Model Output Discussion - Into February

[bluearmy]

1 hour ago, nick sussex said:

BA should we be unduly concerned that the GEFS show no downwelling ?

The ECM clusters 2 and 3 look like they do have that . 

there are quite a few gem members that are finding amplification 

the best tool for week2 strat modelling are the eps with their higher resolution on levels up there 

the gefs will see it eventually if it’s there 

always the thought that an eps suite can be skewed so continuity required 

1 hour ago, Ladyofthestorm said:

Just a thought the PV and stratosphere is warming off the backend of a record breaking low point. 

 

Maybe we should be looking for historical patterns of below average Stratospheric temps and reversals.  It's a big hill to climb! 

 

The warming late January took care of that 

 

1 hour ago, nick sussex said:

It would be ironic if when we wanted coupling between the strat and trop it went AWOL . And when earlier in the year we didn’t want it , it of course happened ! 

It’s also frustrating that we don’t have the ECM zonal mean sections which Berlin University hasn’t updated since last year .

Exeter have sight of the eps cross sections - it’s social media where we’ll some info, especially after the 46 this evening and day 15 on the eps is a good place for the 46 to head into weeks 3 and 4 later

Edited February 9, 2023 by bluearmy

[Rain All Night]

30 minutes ago, knocker said:

In line with the displaced stv being over N. Europe at the end of this period although it should be noted the gfs does not follow. All to play for

All three, days 11-15:

Edited February 9, 2023 by RainAllNight

[Bricriu]

2 hours ago, cyclonic happiness said:

I take it due to the lack of posts, the dirge of boring weather is to continue?

It has been well flagged that anything of interest in terms of cold weather is not going to happen- if it happens at all - till the  end of the month at the earliest.  

[minus10]

Noticeable that the ens mean for 0z Ecm, Gfs and Gem is heading down back towards the LT mean ...admitadly from a fairly high point...will be looking to see if that trend continues..

..at least its a start...maybe...

[feb1991blizzard]

38 minutes ago, bluearmy said:

 

 

Exeter have sight of the eps cross sections - it’s social media where we’ll some info, especially after the 46 this evening and day 15 on the eps is a good place for the 46 to head into weeks 3 and 4 later

its a corking place but only if the 0z eps is backed up (on a broad brush basis) by the 12z, else you would have to be cautious placing too much stock in the 46.

Edited February 9, 2023 by feb1991blizzard

[Rob 79812010]

Going off topic a bit (can't find the winter moans and ramps), this winter may well end up slightly colder than the 91 to 20 average but not 61 to 90. Shame we had the very mild spells really. Had we had average weather with the extended cold spells, we'd have been well below this winter. I think it's been a good winter really. Good snow for some areas, lots of frosty mornings and more recently some great sunsets. Damn the mild spells!!

[bluearmy]

25 minutes ago, RainAllNight said:

All three, days 11-15:

With most of the action beginning around day 14, the five day charts from day 11 are going to be less informative re the possible amplification 

[Rob 79812010]

11 minutes ago, Rob 79812010 said:

Going off topic a bit (can't find the winter moans and ramps), this winter may well end up slightly colder than the 91 to 20 average but not 61 to 90. Shame we had the very mild spells really. Had we had average weather with the extended cold spells, we'd have been well below this winter. I think it's been a good winter really. Good snow for some areas, lots of frosty mornings and more recently some great sunsets. Damn the mild spells!!

Should add that's for UK. If we end up 1 above for Feb we should just be on the slightly colder side. Some model output may just make possible

[Cambrian]

Yes, some notable trends showing through in the 0z GEM ensemble means and anomalies in the later part of the run, especially in terms of the fairly swift demise of the European high. 

From solid Euro high at day 8, heights decaying and getting shoved south by day 12, and by day 16, it’s a complete rout. 

 

 

Amplification up through to Iceland and a break to the link of low heights between the Canadian and Siberian lobes of the PV. Low heights very decisively pushing down into Europe, with the beginnings of a Scandinavian trough.

