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Stratosphere and Polar Vortex Watch


Paul

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On 11/02/2019 at 15:57, knocker said:

But the point is that some posters seem to arrogantly assume, once they have pushed the boundaries of this limitation  that their forecast of, say, pressure distribution in the Atlantic and western Europe brooks no argument. The clue often is when a post starts, or includes, statements such as "the models are not picking up the signals" which patently assumes that the posters knows with certainty what the correct signals are

Of course pushing the boundaries is fine and anyone doing so should be applauder but a little humility and a little less dogmatic assumption wouldn't go amiss.

Succinctly put Knocker.

On 11/02/2019 at 15:24, Catacol said:

 but where I do have an issue is when those characters then choose to pour cold water on the attempts of others to make sense of the longer term.....particularly given that the critic tends to stay within the conservative window of accuracy and then pour scorn on those who are trying to work further ahead. That's just bad from every angle - humanity would have made next to no process throughout history if progress were left to those with that kind of mindset.

"Extenuating circumstance"? - is that just code for another unforeseen factor? Surely it must be....and by its very definition that falls, once again, within the envelope of reading signals. Not sure what point you are trying to make here other than suggesting that teleconnective forecasting ignores the bits that disagree with the "theory" - whatever theory for a season that might be. No - certainly dont agree with that. All signals are valid and I'm sure we are going to learn a lot from this season. Furtado put out an excellent tweet over the weekend on exactly this topic. Test and observe. Isnt that science?

.....

You are right that certainty is limited. But I'd rather push the boundaries of that limitation rather than not even try. 

Wondering if I am one of those characters? 

Extenuating circumstance, unforeseen factor, whatever, the point is this excuses the author from any acceptance that, just maybe, possibly, their assessment was incorrect, or even bunkum.

With the Jason Furtado tweet, more telling was the reply from Prof. Paul Roundy -

Quote

Do U mean a negative angular momentum atmospheric state? I'm not sure what people mean when they refer to an El Nino or La Nina atmospheric State. El Nino or La Nina can reflect into many diff circulation patterns even though they favor certain ones. Just looking for clarity.

So much for that.

The major teleconnection as far as UK and western Europe are concerned is of course the NAO. For those interested enough, NOAA ESRL have handy tables of monthly correlations between various teleconnections. Few correlate well with the NAOhttps://www.esrl.noaa.gov/psd/data/correlation/table/

The signals are generally far weaker than they are given credit for and are largely swamped by natural variability.

NB. There is no issue with long range forecasts, by whatever method, or those attempting them, but it is bemusing when they are reluctant to discuss or debate the ideas on a public forum and view it as a slight or impugnment, bizarre. And not being a "coldie", there is no axe to grind nonsense.

 

Meanwhile, here is a monster chiclet chart of GFS forecasts of u1060 from 09/12/18 to 31/01/19 -

chiclet.thumb.jpg.75c58b6020601699e29ef399e1adb7eb.jpg

Well more a Hovmoller than a true chiclet with the hours shifted to meet in the vertical but this requires discarding data as horizontal resolution is 6 hours, vertical is 3 hours. The low res 12 hourly increments beyond +240 is interpolated to upscale.

Running left to right from Dec 9th 00z, analysis at bottom, T384 at top, positive zonal wind red, negative blue, it captures the full development of the SSW which when signaled by the model in long range from the position of an extant vortex, progresses fairly consistently to T0.  It highlights though the apparent difficulty to be certain of long range once the SSW is imminent or occurring with frequent fluctuations between vortex recovery and extended SSW conditions - whether this is real or an artefact of the GFS requires investigation, but it also over cooked the strength of the reversal in shorter range which didn't materialise (the deepest blue tones in the centre).

However, when the recovery is finally detected, it progresses consistently from long range, and there appears much less variability with the vortex back in place.

 

Edited by Interitus
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Posted
  • Location: Dunstable 446ft ASL
  • Weather Preferences: cold with frost & snow in winter; hot and dry in summer
  • Location: Dunstable 446ft ASL
On ‎14‎/‎02‎/‎2019 at 09:42, TEITS said:

Whatever your opinion on teleconnections, many on here will be rather more sceptical about predictions of a looming cold spell next winter. However this is a good thing because nobody should take any medium/long range forecast as gospel whatever method is used.

