Model Output Discussion - Cold spell ending - what next?

[Hotspur62]

4 minutes ago, MJB said:

GFS smashes up the PV, this is a good trend we are seeing.

Feb 4th, so much potential from here going forward. Yes yes yes yes it's deepest FI but worth keeping an eye on 

Scandinavia and Eastern Europe well and truly in the freezer again.Apart from a few days this week where milder temperatures occur this has been a winter to remember for them .The trough seems to have been stuck over them since late October it seems.A winter of the 80s for them with record cold temperatures.

[Johnp]

Yep, looks like the PV is going to blow itself out by the first few days of Feb, then we have to see where the cards fall.

[Catacol]

46 minutes ago, Cleeve Hill said:

Hi Blue

Not really. Lots of tentative ideas for sure but certainly not as bullish as METO. I'm not being critical at all and when I look at the models we can see a pattern change in time but the signal I see is not as clear and straightforward for NW members to call it as the METO are. I hope they're right. 

Not sure who you have been reading, but the majority of the core posters in here that tried to read the season as a whole were looking at February to be the most significant wintry zone.

Im watching developments in the strat with a sinking sense of doom. Our tropospheric pathway to cold has been positive all season so far, and we have seen 2 out of 3 predicted cold snaps/spells come to pass, early December being better than expected and last week a bit disappointing. Xmas was a bust. But a fully reflective stratospheric response to the warming impacts that occurred through this month is exactly what we don’t want to see, and I have mused over the importance of the strat before as the dominant driver in most winter seasons. Early January we were so close to a major SSW - and it has now turned turtle and looks as though the strat will be above average before too long.

The science of strat warming impacts is still not clear. Even the big guns such as Butler and Cohen called a SSW for early January, reflective impacts not what was expected. It is way over my head as to why in some seasons the warmth is absorbed and breaks the vortex up, and other times the warmth bounces off the vortex core and reflects zonal forcing back into the trop. One thing I do know is that CC is cooling the stratosphere and, on average, this means stronger zonal forcing for each and every winter going forward. It is our CC winter handicap that every year we are going to need to see overcome.

Back to this winter. No doubt that tropospheric forcing is going to support blocking in the right places for U.K. winter starting approx next weekend. The strength of that forcing will build over the following 2 weeks. I had expected that to occur while we still had some blocking in place, but strat impacts have wiped that out in about 72 hours. So we have to build a blocking pattern from scratch. Quite doable….but not if the strat fires up and grabs control. Fine lines as ever, but I would say the odds of a cold February have now lengthened despite the confident assertions of the seasonal models and our reading of pacific led forcing.

Much to watch through the coming week. All eyes on the strat, perhaps for the first time this winter. We may have been guilty of downplaying it this winter, perhaps the result of a quiet @chionomaniac, and we have to hope that reflective impacts are being overplayed and trop drivers can seize control once again. For those of a research mindset this paper is interesting. 44 reflection events identified in the modern record, and on 35 of those events an SSW was prevented. These reflective events are common. See appendix A1.

Stratospheric downward wave reflection events modulate North American weather regimes and cold spells

WCD.COPERNICUS.ORG

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Abstract. The Arctic stratospheric polar vortex is an important driver of mid-latitude winter cold spells. One proposed coupling mechanism between the stratospheric...

So much still to learn.

.

 

Edited January 21, 2024 by Catacol

[Mike Poole]

GEM not without potential at T240.  Retrogression underway and nothing too untoward lurking upstream.

GFS has at least dismembered the vortex by the close of play.  That signal, at least, is consistent.  

But we are increasingly in need of a bit of luck as we move into February.  A commodity that has been in short supply this winter (and last winter…and the one before…etc…)

[bluearmy]

51 minutes ago, Cleeve Hill said:

Hi Blue

Not really. Lots of tentative ideas for sure but certainly not as bullish as METO. I'm not being critical at all and when I look at the models we can see a pattern change in time but the signal I see is not as clear and straightforward for NW members to call it as the METO are. I hope they're right. 

Exeter are calling a higher chance than usual of north or east winds as we head towards mid feb.  That likely places a block to our nw or north. not particularly specific but possibly reflects an agreement between glosea and ec46 clustering.  Whilst the scandi ridge option seemed to catch a few off guard with its appearance within 10 days on modelling earlier last week, the ens suites that pushed that ridge also failed to maintain it and sent lower heights across to scandi as week 2 progressed.  I think many here expected to see HLB showing by the end of jan. Some model runs are expanding a monster of a Siberian high end jan but it seems that the upstream tpv will see that off as far as it influencing w europe.  It seems that we have to go through the cycle of the tpv sending a chunk to scandi and then we wait to see where the wave break sets up the upper ridge that follows. 
 

the seasonals have been fairly bullish on height rises to the wetst or northwest in feb - my take is that many here haven’t seen any reason to dismiss that.  We just have to get through another transition of zonal flow which sadly is longer than many hope to see. 

