Stratosphere and Polar Vortex Watch

[bluearmy]

I bet even @inertius couldn’t find a mean chart like this at T372 from the archives ! 

Anyone ever recall seeing anything like that as a mean ? Those three vortex centres run in pretty well the same place for four days from T276 ..... 

interestingly that’s pretty well the WeatherBell 500hpa anomoly prediction for this winter ! 

Edited December 31, 2018 by bluearmy

[Snowman.]

30 minutes ago, bluearmy said:

I bet even @inertius couldn’t find a mean chart like this at T372 from the archives ! 

Anyone ever recall seeing anything like that as a mean ? Those three vortex centres run in pretty well the same place for four days from T276 ..... 

interestingly that’s pretty well the WeatherBell 500hpa anomoly prediction for this winter ! 

BA I'm unsure what chart you're mentioning?

[bluearmy]

Apologies .. senior moment ......

[Glacier Point]

With the central warming date set at 1st Jan, earliest trop response seems to be 13th onwards. To restate - Stratospheric. Timescales. Are. Extremely. Slow.

I suspect we may be at the longer end of the envelope for trop response (so more like 15-20 day) given that the duration of this warming event is extremely long. For downwelling signature I would normally look for a reorganisation of the upper SPV. That's clearly not evident just yet, and it may well be we are reliant on a massive -U wind signature muscling its way down.

In the meantime, we are in what is a clear teleconnective phase, one where the (enso lead) pattern wants to go cold, but is prevented from doing so by the atmospheric field over the polar region not being conducive.  A clear cut signal for mid latitude highs. The unfavourable AO state is being driven by constructive interference from the stratospheric warming and tropical forcing in the Pacific.

looking at the tropical forcing signal for weeks 2 and 3 with a return of forcing to the far Indian Ocean, that would suggest a slowing and retraction of the Pacific Jet. 

We therefore have a plausible favourable time line for downwelling stratospheric signal and tropical forcing opening up end week 2 into week 3.

For those on the 2001/02 bandwagon, no propagation, I offer this. This was one of my analogues that performed well during the summer and early autumn. Atmospherically it punched above its weight during the autumn with AAM running well ahead of the enso indices. However, this analogue was rejected for the winter as it fell at the complete opposite end of the solar cycle, and could not mirror the enso values experienced this winter. Additionally, and crucially, I cannot see this analogue holding a candle the scale and extent of the major mid winter warming we are about to embark upon. That gives me a 70% chance of downwelling taking place, but more likely on a much longer time scale that many are anticipating.

the broad scale evolution looks to remain as mid latitude high retrogressing north and northwards over time.

Edited December 31, 2018 by Glacier Point

[fujita5]

Thanks GP, excellent description.  Let's hope this message makes into the Hunt for Cold thread to avoid mass suicide....

[Catacol]

5 hours ago, sebastiaan1973 said:

This study uses reanalysis datasets and numerical experiments to investigate the influence of the occurrence frequency of the individual phases of the Madden–Julian oscillation (MJO) on the interannual variability of stratospheric wave activity in the middle and high latitudes of the Northern Hemisphere during boreal winter [November–February (NDJF)]. Our analysis reveals that the occurrence frequency of MJO phase 4 in winter is significantly positively correlated with the interannual variability of the Eliassen–Palm (E–P) flux divergence anomalies in the northern extratropical stratosphere; that is, higher (lower) occurrence frequency of MJO phase 4 corresponds to weaker (stronger) upward wave fluxes and increased (decreased) E–P flux divergence anomalies in the middle and upper stratosphere at mid-to-high latitudes, which implies depressed (enhanced) wave activity accompanied by a stronger (weaker) polar vortex in that region. The convection anomalies over the Maritime Continent related to MJO phase 4 excite a Rossby wave train that propagates poleward to middle and high latitudes, and is in antiphase with the climatological stationary waves of wavenumber 1 at middle and high latitudes. As the spatial distribution of the convection anomalies during MJO phase 7 has an almost opposite, but weaker, pattern to that during MJO phase 4, the occurrence frequency of MJO phase 7 has an opposite and weaker effect on the northern extratropical stratosphere to MJO phase 4. However, the other MJO phases (1, 2, 3, 5, 6, and 8 ) cannot significantly influence the northern extratropical stratosphere because the wave responses in these phases are neither totally in nor out of phase with the background stationary wavenumber 1.

https://journals.ametsoc.org/doi/pdf/10.1175/JCLI-D-17-0476.1

So phase 4 was not so good for 'our' SSW?

