Stratosphere and Polar Vortex Watch 2020

[SqueakheartLW]

What could possibly go wrong for coldies at Day 10 here

10hpa                                                         30hpa                                                     50hpa

70hpa                                                         100hpa                                                     150hpa

What do all of these charts have in common

A lack of any form of polar vortex in the whole of the western hemisphere. Now if this was to replicate in the troposphere you would hope to see lots of high pressure and blocking to our west and a deep trough extending right from Siberia to Europe leaving us in an icy cold blast from the N or NE

But to answer what could possibly go wrong you could say everything as there's always something that will stop the UK getting cold

[Interitus]

3 hours ago, bluearmy said:

Another date record!

Of course this is from a narrow sample of SSW events for any particular day of the winter. So date records now are around 2 S.D. - a 3 S.D. event such as Jan 2009 would give a value today around -26 m/s.

[bluearmy]

20 minutes ago, Interitus said:

Of course this is from a narrow sample of SSW events for any particular day of the winter. So date records now are around 2 S.D. - a 3 S.D. event such as Jan 2009 would give a value today around -26 m/s.

I get the context - but 2021 jan now has two dates with the lowest zonal flow at 10hpa 60N ..... as jan 21  progresses more of these clearly won’t happen! 

[Interitus]

2 minutes ago, bluearmy said:

I get the context - but 2021 jan now has two dates with the lowest zonal flow at 10hpa 60N ..... as jan 21  progresses more of these clearly won’t happen! 

Well, exactly - date records are interesting but not necessarily particularly significant.

[snowking]

7 minutes ago, SqueakheartLW said:

What could possibly go wrong for coldies at Day 10 here

10hpa                                                         30hpa                                                     50hpa

70hpa                                                         100hpa                                                     150hpa

What do all of these charts have in common

A lack of any form of polar vortex in the whole of the western hemisphere. Now if this was to replicate in the troposphere you would hope to see lots of high pressure and blocking to our west and a deep trough extending right from Siberia to Europe leaving us in an icy cold blast from the N or NE

But to answer what could possibly go wrong you could say everything as there's always something that will stop the UK getting cold

Indeed, and what I fear may go wrong towards day 15-20 is that new geopotential wave from the Eurasian side - you would hope that given how weak the vortex now is that this would be the final knockout blow to it (and it may yet prove to be so), however if recent GFS runs have this modelled correctly (ahem...), this is not the case, and instead as Nick referenced earlier the vortex will instead be sent packing to Alaska instead. Assuming that this imprints tropospherically (which seems to me at least to be the direction of travel), that probably sets us up for a potential period of more Arctic mobility sometime in early February whilst we see the broad trough transfer from East to West

There's a lot of assumptions made there, but that would be unfortunate timing should that prove to be the case, but may see us looking NE rather than NW for blocking as February progresses. A lot of water (or icebergs...) to flow under the bridge before we get to there, but one to watch.

[Vikos]

One reason for the uncertainties is that between 1979 and 2019 only 26 sudden stratospheric warmings occurred. In addition to the small amount of data, it was also found that these events were associated with a high degree of variability with regard to the effects on the troposphere, our weather layer.

 

/SiteGlobals/StyleBundles/Bilder/Allgemein/OpenGraphImage-DWD-Logo.jpg;jsessionid=5CDFD43526DF0C94149AE6E94A24DED6.live11042?__blob=normal&v=3

 

[Vikos]

ECMWF is amazing!

Prediction from 10 days ago (UPDATE: charts are +216h now, they updated)

 

Outcome today

 

Considering the really great 10day-performance of ECMWF we have to look at this chart then for the lower Stratosphere (can be mirrored to the upper Troposphere/Tropopause)

We see the large displacement of the Vortex is locked down solid until at least the 24th.

We are currently in the transition phase in the troposphere towards displacement, which acts on the tropsophere from above in the stratosphere. This goes hand in hand with a decrease in the zonal westerly wind in the tropsphere towards an easterly wind. This will happen over the next 3 to 4 days.

    Prediction from 9 days ago --->

 

So NAO and AO will remain stricktly in negative, so wie remain in a strongly disturbed circulation withgin the next 10 days (at least). This is what the zonal mean wind charts is showing, and predicting that ECMWF stays solid with it good calculations, there is little doubt about it.