I have enjoyed reading the posts this winter especially from Catacol. I find his posts to be very informative but at the same time easy to understand.

I fully agree with TEITS views. The subject matter is complex enough without having to try and decipher a complicated narrative and the likes of Catacol and Singularity have done this excellently and at the same time have tried to provide some explanations as to why the teleconnections based forecasts have by and large gone wrong this year. Furthermore, I am sure there will be more on this subject from them over the coming months and I very much look forward to reading their further thoughts. Whilst I acknowledge that no explanation is required or, indeed, in my view expected from those others that have posted on these matters throughout the season, I for one would appreciate and value their thoughts should they have the time and desire to do so. It will, after all, only add to the learning for us all who partake on this great forum.  

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Posted
  • Location: New Forest (Western)
  • Weather Preferences: Fascinated by extreme weather. Despise drizzle.
  • Location: New Forest (Western)

Something truly extraordinary seems to be going on now and until further notice.

ecmwf_T850a_eu_1.png ecmwf_T850a_eu_8.png ecmwf_T850a_eu_11.png

Seeing that magnitude of 850 hPa temperature anomaly twice in the space of a week and three times in the space of 11 days is just staggering.

ecmwf_z500a_eu_1.png ecmwf_z500a_eu_8.png ecmwf_z500a_eu_10.png

The 500 mb height anomalies are also very impressive, especially later next week.

All assuming the 12z ECM (with the 12z GFS similar but the 06z having been more so) that forms the basis for these charts is along the right lines - but the signal is proving very strong in the modelling now that the chance of some cross-polar ridging has largely been dropped (yet again this winter).

 

Looking for the causes of this, well it's going to be an unusual combination and I have a theory that firstly, the propagating anomalies from the strong MJO passage across the tropical Pacific are being distorted by a negative AAM anomaly at 30*N (a Nina-like feature) that continues to resist change even in the face of an extremely strong WWB across the Central Pacific, and secondly, the lack of a strong lower stratospheric vortex (it's near the LTA which is a good deal lower than it is for Dec & Jan) is providing little in the way of zonal push on the blocking high, meaning that Atlantic troughs only serve to pump it up further via warm air advection aloft.

If it wasn't for the continued Nina-like interference, the high-latitudes would be permitting the height rises needed to set up a powerful retrograding HLB from Scandinavia to Greenland, as is typical following MJO propagation through phases 7 & 8 with a Nino background (though given the weakness of the Nino we'd probably have seen the blocking head too far west for us pretty soon - like what happened to start March last year, but probably less dramatic!).

One factor I'm unsure of the role of is the QBO; does a westerly QBO at 40 mb and above have a direct ability to keep the AO more positive? I don't expect so based on what I currently know (it impacts the stratosphere's interactions with the troposphere, not the troposphere's interactions with itself) - but I could be missing some crucial information.

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Posted
  • Location: Mytholmroyd, West Yorks.......
  • Weather Preferences: Hot & Sunny, Cold & Snowy
  • Location: Mytholmroyd, West Yorks.......

Would anyone like to take a punt at what a 'later than normal' final warming translates to on the ground?

Is it too simple to just see polar cold trapped in the Arctic for longer before the final 'seep out' the collapse of the polar night jet allows?

Does the delay just mean that the lower Lat.s get to build more of a defence to any cold incursions due to higher sun/warmer land?

Will it mean a very 'unstable' atmosphere with cold PM air masses passing over a warmed land leading to more storms forming?

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Posted
  • Location: New Forest (Western)
  • Weather Preferences: Fascinated by extreme weather. Despise drizzle.
  • Location: New Forest (Western)

Very broad-brush, but I believe it tends to encourage more mid-latitude ridge dominance than usual during Mar-Apr, as the polar jet retreats north in tandem with the Arctic cold pool shrinking as the sun gets to work, and the organised vortex keeps high-latitude blocking to a minimum. 

Needs researching to be sure though (isolation of late warming years and then filtering out of strong Nino cases - as they distort things - to look for common patterns). Not something I've got the spare time to do at the moment.

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Posted
  • Location: New Forest (Western)
  • Weather Preferences: Fascinated by extreme weather. Despise drizzle.
  • Location: New Forest (Western)

Yes... common aftermath to a strong SSW as it shuts down the upward transport of wave breaks that otherwise inject areas of anomalous warmth and higher heights to keep prodding and poking at the vortex (or, of course, to trigger a SSW when conditions come together right).

