Model discussion highlights

[Mike Poole]

31 minutes ago, Ali1977 said:

Interesting strat at day 12, then it starts heating up again in deep FI. 

These things are all different aren’t they?  The two pockets of warming look unusual.  The 6z reverses at 10 hPa T204, and the zonal wind at 50 hPa is zero at T384, which suggests it is downwelling.  Also, lower down at 30 hPa and 50 hPa there is a split (not at 10 hPa). 50 hPa picture:

I think there is enough uncertainty in the strat evolution of the various GFS op runs, let alone the trop response, to allow for the possibility of something surprising out of this one…very interesting.

Original post: https://community.netweather.tv/topic/98326-model-output-discussion-into-february/?do=findComment&comment=4802977

[Catacol]

2 hours ago, sebastiaan1973 said:

In 2018 the MJO was extreme. This time probably not.  

Yes - near perfect synergy in 2018. High amplitude phase 7 MJO mid Feb, just perfect for getting the high lat blocking regime reinforced as the vortex split and downwelled super quick. It really was the most fabulous period of weather watching I have ever experienced. Happy memories.

One development today - the GFS run yesterday produced such a violent wave 1 warming that the vortex split. Not sure this is the most likely outcome...but a split rather than a displacement would offer a different route forward....

Original post: https://community.netweather.tv/topic/98326-model-output-discussion-into-february/?do=findComment&comment=4802984

[Ali1977]

A good METO blog on their latest SSW thoughts. I still think the last 3rd of the month could hold surprises but we’ll see!! 

Are we expecting a Sudden Stratospheric Warming? | Official blog of the Met Office news team

BLOG.METOFFICE.GOV.UK

---

Following a minor Sudden Stratospheric Warming (SSW) event in January, the Stratospheric Polar Vortex (SPV) has now recovered. Our forecasts for the coming week also...

 

Original post: https://community.netweather.tv/topic/98326-model-output-discussion-into-february/?do=findComment&comment=4802970

[Cold Winter Night]

20 minutes ago, North-Easterly Blast said:

We any of the SSWs in the 1960s to 1980s followed by a significant cold spell in the UK shortly afterwards?

Apart from the SSW in January 2009 leading on to the cold spell in early February that year, I do not think that any of the other SSWs in the 2000s were followed by much in the way of a cold spell shortly after, so unless we know when all the SSWs were, and if the UK did get a cold spell soon after, we do not know how favourable SSWs are in bringing a significant cold spell to the UK.

It remains difficult to attribute cold spells to SSW's with certainty.

Take for example the one in late January 1963. That winter had already earned a place in the hall of fame as the SSW hit, but more cold was produced in February. We can speculate, was that Feb 63 cold the result of the SSW? Or would it have followed anyway, since it was a cold one already? Or did the SSW perhaps prevent an even colder month?

Some SSW's were followed by cold spells, some were not. It is far from 1+1=2, if you consider that, for example, SSW's can be both the result and the cause of blocking events. That's why in many cases a serious cold spell preceded the SSW.
If you subdivide SSW's according to ENSO state and seasonal timing, you are left with very small sample sizes that do not show homogeneous outcomes. The complexity increases even more if you include MJO phases.

It is a subject that still needs a lot of research, that's for sure.

Original post: https://community.netweather.tv/topic/98326-model-output-discussion-into-february/?do=findComment&comment=4803160

[Mike Poole]

4 minutes ago, North-Easterly Blast said:

We any of the SSWs in the 1960s to 1980s followed by a significant cold spell in the UK shortly afterwards?

Apart from the SSW in January 2009 leading on to the cold spell in early February that year, I do not think that any of the other SSWs in the 2000s were followed by much in the way of a cold spell shortly after, so unless we know when all the SSWs were, and if the UK did get a cold spell soon after, we do not know how favourable SSWs are in bringing a significant cold spell to the UK.

I’ve posted this up before, it’s a chart of winter weather regimes (+NAO, -NAO, scandi blocking, atlantic ridge) which I’ve hacked to mark the approximate time of all the SSWs with an ‘S’.  A string of -NAO or scandi blocking days after a SSW might indicate a cold spell, +NAO the reverse. Obviously the regimes are wider than the UK, so no guarantee as to exactly what weather the UK experienced.  

Original post: https://community.netweather.tv/topic/98326-model-output-discussion-into-february/?do=findComment&comment=4803152

[Cheshire Freeze]

9 minutes ago, Weather-history said:

What is the success rate of CFS so far out? Out of  all the posters on netweather, you seem to champion CFS more than anyone. I would have thought out of anyone, you would know just how accurate these charts are?

They can be fairly useful. Essentially you need to treat them with caution when using them. Taking a snapshot of any given run in isolation  is obviously a no no but to keep tabs on the mean pressure anomalies etc and look for trends can be fairly fruitful.