No - but the renewed pacific cycle saw the MJO in phase 4 for less than a week as it moved swiftly towards the maritime continent where the forecast is for a decent spell in the much better 6-7 orbit of the western pacific. I don't think we need worry about the less "good" phases of the MJO again for a decent while yet. This is the key aspect of the positive timing that we have this winter - MJO forcing from a pretty active pacific envelope and Nino signature alongside a trend for high AAM set alongside impacts on the vortex from the positive tropospheric pattern we had in November and into early December.

[Catacol]

2 hours ago, johnholmes said:

Thank you to R and b for your replies. I have little understanding of the complexities of this area. Like you mention b I have used it some years ago, perhaps the winter og 2009/10 but not sure and other times. It had a success rate of no more than 50% according to my files. Not sure if one can do another 10-14 days from the start of the second spike as the first one never gave anything.

We know so little really but are not alone as some 10 years ago the Met O, if my memory is correct dismissed some of the events they now use as being useful!

John - I think it is a pretty blunt tool now, given that we have access to the layered charts at the Berlin site and graphics from those like Zac Lawrence. As far as it goes it demonstrates pressure on the vortex at 30hpa and that is broadly speaking a good thing for blocking...but it tells us little about the nature of the pressure on the vortex (ie split or displacement) nor how the warming at 30hpa is interacting with the layers below. 

[Catacol]

34 minutes ago, bluearmy said:

Apologies .. senior moment ......

As a mean chart that looks impressive to my eye especially at that kind of range. If we get the downwelling in place then this kind of reinforcement from the trop should assist in some proper longevity to a very disrupted trop vortex pattern.

[Catacol]

13 minutes ago, Glacier Point said:

With the central warming date set at 1st Jan, earliest trop response seems to be 13th onwards. To restate - Stratospheric. Timescales. Are. Extremely. Slow.

I suspect we may be at the longer end of the envelope for trop response (so more like 15-20 day) given that the duration of this warming event is extremely long. For downwelling signature I would normally look for a reorganisation of the upper SPV. That's clearly not evident just yet, and it may well be we are reliant on a massive -U wind signature muscling its way down.

In the meantime, we are in what is a clear teleconnective phase, one where the (enso lead) pattern wants to go cold, but is prevented from doing so by the atmospheric field over the polar region not being conducive.  A clear cut signal for mid latitude highs. The unfavourable AO state is being driven by constructive interference from the stratospheric warming and tropical forcing in the Pacific.

looking at the tropical forcing signal for weeks 2 and 3 with a return of forcing to the far Indian Ocean, that would suggest a slowing and retraction of the Pacific Jet. 

We therefore have a plausible favourable time line for downwelling stratospheric signal and tropical forcing opening up end week 2 into week 3.

For those on the 2001/02 bandwagon, no propagation, I offer this. This was one of my analogues that performed well during the summer and early autumn. Atmospherically it punched above its weight during the autumn with AAM running well ahead of the enso indices. However, this analogue was rejected for the winter as it fell at the complete opposite end of the solar cycle, and could not mirror the enso values experienced this winter. Additionally, and crucially, I cannot see this analogue holding a candle the scale and extent of the major mid winter warming we are about to embark upon. That gives me a 70% chance of downwelling taking place, but more likely on a much longer time scale that many are anticipating.

the broad scale evolution looks to remain as mid latitude high retrogressing north and northwards over time.

Thanks Stewart. You looked in on 33andrain yet? Your views would be interesting over there.

Yet more delay - but I think we are all beginning to understand that any propagation this time around is going to slow, unlike the lightning quick response earlier this year. Is this wQBO related in your mind - given the QBO is westerly now probably down to around 50hpa? How closely does QBO shear at various levels relate to activity over the pole?

And as a teleconnection junkie can I ask you to elaborate on what you mean by "pattern wants to go cold, but is prevented from doing so by the atmospheric field over the polar region....a clear cut signal for mid latitude highs". I've been expecting a GSDM driven move towards high lat blocking for around a week now, and been scratching my head as to why it hasn't occurred and why the models continue to sustain the limpet UK high. What do you mean by "atmospheric field" - never encountered this phrase before. Is this something to do with the magnetic field, and if so how can we read it, and how does it help conduct the teleconnective orchestra?

[Singularity]

Hmm, very insightful points from Stewart and a reason why there's no need to panic about the slow propagation rate of the MJO; there's more time left than some may have thought, though I'd argue that mid-month is still the most optimal timing unless this warming & reversal proves really exceptional in duration.

