Polar Vortex / Stratosphere Watch 2022 / 2023

[damianslaw]

16 minutes ago, SqueakheartLW said:

The disconnect shows up nicely here with those above average red anomalies from 40hpa upwards and those below average blue anomalies below 40hpa.

I'd say we are still very much game on for trop blocking and a year similar to 1995/96.

I'd be happy with a 95/96 but with a less mild period first two thirds of January, from about the 21st Jan it was cold all the way with exceptional snow here. Late Dec was freezing.

[Don]

7 minutes ago, damianslaw said:

I'd be happy with a 95/96 but with a less mild period first two thirds of January, from about the 21st Jan it was cold all the way with exceptional snow here. Late Dec was freezing.

I suspect if NW had been around in 1995, the mood would have been rather sombre in the model thread around New Year?! 

[bluearmy]

I wonder what the record speed is for 1hpa ? 
current modelling has us approaching 100 m/s late week 2 

[swebby]

23 hours ago, Frostbite1980 said:

This isn't what you want to see if we are looking for a SSW?

A slightly tangential what if - But! 

What would the likely impact be for our Spring weather if we have strat PV @ +60m/s in late March?

[chionomaniac]

6 hours ago, bluearmy said:

I wonder what the record speed is for 1hpa ? 
current modelling has us approaching 100 m/s late week 2 

It’s definitely been above 100m/s I seem to remember. But not often

[bluearmy]

17 minutes ago, chionomaniac said:

It’s definitely been above 100m/s I seem to remember. But not often

Do we have enough historical data to see what happens if we have a disconnected roaring spv and then we manage to get some sig trop waves up into there ???

[chionomaniac]

7 minutes ago, bluearmy said:

Do we have enough historical data to see what happens if we have a disconnected roaring spv and then we manage to get some sig trop waves up into there ???

I don’t think there will be anything to compare to, because the mirror image trop pattern is so unusual. But any strong Strat PV can be brought down if the trop wave activity is strong enough. Feb 2009 split SSW being a perfect example of that. 

[phil nw.]

Just signs that increasing zonal wind speeds will be filtering lower down towards month end. 

The Upper Strat. zonal winds continue apace with the latest gefs forecasts for further increases in the next couple of weeks.

Up to now the ongoing wave action has been battering the lower strat vortex and keeping it weak and split creating a protracted and unusual December period of Arctic blocking and thus a disconnect from the strong westerly winds high up..It does look like something of a change is underway.

Post Christmas forecasted speeds lower down look like gaining some westerly momentum as some filtering down of westerly zonal winds is shown. Expected speeds around 10/15 m/s after this current period of negative readings

This would indicate a reduction of potential blocking at higher latitudes as the westerly momentum picks up. 

Another indication perhaps of a change to something more typical for a while. as we see a trend to lose our current blocked pattern and gradually move the mean jet stream path north from around 45N  towards 55N bringing the UK into the boundary of the polar and sub-tropical airmasses.

Hopefully we see another round of warmings before too long to keep the SPV on it's toes.

 

 

Edited December 14, 2022 by phil nw.

[Mike Poole]

I’m still of the view that a SSW this year is slightly odds against.  But, don’t know if there’s any science behind this, I reckon if we do have one given the current setup in both the trop and the strat, it will blow the vortex to smithereens.  The faster it spins, the harder it falls!

[Frostbite80]

That is just insane!!

u 60N 10 hPa

WWW.WEATHERISCOOL.COM

 

[Don]

Could it be that 'normal' mild winter weather will likely prevail now moving forward?!

[SqueakheartLW]

Looks like GFS and CFS are starting to tone this one back down a bit now

These were both heading for DOOM territory recently but the latest output now sees a downwards trend in zonal winds later on in the run and the feared coupling between the strat and the trop is now looking less evident here than before.

Are we about to be saved from the brink of a boring mild fest for the rest of the winter?

[Don]

2 hours ago, SqueakheartLW said:

Are we about to be saved from the brink of a boring mild fest for the rest of the winter?

Hopefully but some of the knowledgeable posters believe the pattern is about to collapse into a period of zonality!

[chionomaniac]

Just a moment...

AGUPUBS.ONLINELIBRARY.WILEY.COM

I think that this is fair enough sPV is PV. Anything trop based is jet stream variation. 

[Don]

15 hours ago, chionomaniac said:

Just a moment...

AGUPUBS.ONLINELIBRARY.WILEY.COM

I think that this is fair enough sPV is PV. Anything trop based is jet stream variation. 

Any more recent thoughts Chiono?

[feb1991blizzard]

any news @chionomaniac please?  

I must admit i have followed the Stratosphere charts less this year than in any of the last 10 - because the ECM berlin site is down and the GFS instantweathermaps is miles behind always, so only really being looking at 30mb gfs heights on NW and 10mb temps on meteociel.