In this instance the EC seasonal and CFS are both showing us the same thing, so we can have a bit more confidence in what the two of them are demonstrating for spring.

 

Original post: https://community.netweather.tv/topic/98326-model-output-discussion-into-february/?do=findComment&comment=4803319

[Met4Cast]

ECM showing a displacement of the SPV to Asia

Original post: https://community.netweather.tv/topic/98326-model-output-discussion-into-february/?do=findComment&comment=4803351

[Catacol]

18 hours ago, Mike Poole said:

Thanks, looks interesting, will have a read.  Just looking at the conclusions, my gut reaction is they look maybe slightly over-confident.  The reason I think that is that in recent years the QBO has been behaving somewhat erratically - which is a new phenomenon.  I’m not sure how this plays with frequency of SSWs (currently about 6 per decade) but the QBO is an important factor, so an impact is, I would have thought, possible.  

Worth saying that we know SSW events are often led by tropospheric patterns and we know that tropospheric patterns are forecast to be impacted by CC. eg northerly drift of the Hadley Cell with particular impacts on Europe. If trop patterns are shifting then SSW precursors are shifting in probability. I haven't read the research - but would want to know which variables were being looked at.

Original post: https://community.netweather.tv/topic/98326-model-output-discussion-into-february/?do=findComment&comment=4803455

[bluearmy]

Awaiting the cross sectional on that gfs op 

the heights through the atmosphere from 500hpa to 10hpa seem to respond in tandem with  that n pacific ridge punching into the pole 

It does look more trop led on the timeline but there could be a reflective wave back down from higher up - the cross sections charts will show how fluid the whole strat is on the reverse flow 

I think we are too hung up on what happens at 60N at times like this. 

Original post: https://community.netweather.tv/topic/98326-model-output-discussion-into-february/?do=findComment&comment=4803441

[Eagle Eye]

The +VE EAMT right now is likely to extend the Pacific jet and that may flatten out the North Atlantic pattern especially given the -VE EPO exiting wave recently. Unironically, an extended Pacific jet would help retract the Atlantic jet but the timing just seems slightly off from this and we look fairly likely to see -VE Greenland heights to fire up the jet. So unless the MJO Phase 6-7 can really get strong around the same time, I suspect we'll mostly be looking towards how this potential SSW acts until March.

GEFS

EPO-Fast

Don't be fooled by some of the anomalies such as the +VE heights over the Arctic mid-term as they aren't strong enough to just be a small deviation from normal.

Original post: https://community.netweather.tv/topic/98326-model-output-discussion-into-february/?do=findComment&comment=4803494

[Catacol]

OK - watching the impacts of next week's SSW roll forward is going to be interesting. GFS from yesterday much less aggressive with the warming which, the day before, was flagging a very rare wave 1 induced split. Today's image much more like what we might expect realistically I think, though snow hunters should certainly keep fingers crossed that the extreme split option reappears

:

With a much weakened vortex over the European side I continue to see a window for a cold high lat block to appear towards the end of February, a probability enhanced by MJO phases. So - we need to look for anomaly charts to move from the +NAO signature to one that sees ridging begin to push north.

EPS for 22nd Feb from last night's run

compared to the same date from the run the night before

I suspect 22nd Feb is a bit soon in any case to see a significant response to the SSW, but around about month's end I could see interest really pick up. It is all about timing and today is Feb 8...so bear in mind the fluidity of this timing context at such long range. But I am sticking my neck out and stating the direction of travel is set.

 

Original post: https://community.netweather.tv/topic/98326-model-output-discussion-into-february/?do=findComment&comment=4803482

[Singularity]

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. 

Original post: https://community.netweather.tv/topic/98326-model-output-discussion-into-february/?do=findComment&comment=4803777

[bluearmy]

We have lift off on the eps in the extended 

Original post: https://community.netweather.tv/topic/98326-model-output-discussion-into-february/?do=findComment&comment=4803821

[bluearmy]

6 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. 

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. 

Original post: https://community.netweather.tv/topic/98326-model-output-discussion-into-february/?do=findComment&comment=4803804

[bluearmy]

6 minutes ago, RainAllNight said:

Nice, is that where you were expecting a ridge to go?

Ideally yes - just concerned it would be extended into the east Atlantic - you’ll like the control at day 15 - solid trop response at day 10 

good starting point for the 46 weeks 3 and 4 later ……

Original post: https://community.netweather.tv/topic/98326-model-output-discussion-into-february/?do=findComment&comment=4803826

[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.

Original post: https://community.netweather.tv/topic/98326-model-output-discussion-into-february/?do=findComment&comment=4803878

[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).