With respect to Catacol's latest post - a combined consideration of the QBO shear level, ENSO and solar cycle in combination would be of great interest, though I fear we'd end up with too few years in most categories to be able to infer much of use.

[damianslaw]

Good postings in here today. A slow effect rather than rapid one, is being touted.. hopefully the long wait will result in something significant and sustained right in what I call true mid bleak winter i.e roughly mid Jan to early Feb, with a very cold snowy interlude. The first half of winter 18/19 for cold and especially snow lovers, looks like being exceptionally disappointing, more so given how weak the atlantic has been, high pressure sitting in the constant wrong position.

I

Edited December 31, 2018 by damianslaw

[Blessed Weather]

The thoughts of Severe-Weather.EU on the SSW.

With supporting analysis and charts in their forecast issued today, 31st Dec:

http://www.severe-weather.eu/long-range-2/sudden-stratospheric-warming-underway/

[Bristawl Si]

Having read the above link they are hinting at greater cold/snow effect for central and eastern Europe. Maybe our HP will stay over us.

[Derecho]

For the strat geeks on here? what do you think will happen next 

One thing I'm not clear about is the timing of the event, I've heard from some that the reversal of the zonal winds will occur within the next few days. However judging by the above figure, hasn't it occurred already?

[Radiating Dendrite]

12 minutes ago, Quicksilver1989 said:

For the strat geeks on here? what do you think will happen next 

One thing I'm not clear about is the timing of the event, I've heard from some that the reversal of the zonal winds will occur within the next few days. However judging by the above figure, hasn't it occurred already?

That is just temperature and does not show the zonal winds. 

[Derecho]

4 minutes ago, Radiating Dendrite said:

That is just temperature and does not show the zonal winds. 

I am aware , I just thought the winds in the upper atmosphere may have responded already.

[Gowon]

 

20 minutes ago, Quicksilver1989 said:

For the strat geeks on here? what do you think will happen next 

One thing I'm not clear about is the timing of the event, I've heard from some that the reversal of the zonal winds will occur within the next few days. However judging by the above figure, hasn't it occurred already?

They're different - the first one is at 30hpa and the other is 10hpa

[johnholmes]

1 hour ago, Catacol said:

John - I think it is a pretty blunt tool now, given that we have access to the layered charts at the Berlin site and graphics from those like Zac Lawrence. As far as it goes it demonstrates pressure on the vortex at 30hpa and that is broadly speaking a good thing for blocking...but it tells us little about the nature of the pressure on the vortex (ie split or displacement) nor how the warming at 30hpa is interacting with the layers below. 

Thanks for that C.

It was of course being used perhaps before understanding of more detail on the Stratosphere was known. It was always a 'blunt tool'. The gain in understanding of more aspects does explain why it had only about a 50% success rate when I started to use it quite a long time ago.

[Derecho]

12 minutes ago, D.V.R said:

 

They're different - the first one is at 30hpa and the other is 10hpa

Ooops, the 30hpa for December 2018 is here, still a decent warming event at least.

[Gowon]

1 minute ago, Quicksilver1989 said:

Ooops, the 30hpa for December 2018 is here, still a decent warming event at least.

No worries - it's not bad but it got down to nearly -30 last year

[Interitus]

8 hours ago, bluearmy said:

Looks like the ssw will technically be before midnight so we will have two reversals in 2018 .........

GFS op, FV3 and NASA GEOS all go for reversal from Jan 1st midday onwards - these are 3 hourly instantaneous values, in each case if averaged for a daily value for the reanalyses then the reversal is from Jan 2nd.

[supernova]

This thread really has been weather knowledge gold this year. Appreciative of all contrbutors who’ve made it fun to follow, especially in light of the apparent “slow burner” looming as regards the Trop response. Cheers all, HNY.

[chris55]

1 hour ago, Quicksilver1989 said:

For the strat geeks on here? what do you think will happen next 

One thing I'm not clear about is the timing of the event, I've heard from some that the reversal of the zonal winds will occur within the next few days. However judging by the above figure, hasn't it occurred already?

The reversal of winds in the Stratosphere at 60n (SSW) is happening around now (today - tomorrow) but thats not referring to the zonal winds at our level (the troposphere) it’s the downwelling of those winds way up high that ‘might’ have an effect on our zonal west to east prevailing pattern.

A slow downwelling looks most probable (if the pattern downwells at all) so mid jan the period to watch for a disturbance in our local zonal pattern courtesy of the SSW.

Edited December 31, 2018 by chris55

[Summer Sun]

 

[sebastiaan1973]

So beautiful to see that enthousiasm of a professional. 

Happy New Year to all strat freaks