Edited December 21, 2022 by feb1991blizzard

[chionomaniac]

7 hours ago, Don said:

Any more recent thoughts Chiono?

Lol yes. Basically the upper Strat is forecast to spin like a top. This is likely to filter down to the trop. But how long, and with what strength?  Normally, it would take a few weeks from VI. But I no longer can assume what normal is, so all bets are off, and we need to watch to see how the upper and lower Strat interact and then find why that is so. I know that this is not a lot of help, but it is where we are at. 

[phil nw.]

As expected we now are starting to see the results of the downwelling of stronger zonal winds however maybe there is a light at the end of the tunnel and this expected period of mobility.

Signs in the extended gefs that early in January the lower strat winds again fall away.

The blues(negative anomalies reappearing as it looks like they upwell into mid-layers.

The nice rounded shape that the upper strat is now showing at 10hPa isn't expected to last too long as it becomes squeezed by further warmings. 

 

It looks like a displacement of the upper strat pushes it off it's polar perch in the new year.We just need a bit of luck that this impinges on the 500hPa pattern in a favourable way.

I wish we still had access to the ecm suite to double check but if the gefs is correct then chances of northern blocking will increase in a couple of weeks.

[SqueakheartLW]

First signs of a possible strat warming and maybe a possible SSW if the signal increases. Unfortunately these charts are very much at the far reaches of both the GFS and GEM though

Peak warming temps GFS 00z

Peak          Member
-28             13,16,17,22,27
-24             Op,03,04,05,09,10,14,24,30
-20             01,06,07,08,12,15,18,20,21,25,26,28
-16             Ct,11,19,23,29
-12             02

Av warming peak = -21.50C

Best charts from GFS 00z

Peak warming temps GEM 00z

How does GEM compare with GFS?

Peak          Member
-32             05
-28             06,13,15
-24             01,04,07,10,12,17,20
-20             Ct,08,09,14,18,19
-16             03,16
-12             02,11

  Av warming peak = -21.90C

Best charts from GEM 00z

Summary

 A reasonable early signal from both GFS and GEM with very similar warming peaks showing up with -21.5C from GFS and -21,9C from GEM. We'll just have to see how this one evolves. Could make for an interesting February if this warming comes off from a potential cold perspective.

[Weather-history]

For a layman, I'm confused. Is there a connection or not? 

 

[phil nw.]

Nice little trend also from the ecm zonal winds forecast as we go into January

Comparing the earlier chart with today's it shows a wide spread in the forecast yes,but also a greater number of members showing a reversal.Early days but following on from the post above by squeakheart forecasts from the gefs are also encouraging .

zonal winds forecasted to decrease from the bottom up as we go into week 2.Just the first signs of the spv becoming weaker with a more pronounced disconnect from the strong westerly flow at the top.

Edited December 23, 2022 by phil nw.

[SqueakheartLW]

Another strat update and it appears both GFS and GEM are sticking with the idea of a warming in FI

GFS 12z

GFS 12z 23/12/22
Peak          Member
-24             11,12,16
-20             Op,02,03.04,10,13,15,19,20,21,22,23,24,26
-16             Ct,05,06,07,08,09,14,25,27,29,30
-12             17,18
-8               01,28

AV              -17.75C        Upgrade from -21.50C on the GFS 00z (23/12/22)

GFS sticking with its early prediction of a warming and has in fact upgraded the warming signal with a -17.75C average warming peak showing compared with the -21.50C earlier today on the 00z. Will this trend continue?

Best warming charts from the GFS 12z

 

GEM 12z

GEM 12z 23/12/22
Peak          Member
-32             09,10
-24             04,05,06,08,12,14,17,19
-20             02,03,07,11,13,15,16,20
-16             Ct,01,18

AV              -22.10C        Downgrade from -21.90C on the GEM 00z (23/12/22)

A very slight downgrade on the GEM 12z vs the 00z but there's only 0.2C in it so not really much of a downgrade so very much a consistent signal

Best warming charts from the GEM 12z

 

Summary

Overall taking both GFS and GEM together you could say the signal for a warming is still there and in fact slightly stronger than on the 00z. GEM very much at the same level as earlier with the stronger warming signal focused on the GFS this time around. Is the GFS the trend setter and will GEM follow or does GEM have this right and GFS will fall back?

