Summer Threshold switchover, when High's become warm and Low's are sustained by cooler air

 ~It is just about to happen,   after long sojourning Arctic Basin High pressure system  

~Impacts sea ice survival in a big way

    The reasons why cyclones persist more in cooler summer weather are obvious,  they cast a shade from the sun.  In the Arctic it is a bit more complex,  sea ice helps create clouds as well,  more of it causes a cloudier Polar summer. Moist air hitting an ice pack easily fogs up,  fog is a cloud touching the surface.   Onto itself summer sea ice and cyclones are a pair,  so it is not surprising that summer Lows tend to survive longer above ice. But there is a time,  such as now,  when cold Highs and Lows may subsist simultaneously:

  3 CMC surface progs, 23 May 00 UTC,  23/06 and 23/12 UTC +extra 700 mb 23/12 UTC.  All showing a less imposing Arctic Gyre High,  apparently moving towards the Canadian Arctic Archipelago where it will eventually be just South of it,  and a 1008 mb Low over the Arctic Ocean Gyre.   Where it will stymie the sea ice exodus towards Fram Strait,  just Northeast of Greenland.   The 700 mb chart portrays this High and Low as having about the same temperature,  this anticyclone will warm a lot,  because it is allows sunrays through,  opposite to the Low, basking in cold, sustained by sea ice,  cloudy weather.  The split in behaviors is temporal in nature and will revert back opposite coming September.  Clouds are essentially all there is stopping a massive catastrophic sea ice melt.  But this is a "frustrated" but nevertheless end of La-Nina weather cycle,  meaning over all lesser clouds and especially warmer High's significantly warmer by lesser pollution at end of Covid pandemic.   WD May 23, 2021

A much warmed and disorganized Polar Vortex created a steady deeper cooling at its center.

~Stable warming of the Polar Vortex is seldom uniform in shape or temperatures.  

~This warming can cause a sudden cooling zone anywhere with very long exposures to the frozen ground and of course by prolonged cloudless air

~Recently we have had a very neat example.  

           Early may 2012 Arctic weather was incredibly warm,  this warming has not stopped,  it kept shrinking  a mangled Arctic Polar Vortex,  but suddenly 1 week later ,  under an even warmer rising sun,  what appears to be impossible occurred:

A small deep cooling area appears near the Pole May 10 (still with a low sun),  it moved over the Canadian Arctic Archipelago where the air was clear,  notice its temperature colder than about 2 weeks prior  (May14) ,  although much smaller, it is strikingly keeping cool despite the P.V. even more dismembered and severely encroached by warmer air all around its perimeter.    What happened is a classic Geophysical phenomena, under certain conditions atmospheric temperatures may drop if  the weather is right,  despite the rapidly approaching summer, despite over all abnormal warming.

This feature can be observed at any time of the P.V. existence.  For instance,  the Northern US can

be coldest place of winter to date more than anywhere else in the Northern Hemisphere.  Notice I use use 600 mb temperature because it is the closest pressure level representing the temperature of the entire troposphere.  500 millibars is more representative of the entire atmosphere, on occasions the stratosphere can be unusually warm or cold,  and can distort tropospheric tendencies if judged by 500 mb maps. WD May 16, 2021 

Arctic 2021 almost just as warm as spring 2016??

 ~However spring 2016 was part of the warmest El-Nino in history

~While spring 2021 is part of the coldest La-Nina since

There is something out of the ordinary coming about:

NOAA ENSO Table,  look carefully at 2015-16  ,  it was really the winter of 15-16 which was very warm,  likewise EH2r vertical sun disks of Spring 2016 were amazingly expanded, in fact all time record number expanded.  Followed,  not surprisingly by 2015,  2010,  all El-nino winters. Climate wise,  the Arctic temperatures zoomed up in 2016,  the gold standard warmest since 1998.   

As a useful weighted temperature of the entire Troposphere comparison,  2016  May 3 date ,  can be compared with others,  averaging out a week or or month would blur the image so much,  it would be difficult to judge the extent of warming.  Any ways,  2012 was end of a very long La-Nina starting in summer 2010. Hence we see a marked ENSO footprint.  The Polar Vortex was of a different nature in 2012,  consolidated, less broken,  as if something more frozen just happened....  Of course 2012 is the year when Arctic sea ice minima was lowest to this date.  

2016 vs 19,  both springs had a winter El-Nino,,  both had broken May 3 P.V..

Of which its internal vortices unleashed their own regional climates.  

A neutral look,  Sprig 2020 came after a neutral ENSO period,  the Polar Vortex was more reformed,  much colder than 2016.  But all is not well, the broken up aspect of the P.V..  perimeter persists.  Since after 2016,  spring time vertical sun disk diameters reflected the consolidated coldest vortice hanging about the Canadian Arctic Archipelago.   

Very strange,  2021 May 3,  quite similar to 2016,  in warmed temperatures and configuration.  Yet

as the ENSO table demonstrates,  the ENSO's are polar opposites,  16 followed the back end of El-Nino and 21 back end La-Nina.  A significant  Canadian Archipelago vortice is still important in 21,  but not as strong as previous years since 2016.  While comparing with 2012,   with very similar ENSO,  2021 is warmer than 12,  refigured like 16,  as if current La-Nina had no effect on the Arctic system.  The only reason this can happen, warmer Oceans ultimately affecting sea ice,   if thinner,  the heat emanating from a huge area would erase the Nina effects.  The warmer Northern Oceans had something to do with tis as well.  WD May 9, 2021

EH2r annual spring summer projections, in greater details, massive heat wave foreseen

~Simply extraordinary systematic Arctic surface air warming, caused newly discovered optical phenomena

~Vertical sun disks in the middle of the pack,  analyzing a much weakened out of normal position Cold Temperature North Pole

~Extra clear air,  confirming a depolluted Arctic atmosphere and a quiescent La-Nina  unable to compensate for historically warmest 2016 El-Nino 

    Since 2016,  the year with the warmest El-Nino in history,  everything was changed further, culminating to Nothing:

     No streaks,  pure molecular air,  a sure sign of de-pollution and especially La-Nina,  no evidence of cloud seeding high clouds,  nothing again and again:

  5 days later April 20 2021,  a totally clear high altitude sky,  sure sign there was or  is a raging La-Nina,  but look at the ground,  with a near record snow cover.  It was cloudy of course, much cloudier than a usual La-Nina spring,  but this snow comes from another sea surface, almost inclusively from  the North Pacific:

Impressive North Pacific high temperature blob anomaly,  currently survives the strongest La-Nina since 2016.  The main difference between a North Pacific warm SST and El-Nino  are the clouds, the Tropical Cumulonimbus are incomparable in height and duration,  they fuel the lower stratosphere with cloud seeds,  which go all over the world.  However, a North Pacific cyclone system has considerable moisture,  which during especially during Arctic fall-winter-spring,  turns to snow.   

   Given that I estimate a very much diminished Polar Vortex (P.V.),  despite La-Nina,  the course of things can be a bit strange.  North Americas main moisture source will come from the Northwest for the earlier part of summer.  Leaving the greater portion of the continent only changeable by synoptic weather,  no longer in the grip of the P.V. sphere of influence.  

Vertical Sun disks; what is the score?

     The vertical sun diameter is a giant thermometer,  taken at the right elevation ,  it purely reveals the temperature of the entire atmosphere.  Since 2016,  another shocking turn occurred,  the disks shrank

despite much warmed world temperatures.  That is because the center of the Polar Vortex,  at its heart, is the Cold Temperature North Pole (CTNP).  since 2016,  the spring CTNP remained steadier over  the Arctic archipelago,  as opposed to the past when it was further South.  The pre 2016 CTNP was found mainly to the South of the Canadian Archipelago,  with a slow move Northwards,  culminating at Northern Ellesmere Island by mid spring,  vertical sun disk dimensions traditionally reflected this movement.  With disks usually bigger in late winter,  then shrinking as the sun rose,  because I was eventually measuring the CTNP from within.  It was not unusual for late spring measurements to have the smallest vertical sun disks.  All this changed after 2016, when  I strangely measured smaller disk diameters for a greater portion of time,  almost all the way to spring end. This made the average vertical sun disk measurements at all time lows since 2001.  In effect skewing its predictive powers,  which made it easy to predict the year end Global Temperature results.  

