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Stratosphere temperature watch - 2016/17


Paul

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Posted
  • Location: Camborne
  • Location: Camborne

H/t Amy H Butler

Statistically, w/ La Nina +SSW, anomalies over UK are actually about neutral for the season (they essentially cancel; La Nina=+NAO;SSW=-NAO)

However, on timescales of days to weeks, yes, we would expect a SSW to bring snowy and cold conditions.

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Posted
  • Location: Crewe, Cheshire
  • Weather Preferences: Snow, storms and other extremes
  • Location: Crewe, Cheshire
6 hours ago, Don said:

Yes and unfortunately the GloSea 5 is not on its own with both the latest CFSv2 and EC seasonal models also pointing towards a similar pattern for winter.

Without wanting to veer too far away from all things strat, the long rangers are actually improving ever so slightly in as much as they are incrementally inching mean troughing further S&E with a better polar height profile.

glbz700MonInd4.gif

I've gone from write off territory to 'oh we may see a couple of N'ly topplers' Will be more interesting if the trend can gain traction over the next 6-8 weeks.

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Posted
  • Location: Near King's Lynn 13.68m ASL
  • Weather Preferences: Hoar Frost, Snow, Misty Autumn mornings
  • Location: Near King's Lynn 13.68m ASL

10hPa mean zonal wind continues to track right on the average.

u60n_10_2017_merra2.pdf

However, all but one of the GEFS take us below average for the start of October:

u10serie.png

(Some extreme CFS runs in there too, but not to be taken seriously at this range).

 

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Posted
  • Location: Camborne
  • Location: Camborne

Winter cold extremes linked to high-altitude polar vortex weakening

Quote

When the strong winds that circle the Arctic slacken, cold polar air can escape and cause extreme winter chills in parts of the Northern hemisphere. A new study finds that these weak states have become more persistent over the past four decades and can be linked to cold winters in Russia and Europe. It is the first to show that changes in winds high up in the stratosphere substantially contributed to the observed winter cooling trend in northern Eurasia. While it is still a subject of research how the Arctic under climate change impacts the rest of the world, this study lends further support that a changing Arctic impacts the weather across large swaths of the Northern Hemisphere population centers.

https://phys.org/news/2017-09-winter-cold-extremes-linked-high-altitude.html

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Posted
  • Location: Netherlands
  • Location: Netherlands

http://journals.ametsoc.org/doi/pdf/10.1175/BAMS-D-16-0259.1

Abstract

Over the last decades, the stratospheric polar vortex has shifted towards more frequent weak states which can explain Eurasian cooling trends in boreal winter in the era of Arctic amplification.

The extra-tropical stratosphere in boreal winter is characterized by a strong circumpolar westerly jet, confining the coldest temperatures at high latitudes. The jet, referred to as the stratospheric polar vortex, is predominantly zonal and centered around the pole; however, it does exhibit large variability in wind speed and location. Previous studies showed that a weak stratospheric polar vortex can lead to cold-air outbreaks in the mid-latitudes but the exact relationships and mechanisms are unclear. Particularly, it is unclear whether stratospheric variability has contributed to the observed anomalous cooling trends in mid-latitude Eurasia. Using hierarchical clustering, we show that over the last 37 years, the frequency of weak vortex states in mid to late winter (January and February) has increased which were accompanied by subsequent cold extremes in mid-latitude Eurasia. For this region 60% of the observed cooling in the era of Arctic amplification, i.e. since 1990, can be explained by the increased frequency of weak stratospheric polar vortex states, a number which increases to almost 80% when El Niño/Southern Oscillation (ENSO) variability is included as well.

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Posted
  • Location: Crewe, Cheshire
  • Weather Preferences: Snow, storms and other extremes
  • Location: Crewe, Cheshire

I wonder if what we are seeing unfold strat wise is the reason for the rapid flipping of the CFS from a consistent zonal winter forecast to a more blocked one?

glbz700MonInd4.gif

Will be intriguing to see what the next updates of the GLOSEA and EC seasonal show.

Edited by CreweCold
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Posted
  • Location: Carryduff, County Down 420ft ASL
  • Location: Carryduff, County Down 420ft ASL
3 hours ago, knocker said:

Still begs the question, why does the raised Tropopause induce increased hurricane activity?

 

Is it because it allows for greater cloud tops and instability, more fuel can be sucked into the core?

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Posted
  • Location: Chisinau, Moldova.
  • Location: Chisinau, Moldova.
3 hours ago, knocker said:

Still begs the question, why does the raised Tropopause induce increased hurricane activity?

 

I have another question. How does he define record hurricane activity? Using the ACE Index, while 2017 is up there, it has some way to go to beat 2005 (If we are talking North Atlantic) Looking at things globally, things are quiet elsewhere, making any kind of global record extremely unlikely.

