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Stratosphere and Polar Vortex Watch

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@sebastiaan1973, we expect too much of a ssw, I checked most of them since 1958 and only 1985 (actually new years eve 1984) and 2012 brought could to our region (I looked at hellmann numbers for de Bilt), most ssw  however were actually preceded by marked cold periods 

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Regardless of the amplitude, I expect some cold weather from the SSW most likely in eastern North America and Northern Asia.  However, if the predicted SSW is relatively minor with a quick recovery in the stratospheric AO, even possibly becoming strongly positive, would favor a positive tropospheric AO.  Then an extended mild to very mild period across the NH mid-latitudes could ensue from late December through much of January.  I would expect at some point another PV disruption that would reverse the weather to colder but by then an overall mild winter would be almost a certainty.

Thanks Sebastiaan, bad news for coming winter then.

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8 minutes ago, ArHu3 said:

@sebastiaan1973, we expect too much of a ssw, I checked most of them since 1958 and only 1985 (actually new years eve 1984) and 2012 brought could to our region (I looked at hellmann numbers for de Bilt), most ssw  however were actually preceded by marked cold periods 

February/March 2018 and March 2013.

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8 minutes ago, MattStoke said:

February/March 2018 and March 2013.

February March 2018 were just cold, nothing exceptional, 2012 I included since the warming was new year's eve 2012 iirc 

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1 minute ago, ArHu3 said:

February March 2018 were just cold, nothing exceptional, 2012 I included since the warming was new year's eve 2012 iirc 

February/March 2018 cold spells were exceptionally cold for the time of year. -18 uppers and numerous red warnings for heavy and disruptive snow. If you're only going to count events that were more significant than that, then your dataset is bound to be tiny!

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28 minutes ago, ArHu3 said:

@sebastiaan1973, we expect too much of a ssw, I checked most of them since 1958 and only 1985 (actually new years eve 1984) and 2012 brought could to our region (I looked at hellmann numbers for de Bilt), most ssw  however were actually preceded by marked cold periods 

Jeezo, if that's really true, we might as well shut this thread down!

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15 minutes ago, mountain shadow said:

Jeezo, if that's really true, we might as well shut this thread down!

He's right you know, it was only a little chilly 

feb 18.png

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We probably do always expect too much from an SSW or even 'just' a strong warming event. Personally though, I will always take my chances on one (especially an early one in December)... Even a displacement type, which is probably more likely type this time around.

Anyway, here's today's forecast from the GFS, a further improvement on yesterday, the U mean now down to just +7. Getting there??

u_60N_10hpa_gefs.thumb.png.daec3f6e88a7a9f6cacf217f396483ce.png

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Remember - having an SSW is not the only path to cold weather in the UK (and western Europe as a whole).  It can help, as long as all the pieces of the puzzle align perfectly for us.  It can also be a major hindrance as it can push the trop vortex into a highly unfavourable position.

Don't lose hope just because one forecast (or forecaster) says it'll be a rubbish outcome for the UK.  Winter hasn't even begun yet 🙂

 

 

Edited by fujita5

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1 minute ago, karlos1983 said:

 

But it's not often we see a SSW in December is it, as we enter winter proper? along with entering Solar minimum and a QBO in a W to E phase.. 

I think what's key is that each SSW is different. Fascinating viewing! 

Agreed this is quite unusual territory - we're already seeing decent attacks on the vortex and we're likely to see it get hit very hard when it should be at its strongest.  Expect the unexpected in January.... 🙂

 

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22 minutes ago, fujita5 said:

Agreed this is quite unusual territory - we're already seeing decent attacks on the vortex and we're likely to see it get hit very hard when it should be at its strongest.  Expect the unexpected in January.... 🙂

 

Record warmth knowing the UK 😉

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27 minutes ago, karlos1983 said:

 

But it's not often we see a SSW in December is it, as we enter winter proper? along with entering Solar minimum and a QBO in a W to E phase.. 

I think what's key is that each SSW is different. Fascinating viewing! 