     Now I keep in mind the location of the CTNP,  which this season was mainly to the North, or at various apparently random locations,  a sure sign that the Vortex has left or has become severely weakened and or shrunken.  With this in mind here are the results:

                                                              ranking,    year,    #1 average maximas* 

*Of 12 decimal levels,  from -1 degrees  to 10 degrees astronomical elevation

      2021 has jumped above the last few years bottom trending to mid pack,  10th place, with 6 average decimal elevations being at all time maximum.  From more than 420 measurements,  taken not often from the CTNP center.   Sun disk  ENSO projection  has been completely muddled by the North Pacific blob sst,  although there is still a correlation,   the measurements of this seasons sun disk coincide with the last phases of a modest La-Nina lasting 7 months,  as long and and in a similar period to 2017-18,  the difference being the observation position mostly away from the Polar Vortex center.  A greater number of sun disk diameter expansions was expected because of very warm surface temperatures,  but the Upper Air still was more normally cold. 

Global Temperatures

        Past measurements of sun diameters were sufficient to predict the annual average temperature of the Northern Hemisphere, but the continuous climatic repositioning to the CTNP makes it more difficult to do so.  But the frequent repositions onto itself is a predictor.  As posited on previous general description article,  the P.V. has been consistently way North its usual locations.  There is no way to have winter reformed in the middle of May.  Therefore this high latitude CTNP in late spring means only one thing,  extremely warm temperatures for most of North America,  with rain for Alaskan coast (seasonal temperatures).  

   Arctic Sea Ice 

               There was another astounding event coinciding with the warmer surface  temperatures,  April 2021 will be on top of the list for the warmest April in Canadian Arctic  history.  At present, Arctic sea ice thickness is locally very thin (middle of Canadian Arctic archipelago), likely all time thinnest.  Therefore,  it is easy to surmise, an early collapse and total melt devastation of sea ice,  but not so fast,  North Pacific moisture will bring more rain to the Arctic and of course greater cloudiness.  The question is whether rain can do in sea ice as fast as the very hot sun?  Is a good one,  we shall see.  But I think the NE passage will still open before the NW by a few days.    Over the Arctic basin,  its again a question of clouds,  this time with less rain,  so I predict (as a measure to see if I understand the geophysics) 2021 sea ice minima slightly smaller than 2012.

     Another fact to keep in mind is top of sea ice (implies snow layer as well) ,  never warmed to same temperature as surface air until April 30 (the latest since observations began in 2010).  This can be optically seen,  if the surface air is always warmer than top of sea ice,  the "first melt"  observation can never be made.  First melt is optically   determined when the top of sea ice temperature is the same as the air immediately adjoining.    Every other year had thicker  or much thicker sea ice.  This late f.m. date is understandable considering the current greater snow insulation cover.  It stops the further warming of more exposed top of sea ice.    Thus extreme snow cover will again tend to complicate prediction models. 

March 21 2012 First melt (left),  while a bit later sea ice horizon rises.  The earlier the first melt the worse the coming melting season,  it was once thought,  but now extreme snow cover implies the very opposite but with the same devastating summer melt.  

  With thicker sea ice , and colder (note the April 11  -31.2 C)  clear weather,  it was possible to reach "first melt" elevation level on April 15 (right ) .  When this occurs there is a thermal balance between top of sea ice and the air right above,  the sea ice horizon becomes the astronomical horizon.  

     In summary ,  end of spring and summer 2021 will be hot,  because the Polar Vortex lost its cold air grandeur. The Global circulation will tend to be stagnant,  favoring weather moved by a much lesser temperature differential,  with no significant Polar driven circulation movement until October.  WD May 2, 2021

    

EH2r Annual Spring Summer projection by mainly unorthodox means, brief General Circulation

 ~Hot spring summer for North America,  #1 warmest year in history.

~  Is strange, since La-Nina usually cools the planet

   Lets take a summary look:

 April May, the unusual position of the North American Polar Vortex extreme limit existed nearly all winter so,  this projection not a difficult call,  except we are dealing with unknowns,  such as different patterns from the onset onwards.  Early on, over the Arctic Ocean the usual North of Beaufort sea High will remain strong by not so apparent but somehow present La-Nina,  exacerbating Fram Strait sea ice flushing.  North Atlantic and Pacific usual Lows will impact B.C. Canada and UK along with NW Europe, mainly carried over by the Jet Stream (edge of P.V.).   Obviously the extreme North positioning of the jet stream slows the circulation to its South,  from present gently, to a crawl in the fall, and brings out the best or worst of weather.  This shift makes tornadoes more difficult to form in the deep South.

However this repositioning always dries up California,  not so good.  I would expect a wet UK, not so unusual.  The big story is the not so much measured La-Nina, whose effects are in some regions almost completely smothered by the North Pacific warm surface temperature blob.  So I'd expect less wet than usual a soggy Ireland Norway and UK a weaker flow from the Southeast would do so. 

June July,  Beaufort Gyre switchover from a stagnant High to a near permanent cyclone will occur very early in June if not earlier.  The reasons for this are La-Nina and greater over all Arctic warming. The dumping of sea ice East of Greenland would be less severe, and the cloud cover provided by an Arctic  Low pressure system usually overestimates sea ice melting predictions.   The shrinking Polar Vortex will ultimately provide for higher pressure systems to linger on top of the Norther Hemisphere continents,  as well as high latitude sea born cyclones, the difference being,  with a strong sun the June July High pressures usually provide greater warming,  and a drying feedback contributing to further heat, hence anticyclonic dominating the fleeting less vapor rich weaker cyclones.   Thus Northern Hemisphere lands  will be High pressure prone, leaving the Arctic a haven for cyclones,  a place for clouds to be strong in numbers. NW Europe will witness nice clear truer color sunsets more often than usual.   Siberia will be in a likewise summer 2020 heatwave as well,  the main reason being threefold, one is the invisible La-Nina (less clouds),  the weaker flow of warm Atlantic moisture, and the much cleaner air given by the last days of Covid-19 atmospheric de-pollution. 

August-September much like 2020, except the CTNP will be close to vanish ,  not to be found even where the remaining sea ice will survive the summer heat onslaught.  But at September end, I expect the first winter High near the North Pole Greenland area. The time for switchover back to winter mode over Beaufort Gyre,  will be crucial in saving what is left of the sea ice as well, I think the steady Gyre High will come very late though,  not enough to have a greater melt season impact.  This period is usually very interesting,  because summer rages further South while winter starts at the Pole.  The Low and High pressures switching from favoring warm or cold modes get blurred at the climate starting to expand borders. Likewise, hurricanes,  end of summer creations, clashed with the beginning of the Polar Vortex for milleniums.  These geophysical encounters moved the hurricanes rather rapidly. As a result of dramatic Polar warming they will move less but can cause much more damage,  even if landings to ground become less numerous,  because  lesser longitude wise life  is a direct result of a warmer autumn Arctic.  At about the onset of the North Pole long night,  Greenland, because of its nature of being colder than surroundings, may prompt a  steadier High Pressure above the warmed North Atlantic, encouraging hurricanes to hug the America's coast on a slow journey Northeastwards.  In contrast, of the North Pacific where a lower sun effect will meet the quasi constant Pacific warm temperature blob,  a year round source of strong Arctic 'hurricanes' , the violent cyclones,  which in the past has exposed further the grim state of summer Arctic sea ice. 

     The only thing really unknown is the new state of circulation affairs,  what will a non existent really normally perennially cold Polar Vortex world look like?  We are about to find out.   WD April 25, 2021

Incredibly steady 0 C sst shift, even if it is about our Great Lakes

~Winter 2020-21 was unbelievably warm for North America

~None better example than the 0 C temperature Isotherm

   CMC daily sea surface temperature chart shows also theoretically calculated 0 C line over land,  it has been well North of the Great Lakes for months.  In the recent past winters,  this line was usually at the Great Lakes Latitude.  This is yet another example of staggering warming due to a major circulation change,  which maintained the center of Cold Temperature North Pole (CTNP) ,  on the Siberian side of the circumpolar world.  Ellesmere frequently was the CTNP center of late,  but only for a few day cycles,  always bashed back warmer repeatedly by North Pacific in origin moist cyclones.  As a result a good chunk of North America has has had a warm start of Spring:

        NOAA 30 day surface temperature anomaly,  the blue Siberia Alaska bit portrays the Central Eurasian dominance, tagged along with short time cold air buildup cycles formed in the North Ellesmere area, not captured on a monthly average,  almost continuously sent to the Southwest, giving the brunt of High Arctic cold waves to the Western NWT.  WD April 18, 2021......   Yearly projection is coming next,  as you may guess,  there is absolutely a warm Spring-Summer already set.  