 

What a very exciting thing to see! The continued development and more informed positioning of any Scandinavian trough will be of huge interest over the coming days.

Edited February 9, 2023 by Cambrian

[Rob 79812010]

10 minutes ago, Cambrian said:

Yes, some notable trends showing through in the 0z GEM ensemble means and anomalies in the later part of the run, especially in terms of the fairly swift demise of the European high. 

From solid Euro high at day 8, heights decaying and getting shoved south by day 12, and by day 16, it’s a complete rout. 

 
 
 

Amplification up through to Iceland and a break to the link of low heights between the Canadian and Siberian lobes of the PV. Low heights very decisively pushing down into Europe, with the beginnings of a Scandinavian trough.

 

What a very exciting thing to see! The continued development and more informed positioning of any Scandinavian trough will be of huge interest over the coming days. 

Would you mind explaining the significance of a Scandinavian trough? Have read a few times. Fairly new to all this

[minus10]

Well gfs6z trying to find the scandi high again..

[phil nw.]

1 hour ago, mushymanrob said:

ay up .... whats happening here?

 

Interesting mushy.Models just starting to factor in the ssw and MJO effects,as we thought towards month end.

The Tropospheric pv over Scandinavia is a good trend.

A way to go wrt to surface detail but promising signs if looking for a late cold spell.

[Singularity]

5 hours ago, bluearmy said:

I was just coming on here to say that a ridge to our west is inevitable- but how long it takes to establish and how far west it ends up woukd be my question. If anything, the spv looks to displace into Russia rather than scandi. The U.K. could find itself just that bit too far to the west in the -AO/NAO pattern. 
 

currently, the disconnect between 10/20 hpa and 30/50 hpa is notable at day 10. Until we get that mid spv extension into Canada to retract, we are fighting a losing battle in the trop without some teleconnective help.. so end feb and into March now unless we get an unexpected surprise from the nwp if it hasn’t effectively recognised the strat reversal in its output.  That’s pretty much within a week so not long to wait on the higher res runs. 

Wouldn't that be ironic, to be left high & dry when usually with displacements we're too far east with any -NAO tending to be west based.

Without the MJO helping out I think the negative zonal wind anomalies would struggle to get through the mid-stratosphere. As it is, the SSW itself makes a strong MJO more likely via cooling the tropical stratosphere, and there's good model consensus now for it to be crossing the Pacific as we transition from Feb into Mar.

Interesting to see EPS already exploring some -NAO ideas for the final 4-5 days of Feb. Even with an accelerating trend to the MJO projections, that's a little sooner than I expected but I can see how it could happen if the SSW and MJO both help each other out, so to speak, making it possible for high pressure to establish in the Greenland vicinity sooner than usual relative to the MJO cycle (especially during a La Nina base state when the -NAO response is usually more from phases 7-8 as opposed to 6-7).

Edited February 9, 2023 by Singularity

[North-Easterly Blast]

25 minutes ago, Rob 79812010 said:

Going off topic a bit (can't find the winter moans and ramps), this winter may well end up slightly colder than the 91 to 20 average but not 61 to 90. Shame we had the very mild spells really. Had we had average weather with the extended cold spells, we'd have been well below this winter. I think it's been a good winter really. Good snow for some areas, lots of frosty mornings and more recently some great sunsets. Damn the mild spells!!

I think that there is now a good chance of winter 2022-23 ending up slightly colder than the 1991-2020 average, but being below the 1981-2010 or 1971-2000 average is looking less likely now, let alone being under the 1961-90 average.  For something of note, although this winter has not been particularly cold, this February only needs a CET of 4.3 or less to make it the coldest winter since 2012-13.  This now looks unlikely although it could be possible if a cold spell does materialize later in the month, but something in the 5s looks favourite for this month at the moment, which would mean that winter 2022-23 would finish a little milder than 2017-18, 2020-21 and likely 2014-15.

