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White Christmas?

Tracking latest odds and possible events for the holidays

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so_whats_happening

Stratospheric Discussion 2018/19

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Well it is that time of year again. I will see if I can bring over the other threads from the Accuweather side but if not looks like we will be starting a new which is fine by me. Many remember the format of the first page so I will just copy and paste as such over here. Remember the same rules apply here as they did over at Accuweather this will only be for discussion and forecasting of the Stratosphere PV. You may also post the linkage ideas between strat and tropo PV but that will be it for talking about sensible weather impacts; create threads in the appropriate places for that otherwise enjoy.

I have seen from other forums about opening up a Stratospheric discussion thread where anybody can post questions, have daily discussions on the development of the Polar Vortex (PV), and have an area that people can find decent information on where to find PV data and the basics.

So lets begin what exactly is described as the Stratosphere. The Stratosphere is a portion of the atmosphere directly beyond the Troposhperic, where we live, layer.

post-14460-1506341540.jpg.1d2676c34198ea47c6b9196c950d450e.jpg

The Stratosphere ranges from about 10 to 50km above the surface with pressure values in the range from 100 hPa at the lower levels to just under 1 hPa at the upper levels. They consider the middle portion of the stratosphere to be from ~10-30 hPa.

As we approach the Autumnal Equinox (September 20-22nd) each year in the northern hemisphere the PV begins its strengthening, as this region experiences less solar radiation that hits the ozone located in the Stratosphere allowing the PV to cool and strengthen. The PV will continue to strengthen as we head deeper into the season because of temperature differences between polar and mid latitude regions. The Stratospheric PV has a strong interdependence with the Tropospheric PV as one can effect the other. Strengthening of the Stratospheric PV will usually allow for a connection to allow the Tropospheric vortex to strengthen while the Tropospheric vortex can also influence the Stratospheric vortex strength, but this is not always true.

As we head down toward the surface the strength of the PV dictates what values we look at for the Arctic Oscillation (AO). A strong PV during the winter will set up a positive AO which will tend to retreat the polar jet stream and bottling up the cold in the Arctic regions. While a negative AO translates into a weaker Stratospheric PV and will tend to allow the cold air bottled up in the Arctic to be released into the mid latitude regions around the Northern Hemisphere (NH), now just because we have a negative AO does not necessarily mean every region will experience the same result this also applies to a positive AO.

post-14460-1506341556.jpg.4499d44748f919d0d16a21cc363dca19.jpg

The stratospheric PV can be influenced by different factors such as QBO, state of ENSO, solar influence, ozone distribution and levels, and snow cover and extent. 

OZONE:

The ozone layer is collocated in the middle portion of the Stratosphere and is warmed by the incoming UV radiation. The main circulation is the Brewer-Dobson Circulation (BDC) ozone is formed in the tropical stratosphere and transported to the polar stratosphere. This circulation changes from year to year and can be influenced from time to time by many different factors. The ozone content can dictate stratosphere polar temperatures with collecting of ozone allowing for warming to occur in the polar stratosphere.

Ozone Basics: https://en.wikipedia.org/wiki/Ozone_layer
Ozone Tracking: http://www.cpc.ncep.noaa.gov/products/stra...2to/index.shtml

ENSO state:

The ENSO and the state that we see in the tropical Pacific region play a huge role in tropical regions but also the mid latitudes. During these events the effects on the Stratosphere change, when we experience El Nino (warming of Eastern Portion of the Pacific) the atmospheric upward propagating waves become more centered over the Pacific then the Indian Ocean and vice versa occurs.

http://link.springer.com/article/10.1007%2Fs00382-015-2797-5

http://www.columbia.edu/~lmp/paps/butler+p...er-ERL-2014.pdf

Where these waves occur dictate the "attacks" on the PV as well as the weather that we experience from these changes.