Dramatic Climate optical changes, significant effects from thinner sea ice

 ~In a short time span Arctic spring and autumn days have shortened.

~A very good reason why Northern Hemisphere circulation is changing aside from warming temperatures:  thinner sea ice.

~ This can be visually observed multiple ways,  all to to with atmospheric refraction.

     The latest Arctic warming can be summed up in 3 periods by sunset tardiness, of which some part of the sun disk can be seen well below the astronomical horizon (A.O. :  horizon seen if there was no atmosphere). In the High Arctic Cornwallis Island some sun disks parts have been seen lower than -3 degrees (that is 3 degrees of arc below astronomical horizon).  Furthermore when seen so much below the A.O.  under the violet sky,  sunsets shift Northwards quite a lot,  prolonging the day. 3 recent periods of concern would certainly be 2001-2005 ,  the last thicker ice years,  2005-2010  intermediate warming/thinning of sea ice, 2011 to 2021 severe thinning years,  of which the first period had 6 Month of March sunsets 2 degrees below astronomical horizon,  the intermediate period had 3,  the longest lasting period of 11 March months had  only 3,  this is a serious decline in optical properties caused by sea ice and air interface.   Visually this can be studied in greater details,  although I have no illusions about how convincing these images can be,  atmospheric refraction is very poorly understood,  I'll endeavor to explain nevertheless:

March 20, 2021.  At first the sun appears red and reddish throughout,  by moisture,  March 2021 had more snow,  more encroaching Pacific cyclones, than perhaps in the entire observation period of 2001 to 2020.  This sequence has been captured in a brief cooling  build up period between cyclonic storms.  The sea ice at horizon is also at thinnest recorded levels.  The sunset was not tardy, -1.39 degrees below A.O.  .  The main feature of interest is the lack of laminas,  the lack of roundness.  At end you see the beginning of purple sky light.   Basically there was no great temperature gains near the surface upwards.  This makes for a rather ordinary (for the Arctic) sunset.

 March 19,  2009,  much drier air,  therefore much cooler over all winter,  on this moment -35 C surface. 

These impressive presence of laminas are a feature of a colder atmospheric processing,  these occur when there is layers of warmer air above, but with very cold interface between sea ice and air in light or no winds.  These laminas rose undisturbed by strong winds, forming multiple thermal layers in stable air,  again a feature of a long time cooled surface facing the rising heat and sun as winter ends and spring begins. 

   March 19,2010.  a windier sunset, but with great thermal rate difference,  it was -33 C a few hours back, at this sequence it was -23 C causing a lapse rate favoring an extreme late sunset,  indeed 1.93 degrees below the horizon.  Warm air advection is one cause of sunset tardiness by reasons of refraction optics.  The cold ice did not warm up instantly, as the air just above changed,  for this to happen in greater winds,  the sea ice must be thick and sluggish in warming.  

      One may not conclude a great Climate Change with one observation moment,  rather it be known,  the entire EH2r corpus of data,  likely 10,000 individual sunset sun disk observations, which have gradually evolved into mundane sunsets rather than exciting colorful, extremely strange, lines upon lines stretching to "fire on the ice" sun line before dusk.   What we are witnessing is the signs of drastic warming affecting all visual aspects of land, sea and even winter. WD April 6 2021

Major Circulation change in place for spring 2021

 ~Last few later winter circulation pattern vanished.  

~North Hemisphere current prime CTNP  has been anchored North Central Siberia for a long time

~2021 spring summer weather will of course be different in many locations.  

