A Polar Vortex study; pre & post great sea ice melts

We start with the familiar look,
<<<left<< January 15 to February 15 2013 to 18  temperatures at 600 mb.    Right >>>>>>>>>
same pressure level and period for 1980-1985.               

NOAA daily composites dedicated 238-245 Kelvin (-28 to -35 C ),  the left animation depicts latest years of great ice melts,  to the right  the pre great melt look.    What strikes as significant is the lesser cooling influence of the Arctic Ocean during the greater melt years.  The Vortex appeared always elongated or much warmer over this Ocean,  as opposed to 1980-85 having a mostly much colder Arctic Ocean atmosphere.  We note also very cold vortices above the continents occurring more prominently during the 2013-2018 years as opposed to vortices over East Siberian , North Greenland and Barents seas ,  now a days a very unlikely event given more extensive open water.      Deep cold vortices starting over land can be explained by the specific heat capacity characteristics of land varying a lot depending on snow coverage along with warm cyclonic intrusions circumnavigating vortices perimeters, being largely outside of them (more clouds covering the Polar oceans). .   

Logically we would expect winters to start  earlier and colder during the 1980 to 1985 period.

In fact winters started colder more often, 4 times out of 5  on top of the Arctic Ocean during November 15 to December 7 1980-85 (left) ,  as opposed to starting mainly above the continents  5 out of 5 times during 2013-2018 (center).   I observed the latter frequently for a long time,  was often puzzled by this until making the simple connection,  the Arctic Ocean emitted more warmth during these latest years,  winters can only really start over land when sea ice is thinner along with the greater presence of warmed sea waters.  WD February 15 2019.     

A dwindling coldest atmosphere creates a greater meandering of the jet stream

~The often used presentation of the jet stream causing weather is nebulous and confusing,
it does not intuitively link current Global Warming as its cause
~ A  laser clear and correct description of the generator of extreme weather simply starts with defining where the coldest atmospheres are located
~The worlds coldest  atmospheric regions are shrinking, stretching  and bending in these days of AGW (Anthropogenic Global Warming),  this explains the sudden extremes in temperatures which often happen in the span of a few days.

     Again and again popular medias fail in describing very clearly what is driving these days of extreme weather,  the failed linkage occurs daily, repeatedly to millions if not billions of people.
The description of jet stream being linked with AGW is correct, but utterly does not explain why.
But rather more accurate would be to present the latest "Polar Vortex"  , which made a recent  news blast,  as a stretched out much weakened  in strength winter zone. Such a definition is more a common sense presentation rendering any unspecialized person, immediately very well informed about climate change implications. 

    I can show TV weather videos,  hundreds of them,  always not educating people as perfectly as they can do about extreme weather correlations.  Is best to present it this way:

University of Maine current day weather, February 14 2019.  500 mb Geopotential levels, pressure heights,  is not the best pressure level to express the Polar Vortex.  600 mb is,  in this standard map, pressure heights confuse where the coldest air lies,   but for sake of this presentation, observe and use your mouse pointer at the limits of lower heights (with mostly colder temperatures) match with the location of the jet stream. The jet stream is a creature which lives at the outside perimeter of coldest air and southern limits of intense cyclones. Therefore by simple projections,  jet stream meanders happen when the coldest atmosphere has a much smaller area:

The day a Polar Vortex froze Chicago and environs still had a stretched out coldest atmosphere.  Properly defined like this:

Again use your mouse pointer and determine where the jet stream starts with respect to coldest air.
Temperatures at 600 mb NOAA daily composites,( map largely in red)   at about -30 C  is where the jet stream is formed. look at Japan's intense jet and how cold 600 mb was at that location.  There are also cyclonic peripheral adjuncts  which extend the coldest atmosphere/jet border line by pressure dropping  the thickness of pressure heights.    Basically January 30 had a stretched out coldest atmosphere.  The jet stream morphed around the coldest air, and did not exactly drag Arctic Air southwards.  Equally, colder temperatures in winter can be created over continents well away from the Arctic, and depend on basic geophysics such as snow cover with little or none  and clear or covered skies under very little insolation ......  WD February 14 2019

2016 2017 2018 new class extreme low sea ice extent maxima along with 2019, despite different atmospheric circulations.

       At present,   February 8 2019  Arctic sea ice extent is #2 in lowest extent:
  
       2009----  2010-----  2011-----  2012-----  2013----  2014----  2015----  2016-----  2017----  2018----  2019

   
   January 31 to February 8 JAXA  sea ice measurements reveal only 2018 being lesser in extent by about 16 thousand kilometers square on the 8th.  This is an extraordinary feature of winter 2019 with a distinctively dissimilar general circulation than the preceding 6 seasons.......

