Tom Thomson's Stormy Sky Summer 1915

 Following a pattern established the previous year, Thomson headed to Algonquin Park in the spring of 1915. He arrived in mid-March and except for a guiding job between April 28th and May 19th Tom was pretty much on his own. Recall that Lassen Peak in north central California erupted on  May 22nd of that year. The volcanic sulphur dioxide and ash would colour the sky and strongly influence Tom's panels in late May. This was the stage when "Stormy Sky Summer" was painted. 

Stormy Sky Summer 1915
Oil on cardboard 8 7/16 x 10 1/2 in. (21.5 x 26.7 cm)
Tom's paint box size. 1915.68

As noted, I try to focus on the science and leave the dating to the official  Thomson catalogue raisonné.  In this case, the terrain of the northern basin of Canoe Lake was readily identifiable. Thomson preferred to spend his time painting rather than travel far to locations. This view was from just in front of  Mowat Lodge. Tom was looking east toward Hayhurst Point and the far shore of Canoe Lake. 

Now for the science. This is another skyscape with a very low horizon on the panel. The lifted condensation level of the atmosphere and the base of the prominent towering cumulus are closer to the lower line of the "Rule of Thirds" often employed to artistically balance compositions. The following graphic describes the details that Tom included in his brush strokes. 

The clouds were back-lit and darker in their optically thick central masses. The clouds were brighter on their right flanks which confirmed the easterly direction of view during the mid-morning hours of that spring day. The faint reddish tint to the clouds was the result of Rayleigh scattering of the blue component out of the sunlight during a long path through the atmospheric molecules. The sun was not yet very high in the sky. 

The red lines enclosing the billowing bubbles of ascending air are displayed using finer lines as the convection recedes upward and further to the east. The west winds at the level of the towering cumulus are dramatically different from the southerlies revealed by the low-level turbulent stratocumulus. This is the classic situation of a split cold front where the upper-level front surges ahead of the surface cold front. The following graphic explains the science visually. 

The towering cumulus clouds in the above graphic (white clouds encased in red lines just behind the upper cold front) tip forward and occur in the region between the upper and the surface cold fronts. A "croquet hoop" of rotation encloses the descending dry conveyor belt. The towering cumulus clouds are preferentially located in advance of the cyclonic companion of the dry conveyor belt - identified by the red, swirled arrow above. Using your Coriolis Hand, one can follow the sense of the rotation through the croquet hoop and the orientation of the thumb indicates whether the air is likely to be ascending or descending. Your thumb would point upward at the red swirl and the ascending air would encourage the towering cumulus clouds.  

The following graphic locates Tom within the conveyor belt conceptual model of the weather pattern. The morning sun was rising in the eastern sky. Given the overcast altostratus cloud, daytime heating was not a factor in fueling the vigorous towering cumulus. Some other meteorological forcing had to be in effect and that was the split cold front. 

A close-up view of Tom's location just ahead of the surface cold front is included below. 

Typically vigorous towering cumulus convection as Tom painted is witnessed in summer and that might explain the title assigned to this painting. As explained, such convection can also result from a split cold front that places dry and cooler air above a warm and moist low-level atmosphere. That was the situation that Tom described with his brush strokes. Given the lack of any hint of green in the back-lit forested landscape, I would also suggest that spring before the emergence of the biting insects was a more likely time for this plein air observation. Tom preferred to spend his summers fishing. 

Tom Thomson's "Stormy Sky Summer"
as it would have appeared in his
home-made sketch box. 

Based on Tom's painting, the forecast for Mowat Lodge was clearing and cooler with dry, strong and gusting westerly winds. 

Inscription recto: 

• l.r., estate stamp 

Inscription verso: 

• c. and l.l., estate stamp (stamped twice);
• c., in graphite, 1914 National Gallery of Canada, Ottawa (1521)

Provenance:

• Estate of the artist
• National Gallery of Canada, Ottawa (1521). Purchased 1918

And that is the story of Tom Thomson's "Stormy Sky Summer".  Tom was careful to accurately record the cloud types and their specific shapes. Those facts are all that one needs to deduce the meteorology of the day from which so much more might be discovered. 

This post and most of those that follow were never included in the "Tom Thomson Was A Weatherman" presentations. The live presentation included paintings that were more exciting like thunderstorms, tornadoes and falling trees. Somehow, split cold fronts and isentropic surfaces did not make the cut - although I find them riveting!

Warmest regards and keep your paddle in the water,

Phil Chadwick

PS: Tom Thomson Was A Weatherman - Summary As of Now contains all of the entries to date. 

PSS: Should you wish to have Creative Scene Investigation applied to one of Thomson's works that I have not yet included in this Blog, please let me know. It may already be completed but not yet posted. In any event, I will move your request to the top of the list. If you made it this far, thanks for reading! There is a lot of science in this small panel and I wanted to cover most of it...