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whoops - I didnt realise that the final warming could be this early !

just checked back through the merra data and it certainly can.  2016 was the 6th march!

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21 hours ago, bluearmy said:

whoops - I didnt realise that the final warming could be this early !

just checked back through the merra data and it certainly can.  2016 was the 6th march!

I have posted about this previously -

Quote

only 3 times in the MERRA data since 1979 has the 10mb 60°N wind become easterly in March and remained so onwards for the rest of the summer.

Last year was the earliest on 05/03, a whole two weeks earlier than 19/03/86, then 24/03/85. Further to the previous post that the average 10mb 60°N wind speed becomes easterly on 12th April, the actual average date is 17th April.

The latest are 09/05/09 (after record SSW in Jan), 10/05/01 and finally 13/05/81.

The date of 5th of March 2016 rather than 6th March was taken from the original MERRA data instead of the current MERRA2 reanalysis.

Of course the effects from a final warming induced through wave forcing may be quite different from those of a vortex which gradually dissipates - often the later dates have just very feeble westerlies for some time - this limits wave propagation and it is questionable whether there is much impact with the onset of easterlies.

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Is there a knock on into the summer months ie a predominance of easterlies would promote warm/hot conditions after June?

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32 minutes ago, jam said:

Is there a knock on into the summer months ie a predominance of easterlies would promote warm/hot conditions after June?

Probably say no to that.

We've have a final warming all or most years and very rarely gives us hot se,e in summer. Plus the vortex in summer is very weak,non existent at times.

That's just my amateur take.

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20 hours ago, Summer Sun said:

 

Effectively the final warming but winds are likely to return to weak westerly for a while before final reversal still probably over a month away.

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On 3/8/2018 at 16:12, jam said:

Is there a knock on into the summer months ie a predominance of easterlies would promote warm/hot conditions after June?

No known link. My own look at 18C summer months in the UK suggests that the strongest link is with +MEI conditions which makes sense since MJO phases 6 and 7 in summer look extremely good for the UK.

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I have a question, or a request for help from our stratospheric experts, I would like to read the full version of Baldwin/Dunkerton study about stratospheric/troposferic coupling etc. Is there a free version online? The one I found online was just an abstract,thanks in advance

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12 hours ago, jules216 said:

I have a question, or a request for help from our stratospheric experts, I would like to read the full version of Baldwin/Dunkerton study about stratospheric/troposferic coupling etc. Is there a free version online? The one I found online was just an abstract,thanks in advance

https://www.researchgate.net/profile/Timothy_Dunkerton/publication/11709083_Stratospheric_Harbingers_of_Anomalous_Weather_Regimes/links/54ca9d960cf2517b755ede4c.pdf

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Interested to know thoughts in here regarding the final warming. Looks to me currently like a very weakened stratosphere polar vortex, but hasn't been fully finished off yet like some had expected (Amy Butler tweet quoted at top this page of the thread, 17th March as possible final warming based on GEFS/GFS data).

Looking at the available stratosphere charts from meteociel at 10mb and our very own 30mb chart it looks like another small warming hit end of March start of April?

5aaec37f4de7d_ScreenShot2018-03-18at19_41_41.thumb.png.0cdc66c58b51879a365f12b81a74aa1f.png 5aaec38f835a1_ScreenShot2018-03-18at19_42_12.thumb.png.39f987a90976d1148f1fbe0f834b76e5.png 5aaec39c23d66_ScreenShot2018-03-18at19_42_49.thumb.png.77412a876565baa1908d063b27052a52.png 5aaec3a75aee1_ScreenShot2018-03-18at19_42_59.thumb.png.4eb218bb70ec7044bde30e149a6d1fa3.png

5aaec3b5507f5_ScreenShot2018-03-18at19_44_07.thumb.png.545edf07e07901b05bf9d11a8735bb14.png 5aaec3c5610c2_ScreenShot2018-03-18at19_44_23.thumb.png.5adbcc00dbfe8e4bd0166be14b91ab1b.png 5aaec3d0b0f5b_ScreenShot2018-03-18at19_45_59.thumb.png.4788bbf1ebcb4e06c05475815c83f4cb.png current 60 N winds trending close to the mean, total heat flux barely noticeable currently but enough to finish things off towards the end of the month?

I had a read of the following abstract and to me its clear from this, that during years with late winter major warming, the final warming will also come later.

