Winter's coldest thermal machine, almost bare ground in darkness

~When a thick snow layer becomes a thermal insulator roof for ground heat

~We explore the 2 current Cold Temperature North Poles of the Northern Hemisphere


   Presently there are 2 CTNP's in the Northern Hemisphere both rated almost as cold as each other:

     The nearly pervasive CTNP's of this cold season,  the CAA (Canadian Arctic Archipelago) and Northeast Siberia.  Taken from CMC 700 mb map 22/0000 UTC this winter solstice day.  Have had an early winter link with extensive snow layerings ,  now in darkness this link is broken,   Arctic locations with less of a snow have become the spawners of extreme cold temperatures:

  We know from a previous article (here),  that snow cover may not exactly be pin pointed correctly,  however the Baker Lake Kiwatin area  has a neat center of more bare land,  source Eisbedeckung und Schneehoehe from Wetterzentrale Dec 22 2017 0600 UTC.   Alaska seems to have a lot of snow, a likely reason for why winter is not becoming one massive Arctic block.  We note with interest Alberta which should be prone to massive cooling given that it is a corridor of no snow.  But here just West of the sea of Okhotsk East Siberia Russia has a similar land based snow lacuna.  Both relatively left unperturbed by weather events are great areas to cool the Northern world further in these highly localized geographies with hardly a sun to warm them.  As we have learned, the cooler the CTNP the more "attractive" it becomes to Cyclones.   They become unstable by their strength,  but come back once perturbed by weather  bondings which can't last due to the very nature of dark rapid cooling in these polar zones. WD Dec 22,2017

   
   

T***<= Ts is probably the greatest winter equation

~Extremely simple to express another matter to explain mathematically.

~Down past the skin, snow layers thermal profiles literally change with weather

~ One can estimate sky conditions by the thermal profile of  a snow drift

         Going back to the Horizon refraction discovery of a few years ago:

                                          Tice<=Ts 


              Tice<= Ts,   which has never been disproved optically,  but never been measured physically except from sea ice buoys during the sunless long nights.   The temperature on top of sea ice (including snow)  is always colder of equal to surface temperature,  this discovery,  prompted the question about snow on top of land,  is it the same?


     After many thousand observations with measurements,  T***<= Ts (***= top of snow layer) was very very elusive to measure,  the first problem was sunlight,  some of my readers know ,   sunlight induces a temperature error to all surfaces with a snow layer.  There are no easy,  readily observable  temperature readings with relatively inexpensive instruments.  Temperature stratas in a column of snow  vary with weather,  which is amazing.   On many occasions, optical observations suggested T***=Ts   the top of snow temperature did not confirm so,  when optical observation interpretation  had an obvious inversion,  the snow was warmer than air.   Even in the thick of winter, when everything is more refracted,  snow readings denied what was seen,  in great conflict with horizon sea ice observations.

   Turns out it was the measurement method,  and the crucial understanding which is that snow temperature columns vary in tandem to weather ,  which broke the mystery. 

    What does this mean?

     In particular,  it is the build up formula for winter on planet Earth,    albedo up to 90% renders sunlight heat practically irrelevant,  but winter comes from  a dark world,  where  the sun is forgotten only reminisced by a faint twilight.    It is in this star lit world,  where winter becomes fierce or faint.    If winter starts earlier,  it can only be by pervasive dark moisture rich clouds, which imprints a snow carpet,  nullifying any warming by whatever sunlight gets through.    In the days of anthropogenic enhanced Global Warming,  this frozen moisture should be greater,  therefore more snow should be expected,  as it does happen yearly  more often than not,



"As sea ice shrinks, the Arctic becomes warmer and wetter, study finds8 / 2015 - Present


http://www.adn.com/article/20150809/sea-ice-shrinks-arctic-gets-warmer-and-wetter-study-fi November saw the biggest increases in “skin temperature” (defined as temperature at the Earth’s surface), and air temperature, with an average annual rise of 0.42 degrees Celsius on the surface and 0.32 degrees Celsius in the air, said the study, by Linette Boisvert of the NASA-affiliated Earth System Science Interdisciplinary Center at the University of Maryland."