2019's general circulation to date can be characterized in part by by a snow footprint:

                    Snow cover has very similar features to sea ice extent,  it can define the degree of winter,
mild , severe or extreme.  If sea ice is widely spread out and thick,  Northern Hemisphere winter may be more  severe as well.  These two Cryospheric features make the story of winter which shapes the Arctic Polar Vortex:

   NOAA daily composites 600 mb temperatures (close to the density weighted temperature of the entire troposphere),  Arctic Polar Vortex average location January

4 to February 4 2019.   Siberia dominates,  which is contrary to all winters going back to 2012.  There are some similarities from season to season, but very prominent differences were distinguishable by analyzing maps daily,  overall PV average extent calculations may appear somewhat similar,  but they are not:

The way to analyze any given Polar Vortex season,  is to break it down in smaller periods,  January 24 to February 4  sequences 2016 to 2019 demonstrate differing flow structures.  These are winters of interest having the least sea ice extent in history.  All 4 recent seasons including 2019  had different Arctic Polar Vortex configurations,; 2016 had a very mangled weaker  and smaller Polar Vortex,  with mainly 2 continental much weaker and smallish  vortices acting independently from each other. Arctic Ocean  sea ice  became badly broken up by minima 2016.   2017  had a Pole warming  flow pattern in particular with North of Greenland Atlantic in origin cyclones heading Northwards,  2018 had a massive extreme Polar vortice dwarfing all others above the Canadian Arctic Archipelago,  Russian side vortice appeared weaker on most occasions then.   2019 to date has the opposite of 2018,  but with a difference,  continental vortices within the Polar Vortex were more balanced with Siberia dominating on most days, so far  the Polar Vortex rarely split  in two and appears stretched out.  This gives open sea water inroads from the North Pacific,   a strong  Siberian vortice pushes massive cyclones Northeastwards more often,  To date, North Atlantic cyclones went towards Eurasia, and in effect help refreeze the North Pole area sea ice which keeps the Polar Vortex more or less together.

    Given that 4 recent seasons created differing circulation features,  it is amazing that sea extent at Maximum extent date remains near all time record lows.  This strongly suggests a greater warming of the Oceans and sea ice has the potential to collapse to extreme low summer extents only not doing so because of,  you guessed it, summer circulation features. WD February 9th 2019

-39.3 C 700 mb coldest temperature of winter to date, where?: White Lake Michigan USA

~The entire Arctic winter of 2018-19 was never colder at that altitude.
~Until next day in Siberian Russia
~North American continent is easily capable of creating such temperatures
~Provided less snow insulation covering ground frozen hard from extensive exposure at the peak of darker winter, from a just prior warmer or late coming winter,  a barer dark lit Great Plains ground is onto itself a byproduct of Antthropological Global Warming (AGW).

    The specific heat capacity of dry soil is less than snow or ice, it means soil can loose (or gain) its temperature quicker,  especially if continental snow coverage has been reduced:

                                                 
     ASCAT 02/28 2019 gives a good idea of where the snow lies,   it shines bright white here,  there are many locations with scant coverage namely the Prairies or the Great North American Plains:

  January 29 2019 winds over none existent forests areas (link)  coincided with the 700 mb flow hitting  the State of Michigan (link).  Consider also vast American deforested farmlands adding to different specific heat capacity characteristics of the landscape.  Note ,  same day entire  North American Arctic was warmer than Michigan at that level as well,  even for since the start of winter (from actual Upper Air measurements)!  This is a very compelling bit of evidence suggesting that vortices within the Arctic Polar Vortex,  may take quite independent temperatures then the rest of the APV.    I call one of these vortices simply as a vortice.  Usually a Southern NE American vortice becomes rogue because it is pushed Southwards by Quebec\Labrador massive cyclones ascending towards Baffin Bay,  which also warms a great chunk of the Polar Vortex concurrently,  cutting off the Southern vortice to be on its own, thus a rogue.  The idea suggesting the jet stream pushing down a rogue vortice has long been accepted as the reason why they are displaced,  but a vortice is usually part of the Polar Vortex where the jet stream is at its perimeter,  not within.

   As the world warms extreme weather increases because the Polar Vortex is shrunken and or stretched. 

         To make this evident,  consider thinner Arctic Ocean sea ice warming the Upper Air directly above.  Observing what happens to the Upper Air there is key.  What has and is happening is Arctic Polar Vortex stretched to from Maine towards Northern China, on the Axis aligned with Greenland to Vladivostok.  The core of the Vortex is hollowed over this Ocean once frozen with mainly 10 meters of sea ice, now reduced to 1.5 to 2 meters.   therefore the Polar Vortex of late is usually stretched and can split in two,  especially  during a warm winter similar to 2016.    The weather of the Northern Hemisphere is thus rapidly changing by the shrunken Polar Vortex which favors the winter warming of Alaska and Norway,  but cooling at times of Central Southern Russia  and Midwest North America during winter.  As an example I use the Polar Vortex event of January 29 2019:

                             White Lake         Fairbanks
                            Michigan  USA  Alaska USA
January 29              -19.7                     -11.5
January 30              -39.3                      -9.5
January 31              -28.3 C                  -16.5   700 mb temperatures.

      The North was and is very often warmer some 3000 Southwest miles away

    It is very possible to have such extreme events given the right circumstances.   However winters great deep freezes well South of the Arctic are furtive,  they may not be long lasting,  as White Lake's current +9C weather may attest, compared to Fairbanks current -13 C even still warmish.  As AGW increases,  the weather in many places in the Northern Hemisphere will get even more strange and extreme. WD February 3 2019