5aaec4804f9f3_ScreenShot2018-03-18at19_51_08.thumb.png.3c90eb920104e7cd8503e8a4ce9e53da.png

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Posted (edited)
19 hours ago, ghoneym said:

Interested to know thoughts in here regarding the final warming. Looks to me currently like a very weakened stratosphere polar vortex, but hasn't been fully finished off yet like some had expected (Amy Butler tweet quoted at top this page of the thread, 17th March as possible final warming based on GEFS/GFS data).

Looking at the available stratosphere charts from meteociel at 10mb and our very own 30mb chart it looks like another small warming hit end of March start of April?

current 60 N winds trending close to the mean, total heat flux barely noticeable currently but enough to finish things off towards the end of the month?

I had a read of the following abstract and to me its clear from this, that during years with late winter major warming, the final warming will also come later.

 

Thought I already said above that the 10mb wind would probably be westerly after the weakening alluded to in the various tweets? :)

Regarding said current weakening, GEOS and GFS have consistently shown now for a number of days that it will have just one day of reversal on the 20th, which if following the common convention means there were only 19 days of westerlies at 10mb 60°N so it is part of last month's SSW and not a separate event which requires 20 days .....

Anyway, the data does tend to show that a later major warming may have a later final warming - well final wind reversal - there may not be a discernible warming spike to speak of with a dissipation of the vortex gradually warmed by the sun.

But of course this also depends on definition - a late major warming may be an early final warming so breaking that rule of thumb.

Heat flux will be low now throughout as little wave activity propagates when the wind speeds are weak, but basically if the SSW is early enough, the vortex can recover somewhat and be prone to further wave activity and possible earlier FW.

If the SSW is later and depending on its strength, the vortex can maintain a feeble westerly for some time without strengthening appreciably before gradual dissipation. This is looking like what may happen this year, though as you mention there is another possible weakening on the forecast horizon.

edit: actually there may be a group of years where the recovery from the SSW occurs at such a time that the vortex can regain some strength and not be disturbed leading to very late FW, this chart shows final reversals of 10mb wind for the dates 09/05/09, 10/05/01 and 07/05/06 which show very close similarity from time of SSW to FW -

lateFW.thumb.gif.9ed5f6ebf05922a8dd47b01c3f6be6a2.gif

Edited by Interitus
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On 19/03/2018 at 15:45, Interitus said:

Thought I already said above that the 10mb wind would probably be westerly after the weakening alluded to in the various tweets? :)

 

Thanks for your views / opinions Interitus. 

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I've added to this week's AER blog from Dr Cohen to take a look at developments with the Strat PV over the next couple of weeks.

First of all the forecast wave activity mentioned by @ghoneym above. Here's Dr. Cohen's comment and his chart that I've marked with an arrow pointing to WAFz around the 24th - 26th March.

"The plot of Wave Activity Flux (WAFz) or poleward heat transport shows first pulse of above normal energy transfer from the troposphere to the stratosphere in quite some time (Figure 11). This is consistent with the predicted further weakening of the stratospheric PV and could potentially even lead to the Final Warming and the disappearance of the stratospheric PV in the NH until next fall."

5ab20b8d4b71f_AERBlog190318WAFz.thumb.jpg.ebb4a15f6c55a1e679595ff8f30cdc03.jpg

Looking at the latest GEFS graph of Strat zonal mean zonal wind at 10hPa 60N from http://weatheriscool.com/index.php/stratospheric-forecast-zonal-mean-u-wind-60n-10hpa-gefs/ suggests an immediate impact on the PV, with winds turning down on the 26th - 27th March. But also note a recovery to weak westerly zonal winds not long thereafter, so no final warming yet (requiring 20 days of negative/westerly winds).

epsmean10hPa60N.png

Next, a look at possible impact on our weather over the next couple of weeks. This from Dr. Cohen:

"The PV is predicted to linger across Western Siberia  over the next two weeks.  This will contribute to persistent troughing/negative geopotential height anomalies across northern Eurasia including Europe.  This will allow cold temperatures now stretching from Northern Asia to Europe and the United Kingdom (UK) to mostly remain in place  with some fluctuation in intensity over the next two weeks."

