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Stratosphere and Polar Vortex Watch

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1 hour ago, Glacier Point said:

GFS still very keen on developing a strong suppression signal for the tropics weeks 1 -2, and a very strong MJO / GWO phase 8 signal attached.

twc_globe_mjo_vp200.thumb.png.ace3d591a7cb1a4c65f8a0aef0112983.png

Twin anticyclones developing in the east Indo / Asian region, drifting slowly east and an associated downstream anticyclone impact on mountain torque and upper level flows across the eastern half of Asia. Essentially an ingredient for suppressed levels of wave activity flux, and colder air now being forecast to develop across Asia at 10 hPa.

gfs-ens_z500aMean_asia_6.thumb.png.458e0ce6646120dc1b3076ecf54839c1.pnggfs-ens_mslpaNorm_io_29.thumb.png.936c29e6d289ed1f678b44adf14e86af.png

Both GEFS and EPS in agreement on a stronger than normal North Pacific ridge in the Stratosphere to be in place in the meantime, and displacement continuing into middle part of December. This looks plausible..

NH_HGT_10mb_348.thumb.gif.98e5633b50d1cc068c4ffd11b274586f.gif

With the transition of the next MJO forecast for middle of December (passage through east India Ocean key), latter part of December would place us on full alert for stratospheric warming potential. Split vortex type.

@Glacier Point Similar passage of MJO through Indian ocean happened last year that triggered SSW,but we only felt the benefits of blocking at the end of February,woudnt we be hoping again for late winter cold,but perhaps a week or two earlier than this year? Can we rescue January re. Blocking after SSW?

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Here's the importance of the wave 2 attack that is happening right now. That is opening the channel and the low frequency forcing that will manifest itself during the early and middle part of December will keep that (Scandinavian) channel open. 

So when the next phase of vortex disruption takes place, the response time will be a whole lot faster than the strat warming which was associated with the strong MJO last middle February.

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5 minutes ago, Glacier Point said:

Here's the importance of the wave 2 attack that is happening right now. That is opening the channel and the low frequency forcing that will manifest itself during the early and middle part of December will keep that (Scandinavian) channel open. 

So when the next phase of vortex disruption takes place, the response time will be a whole lot faster than the strat warming which was associated with the strong MJO last middle February.

What impacts do you reckon this is likely to be for the UK gp?? What your thoughts on next month

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I think this new report of KNMI might be useful for get an insight of the impact in the tropshere. 

http://bibliotheek.knmi.nl/knmipubIR/IR2018-05.pdf 

Summary
In this study a new classification has been developed to classify Sudden Stratospheric Warmings
(SSWs) based on their vertical depth. This new classification was developed because the depth of a
SSW has been found to be important for the magnitude of tropospheric impact (Gerber et al., 2009;
Palmeiro et al., 2015), and the official SSW classification does not tell anything about the vertical
extent of a SSW.
The new classification adapted from a previously developed classification of Kramer (2016; hereafter
referred to as K16)). It prescribes that the zonal mean zonal wind between 60N and 70N should
reverse over a depth of at least 80 hPa between 10 and 100 hPa for at least two days in a 5-day
period. This classification was termed a ‘Deep Stratospheric Warming’ (DSW).
In the stratosphere, the new DSW classification was compared to both the SSW-classification and the
K16-classification. However, the K16-classification included events that were too weak to be
considered important for tropospheric impact. Coupled to the fact that K-16-events did not contain
any information about the vertical depth of SSWs, this classification was not taken into account in
subsequent analyses.
Compared to the official SSW classification, it appeared that DSWs were less frequent; whereas SSWs
occurred about 6 times per decade, DSWs were found to occur only 4 times per decade.
Furthermore, the SSW and DSW classifications were connected: most DSWs occurred a few days to
weeks after the SSW date. This was explained by the behavior of SSWs and DSWs: first a warming at
10 hPa took place (the SSW date). After that, the wind reversal extended downward in an irregular
fashion, during which after some SSWs at some point the wind reversal extended sufficiently far to
the lower stratosphere to cause a DSW to be classified.
Connected to the differences in classification date, the DSWs were rarely located close to the
moment of rapid warming in the stratosphere. Thus, unlike SSWs, the DSWs did not show the
‘sudden warming’ behavior. Rather, (most of) the DSWs seemed to be a result warm anomalies in the
mid-stratosphere that developed sometime during or after the SSW and subsequently downwelled
on a timescale of about a week.
In terms of upper tropospheric impact, the DSW classification resulted in a similar response
compared to the SSW classification: anomalously high temperatures near the pole and a southward
displaced jet stream. Furthermore, the jet stream was found to become slightly more meridionally
oriented in the midlatitudes and slightly more zonally oriented in the subtropics, but this signal was
fairly weak. The main difference between the DSW and SSW was that the DSW effects were mostly
stronger in magnitude than the SSW effects. Thus, a DSW results in stronger upper tropospheric
impacts compared to a SSW.
A similar story was found in terms of surface impacts. Both the SSW and DSW classifications resulted
in positive pressure anomalies over the pole and generally negative pressure anomalies in the
midlatitudes (indicative of a negative Arctic Oscillation); but the anomalies were more pronounced
after a DSW. The surface temperature response after both a SSW and DSW was chaotic, though,
showing that the DSW classification did not result in a stronger or more structured surface
temperature response.
Finally, a thermodynamic perspective was presented to explain why the DSW classification resulted
in a stronger tropospheric response compared to the SSW classification method (only in terms of a -
AO and a weaker jet stream in the midlatitudes). The cause was speculated to be that the warming

accompanied by a DSW extended further to the upper troposphere. This is important for two
reasons, being:
1) A deeper warming causes the pressure surfaces to be less tilted from the midlatitudes to the
pole, resulting in a more pronounced weakening of midlatitude westerlies, including the
polar jet stream.
2) A warming that extends more towards the troposphere exerts more pressure on the
underlying air, because the density of air closer to the troposphere is higher. This results in a
higher surface pressure. `
In short, the new DSW classification enables to better assess the zonal mean timing and intensity of
tropospheric impact compared to the SSW classification. However, no specific conclusions could be
drawn about the zonally asymmetric effects of DSWs.

Edited by sebastiaan1973

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@Glacier Point I think this tropospheric pattern would be promising for further attacks on SPV from both Pacific and Atlantic sectors

FB_IMG_1542893084477.jpg

Edited by jules216

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Sliders tend to create excitement on the NWP - never really considered following the wave breaks through on the NASA plots to see how they map over to NWP- a) if at all, b) if there is a lag c) do they lead the NWP and at what stage.

This to me looks like it has the shape and track to be classed as a Strat-slider..https://acd-ext.gsfc.nasa.gov/Data_services/Current/arctic/anim_EPV_0320.html So will try and keep an eye on when it gets nearer verification date on how it looks at this level of the atmosphere and at what time we can gauge this playing into modelling...

EPV_2018113000_F216_320.thumb.png.126bb09a4711b191100713b34ecaff0d.png

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10 hours ago, lorenzo said:

Sliders tend to create excitement on the NWP - never really considered following the wave breaks through on the NASA plots to see how they map over to NWP- a) if at all, b) if there is a lag c) do they lead the NWP and at what stage.

This to me looks like it has the shape and track to be classed as a Strat-slider..https://acd-ext.gsfc.nasa.gov/Data_services/Current/arctic/anim_EPV_0320.html So will try and keep an eye on when it gets nearer verification date on how it looks at this level of the atmosphere and at what time we can gauge this playing into modelling...