 

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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
20 hours ago, jvenge said:

I have another question. How does he define record hurricane activity? Using the ACE Index, while 2017 is up there, it has some way to go to beat 2005 (If we are talking North Atlantic) Looking at things globally, things are quiet elsewhere, making any kind of global record extremely unlikely.

 

September has broken the ACE record is probably what he was referring to. 

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Posted
  • Location: Roznava (Slovakia) formerly Hollywood, Co Wicklow
  • Weather Preferences: continental climate
  • Location: Roznava (Slovakia) formerly Hollywood, Co Wicklow

zonal wind anomalies may be running below average for the month of october,maybe weak polar vortex early? actually quite curious to see if northern hemisphere look will show perturbed vortex mid. October onwards

u_65N_10hpa.png

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Posted
  • Location: Portrush. (NI) UK
  • Location: Portrush. (NI) UK
On 26/09/2017 at 09:01, knocker said:

Still begs the question, why does the raised Tropopause induce increased hurricane activity?

 

Ryan Maue is my source of knowledge on this question. At -70 cold air convection enables hurricanes to evolve towards Cat 4.

Current QBO state raises Tropospheric heights and provides opportunity to reach the colder convection I.e Maria IMG_4386.thumb.JPG.d6add0488e26fb01e9f94bc92fcf27ca.JPG

Maue states that this is the base requirements for Pacific Super Typhoons. -70 C, followed by crucial 3-4 hours of eye temp increases to produce environment for CAT 5,5+. 

 

* This next section is my thoughts on the similarities in physical development of powerful Hurricanes to strong Polar Vortices. 

IMG_3266.thumb.JPG.a864b935e5569f3337add37ba6745464.JPG

The colder the convection the stronger the PV

The more electromagnetism from solar output the most increased heights for PV to reach and the colder the convection. 

The shringage caused by less solar electromagnetism during hibernation then the weaker the PV. Less rigid, more flabby and therefore more susceptible to break down. 

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Posted
  • Location: Camborne
  • Location: Camborne
20 minutes ago, KyleHenry said:

Ryan Maue is my source of knowledge on this question. At -70 cold air convection enables hurricanes to evolve towards Cat 4.

Current QBO state raises Tropospheric heights and provides opportunity to reach the colder convection I.e Maria IMG_4386.thumb.JPG.d6add0488e26fb01e9f94bc92fcf27ca.JPG

Maue states that this is the base requirements for Pacific Super Typhoons. -70 C, followed by crucial 3-4 hours of eye temp increases to produce environment for CAT 5,5+. 

 

* This next section is my thoughts on the similarities in physical development of powerful Hurricanes to strong Polar Vortices. 

IMG_3266.thumb.JPG.a864b935e5569f3337add37ba6745464.JPG

The colder the convection the stronger the PV

The more electromagnetism from solar output the most increased heights for PV to reach and the colder the convection. 

The shringage caused by less solar electromagnetism during hibernation then the weaker the PV. Less rigid, more flabby and therefore more susceptible to break down. 

Thanks for that. Need to go away and think about it. :)

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Posted
  • Location: Wakefield, West Yorkshire
  • Location: Wakefield, West Yorkshire
36 minutes ago, Dennis said:

next phase of zonal winds.....

4.png

This would appear to be a good thing? (If you are wanting to get a good start to the season for weather of a colder persuasion?)

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Posted
  • Location: Portrush. (NI) UK
  • Location: Portrush. (NI) UK
1 hour ago, Paul_1978 said:

This would appear to be a good thing? (If you are wanting to get a good start to the season for weather of a colder persuasion?)

Very early days, but in shortest of answers, it's a yes.

It would have to remain constant. It means that for a reversal of wind speed (below 0 m/s) it doesn't have far to go and the Polar Vortex is in a state of structural weakness.

Here is the BUT part, there has to be either atmospheric energy transfer via waves into Stratosphere to allow creation of SSW ( Which is required to be successful) or Trop lead via coupling.

Both of which then need the response of HP placement to Greenland/Scandinavia etc. 

 

 

 

 

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

Another key aspect last winter was long periods of moderate-strength stratospheric warming with positive height anomalies frequently having some but not a lot of influence on tropospheric patterns... yet still enough to - ironically I suppose - interfere with the vertical wave activity needed to produce a bigger, more effective warming event.

Or at least, that's what J. Cohen deduced from how things panned out.... he's not had the best track record these past few winters so there's no guarantee that this is an entirely valid theory. What do others make of it? TIA :hi:

If it does hold truth then I will have some concern if the vortex is consistently very weak from early on as this seemed to be what facilitated the long-duration-yet-weak-magnitude warming tendency of last winter. Just my take on things though!

Edited by Singularity
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