Looking at 10hPa and 100hPa height anomaly charts from Hannah Attard and comparing with this morning's GFS 500hPa anomaly and pressure charts shows the strat located over Siberia and still reasonably coupled to the trop, supporting the outlook for ongoing below average surface temps for the time of year with the UK looking to the N and NW for our weather:

Today

10_nh_stanom_1.png100_nh_stanom_1.pnggfsnh-12-6.pnggfsnh-0-6.png?0?0

T120

10_nh_stanom_21.png100_nh_stanom_21.pnggfsnh-12-120.pnggfsnh-0-120.png?0?0

T180

10_nh_stanom_31.png100_nh_stanom_31.pnggfsnh-12-180.pnggfsnh-0-180.png?0?0

AER (Dr. Cohen) blog: https://www.aer.com/science-research/climate-weather/arctic-oscillation/
Hannah Attard charts: http://www.atmos.albany.edu/student/hattard/realtime.php

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The Met Office yesterday published a (disappointingly) short blog on the SSW event that occurred on 12th February and the second, less intense SSW that has occurred 2 days ago (20th March) with Zonal Mean Zonal Winds again reversing (switching easterly) at 10hPa 60N. This graph from the blog:

5ab3a1dac83e1_MetOffZMZWGraph20Mar2018.thumb.jpg.1a52fd467a428444594b46061d7379fb.jpg

Some extracts from the blog:

"Following a recovery in the first half of March, a second but less intense sudden stratospheric warming has just occurred consistent with the continuing risk of cold easterly winds.”

"The lower stratosphere was already disturbed and this new event is unlikely to add much extra to what was already there."

I was particularly interested in the statement made in the blog that the the SSW "was triggered from the tropics at the beginning of February.......", but disappointed that this was such a fleeting mention of the tropical>extra tropical>stratosphere sequence that took place and finally led to the SSW.

There was a high amplitude MJO Phase 6/7 in the weeks preceding the SSW and published studies suggest this can be an important factor in the events leading up to a SSW. But as I am learning from the excellent posts from @Tamara , the tropics (MJO) is the starting point, and the poleward propagation of Rossby waves through the extra tropics with onward impact through other events such as frictional and mountain torque can be just as important when trying to understand the end-to-end sequence that culminates in a particular SSW.

I'm very much looking forward to joining in the post-SSW analysis and discussions that @Bring Back1962-63 is planning to take place in the 'Learning about Teleconnection Science and Background Signals' thread in due course, when hopefully we can better understand exactly what sequence played out in the run-up to this February's event. 

Met Office blog: https://blog.metoffice.gov.uk/2018/03/21/will-cold-conditions-return/

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1 hour ago, Blessed Weather said:

I was particularly interested in the statement made in the blog that the the SSW "was triggered from the tropics at the beginning of February.......", but disappointed that this was such a fleeting mention of the tropical>extra tropical>stratosphere sequence that took place and finally led to the SSW.

 

Met Office blog: https://blog.metoffice.gov.uk/2018/03/21/will-cold-conditions-return/

There's no mention of tropical-strat connection, be there one or not. What the author actually says is -

Quote

The pattern of easterly winds leading to the repeated freezing conditions, was triggered from the tropics at the beginning of February and then exacerbated by a Sudden Stratospheric Warming on 12 February.

 

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I think if he was to expand on his comments then he would be referring to tropics > extra tropics > MT> Stratosphere > troposphere > high lat blocking > Easterly > further assisted by continued downwelling courtesy of SSW ? Lets ask him mr Sciaffe in the comments section of his blog :D

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12 minutes ago, ghoneym said:

I think if he was to expand on his comments then he would be referring to tropics > extra tropics > MT> Stratosphere > troposphere > high lat blocking > Easterly > further assisted by continued downwelling courtesy of SSW ? Lets ask him mr Sciaffe in the comments section of his blog :D

I believe you jest, but if seeking confirmation bias it potentially misses an important point made in the blog - forget the SSW, the pattern which led to the cold spell was triggered from the tropics at the beginning of February (not preceding the SSW - this was already under way).

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Posted (edited)
28 minutes ago, Interitus said:

I believe you jest, but if seeking confirmation bias it potentially misses an important point made in the blog - forget the SSW, the pattern which led to the cold spell was triggered from the tropics at the beginning of February (not preceding the SSW - this was already under way).