  At present, the great Canadian Archipelago Spring CTNP (coldest vortice) has a hard time establishing itself, largely because there has been a constant streaming of North Pacific warm cyclones destroying its formation,  on every 2 or 3 days of build up this vortice gets banged up by cyclonic heat advection.  As a result Siberia has dominated as CTNP prime region,  shifting the entire circulation picture of North America,  from mainly cold to much warmer:  

NOAA daily composite March 1 to 17 picture at 600 mb temperature,  roughly the weighted temperature of the entire troposphere,  has morphed from, 1977;  when the North Pole was CTNP prime vortex, 2012:  by continental split vortices,  very bad for sea ice,  2016;  very strong El-Nino year , again with the spit cold temperature vortices,  2020,  really 2018, 19, 20 dominant Archipelago CTNP.,to 2021 the North Pacific flow year so far.   Basically if this continues,  and there are no signs otherwise.  It will be a dry summer for much of North America,  particularly mi-west eastwards. What really matters for California coastal fires  is the green to yellow threshold,  basically the jet stream hangout region,  in 1977 it was close to Mexico USA border,  now well to the North.   The early preliminary tentative outlook is for  very warm weather to come,  refraction measurements of vertical sun disks also suggest this will be warmest year in history yet again.  WD March 21 2021...

How does the CTNP move? Wherever the ground feedbacks it.

 ~Ongoing essay on predicting the location of the Cold Temperature North Pole

~ The most underrated weather factor,  the location of the CTNP,  in fact rules the world hemispheres weather.

~Locating where they will be basically enables long term weather projections to be easy. 

~Short term wise as well

~Refraction techniques can laser predict wether the CTNP be, or not.  

    CTNP's are known to mainly slowly wobble,  from one point to the next.   Or surprisingly vanish only to reappear thousands of kilometers away.  They basically control weather circulation of planetary waves,  nothing more important weather or climate wise.  The mystery is why do they wobble in the first place,  rather than be moving around according to basic meteorological tenures;

A common contradiction,  CMC 700 mb map,   pressure contour isoclines  do not consistently match  the true center of what would be the coldest point on the Eurasian Continent in the morning of March 5, 2021,  -36 C is well off center.  I would rather pick from a 600 mb map,  but it is not easy to find.  However,  this should indicate that the center of cold is unstable,  in motion,  as they very rarely remain in place, with great understanding that such an event on rotating Earth would be fascinating.  

   The main problem with respect to predict where the CTNP will move is extremely complex.   With numerous variables to consider.   Probably the most complex component, on top of advection, clouds,  radiation balance, presence or lack of precipitation,  albedo, insolation,   on top of all these,  is surface properties.  Not a black and white issue at all,   water surface alone, is not as simple as a mirror lake, the waves,  and there are many kinds of waves, the mixing going about,  salt,  fresh water,  top it with ice, grey, fast, 1 year, multiyear, snow covered, hummocked,  ridged,  mix pans including all types,  not forgetting ice and open water combinations.  And we go to land, more complex than water surfaces,  by wildly varying topographical features,  what is on it,  vegetation, rocks,  a mix of both, flooding, snow, and snow cover is not uniform at all:

06/00 ,  06/12 and 07/00 UTC CMC 700 mb  analysis.  Nowhere else to go but Northeastwards,  the warmer North American side CTNP heads North.  While so,  it will get warmer much further South.   This far away action will only be felt as a significant warming,  innocuous, strange, announced as if it appears like magic, in  Windsor Ontario for instance,  jump warming from -3 to +11 C.  The movement of this CTNP also engenders the jet stream to bring up a blizzard giving warm cyclone from left.  In this case North Greenland is the coldest place in North America, until the CTNP moves further towards Spitsbergen,  not far away from an Eurasian cold cell buildup. But this cold center was created by steady weather,  a mere day or two,  over the Archipelago,,  no significant wind,  clear air,  the recent past warmed by advection  surface vanished,  quickly building extreme cold in its wake, until by virtue of its presence,  the general circulation changed favoring instability.  If there was greater factors,  such as profound long night continuous cooling in  the Canadian Arctic,  this CTNP might have outgrown itself creating rogue vortices 2000 nautical miles further South.    But it isn't winter 2020-21 thing,  which was mainly a late weaker cooling of the Canadian Arctic namely because the prime CTNP of Northern Hemisphere started and stayed in Eurasia for a long time.   However,  in a mere two days,  the weighted temperature of the entire atmosphere dropped quickly.  If circumstances were other,  the Low pressure on this animation above would have headed South instead.  But for now,  the surface ground and icy ocean "fridge walls" are bereft of deep cooling potential,  the power to fabricate colder air not as strong as it was decades or so back.   