EPV_2018113000_F216_320.thumb.png.126bb09a4711b191100713b34ecaff0d.png

It will be basically the same as the NWP - the 320K potential temperature is used as an indicator of the dynamic tropopause. For the polar region it tends to be just above the tropopause in the winter half of the year and just below in the summer - the UTLS region in general. In the chart above and animation, the shading shows the potential vorticity which is much higher in the stratosphere than the troposphere because of the increase in static stability. So in this particular chart the green and blue colours show where the air with 320K theta is in the troposphere (< 2 potential vorticity units) and the oranges and reds where it is in the strat (>2 PVU).

 

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More strat. warming advocated by GFS in FI, also we have reasonable wave 1 amplitude higher up.

 

ECMWF looks like it may produce +EAMT event day 11-14?

In the same time MJO could be passing Indian ocean with strong amplitude come mid month

I would say this is a very good position coming in to best part of winter, also we seem to be keeping the Scandi-Euro high anomaly.

 

gfsnh-10-384.png

00.png

image.png

image.png

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1 hour ago, Allseasons-si said:

Jma.

JN264-5.thumb.GIF.2bc1999006dddafdf45798090c11d901.GIF

10hpa,are we going to see this rise further tomorrow?

pole10_nh.thumb.gif.cb19a158999721e2448fd5550cb284ec.gif

Indeed,  but a lower than usual starting point? 

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Wave amplitudes this cold season are very high.

Wave 2 first ...

416971583_wave2current.thumb.png.5326b5e235a2b2d2cb84995036856b3c.png

Wave 1 now ...

1156413218_wave1current.thumb.png.90ff4900567f5767b48220956ad6f9bc.png

Very similar in evolution to 1986, wave 1 likely to be shorter duration this time round though as the Pacifc ridge becomes more of a trop feature in the coming 2 weeks.

1986wave2.thumb.png.647e58601d6c4f83cf05cac343bac9fb.png1986wave1.thumb.png.810cc0d4fddce69870583fe625647750.png

GEFS and EPS modelling continues to advertise a steadily weakening stratospheric vortex as we enter the core climatological vortex intensification period. 

Edited by Glacier Point

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Wintertime high-latitude blocking is associated with persistent changes in temperature and precipitation over much of the Northern Hemisphere. Studies have shown that the Madden–Julian oscillation (MJO), the primary form of intraseasonal tropical variability, significantly modulates the frequency of high-latitude blocking through large-scale Rossby waves that alter the global circulation. However, the characteristics of MJO teleconnections are altered by El Niño–Southern Oscillation (ENSO), which modifies the global flow on interannual time scales, suggesting that the MJO influence on blocking may depend on the ENSO phase. The characteristics of MJO Rossby waves and blocking during ENSO events are examined using composite analysis and a nonlinear baroclinic model. The ENSO phase-dependent teleconnection patterns are found to significantly impact Pacific and Atlantic high-latitude blocking. During El Niño, a significant persistent increase in Pacific and Atlantic blocking follows the real-time multivariate MJO (RMM) phase 7, characterized by anomalous enhanced tropical convection over the East Indian Ocean and suppressed west Pacific convection. The maximum Atlantic blocking increase is triple the climatological winter mean. Results suggest that the MJO provides the initial dipole anomaly associated with the Atlantic blocking increase, and transient eddy activity aids in its persistence. However, during La Niña significant blocking anomalies are primarily observed during the first half of an MJO event. Significant suppression of Pacific and Atlantic blocking follows RMM phase 3, when east Indian Ocean MJO convection is suppressed and west Pacific convection is enhanced. The physical basis for these results is explained. https://journals.ametsoc.org/doi/10.1175/JCLI-D-17-0721.1

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7 minutes ago, Glacier Point said:

Wave amplitudes this cold season are very high.

Wave 2 first ...

416971583_wave2current.thumb.png.5326b5e235a2b2d2cb84995036856b3c.png

Wave 1 now ...

1156413218_wave1current.thumb.png.90ff4900567f5767b48220956ad6f9bc.png

Very similar in evolution to 1986, wave 1 likely to be shorter duration this time round though as the Pacifc ridge becomes more of a trop feature in the coming 2 weeks.

