Tom Thomson's "Early Spring"

What was Tom’s motivation to “record” this particular observation? Perhaps the colours of the hills and the cloud structure piqued his interest. The natural world is always so very interesting. The weather story behind this particular observation is special! Creative Scene Investigation can unravel the layers of that weather plot and reveal the hidden mystery... Please read on and I will slowly peel the layers back to reveal the truth. 

Early Spring, 1917 
8 7/16 x 10 9/16 in. (21.5 x 26.9 cm)  Thomson's Sketch Box size 
Art Gallery of Ontario

The low horizon on this painting says that this is another skyscape with the clouds and their structure as the main stars of the show. The clouds were painted with sufficient detail to disclose some very interesting meteorology.

Unfortunately, there are no shadows as hints in this painting. That itself is an important clue. Tom must have been painting near midday as otherwise, the shadows would be more likely to be longer and thus more probable to appear in Tom’s art. Either that or what shadows were present had to be trailing away from Tom so that he could not see them.

Another fact to back this up is that there are no yellow or orange hues to the colours in the painting, so Tom was not working either in the early morning or late afternoon. The sun was not in the painting and the colours were strong (not in shade). There was also no evidence of sun glint off the ice or snow. 

The lack of shadows and the strong colours both support the analysis that Tom’s view was northerly near midday with the spring sun on his back.  One can typically start with the premise that the plein air artist is not looking into the blinding sun and progress from there. That clearly appears to be the case with “Early Spring”.

Anatomy of Wind Shear Cloud. 
Vertical wind shear shapes cumulus as well as 
Kelvin-Helmoltz Waves. The patterns drift in
the direction of the dominant wind component.

Now here is where the clouds enter the creative scene investigation. The clouds on the lower horizon are discrete cumulus indicating that daytime heating over the snowpack had been sufficient to create some surface-based buoyant lift. This isolates the painting to midday or later.

The shape of the cumulus also reveals the wind direction. The breeze within the planetary boundary layer had at least a component from right to left. In the accompanying graphics, I have drawn the upstream edge of these cumulus clouds which angle upward. Given that Tom was looking northerly from the earlier discussion, the wind at the cumulus cloud level were easterly and rather strong. The clouds appear quite low within the planetary boundary layer indicating that the air mass was significantly moist as well. Like heat energy, moisture is fuel for clouds and storms. 

The Cumulus Clouds within the Planetary Boundary Layer
reveal the wind direction and much more.

Note the colours of the clouds. These clouds were front lit and brighter in their middle reinforcing the analysis that Tom was looking northward away from the sun. Young growing cumulus clouds are comprised of more and smaller droplets. The large number and small size of those cloud droplets in the young cumulus are very efficient at scattering white light through Mie scattering. Older clouds tend to be greyer as cloud droplets grow with time through riming, coalescence and accretion. The amount of moisture in a cloud is fixed so there are fewer but larger particles in an older cloud. The fewer particles scatter less light and the larger particles scatter this light more in a forward direction away from the sun and in this case, the observer as well. The net result is that the older clouds must appear darker than the more junior cumulus. 

The east wind of the planetary boundary layer can either be generated by a ridge of high pressure retreating to the east or a low-pressure area approaching from the west. The strength of the pressure pattern creating the wind in this weather situation was significant.  In either case, gentle large-scale ascent in the mid and upper atmosphere can be expected. This type of gradual ascent can generate altocumulus clouds in the mid-levels of the atmosphere. It can also generate cirrus at higher elevations but if that cirrostratus cloud existed, it was above the view of the painting. 

Note also that the elements of altocumulus clouds were packed together as spatially economically as possible. This arrangement is the popular “egg carton” fashion. Large areas of gentle ascent can be effectively balanced and separated by small areas of descent. 

Also, note there were no gravity wave patterns superimposed on the egg carton altocumulus clouds. This tells us that although there was a fairly stable layer at the level of the altocumulus, the wind shear and wind were not strong enough to create gravity waves within that cloud deck. The line separating the overhead cloud from the clear blue sky further to the north was a deformation zone. The col in the deformation zone pattern was directly overhead Tom. 

Altocumulus cloud pattern photographed as a comparison 
to what Tom Thomson observed and painted. I was looking 
northward with the sun on my back and a deformation zone
separating moisture to the south from dry air to the north.

The final piece of the puzzle is how these clouds were placed geographically. There was a definite leading edge to the altocumulus. This was the deformation zone identifying the leading edge of the warm conveyor belt associated with the approaching low-pressure area. 

