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50 minutes ago, supernova said:

Guys, saw a chart the other day where Dr Butler was predicting a -37.5m/s wind reversal - can anybody point me in the right direction of what actually verified if indeed the SSW has peaked yet?

The chart below from Hannah E. Attard shows Zonal Wind dipping below -30 m/s (the black analysis line) around the 14th Feb and the GEFS forecast (red forecast line) suggests the maximum negative Zonal Wind flow will have been reached sometime today (15th) around -34 to -35 m/s.

5a8601000062a_ZonalWind10hPaGEFSHannahEAttard.thumb.png.be79752bf0875af24166fc73a2da8be8.png

http://www.atmos.albany.edu/student/hattard/realtime.php

Edited by Blessed Weather
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Some useful tropospheric developments upcoming which are likely to have stratospheric impacts towards the end of November and more particularly into December. A strong convectively coupled tropic

so after many days the GFS & FNMOC & canadian finally now follow the Euro with 44 out 64 Members with a split at day 9- The ECM is day 8. We will call it - SSW & Split for 1st Ja

For all that watch the zonal winds. Let me urge you to look at the geopotential heights more. At least as far as weakening/strengthening trends go. Because as the polar vortex cries for help, you migh

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28 minutes ago, Blessed Weather said:

The chart below from Hannah E. Attard shows Zonal Wind dipping below -30 m/s (the black analysis line) around the 14th Feb and the GEFS forecast (red forecast line) suggests the maximum negative Zonal Wind flow will have been reached sometime today (15th) around -34 to -35 m/s.

5a8601000062a_ZonalWind10hPaGEFSHannahEAttard.thumb.png.be79752bf0875af24166fc73a2da8be8.png

http://www.atmos.albany.edu/student/hattard/realtime.php

At 65N I would say -35 m/s today will just be breached. it’s a tad confusing with some using 65N but generally 60N being the standard. 

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8 hours ago, bluearmy said:

At 65N I would say -35 m/s today will just be breached. it’s a tad confusing with some using 65N but generally 60N being the standard. 

Yes, I agree Blue, it is a tad confusing. Dr Amy Butler uses 65N and it was her that published a paper in 2015 "Defining Sudden Stratospheric Warmings" in which she stated:

It has been over 35 years since the WMO offered a definition of SSWs, during which time many more SSWs have been observed. We suggest the time is ripe for improvements and updates.

In her paper and conclusions she suggested:

......using 65°N instead of 60°N, may decrease sensitivity to changes in the vortex edge.....  then about 20% more events will be detected compared to using 60°N only.

Full paper: https://journals.ametsoc.org/doi/full/10.1175/BAMS-D-13-00173.1

But back to the current event and I see that http://weatheriscool.com/ is reporting (with their exclamation marks):

The strat. vortex is currently weaker than all other years in the ERA interim record!!! 
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1 hour ago, Chevron12345 said:

Has there been any response to the SSW anywhere? The PV just looks strong as normal with no change.

This is a fair point - there is nothing particularly unusual in today's weather pattern for example. The models are clearly struggling to work it out - take a look at this morning's ECM and GFS for example. Chalk and cheese at T+120 with major divergence starting at T+96.

ECM then goes onto have a full on easterly by T+144 whereas the GFS has us in south-westerlies!

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6 hours ago, Chevron12345 said:

Has there been any response to the SSW anywhere? The PV just looks strong as normal with no change.

It’s pretty obvious ??

497837B4-97E5-4644-9928-F4A347F04197.thumb.jpeg.c6fd09d7d113379a20b4cb39da6e5119.jpeg

the canadian vortex was so strong that it will take another warming (due shortly) to begin to down that monster 

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On 2/3/2018 at 20:34, lorenzo said:

Whilst the above is the nuke heat flux aggregate - we also have on NASA the momentum flux plots - would be interested to hear @Interitus thoughts on propagation given the excellence shown in previous posts tracking the strat interplay with trop, and thoughts on precursors given this turnaround is against thoughts of the last 7 days. This is not an I told you so, this is an examination of the validity of precursors vs the precision in analysis.