Edited December 23, 2022 by SqueakheartLW

[snowking]

Always good to check the ensemble mean output at such range (again, crying out here for ECM data on this to become available freely somewhere soon).

https://ftp.cpc.ncep.noaa.gov/htlee/StratoMonitorPolar_GEFS_v2.0/TMP_10mb_fcst_nh.html

You can see here fairly impressive continuity between the deterministic run and the ensemble mean (note: this data seems to run a couple of days in arrears, hopefully we’ll see the more recent days data shortly) on the location of the warming wave at 10mb. This works its way down to 100mb fairly cleanly too towards days 15 and 16:

https://ftp.cpc.ncep.noaa.gov/htlee/StratoMonitorPolar_GEFS_v2.0/TMP_100mb_fcst_nh.html

We then see the first signs of some wave 1 forcing coming from the Pacific sector of the NH at this time too, most prominently at 10mb:

https://ftp.cpc.ncep.noaa.gov/htlee/StratoMonitorPolar_GEFS_v2.0/HGT_10mb_fcst_nh.html

Even at 50mb at this timeframe though we see some imprinting on heights from wave 1, though note at this level the initial pressure seems to be forecast more from Canada than the Pacific

https://ftp.cpc.ncep.noaa.gov/htlee/StratoMonitorPolar_GEFS_v2.0/HGT_50mb_fcst_nh.html

Which is a good prompt for my point here. Firstly it’s worth throwing in the usual 2 caveats of 1) this is a considerable distance away still, and 2) this is the GEFS suite, confirmation from European suites would be much welcomed. However, assuming any activity from above imprints itself on the troposphere (which is far from a given even at this stage of the winter this year it seems), Wave 1 is always a gamble for the UK. What we can sometimes see is a wave from the pacific side pushing the core of the stratospheric vortex over to the Atlantic sector, which when imprinted into the troposphere results in a net gain in jet stream strength in our part of the northern hemisphere. Always worth reiterating this - such is the very complex nature of stratospheric impacts on the troposphere.

However we should be able to take heart that even in the single forecast snapshots from above, just moving from 10mb down to 50mb we see a rotation in the angle of the wave activity from closer to the Aleutians around to Canada. This goes to show that rarely do we see a direct downwards propagation of the heights pattern imprint through the layers of our atmosphere, instead we tend to see some slight rotation of the pattern in its journey downwards. This means that even if we make the massive assumption that the GEFS is modelling this in any way correctly, at this stage it is pretty fruitless to speculate on where any such downwelling wave would end up imprinting itself in the troposphere (which probably makes this entire post pointless - merry Christmas all eh?)

So for now very much a watching brief, but interest at least partially piqued stratospherically for me

[SqueakheartLW]

Latest GFS and GEM ensemble data regarding the potential strat warming based on the 12z runs.

GFS 12z

How does today compare with yesterday's 12z run for peak warmings of the strat.

GFS 12z    24/12/22
Peak          Member
-28             21
-24             11,16,19,20
-20             02,05,06,08,09,10,13,23,27,28
-16             Ct,03,04,07,12,14,15,25
-12             01,17,18,22,24,26,29,30
0                Op

AV    -17.13C        Upgrade from -17.75C on the GFS 12z (23/12/22)

Overall a small upgrade on yesterday but of note is how the highest resolution run, the Op goes up to 0C for it's warming peak. It appears to be a bit of an outlier here as the rest very much cluster between -12 and -20 with a small number less warm. A tiny upgrade and with the Op going bold with that 0C could it be the trend setter and the ensembles then eventually follow suit.

Best warming charts from GFS 12z

 

GEM 12z

How does GEM 12z compare with both today's GFS 12z and yesterday's GEM 12z

GEM 12z    24/12/22
Peak          Member
-24             05,06,07,09
-20             Ct,04,12,14,17,18,19,20
-16             08,11,15
-12             03,10,16
-8               01,02,13

AV    -17.33C        Upgrade from -22.10C on the GEM 12z (23/12/22)

Quite a notable upgrade on today's GEM 12z vs yesterday's GEM 12z and in fact brings the GEM into line with the GFS 12z today. I'd say a consistent signal with the -17.13C on GFS 12z and -17.33C on GEM 12z. No 0C members on the GEM but a narrower range of options with -24 as the least warm and -8 as the warmest.

Best warming charts from GEM 12z

 

Summary

Overall I'd say the signal has upgraded somewhat with the GEM moving more into line with the GFS today and with an increased number of options getting to -12C peak or warmer I'd say the warming level is also upgrading. I think we would want to see more members doing what the GFS 12z Op has done today to be more sure of a SSW rather than just a warming that doesn't cause a reversal of the zonal winds.

Edited December 24, 2022 by SqueakheartLW

[Taxe]

12 hours ago, snowking said:

....  (again, crying out here for ECM data on this to become available freely somewhere soon) ...

Don't know, if this source has been posted, yet. But there is some open source for ECMFW ensemble forecast for at least the 10hPa level:

ECMWF | Charts

CHARTS.ECMWF.INT

 

12 hours ago, snowking said: