Stratosphere and Polar Vortex Watch

[bluearmy]

1 minute ago, chionomaniac said:

I found that a bit odd. Anyway, it will be interesting to see how the strat behaves if these trop HL blocks do develop. I know what I expect to see but predicting a possible SSW 4 weeks in advance is a risky business, lol.

Given the way things have planned out thus far this winter I wouldn’t be predicting anything !!

[Chesil View]

31 minutes ago, bluearmy said:

Don’t upset Judah again ed ...........

he seems a bit precious sometimes ! 

and wrong as well.

[frederiksen90]

1 hour ago, bluearmy said:

Given the way things have planned out thus far this winter I wouldn’t be predicting anything !!

Further displacement and weakening of Polar Vortex in both GFS-ENS and EC-ENS. Recent forecasts dislocate PV completely across Baffin and America in mid January. In addition, there are significant dives in AO 10-15. January. Hope for the winter lives to that extent.

Trends also look extremely promising in 500 hPa geopotential height anomalies from both EC-ENS and GFS-ENS. Rising pressure anomaly over Scandi and later Arctic and Greenland from January 10th and onwards:

http://www.meteociel.fr/.../2018010100/EDH101-240.GIF...

http://modeles7.meteociel.fr/.../2018.../gensnh-21-5-240.png http://modeles7.meteociel.fr/.../2018.../gensnh-21-7-300.png

Edited January 1, 2018 by frederiksen90

[Catacol]

2 hours ago, chionomaniac said:

I found that a bit odd. Anyway, it will be interesting to see how the strat behaves if these trop HL blocks do develop. I know what I expect to see but predicting a possible SSW 4 weeks in advance is a risky business, lol.

GWO seems intent on maintaining a decent orbit despite the gloom that surrounded the collapse of the last mjo progression. I await the latest cpc report on the mjo later today before posting anything on the mod thread in detail, but the suspicion is growing that sustained mjo progress through the IO plus some favourable mt activity (we have a tropical mt in progress now) could see mjo hit phase 3 at decent amplitude alongside GLAAM numbers that haven’t sunk into the low orbit phase 2 that GP posted about before Xmas...and lo and behold our signal for reemergence of a solid scandy high is back in place. 

Later than hoped for, but early enough to allow a disturbed vortex to add a surge of Siberian cold to the blocking pattern. At least that is the tentative hope. ?

Our comrades over in the US seem pretty sold on the Alaskan ridge rising once again to prominence mid Jan. 

An exciting season just keeps on delivering interest.

Edited January 1, 2018 by Catacol

[pyrotech]

The MJO has traversed the all important phase 6 and is now in a moderate phase 2, However on getting to this we had a period in COD

This should equate to Scandi high staying in place for a little longer and maybe strengthen a little. The issue is we are quickly heading into a fairly strong phase 3. The NAO should there fore fire up and by 17th of January the Scandi high pushed further North and East

At that point we will see a more Atlantic driven scenario and less cold. To get there we see a transient period with us often on the north side of the Jet, This effected by the High.

Around 14th january the effects of MJO phase 1 and 2 start to allow the Azores high to nudge Northwards with the jet running along the top. This also coincides with Siberian High moving North and East

Those looking for something wintry will see opportunities between now and 13th and then start  to see the Less Cold Atlantic Attack.

We are also then heading rather quickly towards Phase 6 again and i suspect around 20th we will be back in that region (Western pacific)

This leads nicely in to February around the 4th for another opportunity for wintriness 

The biggest challenge is do we have a moderate phase 4 and 5 to get there or will it be via the COD and will the phase 6/7 be strong enough.

The MJO was in phase 5, 10 days before the snow that many had around 10th December so the less cold period may be rather short lived.

The NAO appears to agree with that analysis too but as always time will tell

[lorenzo]

Plenty of good material out there around MJO and SSW links. P2/3 associated with Vortex Split events later down the line...

[pyrotech]

This is rather interesting thou with 10hpa temperature rising quickly over the last few days

We were in COD 12 days before this really started 

Edited January 1, 2018 by pyrotech
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[Singularity]

17 hours ago, pyrotech said:

The issue is we are quickly heading into a fairly strong phase 3. The NAO should there fore fire up and by 17th of January the Scandi high pushed further North and East

 

Just this one point I wonder about; I have read that phase 3 has some association with a negative NAO, albeit fairly weak in January. At the least this runs counter to the NAO turning more positive as you imply...?

If you can clarify that would be great, thanks .

[Blessed Weather]

Some positives from Dr. Cohen's latest weekly blog (1st Jan). He has previously expressed his view that this winter will "reach a fork where the outcome hangs in the balance". The positive news for cold prospects is that he now believes....

"As far as this winter it does seem increasingly likely that a cold winter will be realized across the Eastern US, Southeastern Canada, Western Europe including the United Kingdom (UK) and East Asia including large parts of Siberia."