Quasi-Biennial Oscillation (QBO):

The QBO is a wind pattern of alternating (easterly and westerly), descending winds that occur in the Tropical Stratosphere over a period of 26-32 months, with an average of around 28 months at about 30hPa is the main region to measure QBO but stretches over an area from 10-50hPa. The easterly (negative) phase is thought to contribute to a weakening of the stratospheric polar vortex, whilst a westerly (positive) phase is thought to increase the strength of the stratospheric vortex. These changes and how quickly or not these winds descend can have substantial implications in the NH winter PV

.qbo_wind.thumb.jpg.0028e7badb6d3efd7b9e94e15606e921.jpg

Forgive me Ill see if I can find another the site has not updated in awhile.

http://www.geo.fu-berlin.de/en/met/ag/stra.../qbo/index.html

As mentioned before about the Ozone and the BDC, the QBO seems to play a role in distribution from the Tropical Stratosphere. The tropical upward momentum of ozone is stronger in the eQBO , whereas in the wQBO ozone transport is stronger into the lower mid latitudes, so less ozone will enter the upper tropical stratosphere to be transported to the polar stratosphere.

post-14460-1506341692.png.a941bfaf2d2b1be7d84aeca77e003160.png

When the QBO is in a west phase during solar maximum there are more warming events in the stratosphere, as there is also during an easterly phase QBO during solar minimum, so the strength of the BDC is also affected by this also known as the Holton Tan effect .

Sunspots and QBO
http://strat-www.met.fu-berlin.de/labitzke...-et-al-2006.pdf

Holtan-Tan:
http://onlinelibrary.wiley.com/doi/10.1002...021352/abstract

Solar Cycle also plays a role in conjunction with other factors as stated above here is the solar indices as we head into what looks to be a solar minimum.
http://www.swpc.noaa.gov/products/solar-cycle-progression
So far we have gone over the ideas of QBO, ENSO, sunspots and Ozone on the startosphere and how they can influence the progression of the Stratosphere. We now turn to Sudden Stratospheric Warmings (SSW).

SSW:

There is another name for these types of warmings called Major Midwinter Warming (MMW), does not necessarily mean this takes place in the middle of winter. SSWs can be caused by large-scale planetary tropospheric (Rossby) waves being deflected up into the stratosphere and towards the North Pole, often after a strong mountain torque event. This can lead to warmer then normal temperatures from the mid latitude to rise into the polar stratosphere and cause a drop in winds associated with the PV, and even allow a reversal of winds. To start these type of events we usually have to look into the Troposphere for activity that could spawn a change into the Stratosphere. We can look at tropical flare-ups in convection as a way to see a start of an atmospheric Rossby wave. The positioning and strength of the tropical activity is very important and can be seen from the Madden-Jullian Oscillation (MJO) and the surrounding ENSO state. As the rossby wave forms from such convection processes it can moved and deflected by various mountainous regions across the globe which can be monitored by changes in the Global Wind Oscillations (GWO).

MJO monitoring:
http://www.cpc.ncep.noaa.gov/products/prec...k/MJO/mjo.shtml

ENSO monitoring:
http://www.cpc.ncep.noaa.gov/products/prec.../MJO/enso.shtml

GWO/AAM:
http://www.atmos.albany.edu/student/nschiral/gwo.html

When we do happen to get a Rossby wave to form from this process of tropical convection there is the possibility of this Rossby wave, after being deflected, to break. If the Stratosphere is more responsive to wave breaks then as time goes on we can see the development of a SSW or MMW. When a Rossby Wave break occurs in one place we see a wave 1 disturbance occur, usually involving a displacement of the PV. If we see two wave breaks, a wave 2 disturbance, we can see a squeeze on the PV occur and allow for a split.

Rossby Wave Break (RWB) Diagram:
post-14460-1506341702_thumb.png.21716edd2864bc6ad55487ab233cc85f.png

post-14460-1506341715_thumb.png.91e36340cc74f39354bf647e04c24b58.png

post-14460-1506341707.png.8a4c9f5bc4ead68377cc5faf3a5c0ddd.png

Currently the SSW is defined by a reversal of mean zonal mean winds from westerly to easterly at 60ºN and 10hPa, but this is being reviewed as to whether this definition will hold. If we do manage to see an SSW form this can lead to high latitude blocking (HLB) to occur, now this is not always the case but SSW's provide a better chance of this occurring where colder air is able to be transported to lower latitudes. The lag associated with an SSW to seeing tropospheric conditions seems to be around 6 weeks but there have been times where this is not quite the case.