My Thomson friend noted "To me the light looks rather flat, as though the sky above and behind Tom might have been thinly overcast.  Would that have been possible?" The previous science confirms that observation. Not only was it possible but it was likely that the sky over Tom was overcast with cirrostratus. 

Surface-based cumulus clouds in the easterly wind are typically displaced just to the north of this deformation zone. Daytime heating from the sun is required for cumulus development. Surface heating by the sun is reduced or blocked by the altocumulus flooding in on the warm side of the deformation zone. Further north, on the sunny side of the deformation zone, there was sufficient daytime heating to send the buoyant parcels of air aloft from the ground. Those rising moist air parcels turned into cumulus clouds. Note that there were no cumulus clouds over Tom. 

The easterly winds mentioned were the “cold conveyor belt” of the system labelled as the blue "CCB" in the accompanying graphic.  

 

The fact that the cold conveyor belt was revealed by an easterly wind within the earth frame of reference tells another important weather fact.  The approaching storm was either more intense or slower moving than average. The science of this deduction may be found in greater detail in "Weather Lessons for Everyone from the Cold Conveyor Belt Wizard". For completeness, the vector addition required to achieve an easterly surface wind ahead of an approaching system is included in the following graphic. The purple block arrow is the motion of the system with respect to the earth. The blue block arrow is the speed of cold conveyor belt in the atmospheric frame of reference. The green block arrow results from the vector addition of the purple and blue vectors and is the wind as observed within the earth frame of reference. 

Even the vegetation has a story and the forest types also support the above diagnosis. Evergreens tend to be located in lower and more moist environments while deciduous trees take over at higher and drier elevations. The sun cannot shine directly on the northern slopes of hills where the soils stay more moist and are more supportive of evergreen vegetation. These southward-facing slopes seem to confirm the forest habitat preferences with the leafless deciduous trees dominating the higher elevations of the distant hills. 

Early Spring, 1917 

My Thomson friend also noted: "As for the location, I suppose a good guess might be somewhere near Mowat Lodge... The nearer ground is clear of trees, so it could have been logged, or perhaps, if not in the Park, it is farmland somewhere.  There is nothing very distinctive about the shape of the hills.  The lines of blue in the snow on the left side of the sketch possibly suggest a road or a path (with a little imagination)." I quite agree and believe this could be looking northward from just north of Mowat Lodge. I have walked along that road. A good artist does not need to go to the south of France to be inspired - just my opinion of course... 

Summary of the Creative Scene Investigation Results
including two views of the Conveyor Belt Conceptual Model.
A PowerPoint slide from "Tom Thomson Was A Weatherman".

The forecast for the next day was for overcast conditions with a possible variety of precipitation types starting with snow, possibly changing to freezing rain and then maybe changing to rain before switching back to flurries. This all depends on the strength of the low-pressure area but the easterly cold conveyor belt was indicative of a stronger-than-average low.  It is even possible that “After the Sleet Storm” was painted the following day. The catalogue raisonné for Tom Thomson contains some errors in dating and locating his work so such a sequence of events is not impossible. 

These patterns are actually quite common. Here is another such
example that I photographed while I was preparing the
"Tom Thomson Was A Weatherman" book.
These and similar patterns develop with the approach
of every low-pressure area.

The title "Early Spring" was used several times in the catalogue raisonné for Tom Thomson. Plein air painting is indeed best in the spring after a long winter and before the biting bugs emerge. It is an inspiring time to be outside, surrounded by nature as it awakens, armed with a brush in one's hand. As well, Tom's friends were running out of names. Unfortunately, Thomson did not make notes about when, where or why he completed these works. It was certainly a very difficult challenge for his friends to construct the catalogue raisonné after his passing in 1917. If you look closely enough, there are errors and inconsistencies to be discovered within that catalogue. 

I was not there painting with Tom so all of the preceding analysis is based on science and deduction. I could be much more precise if I had some weather observations from the actual day. Tom Thomson was looking northerly near midday with the spring sun on his back and a steady easterly wind blowing on his right cheek. Tom was under the leading edge (deformation zone)  of the warm conveyor belt of a developing weather system. The approaching storm was stronger or slower moving than average. Altocumulus clouds overhead would become overcast while he painted. 

Tom was using the paint box that he had purchased in 1914. He had sometimes thrown that box into the bush out of frustration when he failed to achieve the desired results. His friend and mentor, AY Jackson retrieved that pochade box on at least one occasion and helped to repair it. 

Never give up... paint on Tom! 

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.