This conclusion, he believes, is down to the continuing repetitive minor disruptions to the PV.....

".....as we get later into winter I do believe that persistence grows in importance and even just one more stratospheric PV disruption may be sufficient to carry cold temperatures into the month of February regardless of the behavior or strength of the stratospheric PV. And there are already signs of yet another energy pulse mid-month that often disrupts the stratospheric PV."

Full blog: http://www.aer.com/science-research/climate-weather/arctic-oscillation

[Interitus]

Just to counter some of the positivity here, for the GEOS forecast 30mb 80°N temperature of 189.94K for 10/1/18, the earliest that an SSW has been achieved is 24 days (which would be Feb 3rd). Although Jan 2009 does feature as an analogue at the moment - principally because of the period of VI - the wave 2 heights that led to that split was a spell above 2000m at 10mb - nothing like that has been forecast at the moment, with the middle vortex looking cold and largely barotropic

[pyrotech]

7 hours ago, Singularity said:

Just this one point I wonder about; I have read that phase 3 has some association with a negative NAO, albeit fairly weak in January. At the least this runs counter to the NAO turning more positive as you imply...?

If you can clarify that would be great, thanks .

No positive NAO, with Phase 3

Time lag (days)

• The probability of a positive phase of the NAO is significantly increased about ten days after the MJO is in phase 3 (phase 3+10 days), and significantly reduced about ten days after the MJO is in phase
6 (phase 6+10 days).

We do of course have other drivers which can enhance or mitigate the MJO effect

[chionomaniac]

3 hours ago, Interitus said:

Just to counter some of the positivity here, for the GEOS forecast 30mb 80°N temperature of 189.94K for 10/1/18, the earliest that an SSW has been achieved is 24 days (which would be Feb 3rd). Although Jan 2009 does feature as an analogue at the moment - principally because of the period of VI - the wave 2 heights that led to that split was a spell above 2000m at 10mb - nothing like that has been forecast at the moment, with the middle vortex looking cold and largely barotropic

It's not surprising that anything like that is being forecast at the moment because any strat disturbances will rely on the trop blocking forecast being correct. If (and a big if) it is, then one would not expect to see the first strat knock on ( at the upper levels) until post 20th Jan anyway and these would take time (approx 10 days) before at 10hPa any SSW could potentially occur. So I will stick with my forecast for a possible SSW at the end of Jan ( depending on the trop precursors verifying) but would take any reversal within 10 days of this as a good forecast either way! Always happy to put my neck on the line but if the trop blocking doesn't occur then this will have to be revisited.

What do you think is likely in the next month?

On another note the best chance of blocking in a Strat VI period is through the Scandi route as this is more likely when the trop/strat vortex is strong. This then can feed back to the strat and weaken the barotropic vortex.

[bluearmy]

Note that 30hpa splits 6 hours before 50hpa ......... (some will say this isn't a true split yet) 

10hpa looks stretched by day 10

 

Edited January 2, 2018 by bluearmy

[Dennis]

we do see some good action in the strato for west euro

[bluearmy]

20 minutes ago, Dennis said:

we do see some good action in the strato for west euro

Whilst that heights chart is quite low at 150hpa, the morning run again shows a ridge right up to 30hpa. Bit more marked than the Berlin run from yesterday's 12z

 

[Dennis]

3 minutes ago, bluearmy said:

Whilst that heights chart is quite low at 150hpa, the morning run again shows a ridge right up to 30hpa. Bit more marked than the Berlin run from yesterday's 12z

 

nice 

[bluearmy]

1 minute ago, Dennis said:

nice 

Yes Dennis - I posted it above 11 hours ago ?

[Interitus]

43 minutes ago, Dennis said:

nice 

GFS 180103 00z had a brief 30mb minimum below -90°C/183K on 14/01 which would place it in the top 30 coldest daily temperatures since 01/01/79 (MERRA data).

Edited January 3, 2018 by Interitus

[bluearmy]

1 hour ago, Interitus said:

GFS 180103 00z had a brief 30mb minimum below -90°C/183K on 14/01 which would place it in the top 30 coldest daily temperatures since 01/01/79 (MERRA data).

Did you ever see/read jack and the beanstalk ineritus ?

Edited January 3, 2018 by bluearmy

[Interitus]

14 hours ago, chionomaniac said:

It's not surprising that anything like that is being forecast at the moment because any strat disturbances will rely on the trop blocking forecast being correct. If (and a big if) it is, then one would not expect to see the first strat knock on ( at the upper levels) until post 20th Jan anyway and these would take time (approx 10 days) before at 10hPa any SSW could potentially occur. So I will stick with my forecast for a possible SSW at the end of Jan ( depending on the trop precursors verifying) but would take any reversal within 10 days of this as a good forecast either way! Always happy to put my neck on the line but if the trop blocking doesn't occur then this will have to be revisited.