1986wave2.thumb.png.647e58601d6c4f83cf05cac343bac9fb.png1986wave1.thumb.png.810cc0d4fddce69870583fe625647750.png

GEFS and EPS modelling continues to advertise a steadily weakening stratospheric vortex as we enter the core climatological vortex intensification period. 

Wave 1 is also very similar to last year unfortunately, it showed a lot of promise until it died off mid December 

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5 hours ago, ArHu3 said:

And only yesterday Judah Cohen tweeted the exact opposite happening 

https://twitter.com/judah47/status/1066685721933750273?s=09

 

5 hours ago, Weather-history said:

Yes I noticed that but he himself says at the moment its a low probability

Cohen was talking about a gfs op forecast for 9th dec

ventrice is talking about an event predicted end this week

of course we could assume that the latter may not happen if the former occurs but the question needs to be asked if the upper strat will become coupled with the lower as we head through December …...

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13 minutes ago, bluearmy said:

 

Cohen was talking about a gfs op forecast for 9th dec

ventrice is talking about an event predicted end this week

of course we could assume that the latter may not happen if the former occurs but the question needs to be asked if the upper strat will become coupled with the lower as we head through December …...

Sounds like Exeter are expecting worse case scenario for coldies .. their outlook is rapidly deteriating ..now any high is expected to sink by Mid Dec!!

Sounds like coupling to me..

Edited by northwestsnow

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The vortex is under attack, indeed. A next heat flux (not visible on the Eddy heat flux plot so far) starting December 12th will likely cause a further displacement towards Siberia and the zonal winds may drop a lot more. It looks like we are heading towards a Canadian Warming, in the second half of December.

 

Knipsel2.PNG

Knipsel3.PNG

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On 26/11/2018 at 11:40, Glacier Point said:

Wave amplitudes this cold season are very high.

Wave 2 first ...

416971583_wave2current.thumb.png.5326b5e235a2b2d2cb84995036856b3c.png

Wave 1 now ...

1156413218_wave1current.thumb.png.90ff4900567f5767b48220956ad6f9bc.png

Very similar in evolution to 1986, wave 1 likely to be shorter duration this time round though as the Pacifc ridge becomes more of a trop feature in the coming 2 weeks.

1986wave2.thumb.png.647e58601d6c4f83cf05cac343bac9fb.png1986wave1.thumb.png.810cc0d4fddce69870583fe625647750.png

GEFS and EPS modelling continues to advertise a steadily weakening stratospheric vortex as we enter the core climatological vortex intensification period. 

There are some similarities with 1986 however there are closer similarities with other years. Some of the analogues are much more interesting than 1986, for example the closest 15-day 10mb wave 1 height to the GEOS forecast for December 6th is 6/12/98 -

w1.thumb.png.18b7b9ba222836c90cbf29ce7413e074.png

While the closest combined wave 1+2 is 25/11/81 -

779437890_w12.thumb.png.1a70e8cbe448716ba3a99924c8f1099d.png

What happens to the zonal winds from these dates is quite remarkable -

u1060.thumb.png.579f0ceab8efab0f0af480f5029420cc.png

In both cases there is a SSW 9 days later - two of the rare December events.

The dates chosen are for the same time of year to ensure a fairly close time for seasonal vortex evolution, but returning to the wave 1 there is a closer match than 1998 with 17/2/99, which is not just similar to December 6th this year for 15 days but for a full 30 days -

467758039_w130day.thumb.png.abddf1b5c27ed1bbdeadaac6bb883718.png

Adding 17/2/99 to the zonal wind chart from above -

1080980410_u10602.thumb.png.517345f516230939ff9fd15ee12b2152.png

Incredibly, SSW 9 days later once again.

There would appear to be something in this, but it isn't clear cut - the SSW of Dec 98 and Feb 99 were very similar while Dec 81 was quite different, little warming and wind reversal (and yet linked to some dramatic weather for the UK). Also many other close analogues don't feature SSW of course.

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