The upper vortex is rarely happier than when there's downwelling anomalies from an earlier SSW beneath it. Same goes for the mid-level vortex as the downwell continues further, and then finally the lower-vortex.

 

This is prevented if the SSW occurs late enough in the season and is also persistent enough, much as we saw with the enormous event of 2017 that proved to be the end for that winter's polar vortex.

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Posted
  • Location: Coniston, Cumbria 90m ASL
  • Weather Preferences: wintry
  • Location: Coniston, Cumbria 90m ASL

Been looking at this again...there's a persistent warm sector above E Russia / Japan, been there for a few weeks now...unusual or not?

https://earth.nullschool.net/#current/wind/isobaric/10hPa/overlay=temp/orthographic=104.77,31.36,327/loc=135.402,51.819

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Posted
  • Location: Camborne
  • Location: Camborne

The impact of strong El Niño and La Niña events on the North Atlantic

Quote

Abstract

The impact of strong La Niña events on January–February north Atlantic Mean Sea Level Pressure is unknown, as these events have never been observed. Using large ensembles from the Met Office decadal prediction system, examples of strong La Niña events are simulated and the Atlantic response to these is found to be a positive North Atlantic Oscillation. This is very different to the wavelike response observed and simulated for strong El Niño events. The reason for this difference is traced to the fact that the December–January–February mean tropospheric teleconnection of ENSO to the north Atlantic dominates for strong El Niño events, while the stratospheric teleconnection dominates for strong La Niña events. The strength of the tropospheric pathway grows linearly and symmetrically with ENSO. The stratospheric pathway is the source of the asymmetry between January–February surface responses to strong El Niño and strong La Niña events.

Quote

Plain Language Summary

The El Niño Southern Oscillation (ENSO) has a large impact on January‐February North Atlantic Mean Sea Level Pressure (MSLP), important for forecasting the mean climate over the UK and Northern Europe during these months. Simulations from the Met Office decadal prediction system are used to research the impact of strong negative (La Niña) events, not yet observed in nature. Really strong positive (El Niño) and negative (La Niña) events are found to have an asymmetric impact on the North Atlantic. This paper studies the reasons why. ENSO impacts the North Atlantic via two routes ‐ one through the tropical Atlantic in the lower atmosphere (troposphere) and one through the middle atmosphere (stratosphere) in polar latitudes. It is found that the tropospheric pathway dominates for El Niño events, leading to a wavelike response in north Atlantic MSLP, characterised by a high pressure west of the UK. However, the stratospheric pathway dominates for La Niña events leading to a different MSLP pattern, characterised by high pressure over the Azores and low pressure over Iceland. Therefore, if a really strong La Niña event were ever to occur, the UK and Northern Europe might experience a very wet winter.

https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2018GL081776#.XHgH5udOOKk.twitter

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Posted
  • Location: Coniston, Cumbria 90m ASL
  • Weather Preferences: wintry
  • Location: Coniston, Cumbria 90m ASL

I know I keep on about this illustration of the situation, but https://earth.nullschool.net/#current/wind/isobaric/10hPa/overlay=temp/orthographic=15.56,82.47,216

Shows a couple of areas of above what would appear to be normal temps at 10 Hpa. 

No idea if this is normal situation at this stage of the end of winter /early spring, or if this would be a precursor to the final warming ? 

Screenshot_20190303-215526.png

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Posted
  • Location: Leeds/Bradford border, 185 metres above sea level, around 600 feet
  • Location: Leeds/Bradford border, 185 metres above sea level, around 600 feet
12 hours ago, JeffC said:

I know I keep on about this illustration of the situation, but https://earth.nullschool.net/#current/wind/isobaric/10hPa/overlay=temp/orthographic=15.56,82.47,216

Shows a couple of areas of above what would appear to be normal temps at 10 Hpa. 

No idea if this is normal situation at this stage of the end of winter /early spring, or if this would be a precursor to the final warming ? 

Screenshot_20190303-215526.png

There is currently some wave 2 activity pushing at the vortex. It is not forecast to have a material impact anytime soon.

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Posted
  • Location: Coniston, Cumbria 90m ASL
  • Weather Preferences: wintry
  • Location: Coniston, Cumbria 90m ASL
19 hours ago, summer blizzard said:

There is currently some wave 2 activity pushing at the vortex. It is not forecast to have a material impact anytime soon.

