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Stratosphere and Polar Vortex Watch


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12 minutes ago, bluearmy said:

Exeter continue to cover the standard two week downwelling wave on their 30 dayer so they consider it feasible 

Hope so Blue..

Dont think i am alone in getting jittery..

If mid Jan doesnt happen the clock will be ticking for 'winter'..

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Some useful tropospheric developments upcoming which are likely to have stratospheric impacts towards the end of November and more particularly into December. A strong convectively coupled tropic

so after many days the GFS & FNMOC & canadian finally now follow the Euro with 44 out 64 Members with a split at day 9- The ECM is day 8. We will call it - SSW & Split for 1st Ja

For all that watch the zonal winds. Let me urge you to look at the geopotential heights more. At least as far as weakening/strengthening trends go. Because as the polar vortex cries for help, you migh

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3 minutes ago, northwestsnow said:

Hope so Blue..

Dont think i am alone in getting jittery..

If mid Jan doesnt happen the clock will be ticking for 'winter'..

Things do seem to have trended the ‘wrong’ way during the last few days.  However, more twists and turns to come and what will be will be.

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39 minutes ago, Weather-history said:

 

Be good to see these soundings day by day to check how the reversal is working down ... also means that gfs willl now have this in it’s starting data ..... we may see some further changes in the 5/7 day range ...

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1 hour ago, bluearmy said:

Be good to see these soundings day by day to check how the reversal is working down ... also means that gfs willl now have this in it’s starting data ..... we may see some further changes in the 5/7 day range ...

Looking at the 3d vortex being modeled I understand why the models are struggling and average winds might not be very useful 

 

https://www.stratobserve.com/misc_vort3d

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57 minutes ago, ArHu3 said:

Looking at the 3d vortex being modeled I understand why the models are struggling and average winds might not be very useful 

 

https://www.stratobserve.com/misc_vort3d

It's quite fascinating how the vortex shatters and basically ceases to exist at 10 hPa (GFS 12z FI). This translates to a pattern with relatively high geop. in the Canada/Greenland sector in the lower strat. Yet there is nothing (yet) to be seen in troposphere, not even a cute tiny baby polar high. 

Edited by Ruben Amsterdam
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2 hours ago, bluearmy said:

Be good to see these soundings day by day to check how the reversal is working down ... also means that gfs willl now have this in it’s starting data ..... we may see some further changes in the 5/7 day range ...

I really like the way this site depicts it graphically https://earth.nullschool.net/#current/wind/isobaric/10hPa/overlay=temp/orthographic=-4.20,87.90,216/loc=89.099,75.437

 

Screenshot_20181226-170023.png

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I’ve begun wondering whether this huge and prolonged multi-pronged warming, with a big contribution from internal resonance, is sacrificing quick trop response for an extra-large lagged one.

Downwelling of zonal winds ahead of this slow reversal could then be the reason for the various model runs of late that have boosted the trop. zonal winds a lot past D8. This should come up against fierce opposition from MJO forcing in the vicinity of the UK though... results could become messy - or we just see ridges keep on reloading across the UK until the zonal winds relax enough to permit a sustained build then shift to high latitudes.

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4 hours ago, stodge said:

From this night 12 months ago, this was the projected state of the PV on 11th January 2018:

image.thumb.png.686a5daa88e5cfc80ccc3d0ded8761cb.png

Tonight's 12Z Parallel offers us this:

image.thumb.png.7cb69a3cea761b4c293ed7e2521c7d7e.png

Quite a difference.

I’d rather be seeing this at under 200 hours!

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22 hours ago, summer blizzard said:

One must remember that the vortex is a bit like a tornado spinning so although we'd prefer a large downwelling to completely remove it, the upper to mid layers stopping will significantly harm the thing as a whole. If we go with the proviso of a friendly trop (bar weeks 1 and 3 of December we have seen strong mid-latitude blocking) as default then i'm optimistic that it will do the job.

The interesting question is how well the vortex recovers when we get to the next bout of strong pressure on it in early to mid Feb.

This does all remind me of 2013 in timing and potential impact. Possibly cold second half of Jan and then potentially a cold later half to feb into March.

Yes very similiar timings - I think the warming occurred a bit later in 2012/2013, but the effects were quick, and we had a decent 2 week cold spell mid-late month, the effects overall being very long lasting with the exceptional March. Also remember second half of 2012 and into New Year being very mild and drab, just as we have now, though we had more wind and rain at times. 

Hoping the warming has a quick effect, and kicks us out of this gloomy mild lacklustre fest we are in.

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I have to confess I have been pretty underwhelmed with the tropospheric downwelling modelled by the ECM op so far, this from yesterday’s 12z at day 10:

AB579BA8-4F50-43CC-B497-9799C0742086.thumb.gif.b84633e222358df00c73d956254a14ad.gif

I guess that’s what’s to be expected from an attack on the vortex during a VI period (and probably with a wQBO). That said, it’s still a significant slowing down of the zonal winds throughout the vertical profile and will create opportunities for northern blocking as we head into January.