Below is 500hPa and hence the reason we need a few days to see the mechanics in play.

5a761a536f86c_momentumflux500hPa.thumb.PNG.1b3bc5089656dd6a245817f0e2a7754e.PNG

Wild cards are also the 7-8-1 MJO with MJO wanting to push through the 6-7 regime into 7-8-1 - pretty astounding in itself given pacific proclivity( Nina). Also the uptick in the MJO to plus 3-4 sigma is as @Catacol mentioned on the mod a 1/10 yr event. - Genuinely is, and perhaps longer lead than that. I surmise the routes are in peak solar min and modulation of the hadley cells.. EPF forcing juices cells - when there is none... we have other modes imprinting on the atmosphere.

Also within that the inflection on both GFS and ECM NWP and @chionomaniac identifying a second pulse of warming artefact over hudson at time when MJO 8-1 would build blocks...

Tantalising - I had thought we were overdue a signature strat event, the garfinkel study telegraphs P2 MJO as lagging thru the vortex at 30-35 days and it is literally bang on the money right now. Impressive, add in the mitchell prescursors highlighted by Ed, this SSW is proving to be textbook for the science written over the last decade on SSW. Exciting times... Where it lands trop wise... that is the absolute fun of it all ! Genuinely not sure but spillage of that level of cold,gotta love that !

 

Sorry, not had chance to reply. Not sure about the turnaround and "the validity of precursors vs the precision in analysis".

My specific analysis from 2nd Jan was for no SSW in January with the forecast data for 10th suggesting it was unlikely before 3rd Feb at earliest, which was correct. It was predicated on simple observation of the stratosphere climatology. Using the 80°N temperature at 30mb it can be seen that there tends to be a clear trend over time prior to an SSW. The graph below shows this with day 101 = date of reversal, and the green line the 2017/8 temperature up to 10/1/18 -

SSWtemp.thumb.gif.9daa43c7de3b1f1a3ad164adf269af44.gif

The trend can be seen in other temperature data too and at different levels, though 30mb values tend to correlate best of all with 10mb (better than at 10mb itself), and results from a global circulation model suggest that the most significant temperature indicator of SSW is at 36mb (Jucker et al http://onlinelibrary.wiley.com/doi/10.1002/2014JD022170/full)

This chart shows that it was at least 24 days before a similar temperature preceded a SSW. Temperatures have risen to values that have seen SSW in a shorter time, but without actually achieving one. If assuming the temperature trends to be roughly gaussian (normally distributed) it was 16 days outside of what would be 2 s.d event SSW -

3080t.thumb.gif.10fa192ba647691b093812b6fce4646f.gif

It might be that the temperature is a simplistic proxy for vortex strength which typically requires a certain time to overcome.

The 10/1/18 temperature was on the low side for SSW years so maybe a small sample of similar values wouldn't be representative. However, when including non-SSW years also it can be seen that no SSW has been achieved within 21 days of a 30mb 80°N temperature of 191K a couple of degrees above the value of the tenth, and that these low temperatures are not that unusual, having been reached in half of the winters since 1979, shown below -

tempwind.thumb.png.f80f012aa39587762b72aa27dd535cf2.png

Knowing that the Glo5eas ensembles use climatology combined with a raft of hindcasts means that it not predicting an SSW from early January while the GFS long range was 'going off on one' wasn't particularly surprising.

I have posted similar temperature data before, in early December 2015 ( https://www.netweather.tv/forum/topic/84231-stratosphere-temperature-watch-20152016/?do=findComment&comment=3300215 ) which suggested that an SSW might not be likely 'til February (no likes, lol) contrary to excitement and clamour over the forecasts (including from JC a couple of days later) and of course there wasn't an SSW until the very early final warming in March.