 

However, it should also be mentioned that Central Europe will be located pretty much at the southern end of the elongated displacement. Sometimes on the edge, sometimes well covered by it. The further the displacement expands to southern Europe, the more wintry it will be in Central to West Europe. Another aspect is that if the displacement is very southerly, it will probably not be able to expand further to North Africa, but will then form a western axis. This may lead a mild component to Central/West Europe. How strong or if at all is still not knwon. The models will have their problems with it, because all of this is a very rare starting point and the past values are certainly missing in the programming in those global weather models. As mentioned before, we only had about 26 SSW in the last 40 years. And 40 years ago there where no giga Computers...

So, let's keep the faithm things are looking really good! And if the TPV splits...

 

Edited January 15, 2021 by Vikos

[mushymanrob]

11 minutes ago, Vikos said:

ECMWF is amazing!

Prediction from 10 days ago

 

Outcome today

 

Considering the really great 10day-performance of ECMWF we have to look at this chart then for the lower Stratosphere (can be mirrored to the upper Troposphere/Tropopause)

We see the large displacement of the Vortex is locked down solid until at least the 24th.

We are currently in the transition phase in the troposphere towards displacement, which acts on the tropsophere from above in the stratosphere. This goes hand in hand with a decrease in the zonal westerly wind in the tropsphere towards an easterly wind. This will happen over the next 3 to 4 days.

    Prediction from 10 days ago --->

 

So NAO and AO will remain stricktly in negative, so wie remain in a strongly disturbed circulation withgin the next 10 days (at least). This is what the zonal mean wind charts is showing, and predicting that ECMWF stays solid with it good calculations, there is little doubt about it.

 

However, it should also be mentioned that Central Europe will be located pretty much at the southern end of the elongated displacement. Sometimes on the edge, sometimes well covered by it. The further the displacement expands to southern Europe, the more wintry it will be in Central to West Europe. Another aspect is that if the displacement is very southerly, it will probably not be able to expand further to North Africa, but will then form a western axis. This may lead a mild component to Central/West Europe. How strong or if at all is still not knwon. The models will have their problems with it, because all of this is a very rare starting point and the past values are certainly missing in the programming in those global weather models. As mentioned before, we only had about 26 SSW in the last 40 years. And 40 years ago there where no giga Computers...

So, let's keep the faithm things are looking really good! And if the TPV splits...

 

attatchments dont open...

 

[Vikos]

6 minutes ago, mushymanrob said:

attatchments dont open...

 

Thanks, updated them

Press STRG+F5 for full refresh of this site

[Weather-history]

Judah Cohen has tweeted this

 

[Catacol]

7 hours ago, snowking said:

Indeed, and what I fear may go wrong towards day 15-20 is that new geopotential wave from the Eurasian side - you would hope that given how weak the vortex now is that this would be the final knockout blow to it (and it may yet prove to be so), however if recent GFS runs have this modelled correctly (ahem...), this is not the case, and instead as Nick referenced earlier the vortex will instead be sent packing to Alaska instead. Assuming that this imprints tropospherically (which seems to me at least to be the direction of travel), that probably sets us up for a potential period of more Arctic mobility sometime in early February whilst we see the broad trough transfer from East to West

There's a lot of assumptions made there, but that would be unfortunate timing should that prove to be the case, but may see us looking NE rather than NW for blocking as February progresses. A lot of water (or icebergs...) to flow under the bridge before we get to there, but one to watch.

Ha - best that Asian WaF bloody well splits it good and proper then! Right now, up until Jan 24 at least, it doesn’t look strong enough. I have stopped looking at more distant GFS charts. Fingers crossed. I don’t think the current holding pattern is much further forward yet. Like you I can see a disappointing worst case scenario and a pretty pleasing best case one - with a “waffer thin mint” separating them. I’m clinging to the big monthly forecasts that see a -NAO Feb and hoping they are seeing something through the mist....and better than they plotted January!

[Catacol]

 

49 minutes ago, Weather-history said:

Judah Cohen has tweeted this

 

Yes. More evidence of the quite extreme and rare nature of the current event....now possibly a chain of events. As a result I’m really not sure anyone can have a scooby about the likely trop forecast over the next month - and maybe a lot more than that if we have another major bash at the vortex as January closes out. Ought to prevent any major reforming for the rest of the season which smells like arctic cold floating around at mid latitudes throughout Feb and March. 

Edited January 15, 2021 by Catacol

[Bricriu]

I  wonder will this warming be enough to destroy the vortex? It certainly looks like spring might be delayed this year with all these warmings.