It looks rather like, for now, we’ll need to rely on a coupling of the stratospheric and tropical forcings - which continue to look pretty favourable the further we head into Jan with a like phase 8/1 MJO.....some of that should encourage further pressure on the vortex too and whilst AAM continues to ping backwards and forwards as it has done in recent months, further mountain torquing should create additional further pressure through January.

It’s far better to have continued attacks on a weak vortex than a raging one

 

Edited by snowking
Wrong image showing - updated now
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Looking at the last ecm outputs i am less than impressed with this current warming now.

Day 10 shows the quite rapid fall off in the reversal trend and again at 60N it has been delayed until nyd ,remember some while back we were looking at around 25/26th December.

ecmwfzm_u_f144.thumb.gif.f046a360852aa34c03f2a3725c63cc6e.gif

A look at day 10 now and this shows this reversal trend is pretty much held above mid-levels and looking like weakening.The graph alongside is confirming a leveling out of it's effects at 10/30h Pa. 


748069866_ecmwfzm_u_f240(1)mid.thumb.gif.13c6b3af07676dcd234cbc42786925ae.giffluxes.thumb.gif.f901426d4fcf3e2dd394dda8529ec491.gif
 

This really isn't promising to be the dramatic event we had hoped for with the expectation of splitting the vortex lower down.

Day 10 pressure forecasts at 10 hPa and 100 hPa

ecmwf10f240.thumb.gif.cda415feabf867a138ae826411804299.gifecmwf100f240.thumb.gif.8d787ebf478c2abdb615ab30a58bbf2b.gif

show a split higher up but lower down the pv is still across the pole,stretched yes, but importantly still with a notable segment to our north west.Some room for ridging in between,as we have now,but no chance of a stable high latitude block in that pattern.

Understandably 500 hPa modelling is reflecting this- current day 10 ens forecasts.

ecmwf-ens_z500a_nhem_1.thumb.png.b5997068c85beca7e4a544930a31251e.pnggfs-ens_z500a_nhem_40.thumb.png.8207517a57e0c0304fc7ab410e825472.png
 

Yes the slowing of the zonal winds will filter down but only enough to permit further possible mid-latitude ridging before the next upstream trough meanders across.

We do need to see more help from the tropics going forward and hope that the forecasted move into the MJO high amplitude phases 7/8 in January are correct as this will re set the NH pattern.

 

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6 minutes ago, mountain shadow said:

Fawkes has been spot on with his tweets thus far.

Well his latest one says second half jan will be changeable with mild and cold spells ......... perhaps glosea was late to the party on the dismantling of the uk block early jan .......still think there are some changes afoot 

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A reminder (if of course one is needed)

Predictability of downward propagation of major sudden stratospheric warmings

Quote

Abstract

Major sudden stratospheric warmings (SSWs) are striking phenomena of wintertime stratospheric circulation usually defined as a reversal of zonal mean circulation from westerlies to easterlies. SSWs often have significant impact on tropospheric circulation and cause anomalies in surface climate lasting for up to 2 months. For this reason, dynamics and predictability of SSW receive considerable attention. It is however well‐known that not all SSWs cause significant, long‐lasting impact on the troposphere. In order to explain differences in tropospheric impacts following SSWs, several reasons have been previously proposed, including differences in type of SSW (split or displacement), persistence of stratospheric anomalies, preconditioning of the tropospheric circulation, and whether or not SSW was accompanied by a planetary wave reflection in the stratosphere. Here we address the predictability of tropospheric impacts by SSWs by seeking early precursors of the impacts. We separate midwinter SSWs into two groups: those which are followed by significant, long‐lasting impacts on the tropospheric circulation (defined in terms of anomalous Northern Annular Mode) and those not followed by significant anomalies in the annular mode. We show that SSWs characterised by a more negative Northern Annular Mode index in the lower stratosphere around 150 hPa and enhanced wave activity propagation to the stratosphere during the first few days following the central date have a larger probability of being followed by tropospheric impact, both in reanalyses and in climate model runs. These anomalies play a more important role in the subsequent downward propagation of the signal to the troposphere than the type of SSW: whether it is a split or a displacement, or absorptive or reflective SSW. We propose that using these anomalies as precursors of tropospheric impacts of SSW can enhance climate predictability.

https://rmets.onlinelibrary.wiley.com/doi/abs/10.1002/qj.3017

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19 minutes ago, lorenzo said:

And, what's wrong with being a fan of cold and snow I wonder? Don't understand why Liam Dutton is so derogatory to folks enthusiastic about weather ?

Well I for one fully understand as one who had to work in a Met Office that was just a wooden hut with a coke stove in 62/63. And the upper air building and GL radar had no heating at all. Many of those who view this winter through rose tinted glasses weren't even born then, let alone had to work in it. It severely impacted millions of peoples lives and it went on for weeks.

And I don't think people being enthusiastic is the problem, it's the deluge of over the top hyperbole

Edited by knocker
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