Now after considering the temperature tendencies as a viable probability density function, compare with the trends of MJO phase preceding SSW - only Jan and Feb included for clarity -

 

mjophase.thumb.gif.e88e9c58d9054cd0b619363a17b7ed75.gif

Pick a trend...any trend.

The use of phases is too granular, so here are the RMM1 + 2 combined as angles of the Wheeler-Hendon phase space -

mjoangle.thumb.gif.c6e4fe58499cceb6f2c1254b0f757774.gif

- bit better, perhaps some clustering but nothing clear.

The reference to Garfinkel et al with Indian ocean phase 2 (or 3) is interesting because as they note with regards to MJO effects - "The lag between MJO phases 3 and 7 is consistent with the 30-60 day periodicity of the MJO", and the emphasis is upon the later phases affecting the Pacific, despite finding that they tended not to lead to tropospheric NAM anomalies from the strat, unlike phase 3. In subsequent papers, he only considers phases 6/7 (http://onlinelibrary.wiley.com/doi/10.1002/2016JD025829/abstract and http://onlinelibrary.wiley.com/doi/10.1002/2017GL074470/full)

A better choice for referencing phase 2/3 might be Liu et al ( http://onlinelibrary.wiley.com/doi/10.1002/2014JD021876/full ) the results of which are largely similar to Garfinkel et al with SSW following shortly after late phases - but that the initiation likely occurs during phase 3. There is however one important difference - they set out to examine if there were any differences between displacements and splits with regards to the MJO - and that progressive and strong MJO lead to split SSW which explains the Garfinkel results. Schwartz and Garfinkel countered that the results following p6/7 were fairly even between splits/displacements so it is not significant.

Liu et al produced different composites for MJO responses prior to splits/displacement - one size does not fit all, composite users take note, but most interesting is that there is little MJO effect for displacements, which are most commonly preceded by phase 0 or "circle of death".

So where does that leave this event? It's a split, but it was preceded by a long period of displacement with wave 2 only peaking immediately before splitting. Throw in research from the likes of Albers and Birner ( https://journals.ametsoc.org/doi/abs/10.1175/JAS-D-14-0026.1 ) and the wave 2 may not even have propagated from the troposphere but be actually internal to the stratosphere, a symptom of the vortex splitting, not the cause. But also, it is gravity wave drag that may be the important factor for splits, once again displacements little influenced.

But it has been very hard to find good analogues for this year's MJO which show similar patterns of propagation through the varied indices to the stratosphere - no analogues also means the value of composites is questionable - so I would like to see more evidence before ascribing more than a tenuous link to the MJO, despite it's recent amplitude.

 

 

 

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Great update @Interitus thanks for coming back on this, appreciate the use of the word 'tenuous' for MJO - would challenge that in two regards a) Chaim Garfinkel seems to be a smart cookie and b) who is to say it is indeed tenuous, nevertheless sentiment understood.

Thanks for the reply - I have recently lost an entire laptop so do not have all my papers to hand the Albers one is not one I recall, although Liu from memory yes.

What I did see circal 20th Jan was a post from Jason Furtado around a new paper he is working on regarding shorter lead times and the u pulse episode ahead of a MMW or SSW and although what he shared was only a glance at the full paper this looks to have credence.

I think we can all agree that this event is invaluable for a couple of reasons

a) it allows the recent science displayed in these papers to be tested

b) Early consensus appears to be that whilst we understand 'some' of the drivers and precursors for SSW events, we do not have any science which can accurately capture the x = y of strat-trop coupling, nor as a second part to that what governs this.

Your point above around internal stratospheric vacillation am completely on board with, Tripath et al, as I feel there is solar influence that governs a mode where the vortex is more predicated to trop influence vs. where it 'runs on it's own steam'. Too tricky for me as not an expert - I suspect though this is a combination of EP forcing, the QBO and BDO - and, I think that this begins in the mesosphere as any meaningful climatic lead.