 except for when major climate event,  such as from ENSO which changes cloud formations.   I recall in the fall of 1998,  a lack of High Arctic snow carpet was ever present:

      EL-Nino creates low stratospheric cloud seeds, which propagate easily throughout the world.  1998 was then the warmest year in history because of an unusualy strong El-Nino,  warmest despite a rapid change to La-Nina within the same year. (as with this October 16 NOAA SST chart) .  The Canadian High Arctic fall in 98 was sunny with hardly any snow on ground as late as early November, with Barrow Strait freezing the latest in 20 years.    ENSO had a long distance impact.  Just like in 2016,   but in 16,  the Arctic fall had more snow because  La-Nina spring trending brutally stopped during summer.   2017 late spring ENSO had an upsurge towards warming,  then now fast trending to La-Nina (with lesser clouds being created worldwide),  therefore less snow on the ground than with autumn 2016 as it is at present.    This late in the year less clouds trending has huge winter implications,  particularly where there is less snow than normal.

     The question is what happens when land areas exceed snow in pure darkness.  The answer is faster cooling tempered by snow cover .   Land surfaces are pretty much like water when it comes to snow or sea ice.    In summer Arctic sea surface water is a near constant in temperature varying quite slowly one day to the next.    In winter, top of permafrost becomes land surface,  a constant which varies at a wider range than surface sea water temperature though,  but varies day to day in similar ways to sea surface.  Depth is key,  in very early winter top of land is very much like open water,  the optical readings suggest warmer land surface than surface temperatures:


                                                                          T *  >Ts   from a sun radiation
                                                     or equality in temperatures morning and evening:

                                                   T * = Ts with low to mid level clouds:
                                                      or         surface cooling at night:  
                                                   T * <  Ts 

            T * is like a snowflake in a wide field,  like a bergy bit in wide open water,  the predominance of land or water is nearly oblivious with scarce presence of snow.    Ts is part and parcel of the air to surface complex, if the surface changes Ts does likewise, a bit of snow on wide land approaches the nature of no snow at all, in darkness or sunshine,  but it can still affect the surface temperature as it can still be measured optically   Then when snow starts to cover the surface more completely , the horizon shifts  to more neutral heights

                                                                          T* * --> = <--  Ts  nearing 50% snow cover tends to make equality in temperatures

          T* * is  near 50 50 area cover snow when  we can literally judge whether the area of snow exceeds land cover or is less than, made more complex  by land temperature differing from top of snow temperature,  if land gains more exposure when warmer than snow,  the horizon drops (the reverse applies).     These small variations are only applicable till cold really sets in especially on top of ground.  When snow carpet approaches 100%,  the optics are all inclined to behave like if snow is the only thing which matters. 

          Then the easiest equation expressing a physical dominance of snow is T*** <= Ts,,  with near or complete snow cover ,  even with sunshine and during Midwinter darkness T***<= Ts,  even during a cooling atmosphere event,  however when low or mid level clouds overcast the sky T***=Ts in all other circumstances T*** is  colder than Ts.


         
                     
 
                       

CAA returns to prime cold spot despite massive prolonged warm advection event

~The return to Cold Center of the Northern world stems from very complex geophysics

~ CAA had short term very warm atmosphere,  remnants of this warming exists but fall as snowflakes.

~Deeply cold but regionally small CTNP's are unstable by the mere presence of  moderate cyclones. 

600 mb temperature charts of November 20-24 December 2- 3 2017,   NOAA daily composites. They depict an astounding warming of the CAA atmosphere peaking on  about November 24.,  note how fast it went from coldest to hardly an existing cold cell.     600 mb temperatures are very close to the Density Weighted  Temperature of the entire troposphere.    Even more fascinating, even when expected,  was the return on December 3 of Canadian Arctic Archipelago  to coldest DWT,  again it is the Cold Temperature North Pole.   How do we explain this?  It is complex because land skin temperatures vary from snow coverage not uniform at all everywhere.  The quick warming of the CAA demonstrated  its canopy of mixed conditions,  with likely not so much snow on the ground,  the top permafrost and snow cover warmed rapidly.  When the Mega blizzard advection event ceased,    it snowed a lot more than previous recent weeks,  this covered the warmed top landscape slowing the cooling.  But cooling did occur nevertheless,  by radiative cooling of top of snow and slowed sublimation,  because of fresh flaky snow fall  relative humidity remained high diminishing  the sublimation rate.  