Thanks SB, is that because the vortex has regained strength and the wave 2 isnt strong enough until maybe the sun gets to a bit higher latitude?

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Posted
  • Location: Leeds/Bradford border, 185 metres above sea level, around 600 feet
  • Location: Leeds/Bradford border, 185 metres above sea level, around 600 feet
2 hours ago, JeffC said:

Thanks SB, is that because the vortex has regained strength and the wave 2 isnt strong enough until maybe the sun gets to a bit higher latitude?

Wave activity occurs every winter which is why a vortex is rarely completely circular and right on top of the world. Most of the time it’s just like prodding jelly.

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Posted
  • Location: Mytholmroyd, West Yorks.......
  • Weather Preferences: Hot & Sunny, Cold & Snowy
  • Location: Mytholmroyd, West Yorks.......

As the vortex collapses for the year will we see one final shot of cold from the north or will we be on the WAA side of things?

Either a chilly start to April or a benign one!

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Posted
  • Location: Leeds/Bradford border, 185 metres above sea level, around 600 feet
  • Location: Leeds/Bradford border, 185 metres above sea level, around 600 feet
8 hours ago, Gray-Wolf said:

As the vortex collapses for the year will we see one final shot of cold from the north or will we be on the WAA side of things?

Either a chilly start to April or a benign one!

Vortex is stronger than average so i suspect we may see a minor warming rather than slow death. That may cause a few weeks of -AO and a somewhat slow spring.

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Posted
  • Location: Leeds/Bradford border, 185 metres above sea level, around 600 feet
  • Location: Leeds/Bradford border, 185 metres above sea level, around 600 feet

https://acd-ext.gsfc.nasa.gov/Data_services/met/metdata/annual/merra2/wind/u60n_10_2018_merra2.pdf

GFS currently forecasting a sharp drop in zonal winds after reaching near record highs for the time of year. 

Perhaps a troposphere response into early April. 

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Posted
  • Location: Mytholmroyd, West Yorks.......
  • Weather Preferences: Hot & Sunny, Cold & Snowy
  • Location: Mytholmroyd, West Yorks.......

https://earth.nullschool.net/#current/wind/isobaric/10hPa/orthographic=-68.80,77.38,329

Well the circulation looks to be breaking down from the fierce circle of winds of a week ago?

Will it just flop out of being this year with those low wind speeds working back around the circulation as we lose the polar night Jet until autumn?

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Posted
  • Location: Mytholmroyd, West Yorks.......
  • Weather Preferences: Hot & Sunny, Cold & Snowy
  • Location: Mytholmroyd, West Yorks.......

https://earth.nullschool.net/#current/wind/isobaric/10hPa/orthographic=-26.78,80.92,250

Still looking like a very 'gentle' breakdown of the PNJ?

I have concerns that GFS FI at present is trying to show a more typical trop response to a final warming but I'm increasingly thinking that the PNJ will just drop to low speeds and fade from the plot?

That might mean the current GFS solution out in FI will be very different when we come to see it?

FWIW I think the high will end up located further east leaving us on the S'ly side of it and not the N'ly side of the high?

 

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Posted
  • Location: Leeds/Bradford border, 185 metres above sea level, around 600 feet
  • Location: Leeds/Bradford border, 185 metres above sea level, around 600 feet
1 hour ago, Gray-Wolf said:

https://earth.nullschool.net/#current/wind/isobaric/10hPa/orthographic=-26.78,80.92,250

Still looking like a very 'gentle' breakdown of the PNJ?

I have concerns that GFS FI at present is trying to show a more typical trop response to a final warming but I'm increasingly thinking that the PNJ will just drop to low speeds and fade from the plot?

That might mean the current GFS solution out in FI will be very different when we come to see it?

FWIW I think the high will end up located further east leaving us on the S'ly side of it and not the N'ly side of the high?

 

We have seen a recent sharp drop which may filtet through albeit yes, i don't expect anything substantial and long lasting.

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Posted
  • Location: South Ockendon, Thurrock, SW Essex
  • Weather Preferences: Severe frosts, Heavy snowfall, Thunder and lightning, Stormy weather
  • Location: South Ockendon, Thurrock, SW Essex

06_180_arctic10 Stratosphere temperature forecast Valid 18GMT Thursday 18th April.png

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