What do you think is likely in the next month?

On another note the best chance of blocking in a Strat VI period is through the Scandi route as this is more likely when the trop/strat vortex is strong. This then can feed back to the strat and weaken the barotropic vortex.

There are 5 SSW (first of winter, since 1979) where wave 2 is dominant over wave 1 at 60°N 10mb on average for a full fortnight beforehand - 22/2/79 (preceding 11 days w2 dominant), 1/1/85 (12 days), 21/2/89 (17 days), 24/2/7 (11 days but 3 days of w1 >1000 just before SSW) and 24/1/9 (15 days and 23 out of 24). The first four all had some wave 1 height contribution >1000m in the fortnight. But 2009 is unique in having no wave 1 >450 metres in the three weeks before, and four weeks after last w1 >1000m.

To get an idea of of duration of wave 2 (arbitrary height >1000m) and when it might need to appear in forecast charts - 22/2/79 10 days before SSW, 1/1/85 11 days, 21/2/89 17 days, 24/2/7 14 days, 24/1/9 13 days (the last 7 >2000m) - the average is 14 days, conveniently close to long range forecast length.

But then large wave 2 values is no guarantee - for one day heights >2000m SSW in 1979, 1985, 1989, 2009; no SSW following the Januaries 1982, 1986, 2014.

For longer periods - at least 1 week >1500m - SSW as above 79, 85, 89, 09 plus 07; no SSW - Jan 80, Jan 82, Jan 86, Jan 91, Feb 94, Feb 96, Feb 97, Jan 03, Jan 08, Dec 09, Jan 14.

Although some things may enhance the chance of a split a little, eg. a Nina'ish background, it is unlikely there will be an SSW this month and though wave 2 may feature at some point, indeed maybe at the death, a period of wave 1 is most likely to do the damage to begin with.

Edited January 3, 2018 by Interitus

[Catacol]

17 hours ago, pyrotech said:

No positive NAO, with Phase 3

Time lag (days)

• The probability of a positive phase of the NAO is significantly increased about ten days after the MJO is in phase 3 (phase 3+10 days), and significantly reduced about ten days after the MJO is in phase
6 (phase 6+10 days).

We do of course have other drivers which can enhance or mitigate the MJO effect

Except not all data seems to be the same. What is your source? I do wonder about composites sometimes - what are these filters applied and how are they created?

JMA sees MJO phase 3 as most definitely -NAO in January as @Singularity mentioned above.

Edited January 3, 2018 by Catacol

[pyrotech]

I use research documents from ECM

 

I also keep records of MJO and effects over Europe

Its good, but occasionally things do the opposite to expected, i believe other factors like SSW and PV sometimes makes it go opposite to as expected, Even when we expect a high pressure to sit at X for example its strength, orientation and exact location can make the NAO less blocked or more so. 6 days ago we were in phase 8 and so blocking likely by 7th Jan or thereabouts but with the MJO moving thru phase 1 and 2 expect it to last around 5 to 7 days where NAO fires up. Research says 10 days for effects over Europe, but my data suggests that must be for first sign of effects as it seems to be more like 12 - 14 days when actual effect takes place.

 

So Nao may start to change day 10 but change more full or complete by day 12/14

But just my take on it and goes somewhat against research from ECM

[lorenzo]

One from the twitter sphere and some amazing analysis of the vortex thus far this winter, new mechanics and approaches here from Zac Lawrence, this tweet leads a chain of thoughts. I recently replied asking around these mechanics used in particular the vortex pre conditioning and any other precursors a la blocking or other regimes - given the focus on vortex area, surf zone mixing etc. Looks like these will come into fruition as science progresses, hopefully of interest and relevant to the perturbations ahead and potentiality of W2.

Not read this paper I just found http://onlinelibrary.wiley.com/doi/10.1002/2017JD027556/abstract 

looks like something of a new era in terms of looking at split vortexes, which, is exactly something we are musing over...

[chionomaniac]

On 1/1/2018 at 13:25, chionomaniac said:

HNY to all.

I may just throw it out there, but the day 10 pattern (mean EPS) is a classic precursor - Alaskan and Scandi high - for a wave 2 type SSW. It seems that the GEFS are starting to show similar H500 anomalies.

If so, then I suspect the chances for a strat warming and vortex split will increase.

Timing wise that would probably lead to significant strat PV disruption by the end of the month and a possible SSW too.

If it is going to happen then we should keep a check on the temps at 1hPA from around the 20th Jan onwards as the first signs of the vortex disruption will occur from then onwards and in this case start at the top of the strat and downwell.

Keep an eye on the EAMT graphs as well.......

Hmmm, just got around to checking this....

 

This is from the 12Z GFS. Worth checking the 18Z

[chionomaniac]

GFS 18Z