     But the atmosphere cooled faster aloft,  mainly oblivious to low clouds,  in other words, 

the clouds cut off heat to the upper mid atmosphere,  enabling its rapid cooling.   Which inevitably exacerbated the cloudiness and extra snow precipitation,  by stronger convection of lower warmer atmosphere.  

     Even though the Northern Hemisphere had one coldest cell over Eastern Siberia (November 24) and the warming event was about 10 days long,  the Jet Stream didn't change that much in position,  because 10 days is apparently not enough to cause major Jet Stream deviations causing disruptive weather or Global Circulation changes.

     Now is the time when little covered or bare Arctic lands start the mega-cooling process,  excess snow cover cooled  some Arctic autumn locations,  this insulation carpet now changes roles  to save the Arctic from extreme deeper freezing.     Areas with very little snow cover will now on start to change the nature of CTNP's,  from 2 current strong ones to a third or fourth  smaller ones.    We look for them around the Urals and Alaska.  Meanwhile CAA cooling along with NE Siberia will undulate the Jet Stream worldwide  WD December 6 2017

Remote sensing snow cover appears to be not measured accurately

~ It is perhaps a great technical fundamental flaw which disables accurate long term forecasting

~ New refraction technique suggests that snow on ground behaves exactly as on sea ice which is :
Top of  wide span 100% snow layer T*** is always colder or equal than surface Temperature   
                                                                T***<=Ts
       (A snow layer is not freshly fallen snow,  it is a layer on ground more than several days old) 

~ Taken on a wider Global scale we can identify where the areas with most snow cover lay.

None of these Remote sensing current maps are similar in any great way.   We have N18 (Dec 1) which is NOAA,  the German one Wetterzentrale (Dec 2) and Canadian CMC (Dec 1).     CMC has central Quebec with a lot of Snow,  unlike Wetterzentrale  which has a lot of snow on its Eastern side and NOAA looking completely foreign to the 2 others with more but less significant snow cover in Nunavik (Northern Quebec).    Wetterzentrale has a lot of snow in Russian Urals NOAA doesn't at all.  NOAA has a vast layer of expansive thick snow in North central Siberia unlike Wetterzentrale which has a thick snow carpet in NE Siberia.    CMC has a lot of snow in central or the Alaskan interior  unlike Wetterzentrale more like NOAA.    It is hard to make out CMC's Canadian Arctic Archipelago snow cover because of numerous Glaciers on its Eastern side.    NOAA has Canadian boreal forest tree line gap of less snow unlike the other 2 maps.

Confused?    Just where are the areas with most snow cover?   If we go by a simple gathered by optical refraction rule:

                                                                       T***<=Ts

           It means that all places with important thick cover will be cooler than normal,  because the sun,  although weaker by low elevation,  would warm the ground more if bare, which was heated up by the summer.  So we look for places with cooler temperature anomalies,  given that even with warm or cold air advection,  time will bring out the cooler locations:

       Last 30 days NOAA reanalysis suggests Wetterzentrale  correct for Northeastern Siberia and NOAA incorrect about the snow gap of the Northernmost tree line (there should be more snow not less there).    However there was a huge anomalous advection of warm air throughout the CAA,  as reported on previous article below.   We must go prior to November 22 to get a better picture:

   NOAA temperature anomaly October 22-November 22 .   We can note the CAA appears cooler before the warm air advection,    the cold was indeed in Northeastern Siberia and the Canadian tree line,  suggesting that these lands are laced with thick snow layer.    But there was a normal CAA cooling despite greater open water:

  The tree line bit was not as cold as NE Siberia and the CAA which prior to November 22 was the coldest place on Earth.   There was early snow over much of the CAA which sublimated and gradually diminished in thickness before the Arctic mega blizzard.    In conclusion ,  there is a lot of snow Northeastern Siberia,  but need to confirm the tree line bit.  December 3, 2017

Global Circulation flipped by mega blizzard with no wind directions change for a week at 40 to 50 knots.