http://birner.atmos.colostate.edu/papers/B...2014_submit.pdf

One last thing is how snowcover could influence changes in the Stratosphere by ways of creating a SSW from such occurrence. Below we see what Dr. Cohen postulates for what could happen do to snowcover as many know this is not an exact science and the correlations are there but again I warn this does not always follow a linear path with so many other influences that can change this outcome.

post-14460-1506341749_thumb.png.609b6417a9f539c1f735f5104ab09f50.png

Various Websites:

GFS
ECM/ Berlin Site
Instant Weather Maps
NASA Merra Site
NASA seasonal Evolution
* Various sites at the bottom of site
Current and previous seasons Temp and Wind

Please Please try to keep this thread on track with not posting single storm impacts unless it pertains to the evolution of the PV. Also if there is any information that anyone would like to add as far as websites, pictures, or any information feel free to add as needed. If you would like to help expand on this 1st post just shoot me a PM and I will add as see fit.

Have fun with discussion! 

Added sites from previous years sorry if there are repeats anywhere:

http://stormhamster.com/climate.htm

https://ozonewatch.gsfc.nasa.gov/facts/vortex_NH.html

https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2003JD004123

https://acd-ext.gsfc.nasa.gov/Data_services...t/ann_data.html

If there are anymore links not listed please add below and have a great discussion!

Edited by so_whats_happening
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Usually the beginnings of the PV have been around late august or early september, more so August. We are currently facing the beginnings of a down-welling westerly QBO event which is starting around 1-10mb region. We still have negative QBO which remains in the low mid portions of the Stratosphere which could make for some interesting times early in the season depending on how quickly these easterlies erode. This will surely impact though the strengthening of the Strato PV in the early stages but to what degree is yet to be seen.

Here is the average daily start of Strat PV over the years from Amy Butler

https://twitter.com/DrAHButler/status/1032020969215459331/photo/1?ref_src=twsrc^tfw|twcamp^tweetembed|twterm^1032020969215459331&ref_url=https%3A%2F%2Fwww.netweather.tv%2Fforum%2Findex.php%3Fapp%3Dcore%26module%3Dsystem%26controller%3Dembed%26url%3Dhttps%3A%2F%2Ftwitter.com%2FDrAHButler%2Fstatus%2F1032020969215459331

It looks as though everything is about as normal as it gets for this time of year but down the road may get a little interesting as we move through September and October we tend to ramp up the PV but some models are suggesting probably otherwise.u10serie.png.94b42bdcc54a16e6a62b61c5bacab18e.png

weatheriscool.com is a great site for a quick glance at what may be coming up.

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Roughly the last 6 months (begins in April) of equatorial (5°S - 5°N) zonal mean winds showing the  QBO westerlies beginning to move down, encroaching into the 30mb.  Easterlies look like they are slightly weakening are 50mb.

ezgif-1-698ce7ac3fb8.thumb.gif.63be842d97a3e7c72de6a6dbd989738c.gif

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On 9/5/2018 at 2:29 AM, so_whats_happening said:

Usually the beginnings of the PV have been around late august or early september, more so August. We are currently facing the beginnings of a down-welling westerly QBO event which is starting around 1-10mb region. We still have negative QBO which remains in the low mid portions of the Stratosphere which could make for some interesting times early in the season depending on how quickly these easterlies erode. This will surely impact though the strengthening of the Strato PV in the early stages but to what degree is yet to be seen.

Here is the average daily start of Strat PV over the years from Amy Butler

https://twitter.com/DrAHButler/status/1032020969215459331/photo/1?ref_src=twsrc^tfw|twcamp^tweetembed|twterm^1032020969215459331&ref_url=https%3A%2F%2Fwww.netweather.tv%2Fforum%2Findex.php%3Fapp%3Dcore%26module%3Dsystem%26controller%3Dembed%26url%3Dhttps%3A%2F%2Ftwitter.com%2FDrAHButler%2Fstatus%2F1032020969215459331

It looks as though everything is about as normal as it gets for this time of year but down the road may get a little interesting as we move through September and October we tend to ramp up the PV but some models are suggesting probably otherwise.u10serie.png.94b42bdcc54a16e6a62b61c5bacab18e.png

weatheriscool.com is a great site for a quick glance at what may be coming up.

