Tom Thomson's Snow Pillars in the Sky 1915

 Tom’s motivation to “record” this particular observation was clearly the snow virga and the cloud structure with several lines of nearly parallel cumulus clouds. I suspect that Tom's patron, Dr. James MacCallum rather poetically named this painting as it ended up in his collection without the estate stamp being applied. The good doctor would visit Thomson's Shack, pick out his favourite works and leave behind an appropriate payment of cash - enough to keep Tom painting.

James Metcalfe MacCallum (1860–1943) 
Portrait of Dr. J.M. MacCallum ("A CYNIC")
by  A. Curtis Williamson, 1917

MacCallum died in 1943 leaving his large and terrific art collection to the National Gallery of Canada. He had also wished that his cottage at Go Home Bay would become a permanent setting for painters to stay and create. MacCallum had built his Georgian Bay cottage in 1911 on a fifty-acre sanctuary that he named "West Wind Island". Guess who might have named another sketch that Tom would paint while accompanying MacCallum in 1916? MacCallum had also met Lawren Harris in 1911 while at his new cottage and the rest is history. 

"Difficulties" with leaving the cottage to artists arose and it passed to his estate from which it was wisely purchased by H. R. Jackman and his wife, Mary. The new owners and their families would prove to be excellent stewards of the cottage and the art. 

This weather observation dates from 1915. Snowsqualls are most likely when the first Arctic airmasses flow over the summer-warmed Great Lakes in late autumn. Thomson was at Mowat from late September through to mid-October after which he went to paint on the decorative panels at MacCallum's cottage until deer season opened in early November. Tom was at Huntsville with Winnifred Trainor after that until late November. 

Snow Pillars in the Sky from 1915 oils on wood 21.4 x 26.5 cm
(8.5 x 10.5 inches Tom's Paint Box Panel Size) Bequest of
Dr. J.M. MacCallum (1860-1943), Toronto, 1944,
Accession number 4697

Snowsqualls are very common over the Great Lakes and onshore right through to mid-winter when the lakes start to freeze over. 

There are several pillars of snow virga in the weather image I found to best illustrate the motivation for Tom to make his weather observations. The cloud streets were front-lit with the sun on my back just as it would have been for Tom Thomson as he painted "Snow Pillars". The westerly winds were driving the snowsquall bands from left to right. My view was northerly and I suspect very similar to Tom's although he could have been looking northeasterly depending on the wind direction in the Arctic air and the fetch over the lake. 

In Tom’s painting notice the clouds are brightest on the right side. If the direction of the view is indeed northerly then this painting must have been executed in the morning.  

The other clue is the deep colour of the blue sky which is characteristic of the northern sky. That strong hue of blue probably also caught Tom's eye. Rayleigh scattering of short wavelength blue light by the air molecules back to the eyes of the observer is responsible for this deep blue colour of the sky that must be in a different quadrant than that of the sun.

Mie scattering explains why the snowsquall clouds in Tom’s painting are white. There are billions of cloud particles and light of all colours must be scattered in all directions. Vigorous convective cumulus clouds also contain many, small liquid cloud droplets in their tops that are excellent scatterers of light and are thus very bright. Research has found that these convective cloud tops are typically dominated by the small, supercooled water droplets. As a result, the observer sees all colours which simply add up to white. 

As the particles get larger, a greater percentage of the light is scattered in a forward direction with less light being scattered backward in the direction from whence it originated.  Large particles scatter most of the radiation in a forward direction according to Mie scattering. This partly explains why the snow virga is quite dark.  The few, large particles that typically comprise snow virga, scatter the bulk of the radiation forward (northward in this case) and not back to the artist. However, there are still enough particles to make the virga visible.

As the snow falls, the flakes can either sublimate directly into water vapour or melt into much smaller liquid drops. Both of these processes cause the snow virga to become less of a visible component per volume of air. Water vapour is an invisible gas which would cause the snow virga to simply vanish as it sublimates. Water droplets fall at 5 to 10 metres per second as compared to the much slower snowflakes which fall at about 1 metre per second. Larger raindrops fall even faster. As a result of snowflake melting, the smaller, transparent water droplets would fall faster than the snowflakes and thus occupy a larger vertical volume than the original snowflakes. This melting would cause the snow virga to disappear as well. That is precisely what Tom painted whether it was the result of sublimation or melting. 

PowerPoint slide from "Tom Thomson Was A Weatherman"

In Tom’s painting, there are also some pieces of altocumulus in the blue sky suggesting that there was some mid-level ascent producing that cloud. The altocumulus means that Tom’s snow pillars were a “combination snowsquall event” created by both dynamic, air mass ascent and the convectively unstable, cold airflow over warm water surfaces. The altocumulus clouds could also be part of the "hang back" from the exiting associated low pressure area so the combination event might have been short-lived. Regardless, with Tom looking northerly, the only possible wind direction was westerly directing snowsqualls off Georgian Bay toward Algonquin Park.

Tom would have been located on the north side of the jet stream looking northerly. The strongest and coldest winds are between the retreating low-pressure area and the advancing high as depicted in the conveyor belt conceptual model. The cold front would have been departing to the east when Tom started his painting. As customary, Tom did not bother to sign this weather observation.

The good doctor had an excellent eye for Canadian art. The 1917 portrait of Dr. MacCallum by Williamson has an odd title, "A Cynic".  In the modern definition, such a person believes that people are motivated purely by self-interest rather than acting for honourable or unselfish reasons. That hardly describes the patron who helped to support and guide Tom Thomson and the Group of Seven and then donated his vast collection of art to the people of Canada. Canadian society and culture owe much to the good doctor. 

My Thomson friend pointed me in a more philosophical direction regarding the origin of the "cynics". Indeed, I discovered that Thomson and Thoreau were cynics as am I and probably Dr. MacCallum. Ancient Greek philosophers originated the "cynic" conception of ethics that virtue is a life lived in accord with nature. Nature offers the clearest indication of how to live the good life, which is characterized by reason, self-sufficiency, and freedom. Nature replaces social convention as the standard for judgment. The Cynics believe that it is through nature that one can live well and not through conventional means such as etiquette or religion. I much prefer this cynical definition. Those Greek thinkers knew what they were talking about. 

As with Thomson's art, we will never know the origin of the name "A Cynic" as applied to Williamson's Dr. MacCallum's portrait. As in these blogs, it is important to have an informed opinion and perhaps discover the undocumented intended truth through investigation, science and even nature. 

 Warmest regards and keep your paddle in the water,

Phil Chadwick

PS: For the Blog Version of my Tom Thomson catalogue raisonné, Google Search Naturally Curious "Tom Thomson Was A Weatherman - Summary As of Now" or follow this link “http://philtheforecaster.blogspot.com/2022/10/tom-thomson-was-weatherman-summary-as.html”