~CAA  Cold Temperature North Pole captured a Low otherwise on its way to NW Europe
~The dynamics were similar to  heat machine fueled by the temperatures contrast between  warm and cold, open Oceans and a frozen Arctic scape.

    A remarkable blizzard spanning a great deal of the Northeastern Canadian  Arctic essentially made winds  coming from a rock steady direction for weeks.    Record temperatures warmed all of the Canadian Arctic Archipelago for the same time period,  heat injected from the oceans displaced and weakened and moved the CAA Cold Temperature North Pole,  which had garnished cooling for months,  further to the South and West in a matter of days.   What happened was a matter of weather dynamics which forced two main geophysical opposites,  warm and cold atmospheres in a fused static stalemate:

From 18th to 24 November this CMC 22 November surface analysis is the picture of the blizzard week.  A perfect,  stuck in place,  heat engine with heat from the East open sea waters meeting the coldest air in the Northern world head on.     At first,  the center of cold was  steady strong over the center CAA:

The main dominant cold air zone of the Northern Hemisphere had a weaker twin Northeastern Siberia,  in between  huge strong anticyclone,  which given the right conditions,  can push the strong CAA CTNP  southwestwards.  The arrival of a low pressure centered about Hudson Bay was just what was needed.  And so the biggest pan Canadian Arctic mega blizzard of 2017 happened with a trowal which lasted as long as the Hudson Bay Low persisted.    As  a result ,  record warming reigned throughout the Canadian high Arctic .      This Low didn't move for a week along with static wind directions everywhere. 

     Global weather circulation was thus changed  in a few days,  making Northeastern Siberia coldest atmosphere at present.  But this is changing quickly,  as the CAA permafrost was seriously cooled prior to this warm air advection, which means that the CTNP will soon return to dominate on the Canadian side of the Pole.wd November 25,2017

Winter 2017-2018 is definitely taking shape.

~ New state of the art refraction technique confirms Canadian Archipelago atmosphere set to dominate Global Circulation.

~Each winter is unique,  2017-18 is set to be dry in most parts.  With normal cold and abnormal warming in about equal distributions.

~ The mystery of the warming Russian Northern Urals.

   Elegance in darkness, winter rises from frozen grounds,  left without snow it starts later,  laced with a thick layer it seems to manifest weeks earlier.  The larger question to ask is whether  deeper earlier snow brings the bitter coldest winter.

   If we look at current data,  compare to winter 2016-17,  the answer to that question is a likely NO:

 Air areas marked in brown are Cold Temperature North Poles (CTNP's),  2  of them,   one over the CAA the other hovering NE Siberia.   Winter 2016-2017 main Arctic feature was the extreme North Atlantic snow dump from Atlantic Cyclones heading strait towards Russian Urals.  This meant a greater injection of moisture  towards Northern Greenland and central CAA (Canadian Arctic Archipelago).   As a result there was a double the normal layering snow carpet.  This prompted an earlier onset of CAA winter,  but over the long run reduced ground surface cooling.

 Current state of the art land refraction observations tend to agree that the beginning of winter 2017-18 is substantially colder over the CAA because of the relation of earlier more snow on ground blocking the heat which would come from a warmed by summer permafrost :

   Early 2017-18 winter has a major circulation change which affects most of the Northern Hemisphere weather.     The CTNP cells have switched roles ,  CAA being colder and bigger than 2016-17.  This is of great interest.   Western North America has cooled,  while Eastern North America has baked to the delight of extended summer lovers.

      As a result,  places like Ottawa Canada,  New England USA,  England UK  and NW Europe
felt the full blast from Gulf of Mexico and South Atlantic heat.