Great thoughts and good to have that analytical eye - am sure this season will be subject to many papers in the years ahead!

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3 hours ago, Interitus said:

But it has been very hard to find good analogues for this year's MJO which show similar patterns of propagation through the varied indices to the stratosphere - no analogues also means the value of composites is questionable - so I would like to see more evidence before ascribing more than a tenuous link to the MJO, despite it's recent amplitude.

 

This is very true. An MJO wave such as the one just starting to fade hitting high amplitude phase 7 is unusual. Interestingly the only examples I could find that come even slightly close are all from the modern record (06, 12 and 17) and none are an especially good match. A truly modern phenomenon - or just a climate record that is too short to give proper data? 

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Temps just starting to wane a little, cursory glance but they're back -'ve at about -4C. Still a long way to go before temps back to normal range though....https://earth.nullschool.net/#current/wind/isobaric/10hPa/overlay=temp/orthographic=-334.50,100.67,509/loc=-84.211,65.698

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So far, text book.

time_pres_HGT_ANOM_JFM_NH_2018.thumb.png.0e21c404c850136253ebb9ddd16eee03.pngbaldwin.thumb.jpg.07ac9b533e162bd52169db9dfc1402d6.jpg

First tropospheric response will not be the last. Second and third waves, the latter with the most pronounced impact in the AO still likely, these timed around mid to final third March into early April.

The MJO wave from January and February left a footprint in the Equatorial Pacific.

wkd20eq2_anm.thumb.gif.809fc05ff0e0f21c4efed5d568891ecf.gif

Don't think this was oceanic Kelvin wave given its timing and duration. 

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12 hours ago, Glacier Point said:

So far, text book.

time_pres_HGT_ANOM_JFM_NH_2018.thumb.png.0e21c404c850136253ebb9ddd16eee03.pngbaldwin.thumb.jpg.07ac9b533e162bd52169db9dfc1402d6.jpg

First tropospheric response will not be the last. Second and third waves, the latter with the most pronounced impact in the AO still likely, these timed around mid to final third March into early April.

The MJO wave from January and February left a footprint in the Equatorial Pacific.

wkd20eq2_anm.thumb.gif.809fc05ff0e0f21c4efed5d568891ecf.gif

Don't think this was oceanic Kelvin wave given its timing and duration. 

Yeah textbook. Currently the second wave is happening:

jikei_uep_nh.gif

but where will this lead us? It looks like this SSW is slowly moving into the final warming? I have never seen this before.

 

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23 hours ago, Glacier Point said:

So far, text book.

time_pres_HGT_ANOM_JFM_NH_2018.thumb.png.0e21c404c850136253ebb9ddd16eee03.pngbaldwin.thumb.jpg.07ac9b533e162bd52169db9dfc1402d6.jpg

First tropospheric response will not be the last. Second and third waves, the latter with the most pronounced impact in the AO still likely, these timed around mid to final third March into early April.

The MJO wave from January and February left a footprint in the Equatorial Pacific.

wkd20eq2_anm.thumb.gif.809fc05ff0e0f21c4efed5d568891ecf.gif

Don't think this was oceanic Kelvin wave given its timing and duration. 

Hi GP, quick Q - if the third wave was to have the greatest impact on AO late March, what would that actually likely to look like?  GFS for instance, this has been churning out some very neg AO charts for early March with NOAA ens indices falling into the range of -4 to -6 for this time period..  So short of an expansive 1050mb high sat over the pole, with LP's circling counter clockwise at <40deg N, i'm not sure how the AO will realistically go any lower than what the models are already predicting for early March? :)    

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ironically, the meandering vortex will begin to split the strat ridge around the pole in about ten days time in a reversal of the ridge splitting the vortex almost three weeks earlier !

assume this is not an unusual post ssw pattern ?? 

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@bluearmy @chionomaniac and others...