So a month later and we are still seeing the GFS long term showing a deep crash and possible reversal early on this season. Showing up now mid december to early january time frame. Wont necessarily happen this way. I would say given the chart from MJ that we could be looking at a stronger upper PV with intrusions from the Tropo to cause some havoc on it. If I had to take a guess it would probably offer up a wave-1 distortion rather then a wave-2 split but again wayyyy too early to know that.u10serie.png.5b67e95265cd15ae80173470771a6334.png 

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Already having various #wxtwitter accounts discussing the PV and how the late November and early December period is interesting. "High Risk" even mentioned. 

Love this tidbit on weatheriscool though!

Quote

####------------------------------------ Polar vortex status ------------------------------------###

The strat. vortex is currently stronger than all other years in the ERA interim record!!! 
The zonal mean zonal wind at 10 hPa 60N is today (GFS analysis): 29.2 m/s 
Weakest zonal wind at 10 hPa 60N in ERA interim record for todays date is: 11.8 m/s 1980 
Strongest zonal wind at 10 hPa 60N in ERA interim record for todays date is: 28.1 m/s 1997

 

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7 minutes ago, jdrenken said:

Already having various #wxtwitter accounts discussing the PV and how the late November and early December period is interesting. "High Risk" even mentioned. 

Love this tidbit on weatheriscool though!

 

You can see it illustrated nicely on this chart. 

 

u10serie.png

 

If there is one thing I have been learning this season so far, it's that my goodness, there are a lot of factors in sub-seasonal/seasonal forecasting. Yeesh.

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27 minutes ago, TheDayAfterTommorow said:

You can see it illustrated nicely on this chart. 

 

u10serie.png

 

If there is one thing I have been learning this season so far, it's that my goodness, there are a lot of factors in sub-seasonal/seasonal forecasting. Yeesh.

Model solutions showing it happening is different from acting like you know exactly how it will impact the CONUS. There are sooo many wxtwitter accounts, as it pertains to the stratosphere, that will provide people correct information vs tweeting something for sales.

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2 hours ago, jdrenken said:

Model solutions showing it happening is different from acting like you know exactly how it will impact the CONUS. There are sooo many wxtwitter accounts, as it pertains to the stratosphere, that will provide people correct information vs tweeting something for sales.

Are you referring to weatheriscool?

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2 hours ago, TheDayAfterTommorow said:

Are you referring to weatheriscool?

I honestly have no idea how you came to that conclusion since all they do is post the models. Look at my pv post in the fall and winter thread for answers.

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If the GEFS long range is correct, those tweeting about the pv need to stop acting like it will help the ECONUS.

 

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On 11/16/2018 at 8:39 AM, jdrenken said:

fluxes.gif

jikei_uep_nh.gif

Models have been on this idea of something early in the season for quite a while now. Still not sure yet how it plays out but will see after turkey day how things continue to unfold. I like the idea of a strong forcing coming in mid december that may get the ball rolling. Whether that means split or shift who honestly knows at this point but if it happens early fun times to be had, or doom and gloom. * insert EVIL LAUGH*

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I feel if maybe we saw a stronger warming showing up over Asia/Siberia region this would something to watch but for now will just post the gif. Think we need to start watching the Atlantic front though with continued blocking showing up just North of England into the Scandinavian region. Some interesting times may be had come the end of the month.

ezgif-1-49b94bfc39dc.gif

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Dr. Cohen is favoring a PV displacement to end the year instead of a PV split:

https://www.aer.com/science-research/climate-weather/arctic-oscillation/

The Euro suggests a SSW from the top to bottom. I'm not knowledgeable enough of the topic to comment any further, but I have gut feeling that some sort of SSW event will occur over the next month or so. No matter what happens with the stratosphere, a continuation of a snowy North American winter seems more likely than not. 

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