   Temperature anomaly map of NASA GISS  describes beginning of winter 2017-2018  quite well,  the heat injection to Arctic in 2016-17 has slowed,  it is still warmer, but nothing like 2016-2017:

 October 2016-17.   Here we see the effect of the CTNP cells  with a different morphology.   The heat injection towards Northern Central Russia has basically vanished because it was mostly spent feeding the Arctic heat wave.

     So the location or lack thereof of snow on the ground literally steers the Global Circulation.  But that is not a constant relation,  if snow cover starts really early in autumn,  this will generate a cold temperature zone,  the center where warm air gravitates.  If the snowfall stops for a long while,  warmed by summer permafrost will be exposed and this warming source will dull's winter's might.   It may sound off,  but snow sublimates and compacts for the greater part of the long Arctic night world.    If not replenished,  mid winter would warm for a while then the ground frozen hard by exposure with radiation to space would be a source of devastating cold air.   If there is greater snow cap on ground instead,   winter would appear brutal early but much warmer at end,  because the ground didn't loose so much heat,  and would help melt light reflective snow earlier.   A very much similar thing happens on sea ice,  but more radical,  a thicker snow layer on sea ice would make it thinner till sunrise from long night,  compelling melting even faster come late spring.

     At present,  2017-18 seems to tend going towards a very warm Euro-Asian Arctic winter, 
while CAA is coldest,  we observe if the cut off of snow supplied from the North Atlantic by way of the the North Pole continues,  if so,  permafrost will freeze hard,  sea  ice will thicken more,  a very cold CAA CTNP will dominate weather as is for quite some time in the foreseeable future.    Meaning the October 2017 NASA GISS anomaly map may twin or thrice repeat for November and December 2017.  WD November 17, 2017


 

New World Order in global atmospheric circulation is taking shape.

~The post 1998 period has a definite simple Global Circulation footprint
~Hurricane track Northeastwards  shift is understood by it. 

   Current autumn 2017 dominant circulation has 2 cold cells,  one NE Siberia,  the other usually strongest coldest Arctic Archipelago -Greenland zone.   This is what dictates a great deal of your weather if you live in the Northern Hemisphere.  In Novembers past ,  the look was different,  with the colder zones much vaster.  In response 2017 autumn was extremely warm for the largest part of North American NE coast and well further inland.  The larger question is whether these cells will remain largely similar for upcoming months. 

     The answer lies in whether we can accurately measure snow cover or not.  Current cold zones were largely built from seasonal snowfall. 

Snow is a widely misunderstood white matter, the coldest zones have naturally more snow on the ground because temperatures are almost always below 0 C. But it does not mean that where snow lies the coldest atmosphere can be.   A snow layer on top of a warmed up by summer permafrost, means that the permafrost doesn't loose so much energy to space. A closer look at the Canadian archipelago reveals far less snow on the ground than Siberia, the Archipelago always had open sea water, yet the weighted temperature of the troposphere is consistently coldest over the CAA (Canadian Arctic Archipelago).    But snowfall has largely stopped,  sublimation and compaction 

has rendered its initial snow cover thinner,  exposing the ground further during darkness only to consolidate the cooling further.

    The perfect coldest Northern Hemisphere winter would start with extensive early snowfall in autumn, then none at all for the long Arctic night followed by extensive snow precipitation April onwards. So far 2017 is following that pattern in the CAA. 

     A curious pattern shift was discovered as cited by PBS 2017 NOVA's killer hurricanes broadcast, the hurricanes use to crash consistently straight Eastwards into middle mesoamerica, now their end tracks tend to have shifted towards the Northeast. A plausible explanation would come from the Global Circulation as cited above. The remainder of the coldest 

atmosphere survives in summers in the CAA-Greenland region. This is due to great sea ice melts, much more frequent than not in the last 2 decades. Only Greenland and CAA glaciers complement the remainding dwindling September Arctic Ocean sea ice. This solidifies the center of Global Circulation to CAA-Greenland in summer and fall, the flow on NE America's coast has now been intensified, dragging everything found within,  warmer weather, Cyclones or hurricanes to move likewise. WD November 5, 2017.   