I really do need to wade in here. I believe that you are over simplifying this to the extent you are missing the point and quoting out of context as well as picking holes in something that does not merit this treatment. My teleconnection friends @Blessed Weather and @ghoneym are certainly not jesting and we have been thoroughly researching and consulting on this and taking it all extremely seriously. I am currently in the middle of preparing a very long post for the MOD (to go live later tonight) and I go through this in rather greater detail. What you need to realise is this relationship: The slight weakening in La Nina/ the spike in AAM (that's the start of the tropical forcing reference) in early Feb/ the time lag to +veFT/then +ve MT which helped to trigger the SSW*** along with other influences. Adam Scaife refers to the forcing but does not go into the key detail. This same process was also partly the cause of the MJO to go into a very high amp phase 7 to further assist with HLB. There is still a lot for "all" of us to learn about the interaction of all these influences but you "must" take on board that some of the very recent thinking is starting to accept the vitally important role of AAM in this whole process.   

***EDIT:  Yes the SSW processes were underway earlier but the main (or one of them) trigger for the impact was the AAM cycle and sequence that followed.

Edited by Bring Back1962-63
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Posted (edited)
16 minutes ago, Bring Back1962-63 said:

I really do need to wade in here. I believe that you are over simplifying this to the extent you are missing the point and quoting out of context as well as picking holes in something that does not merit this treatment. My teleconnection friends @Blessed Weather and @ghoneym are certainly not jesting and we have been thoroughly researching and consulting on this and taking it all extremely seriously. I am currently in the middle of preparing a very long post for the MOD (to go live later tonight) and I go through this in rather greater detail. What you need to realise is this relationship: The slight weakening in La Nina/ the spike in AAM (that's the start of the tropical forcing reference) in early Feb/ the time lag to +veFT/then +ve MT which helped to trigger the SSW along with other influences. Adam Scaife refers to the forcing but does not go into the key detail. This same process was also partly the cause of the MJO to go into a very high amp phase 7 to further assist with HLB. There is still a lot for "all" of us to learn about the interaction of all these influences but you "must" take on board that some of the very recent thinking is starting to accept the vitally important role of AAM in this whole process.   

Back off, Blessed Weather paraphrased the quote to infer something which was not stated - whether it is the author's or Meto's beliefs or otherwise, I quoted the blog verbatim.

edit: your timings look awry, if the AAM spike early Feb is the start is the tropical forcing, how long do you think it takes to impact the strat? Looking forward to your analysis.

Edited by Interitus

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34 minutes ago, Interitus said:

Back off, Blessed Weather paraphrased the quote to infer something which was not stated - whether it is the author's or Meto's beliefs or otherwise, I quoted the blog verbatim.

edit: your timings look awry, if the AAM spike early Feb is the start is the tropical forcing, how long do you think it takes to impact the strat? Looking forward to your analysis.

The timings look perfectly correlated to me. The wave forcing shaped by the AAM spike surely cannot be denied. In terms of time taken to impact the start I believe several days, 6km per day so reaches 100mb in 36 hours or so, during this time waiting for further wave activity the 10mb and 1mb are effected by the previous wave. It takes another few days for the next wave to take effect and an adiabatic heating process starts taking shape giving us the warming. 

5ab3e4d38038f_ScreenShot2018-03-22at17_13_30.thumb.png.b36d8415171393f3254275119853ddde.png  5ab3e4de777b9_ScreenShot2018-03-22at17_14_07.thumb.png.af2e2b3ee04904e335afcc44f017987b.png  5ab3e4e80b08b_ScreenShot2018-03-22at17_14_21.thumb.png.4f77524c0970ea5090a50cefb5237996.png  5ab3e5058e1bb_ScreenShot2018-03-22at17_15_29.thumb.png.9dee79943d634d1010ff8a4c9af8f5a1.png  5ab3e53cd9094_ScreenShot2018-03-22at17_17_32.thumb.png.f19d310fb0a726cd59130fe2cac7327f.png

Could you give us your thoughts please regarding this. A bit more detail would be helpful.

 

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On an unrelated tangent, Amy butler tweeted yesterday that approx 2/3 of aleutian highs are folllowed by notable  strat polar vortex splits ...... i think that’s what she wrote .........

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24 minutes ago, bluearmy said:

On an unrelated tangent, Amy butler tweeted yesterday that approx 2/3 of aleutian highs are folllowed by notable  strat polar vortex splits ...... i think that’s what she wrote .........

 

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