Original post: https://community.netweather.tv/topic/98326-model-output-discussion-into-february/?do=findComment&comment=4803891

[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

Original post: https://community.netweather.tv/topic/98326-model-output-discussion-into-february/?do=findComment&comment=4803860

[Blessed Weather]

From this morning's GFS 0z run -  a great 3D sequence of the sPV coming under severe stress on the Zac Lawrence website. The perfect cylindrical shape at the start of the sequnce on the 14th Feb becoming a wobbling mess by the 20th Feb and not recovering through to the end of the run on the 24th. 

Source: https://www.stratobserve.com/misc_vort3d

Original post: https://community.netweather.tv/topic/98326-model-output-discussion-into-february/?do=findComment&comment=4803972

[Rain All Night]

10 minutes ago, Vikos said:

 

full reversal 

I googled "FNMOC-EFS" which is one of the outputs shown on that plot, and found that it is basically NAVGEM ensembles, which I didn't know existed!

Original post: https://community.netweather.tv/topic/98326-model-output-discussion-into-february/?do=findComment&comment=4803988

[Mike Poole]

31 minutes ago, feb1991blizzard said:

GFS looks a corker to me - reversal a constant in the entire extended. Exceptionally weak displaced vortex at 384.

 

Yes, I was just going to post something similar.  GFS 12z (and indeed 6z) look pretty good for location of the displaced vortex, and reversal T144 right through to the end of the run - bit more consistency on that longevity now too.  

It’s also looking like the MJO might be on a route march towards the favourable phases too, I’m not counting phase 3 in that - it has messed around in the Indian Ocean for long enough, and ECM has a rapid progression now to phase 6 at amplitude; as others have said, this could be very good timing giving some assistance towards blocking from the trop drivers at the same time as the strat pattern hopefully downwells:

I’m thinking that if we get a favourable proper ridge somewhere around the Greenland area it might home in on that location other things being equal - Greenland does seem to be a bit of an ‘attractor’ if the basic pattern is right, so there might actually be a bit of margin of error there if things go well, hint from the extended EPS this morning at day 15.  Nothing obvious at the end of GFS op runs yet though.  

The SSW is nailed now, a prolonged reversal looks favourite but not yet nailed on, the displacement looks favourable as far as we can see at the moment, and we wait developments in the trop end of the month.  Interesting model watching to come…

Original post: https://community.netweather.tv/topic/98326-model-output-discussion-into-february/?do=findComment&comment=4804027

[Uncertainty]

We’re still a good week or so for anything of interest trop chart wise. The reversal is still nearly a week away and the mjo whilst propagating is still in the +NAO phases.

However, the 0z eps chucked a curveball with an ahead of schedule FI dominated by MAR and -NAO types

The latest GEPS is also sort of flirting with the idea

 

This is quite a new signal, the extended range has been dominated by +NAO for a while now. The GEFS are less keen but the odd member really goes for an Atlantic ridge.

It’ll be v interesting to see where the ec46 takes the 0z eps signal. Any high lat blocking was previously progged for early March so we will need to examine the week 3 and 4 signal closely to see if there’s been a change.

For the  end w2 changes, Less time in phase 4 seems the more likely reason rather than a QTR but certainly the weakening zonal winds do allow for such mjo effects to take hold…

Original post: https://community.netweather.tv/topic/98326-model-output-discussion-into-february/?do=findComment&comment=4804055

[Cambrian]

Just to add to the discussion of the potential Scandinavian trough beginning to be hinted later on in the runs of some of the models, the 0z ECM ensemble mean had this at day 12 and day 15…

 

associated with an even stronger looking lobe of PV in the Barents Sea / Svalbard / Northern Scandinavia area than the 0z GEM was showing. 

The 0z ECM control at day 15 is a cracker though! Look at that air digging south.

  

@Rob 79812010 - thank you, to add to our chat via PM, looking at the coincident location of those uppers and all that precipitation this is the kind of northerly setup that could deliver more widely!

The models are in a very different place today than they were even only a day ago. I’m really looking forward to the 12z’s.

Original post: https://community.netweather.tv/topic/98326-model-output-discussion-into-february/?do=findComment&comment=4803959

[Cheshire Freeze]

7 minutes ago, Purga said:

Another appalling set of ENS coming out, not even any overnight inversion frosts now

As you go deeper into February you start to need deeper cold (cold uppers) to achieve a cold spell. By the latter part of Feb the solar input is about as potent as it is during mid October.

Original post: https://community.netweather.tv/topic/98326-model-output-discussion-into-february/?do=findComment&comment=4804032

[bluearmy]

Whilst the mean on the ec46 week 3 looks a bit meh with the ridge too far to the east, the clusters offers a greeny high 

weeks 4 and 5 promise a cold March based on heights and Increasingly damp 

Original post: https://community.netweather.tv/topic/98326-model-output-discussion-into-february/?do=findComment&comment=4804133