[Purga]

Not a single dissenter

[Eagle Eye]

Found a good chapter of Simon Lee's thesis to compare to now and hopefully help with the forecasting effects of the likely SSW. Given the pre-SSW driving AWB North Atlantic-Scandi this is strikingly similar to that chapter

We're in a good position with this attack on the Vortex here though to displace the main barotropic stability driven towards Scandi-Russia in part with the Ekman velocity support not completely breaking the Vortex.

Edited February 9, 2023 by Eagle Eye

[minus10]

55 minutes ago, Rob 79812010 said:

Would you mind explaining the significance of a Scandinavian trough? Have read a few times. Fairly new to all this

Scand trough because of its position usually allows for better advection or movement of polar maritime air and sometimes polar air over us...while at the same time pairing with an atlantic ridge reinforces that air movement...disturbances in the flow could enhance precipitation which if cold enough could result in snow... especially in the north...depending on how potent the whole of uk could see wintery precipitation..late winter/early spring troughs can be more meaningful for cold as sea temps are at their lowest..hope that helps...

[bluearmy]

The gefs are sniffing something - they can’t work out what it is yet …..

[Rob 79812010]

13 minutes ago, minus10 said:

Scand trough because of its position usually allows for better advection or movement of polar maritime air and sometimes polar air over us...while at the same time pairing with an atlantic ridge reinforces that air movement...disturbances in the flow could enhance precipitation which if cold enough could result in snow... especially in the north...depending on how potent the whole of uk could see wintery precipitation..late winter/early spring troughs can be more meaningful for cold as sea temps are at their lowest..hope that helps...

Ot really does and thanks so much!

[Johnp]

12 minutes ago, bluearmy said:

The gefs are sniffing something - they can’t work out what it is yet …..

Just about to say that. Day 12ish onwards and things are starting to happen but no consensus on anything yet. 

[Catacol]

12 hours ago, Singularity said:

The imminent now almost certain SSW has really caught my attention now because of two things: 

- The vortex looks to be displaced to Scandinavia which is at the eastern end of historical precedent. This doesn’t look to be the usual orientation of displacement which places the vortex above the North Atlantic & encourages strong troughs there. Instead, one more supportive of a -NAO pattern as the anticyclone locates above Greenland or close to there.

Provided, that is, the zonal wind reversal propagates down, which brings me to the second thing:

- Active MJO projected to cross Pacific in 2-3 weeks time. This aligns with the lagged displacement type SSW impact window of 2-4 weeks after the event. It means the MJO will be forcing the troposphere toward a -AO while the reversal is looking to ‘connect’ with it from above. So, the troposphere will be receptive to it rather than resistant. I believe this is a key factor behind some displacement type SSWs having major weather pattern impacts and others hardly any.

 

So overall, I think this SSW, provided it occurs, has a higher chance of forcing a -AO & -NAO episode sometime late Feb through mid-March than past precedent for displacement type events as a whole suggests.

No guarantees of course but plenty to keep an eye on in the modelling during the next 2+ weeks. 

Agree. Tag team of vortex positioning and pacific forcing for back end of the month. If the displacement was heading to Greenland then a totally different outlook - but if the models have a handle on the angle of displacement then we don't absolutely need a split to drag in cold air.

Importantly we have had quite an active pacific this season. If this continues then we get magnified MJO forcings.

I'm gonna wait a week or so before getting excited, but right now things are looking good for Winter's Final Act.

[Catacol]

Trend continues as per my post yesterday. EPS picking up on a growing signal for blocking to edge north...

[knocker]

31 minutes ago, bluearmy said:

The gefs are sniffing something - they can’t work out what it is yet …..

Unlikely to be the coffee

[Daniel*]

Change is on horizon folks… AO and NAO drifting negative on EPS in the extended from around 23rd. Winter’s last hurrah?

[bluearmy]

If we pay attention to the mid to upper strat as week 2 progresses on the gfs op (lower down is likely to be wrong because it’s gfs op), we can see much greater propensity to downwell through week 2 over the past few runs than had been the case