Well the 2 cold exceptions both happened new year's eve / day so hopefully this one will be one of the exceptions

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19 minutes ago, fujita5 said:

Agreed this is quite unusual territory - we're already seeing decent attacks on the vortex and we're likely to see it get hit very hard when it should be at its strongest.  Expect the unexpected in January.... 🙂

 

This is true, but it can and often does quickly rebound!

image.thumb.png.33b35b6ff120d05e094eeb1eff6cda67.png

Look at last year for example. Easterlies by mid January, rebounding to above average by mid February, and record speeds by mid March. February ended up very mild too.
 

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1 hour ago, mountain shadow said:

Jeezo, if that's really true, we might as well shut this thread down!

This is the stratosphere and polar vortex thread, not the hunt for cold. But here is the holy grail for cold if we are lucky, you'll know about 2 weeks ahead if we are going to get the jackpot or know the agony when dien welling stalls or the main vortex fragment ends right back in Greenland.... 

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6 minutes ago, Kirkcaldy Weather said:

 

Just for a laugh, i thought I would see what January 1966 looked like following this Dec 1965 event, I'll leave you all to draw your own conclusion..

image.thumb.png.54b0eb6160fdd2f5c965d0e6f5ff7265.png

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32 minutes ago, Kirkcaldy Weather said:

 

different to the GFS which is showing a negative EPO for early Dec

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2 hours ago, Kirkcaldy Weather said:

 

Musing here now. Whether the longer term heads towards -EPO as per GFS or +EPO as per ECM the resilience of the positive anomaly over the Greenland area is striking. Atlantic SSTs are broadly favourable for maintenance of this signal, and we have had this signal remain staunchly resilient through much of this year. The chicken and egg conversation from this revolves around - is this anomaly the product of a jet that is fairly far south, or as the jet fairly far south because of this anomaly? In truth both have to be true because the atmosphere is essentially an interconnected system, and I wonder whether we have an in tandem relationship here that may return time and again through the season. There's no particular science to this statement (apart from the obvious truth that in winter the stormtrack drops south) - there is just a nagging sense that our Greenland High is going to remain part of conversations through winter.

I have lost access to all my GSDM data, for now at least, and the one nagging doubt in my mind is the projected direction of GLAAM under a neutral ENSO state currently, but with a strong cold water block sitting over the Indian Ocean. Without all that data there is a distinct element of "flying blind" but I have one graph still functioning that shows the trend throughout the year heading in a negative direction until a recovery in the last 6 weeks. The graph is in my forecast. Anyway - my sense was that a positive rebound in GLAAM, helping to suppress the influence of the sub tropical high pressure belt and reduce westerly momentum at higher latitudes, would persist for a few more weeks....but I read in other places from those with access to the data that GLAAM may possibly drop again fairly quickly. This is a bit of a concern. If we end up with a Nina-esque atmospheric response to ENSO then the tendency for the pattern at our latitude to flatten out will grow. In this context the extent to which vortex disruption may occur grows in significance - a failed split/displacement event backed up by low orbit Nina GWO phases could be very uninspiring indeed.

To which end I hope ECM has this forecast correct above, and that a +EPO can sustain or reinvigorate the degree of vortex disruption on offer. A vortex split of the downwelling variety would outweigh a neutral ENSO signal and Nina atmospheric base state (in my opinion).

Back to work. Back to more musing. At this time of year chewing over the available data, and evaluating the views of others brave enough to make projections, is a daily pleasure.

Edited by Catacol

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Stratobserve charts for today's 0z output:

image.thumb.jpg.ee9c2f3a4049cde3571c78103dc989e6.jpg

GEFS now have 3 reversals at T384, they are displacements but the angle of the displaced vortex different:

image.thumb.jpg.959d1d1201856ee2af8cd9dcbdc67b01.jpg

Once again the FV3 op not really on the same page at all - I continue to be suspicious of it!

Edited by Mike Poole

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@Catacol another brilliant post thanks, lots going on and will be fascinating to see if we do end up on the colder side of things once the strat events play out. 

 

 

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