[Windysun1]

1 hour ago, Catacol said:

 

Yes. More evidence of the quite extreme and rare nature of the current event....now possibly a chain of events. As a result I’m really not sure anyone can have a scooby about the likely trop forecast over the next month - and maybe a lot more than that if we have another major bash at the vortex as January closes out. Ought to prevent any major reforming for the rest of the season which smells like arctic cold floating around at mid latitudes throughout Feb and March. 

Its great to have all these graphs, showing warmings and splits and displacements but I fear we are still along way off in drilling down into finding how this will effect us at ground level... or at all.

[ItNeverSnowsInWindsor]

30 minutes ago, Bricriu said:

I  wonder will this warming be enough to destroy the vortex? It certainly looks like spring might be delayed this year with all these warmings.

Even with these warmings we’ll still end up getting 17c in the South during February! #globalwarming #messeduparctic

Edited January 15, 2021 by prolongedSnowLover

[sebastiaan1973]

Well. Some time ago, I posted the study by Domeisen et al. There are different types of effect of SSWs related to the regime five days before the SSW onset and five days after.

It is my guess, Cohen tweet points in that direction, we see a dipping effect of the 'European Blocking' type.  If this is true, we can expect more 'dipping' in february.

The role of North Atlantic–European weather regimes in the surface impact of sudden stratospheric warming events

WCD.COPERNICUS.ORG

---

<p><strong class="journal-contentHeaderColor">Abstract.</strong> Sudden stratospheric warming (SSW) events can significantly impact tropospheric weather for a period of several weeks, in...

 

[Catacol]

45 minutes ago, Windysun1 said:

Its great to have all these graphs, showing warmings and splits and displacements but I fear we are still along way off in drilling down into finding how this will effect us at ground level... or at all.

One of the challenges I think is that the strat vortex in general doesnt work like trop patterns. In the trop we know that things move west to east, with flat or meridional shape, and unless you get a BFTE style pattern it is a predictable long wave pattern for the most part. But the vortex is truly 3D. It stretches, bends, splits, wobbles - and can move its centre from one side of the hemisphere to the other relatively quickly. Forecasting of wave forcing on it has improved a lot - but the IMPACT of that wave forcing is still poorly modelled. The experts freely admit that vortex split scenarios are nearly invisible at more than 2 weeks out.

This means that when we DO get a vortex split and disintegration ala 2018 the trop forecast is massively impacted and wildly thrown off course. And as that happens the specific impacts of downwelling, and the speed of downwelling, are also not well modelled.

In short - forecasting in winter during a strong SSW event is very difficult - other than to be fairly sure that extreme weather (cold or indeed warm) is likely in parts. Much is guesswork, and we are seeing some of this now for sure. We didnt get a split - but now the forecast looks like a split is back on the table potentially as we head towards February.

And that means - we have to watch, wait, hope and be patient. NWP will move around dramatically - as can be seen at the moment with resultant gnashing of teeth from mod thread posters who find it frustrating. But - I'd prefer this 100% over a year without a SSW which is much more predictable, largely because I'm not convinced in our modern climate that cold weather of any real depth can arrive in the UK without strat forcing and ideally a full on SSW. The modern tropospheric climate for us in winter is increasingly westerly, and controlled by strong sub tropical highs - namely our old friend the Azores High. When the Azores High bosses the pattern, and reinforces the Icelandic Low, it is curtains for UK cold.

 

Edited January 15, 2021 by Catacol

[sebastiaan1973]

Sudden stratospheric warmings (SSWs) are significant source of enhanced subseasonal predictability, but whether this source is untapped in operational models remains an open question. Here we report on the prediction of the SSW on 12 February 2018, its dynamical precursors, and surface climate impacts by an ensemble of dynamical forecast models. The ensemble forecast from 1 February predicted 3 times increased odds of an SSW compared to climatology, although the lead time for SSW prediction varied among individual models. Errors in the forecast location of a Ural high and underestimated magnitude of upward wave activity flux reduced SSW forecast skill. Although the SSW's downward influence was not well forecasted, the observed northern Eurasia cold anomaly following SSW was predicted, albeit with a weaker magnitude, due to persistent tropospheric anomalies. The ensemble forecast from 8 February predicted the SSW, its subsequent downward influence, and a long-lasting cold anomaly at the surface.

