suggesting the coming week would see a bfte was always pretty far fetched. But something similar after mid Feb would not surprise me at all.

Edited February 3, 2023 by Chesil View

[RhHh]

1 minute ago, bluearmy said:

Upper cold pool 

Thanks all, will watch with interest as nothing showing in the forecast at the moment. 

[feb1991blizzard]

no split yet though.

[Frosty.]

I’m all in with P4 GEFS 12z… WOW Frosty, you’re as cold as ice!..you’re move mr bond!  

[tight isobar]

Redundant/- yet creative cold pool uk encryption wises up a little!. And this should be noted for the clause of gain- as watery Synoptics, can neither dispele/ displace- incursion!!! Ok NO beast rolling sync!.. but as I say numerous times..... there IS lots of scope for an, increase in sharper incurring cold @ 850 hpa.. this is an interesting plot ... 

[Mike Poole]

When a potential SSW is showing, a game I sometimes play is to look at the pressure evolution of the first half of a GFS run, and then guess whether the strat warming will be stronger or weaker in the day 8-16 period.  And I am absolutely rubbish at it!  I thought the 12z would be a stronger warming than the 6z, but actually it isn’t.  It’s good enough to do the job though, with a technical SSW at T264.  

I’ve noted before that the precursor patterns for a SSW are complicated, and the main one we look for is the Ural high Aleutian low combination, which has come back into contention after a week or so’s absence.  My understanding is that this, in and of itself, would lead to only a displacement SSW, not a split, with other patterns also required for the latter.  

There seems increasing evidence now for a SSW around 14th February.  And this one looks as though it could be a proper reversal with zonal winds dipping well below zero, with op and ensemble support:

I can see the obstacles to UK cold being removed one by one in the coming weeks.  The strong trop vortex, maybe aided by the flushing down of westerlies from the previous minor warming, should lose its grip.  The recent ‘failed easterly’ also tells us something - GFS would not have shown the scenario it did if it was completely outrageous, so the atmosphere could be primed for a proper scandi high later.  All the attention has been on the GFS miss, but now it did miss, actually for me the more significant story was how much the UKMO was wrong in predicting a return of the Atlantic on the same timescale - this failed massively!  

If this SSW does occur, in more or less the way shown in the current modelling, the trop response should be pushing at a partially open door to establish a favourable block this time, and an easterly before the end of winter is now a distinct possibility, in my view.  Which may well last into March - a month which, like it or not, seems to offer a greater chance of snow these days than any of the winter months.  

One more push - let’s chase this one down!

All the best.

Mike

 

[Gowon]

The high looks further north on the ECM with colder uppers

[Panayiotis]

I do wonder if the GFS was onto something but caught it a bit early. When it’s done it in the past, the pattern normally shows up quickly on all the models at a later time frame. Will be interesting to see if this is one of those times… 

[Jacob Gamer]

How severe are cold snaps that follow SSWs on average?

[bluearmy]

1 minute ago, Jacob Gamer said:

How severe are cold snaps that follow SSWs on average?

There are no rules I’m afraid Jacob 

one step at a time 

let’s get the ssw within day 10 and see where the vortex segments are likely to be and if it looks to downwell quickly  

[Notty]

1 hour ago, SLEETY said:

UKMO had us in mild West winds start of next week, so it also was miles out, gfs wasn't far out in the end 

I always ‘feel’ that GFS gets a broad idea a couple of weeks out but gets the detail wrong nearer the time. 

Edited February 3, 2023 by Notty
Grammar

[Ali1977]

What percentage of the last EPS went fur a SSW?

I’m Hoping the signal just gets stronger and stronger now, with the faster QTR ever . I also expect to see some outlandish ens appearing - no doubt starting with the pub run

[Frosty.]

The GEFS 12z mean doesn’t support this whatsoever, but hey, I’m an optimist hoping for a nice late surprise in this pathetic winter!…don’t give up on us!!  

Edited February 3, 2023 by Frosty.