March 07 1200 UTC

North Greenland is where the CTNP exists:

The 700 mb Low of 2680 meters is the CTNP.  

Automatically changing the weather all around it.  High altitude winds spin around it , in fact the jet stream is at the North Pole

   

                    There are 2  Polar Vortices at present 

                                                                        There is a  CTNP  in NE Siberia,  the two are close enough                                                                             to cause this jet.   (250 mb map).

North Greenland is not part of the giant glacier Greenland is famous for. It is like Ellesmere Island,

here March 7 Polar View SAR demonstrates it still has a lot of snow.    Now there can be a buildup of cold but it wont be wide, cant be done next to the Atlantic Ocean, the only place to expand is Northwards where the sea ice has been at record low thickness,  so it is stuck in place,  vulnerable,  not ground for cold air expansion. Unlike where much further West the new CTNP forms.  

       To know when the grounds are fertile to create more winter,  it is not just a matter of darkness,  stable atmosphere,  although these are the core factors,  but even now,  the low sun does not create more cold for much of North American Arctic.  What is needed, is for the ground to be deeply frozen, for sea ice to be extremely thick.  A CTNP can exist much further South, given that its grounds are deep frozen for a long time,  the Polar Vortex expands in such happenings.  In many instances the CTNP can be created locally,  1000 nautical miles away from the Arctic.  But to know whether the grounds are apt to do so requires a multi parameter simplifier.    Because the grounds can be immensely complicated:

   Snow cover alone is very far from homogenous,  can't be simplified at all.  Here we have multiple layer forms,  the darker one is ice formed in a wind blizzard, sublimation of which can't be compared with grainy snow cover,  which always changes by the wind.  Here is another factor visible by the halo

ice crystals in sufficient quantities falling from a warmer atmosphere above can alter the energy balance of the surface as well.

   Not to forget ,  a flat snow surface one day may change to snow desert dunes the next,  these increase sublimation as a cooling factor.  

     A new optical refraction method easily recognizes the varying energy flux on the surface,  over wide areas,  as far as the horizon can be.  Also sun disk measurements identify uniform atmosphere or a mixed thermal mash up,  unstable for cold build up.  Through such observations,  we can identify whether deep cooling will build or be demolished.  WD March 7 2021

Winter circulation stall not giving cold from the Arctic, but blocking pattern in the Arctic

~Most fascinating CTNP  parks at the central US Canadian border 

~Meanwhile,  it was substantially warmer in the Canadian High Arctic due to moderate Cyclone stall injecting a lot of warm air,  giving a weird scenario;  High Arctic  -20 C in clear blue skies for a week, 12 C warmer than seasonal.  

 From preceding EH2r article, Ellesmere Island reigned coldest spot in the world only for a few days,  then a strong Cyclone SE of Canadian Archipelago stalled, injected North Atlantic air quickly nullifying its deep freezing status.  This reorganized the centers of the now split Polar Vortex, one for each continent , of which the Canadian one's center reformed much further South,  it has been there since February 10.  Often the Canadian side Polar Vortex remained stable North of Hudson Bay,  recent winter history made this Polar Vortex create rogue vortices.  Not at present though.  If we look at this NOAA animation above,  we clearly see the Canadian PV become much colder at its center, not from Arctic origins,  but self made,  this is yet another frequent recent winters occurrence,  and so in tandem the rest of the US,  particularly Southern US deep froze without the Vortex being blamed,  from what weather broadcasters usually call "Arctic dome... Arctic blast" hovering above them.  600 mb is the pressure level which represents the temperature of the entire atmosphere the most.  It would be very accurate to posit the recent spate of record US cold weather to this circulation stall along with cold weather flow not moving fast: 

2020 same period, center of the single by-continental Polar Vortex was much further North,  favoring a warmer US,  especially NE US coast.  2021 extreme warming of the Arctic is in fact the Climate Change news that never gets heard of,  but this change plays havoc with traditional climate patterns, the smaller North American PV vortex of winter 2020-21 leads to rarely seen but now known results.  WD Feb 18, 2021