Going forward, given the nature of this SSW in terms of sheer strength and the time of year it occurred, do you guys think it will have any impact going forward through summer (I read that strat temperatures have actually peaked higher than the summer average during this event). Also, I remember someone theorising that the December 2010 cold spell could have been 'leftovers' from a SSW the previous season?

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@CreweCold looking at these plots from 2009 then 2010 you can see on the zonal mean temp time series average seasonal temps in 2010 don't really seem to be effected by the 2009 warming, similarly the 2011 chart looks the same you can check it here http://www.cpc.ncep.noaa.gov/products/stratosphere/strat-trop/ 

5a8c7be01a686_ScreenShot2018-02-20at19_47_24.thumb.png.a8e2c08b1cce43f835d97c23b8931912.png  5a8c7bee501f2_ScreenShot2018-02-20at19_47_38.thumb.png.b4a44241b9a4779a3c4d0cb6e4c83441.png  5a8c7bfa2c1c3_ScreenShot2018-02-20at19_47_52.thumb.png.281bfdc831b7c46796a458d88136229e.png  5a8c7c090707e_ScreenShot2018-02-20at19_48_05.thumb.png.f544836d01f7c5d953cd0283a01f5985.png

I've added the 2017 chart and the start of 2018 so far, for comparison. Of course these are mean charts and certain areas / places will experience colder / warmer months that others.

5a8c7c14bc698_ScreenShot2018-02-20at19_48_18.thumb.png.bbba4f1f9357fd1dcd3862f2f8532cfe.png  5a8c7c24c04f8_ScreenShot2018-02-20at19_48_27.thumb.png.2c2d1c1d26c473197d016d1e6602f7c8.png  

5a8c7c3447a3c_ScreenShot2018-02-20at19_48_41.thumb.png.85f8960752dc13899319be2515cd4003.png  5a8c7c3c9491c_ScreenShot2018-02-20at19_48_51.thumb.png.d2c926002fb71f6585ce799c439f620d.png 

 5a8c7c51a1cb8_ScreenShot2018-02-20at19_49_11.thumb.png.2217dfe938203e30e61297fb247abc7a.png  5a8c7c437829e_ScreenShot2018-02-20at19_49_02.thumb.png.cdc26777f40bc67ed79600573fd11a91.png

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Adding on I don't think so. I asked Amy Butler recently about final warmings and does the timing of them affect the trop response and this is probably more relevant than the SSW. Interestingly she was rather coy and said that this was an ongoing area of her research with Mr Jeremiah and that they hope to publish their results soon. 

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36 minutes ago, supernova said:

Fellas, is this double dip reversal typical of a major SSW? Couldn't find any relevant commentary and was surprised at the intensity of second pulse? Apologies if this is a stupid question.

u_65N_10hpa.thumb.png.34fee402af31976dfabc81de047bbce8.png

5a8c926dba8ba_ScreenShot2018-02-20at21_25_41.thumb.png.e768c5059a736f6169633b578882ca39.png

 at 60 N it looks like 3 changes, all part of the same overall reversal however, that 0 line is the reversal point. Some chaos going on up there right now thats for sure. 

Interestingly 83/84 had a similar pattern. However not as strong a reversal or as prolonged. But for the month of the SSW and pattern similarity thats the closest match I can find. I think it is a matter of heat flux waves and intensity causing the quick changes in wind speed / direction.

5a8c933e521d0_ScreenShot2018-02-20at21_29_15.thumb.png.ed7db109bc400df2c1b600baa86ea51f.png

Winter 83/84 was equally topsy turvy, a very mild Dec, followed by a cold and in the north exceptionally snowy Jan under a polar maritime airmass, followed by an average Feb with some snow.

Snapped from the "forgotten winters of the 1980's" in this forum

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Yes and no. 

This is because of the second warming hitting the Hudson Bay daughter Vortex. If conditions are right then this can occur. This has been vital imo changing the synoptics from a transient (but still good) easterly to a block that traverses west to also give a -ve NAO.

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