New signal of a warming Arctic Ocean: the Green flash green sea

~Never observed literal greening of the NW passage
~The likely cause was a much warmer top of sea opposing a quick refreeze caused by light winds...

    30 Years ago Arctic top of sea refreezes,  particularly here,  75 North 94.5 West,  were often in early September,   at the first chance of light winds,  then after October was bitterly colder,  fostering the onset of winter to last till June.  During these older days, the boating season was about 3 to 8 weeks long,  since on shore fast ice came so early  and the sea ice broke up as late as August.  Now this season is almost always more than 16 weeks.

    Freeze-up 2017 was no different than any other except it came late,  a feature of the post 1998 sea ice period.  Grey ice comes almost always when there is a calming of winds during clear air events.
There is yearly one natural cloudy season for the High Arctic from Mid April to Mid September,   this season has changed recently,  it comes often mid April  as usual,  but became more intense,  with heavier precipitation for months.  Post 1998,  this cloudy season stretched often till end of October,  making freeze-up much more difficult,  another component is the -11 degrees C mark,  which is the most observed temperature which causes grey ice.  Although sea ice freezes at -1.8 C,  it takes much colder air temperatures to counter balance the net thermal top of sea state not at all at its freezing point.  If there is a warming of sea water it does not mean that freeze-up will always come later, it is a matter of the right circumstances.

      With right conditions:  clear skies, calm seas, temperature nearing -11 C;   freezing may occur.  So it was  September 19 2017,   the winds were quite slow less than 5 knots,  the sky was clear (an unusual autumnal feature),   some freezing started:

      Never seen before "green flash green" sea,  a refraction effect not entirely understood.    Definitely new,  the green may be a mix between horizon sky and the natural sea water blue we usually observe at all sunsets. 

    Past blue seas at sunset examples abound,  I picked a few:

    Practically all open water sea sunsets are dark blue (grey when cloudy),  even with exact 2017 conditions.   The orange horizon of 2012 is identical to 2017,  yet with dark blue seas.

   September 19 2017 sunset occurred mid air,  signifying thermal inversions,  note the lack of reflection of direct sunlight over the sea, there is a band of thermal layers,  called ducts,  intensely stable temperature wise.  This is done with clear air, light winds and in this case,  the fresh formation of a very thin layer of sea ice.  Right above the newly formed ice the air was automatically colder,  higher up near surface air was warned by sea water before the ice showed up.   Latent heat of fusion also released some heat which ascended higher by buoyancy,

   But this new very thin ice did not last,  temperatures warmed to the -3 to -5 C range on September 20 and 21, come the 22nd.  All new sea ice was gone.   Again,  worth to note that sea ice may melt with surface temperatures above -11 C, 

   This  "green flash green" ocean was a never seen before event,  it showed up roughly 40 minutes after the blue ocean with the sun above the horizon at about 5 degrees C elevation  (first blue sea horizon picture).   With the lower sun,  the orange horizon came about, implying very clean air conditions.  The distant ship seen in dark shade hues was captured upright,  but betrays the very complex layering just below.   One of which demonstrated a Wegener blank strip,  a relatively rare optical event,  implying a steep thermal inversion,  a blank strip is an optical construct consisting of a very long thermal duct,  very distant having no light from above or under which can penetrate it,  therefore the darkened layer black impression you can particularly see in the un-zoomed picture with the green sea.

   Implications:

     The 'never seen before' aspect of this event,   is a major discovery,  the reasons for the greening of the sea horizon,  needs to be modeled,  in other words , replicated by computer animations.  Historical GRIB data should also have steep inversions above the sea surface below 46 meters ASL. 

     This is a splendid example of atmospheric optics readily available to verify state of the art atmospheric computer models.  If the models do not have inversions below 46 ASL,  they need be improved.  WD October 24 2017.   