ResearchGate - Temporarily Unavailable

WWW.RESEARCHGATE.NET

 

[Windysun1]

19 minutes ago, Catacol said:

One of the challenges I think is that the strat vortex in general doesnt work like trop patterns. In the trop we know that things move west to east, with flat or meridional shape, and unless you get a BFTE style pattern it is a predictable long wave pattern for the most part. But the vortex is truly 3D. It stretches, bends, splits, wobbles - and can move its centre from one side of the hemisphere to the other relatively quickly. Forecasting of wave forcing on it has improved a lot - but the IMPACT of that wave forcing is still poorly modelled. The experts freely admit that vortex split scenarios are nearly invisible at more than 2 weeks out.

This means that when we DO get a vortex split and disintegration ala 2018 the trop forecast is massively impacted and wildly thrown off course. And as that happens the specific impacts of downwelling, and the speed of downwelling, are also not well modelled.

In short - forecasting in winter during a strong SSW event is very difficult - other than to be fairly sure that extreme weather (cold or indeed warm) is likely in parts. Much is guesswork, and we are seeing some of this now for sure. We didnt get a split - but now the forecast looks like a split is back on the table potentially as we head towards February.

And that means - we have to watch, wait, hope and be patient. NWP will move around dramatically - as can be seen at the moment with resultant gnashing of teeth from mod thread posters who find it frustrating. But - I'd prefer this 100% over a year without a SSW which is much more predictable, largely because I'm not convinced in our modern climate that cold weather of any real depth can arrive in the UK without strat forcing and ideally a full on SSW. The modern tropospheric climate for us in winter is increasingly westerly, and controlled by strong sub tropical highs - namely our old friend the Azores High. When the Azores High bosses the pattern, and reinforces the Icelandic Low, it is curtains for UK cold.

 

Thank you for taking the the time to reply in a very descritive manner catacol. Ive asked twice before but no takers. Much appreciated.

[Interitus]

8 hours ago, Catacol said:

But - I'd prefer this 100% over a year without a SSW which is much more predictable, largely because I'm not convinced in our modern climate that cold weather of any real depth can arrive in the UK without strat forcing and ideally a full on SSW.

December 2010.

[Interitus]

9 hours ago, sebastiaan1973 said:

Well. Some time ago, I posted the study by Domeisen et al. There are different types of effect of SSWs related to the regime five days before the SSW onset and five days after.

It is my guess, Cohen tweet points in that direction, we see a dipping effect of the 'European Blocking' type.  If this is true, we can expect more 'dipping' in february.

The role of North Atlantic–European weather regimes in the surface impact of sudden stratospheric warming events

WCD.COPERNICUS.ORG

---

<p><strong class="journal-contentHeaderColor">Abstract.</strong> Sudden stratospheric warming (SSW) events can significantly impact tropospheric weather for a period of several weeks, in...

 

The use of 'dripping' paint charts in association with the Cohen tweet is ironic as one of the replies was from Tim Dunkerton (and characteristically slightly off the wall) -

Incidentally, the charts Cohen posted don't really show the expanded geopotential heights at the end of January that he was alluding to, oddly.

Edited January 16, 2021 by Interitus

[Cheshire Freeze]

10 hours ago, Catacol said:

 

Yes. More evidence of the quite extreme and rare nature of the current event....now possibly a chain of events. As a result I’m really not sure anyone can have a scooby about the likely trop forecast over the next month - and maybe a lot more than that if we have another major bash at the vortex as January closes out. Ought to prevent any major reforming for the rest of the season which smells like arctic cold floating around at mid latitudes throughout Feb and March. 

Yes, been thinking an early spring may be off the table this year...

[sebastiaan1973]

1 hour ago, Interitus said:

The use of 'dripping' paint charts in association with the Cohen tweet is ironic as one of the replies was from Tim Dunkerton (and characteristically slightly off the wall) -

Incidentally, the charts Cohen posted don't really show the expanded geopotential heights at the end of January that he was alluding to, oddly.

Why is it ironic? I try to understand/ learn

[Weather-history]

2 hours ago, Interitus said:

December 2010.

Winter 2009-10, the bulk of the cold weather that winter had nothing to do with the SSW event.

 

[Anthony Burden]

Good Morning,a very interesting article on bbc weather regarding SSW,first had no effect on 

early January cold spell in U.K. but second weaker SSW could have an effect.Also causing difficult 

forecasting with charts of any longer term time spell.