[Mike Poole]

13 minutes ago, Catacol said:

Much to watch through the coming week. All eyes on the strat, perhaps for the first time this winter. We may have been guilty of downplaying it this winter, perhaps the result of a quiet @chionomaniac, and we have to hope that reflective impacts are being overplayed and trop drivers can seize control once again. For those of a research mindset this paper is interesting. 44 reflection events identified in the modern record, and on 35 of those events an SSW was prevented.

I think the strat has been very important this winter.  Ever since the Canadian warming event.  There has been a long period where the trop vortex has been allowed to do what it wants, another year - that could have resulted in an epic cold spell.  But as luck would have it, this year, it didn’t.

I think there is a lot still to be understood, and maybe research into the strat events this year will shed some light later.  But it isn’t all about the SSW that wasn’t in early Jan, nor is it all about the SSW that was but probably shouldn’t have been, just gone.  The whole evolution up above has seemed weird.  

[northwestsnow]

4 hours ago, MJB said:

Takes us to May mate..................that really is a Winter is over post lol 

Oh god lol yes I meant 10 days  

[Stephen W]

36 minutes ago, bluearmy said:

Exeter are calling a higher chance than usual of north or east winds as we head towards mid feb.  That likely places a block to our nw or north. not particularly specific but possibly reflects an agreement between glosea and ec46 clustering.  Whilst the scandi ridge option seemed to catch a few off guard with its appearance within 10 days on modelling earlier last week, the ens suites that pushed that ridge also failed to maintain it and sent lower heights across to scandi as week 2 progressed.  I think many here expected to see HLB showing by the end of jan. Some model runs are expanding a monster of a Siberian high end jan but it seems that the upstream tpv will see that off as far as it influencing w europe.  It seems that we have to go through the cycle of the tpv sending a chunk to scandi and then we wait to see where the wave break sets up the upper ridge that follows. 
 

the seasonals have been fairly bullish on height rises to the wetst or northwest in feb - my take is that many here haven’t seen any reason to dismiss that.  We just have to get through another transition of zonal flow which sadly is longer than many hope to see. 

But, haven’t the unexpected strat developments taken everyone by surprise this year including the experts? As per Catacol’s post above, this looks to be bouncing back to above average and could well override any trop led developments that would otherwise have led to cold developing in February.  Also, I have found that the longer term MetO updates sometimes take a little while to update probably because they are waiting for a more difinitive signal, ie waiting to see whether the strengthening strat does indeed become the dominant factor over the next week or so.  I guess we will have to wait and see on that one.

[WYorksWeather]

Wetterzentrale is giving me issues tonight, so here's the chart from TWO instead. Overall a very mild picture once again on the 12z ensembles.

TWO's version of the 2m temperature chart is too condensed to read easily, but Wetterzentrale is still showing raw temperatures which may be compatible with a daily record break on the 23rd (15.2C to beat, raw output 13C-14C), staying very mild but somewhat less extreme to the 26th, then nearer normal but still above average, especially by night.

I note that Met Office are now talking mid-February for any cold spell. Of course this can't be ruled in or out based on ensembles that only run to early February, but it does look like we're now at a point where at a minimum, the rest of January can be written off as far as cold goes, beyond the usual frost and fog in places and hill snow for Scotland.

[bluearmy]

24 minutes ago, Stephen W said:

But, haven’t the unexpected strat developments taken everyone by surprise this year including the experts? As per Catacol’s post above, this looks to be bouncing back to above average and could well override any trop led developments that would otherwise have led to cold developing in February.  Also, I have found that the longer term MetO updates sometimes take a little while to update probably because they are waiting for a more difinitive signal, ie waiting to see whether the strengthening strat does indeed become the dominant factor over the next week or so.  I guess we will have to wait and see on that one.

The reflected ssw last week is something that is adding to the current switch to zonal but I don’t think there’s much more to it 

the last few gfs op runs have been showing notable negative flows above 75N in the lowest part of the  strat and trop.  The last two runs have shown this to be working its way up into the strat and weakening the flow a little higher up.  Infact, looking at the 12z gefs, shows the heights transferring quickly up through the strat from low down.  That takes us back to where we have been for the past month or so with a very coupled atmosphere and the trop in charge of the menu. 

[MJB]

2 hours ago, Hotspur62 said:

Scandinavia and Eastern Europe well and truly in the freezer again.Apart from a few days this week where milder temperatures occur this has been a winter to remember for them .The trough seems to have been stuck over them since late October it seems.A winter of the 80s for them with record cold temperatures.

My colleagues in Scandi have said the snowstorms they had last week were terrific and the cold amazing 

[Mike Poole]

ECM clusters this evening, a bit more promise than this morning.  Not much in the T192-T240 timeframe:

Straight westerlies by day 10 which ever road you take.  T264+:

Now all 3 clusters show an Atlantic ridge by day 15, most pronounced on cluster 1 (20 members).  I thought this was the firm direction of travel yesterday, but the 0z EPS didn’t support it, it is back on now so maybe safe to discount the 0z suite?  The models can be grumpy in the mornings .

[AO-]

4 minutes ago, Mike Poole said:

ECM clusters this evening, a bit more promise than this morning.  Not much in the T192-T240 timeframe:

Straight westerlies by day 10 which ever road you take.  T264+:

Now all 3 clusters show an Atlantic ridge by day 15, most pronounced on cluster 1 (20 members).  I thought this was the firm direction of travel yesterday, but the 0z EPS didn’t support it, it is back on now so maybe safe to discount the 0z suite?  The models can be grumpy in the mornings .

To illustrate with the EPS for NE Netherlands. Milder than average with some colder days inbetween. Even frost is hard to find. Even the precipitation signals have increased dramatically. Can't make much of it. GB is obviously better of when it comes to a Greenland ridge. Nothing interesting with respect to wind direction. 

[Eagle Eye]

Nothing really to add to this for now, I think I've done enough in-depth discussions so far this Winter. US pattern same as late December but longer could mean UK pattern similar. 

[Daniel*]

Evidently a way to go with this but Met Office musing of a cold spell mid month would tie nicely with such a development. 

 

[Daniel*]

Murmurs of a less hostile state into early Feb… a work in progress! Still a long way to go….

[Uncertainty]

Don’t give up hope…

Except if your hope is within the next 15 days that is

Give the above the theme of the mo update won’t change. 
 

@Daniel*having Eric on board is positive too. Somewhere early Feb then for a big pattern change. 

[AO-]

42 minutes ago, Uncertainty said:

Don’t give up hope…

Except if your hope is within the next 15 days that is

Give the above the theme of the mo update won’t change. 
 

@Daniel*having Eric on board is positive too. Somewhere early Feb then for a big pattern change. 

That's only 696 hours away. Luck is the key word these days. 

[Daniel*]

12 minutes ago, AO- said:

That's only 696 hours away. Luck is the key word these days. 

That may be but El Niño winters are known for being more backloaded, so the dice is slightly more in our favour than it would be during Nina winter. GLOSEA was clearly very interested in -NAO this month which it usually isn't. 

Edited January 21, 2024 by Daniel*

[feb1991blizzard]

Decent displacement.

[Rain All Night]

An overview of this afternoon's global model runs.

Deterministic runs from Mon 22nd to Sun 28th

Not the completely dry second half of the week I'd hoped for, but it doesn't look as though anything as bad as the storms of the first half of the week will reach us again.

Ensemble means from Mon 29th to Sun 4th

The south of Britain continuing to have a chance at some dry days by the looks of it. The high pressure to our south still looks like it wants to shift to the west a bit.

Edited January 21, 2024 by RainAllNight

[feb1991blizzard]

At least there are quite a few runs lately really weakening the tropospheric vortex over Greenland, where not so long ago that wasn't the case.

perhaps a response to this.

 

[feb1991blizzard]

Where is everyone? - i know the means are still flat and its only a couple of long range ops but when has this thread ever not gone mad over the aforementioned? in fact it was busier the other day when flat with a big Greenland PV was showing practically unanimously across all suites.

Edited January 21, 2024 by feb1991blizzard

[saintkip]

8 minutes ago, feb1991blizzard said:

Where is everyone? - i know the means are still flat and its only a couple of long range ops but when has this thread ever not gone mad over the aforementioned? in fact it was busier the other day when flat with a big Greenland PV was showing practically unanimously across all suites.

In the storm thread 

[joggs]

10 hours ago, Eagle Eye said:

 

Nothing really to add to this for now, I think I've done enough in-depth discussions so far this Winter. US pattern same as late December but longer could mean UK pattern similar. 

If ne America goes cold, surely that'll just fire the jet up?.

Not really good for us coldies here imo.