    

What was Hurricane Maria pushes the jet stream North, take 2

~ A very fascinating feature of post hurricane cyclones was captured again.

2016 Hurricane Nicole turned extra tropical Cyclone peculiar feature  (explained here),  may seem ancient or distant,  given the comparatively busy 2017 season.  But there were much fewer hurricanes over a longer period,  from 2006 to 2015,  despite much warmer oceans,  in fact the conclusion that there would be less frequent but more powerful hurricanes was correct (Emmanuel),   not like Typhoons,  which are storms from a different huge Pacific Ocean playing field. 

Note the regular feature of Jet stream (drawn green)  on this CMC Oct 7, 2017 1800 UTC surface analysis chart.   It contours the Southern part of Cyclones,  this is a normal for the Polar jet stream ,  except for where a peculiar  Cyclone  near south east Greenland (ex hurricane Maria) seems to push the jet to the Northwards,  the jet contours the Cyclone very unusually.  It seems being more like an anticyclone .WD Oct7, 2017

The Very good work of MIT's Professor Kerry Emmanuel

~ "A-new-study-says-hurricanes-will-get-stronger-and-more-frequent-thanks-to-climate-change"

~  Contrary to fringe media gossipers bent on lying and ignorance,  science at times can be prophetic;

less frequent but very strong  hurricanes are at play.  As published in a journal many years ago (since at least 2005).  

2005 full season 

First system formed 

June 8, 2005 

Last system dissipated 

January 6, 2006

(record latest, tied with 1954) 

Strongest storm Name 

Wilma (Most intense hurricane in the Atlantic basin) 

• Maximum winds 

185 mph (295 km/h)

(1-minute sustained) 

• Lowest pressure 

882 mbar (hPa; 26.05 inHg) 

Seasonal statistics 

Total depressions 

31 (record high) 

Total storms 

28 (record high) 

Hurricanes 

15 (record high) 

Major hurricanes (Cat. 3+) 

7 (record high, tied with 1961) 

Total fatalities 

3,913 total 

Total damage 

$158.9 billion (2005 USD)

(Costliest tropical cyclone season on record) 

2017 partial season 

First system formed 

April 19, 2017 

Last system dissipated 

Season ongoing 

Strongest storm Name 

Irma

• Maximum winds 

185 mph (295 km/h) (1-minute sustained) 

• Lowest pressure 

914 mbar (hPa; 26.99 inHg) 

Seasonal statistics 

Total depressions 

12 

Total storms 

11 

Hurricanes 

6 

Major hurricanes (Cat. 3+) 

3

Total fatalities 

91 total 

Total damage 

> $70 billion (2017 USD)

     The past 12 years were not exactly busy ones for hurricanes,  quite unlike typhoons.  

the South Atlantic has its own weather factors going,  namely its smaller size than the Pacific, ENSO influence and the effects of dust from the Sahara desert.  The latter was observed in late July falling over South Texas.   Perhaps the Saharan dust plume relinquished in later August letting the hurricanes form without dust impediments:

   March 2017 Saharan dust plume North Africa is seen to the upper right.  It makes a great deal of sense that dust may simply inhibit hurricane development,  also likely a warmer planet, in turn Sahara,  will diminish the number of hurricanes forming.  Hence the likely further warming  of "uncooled" South Atlantic sea water,  as it is known,  that hurricanes mix the underlying lower cooler layer of sea water with the very warm surface sea under its path.   The further warmed more stable  sea water may give incredibly stronger hurricanes whenever the conditions are ripe.  

    The good news ,  certainly needed,  is that the last Arctic cell of massively cold air exists at this time in the Greenland-Ellesmere-Devon-North Baffin region, is as strong as can be according to current High Arctic vertical sun disk measurements,  quite compressed, similar to March even though the density weighted temperatures are 10 degrees warmer.  The mid to higher upper atmosphere is much cooler because there is less clouds than over the rest of the Arctic.   This cooling positions the jet stream and or circulation directly further South towards where the hurricanes are.   This is a better scenario than what happened with Harvey in Texas. WD September 7, 2017