Tom Thomson's "Spring" 1917

I have always admired this classic Thomson weather observation. It is characteristic of Tom's work as it quietly and accurately depicts everyday weather - spoiler alert, it is a warm frontal surface. It apparently struck a chord with another of my favourite artists, Lawren Harris.

In the spring of 1918 almost a year after the sudden passing of their friend, Lawren Harris and J.E.H. MacDonald met in the Studio Building. Tom's paintings from the Shack had been stacked in the Studio Building where he had painted with A.Y. Jackson, sharing Studio 1. Tom's tenure in the Studio Building ran from January 1914 to December 1915. The time spent painting in "The Shack" was more creative and was where Tom really shone. A lot of panels were moved from the Shack into the Studio Building.

Harris and MacDonald planned to sort through Tom's art, make comments on the back and distribute what they felt were the best examples of his genius. The ultimate goal was to ensure that Tom was acknowledged for his brilliance. It was a daunting task to shift through that pile of panels. It explains why so much was left unnoticed and unexplained. I must admit that I never wish to empower others with so much authority over my art but after death. That also discloses why my catalogue raisonné is so very complete in sharp contrast to the lack of detail in Tom's. I prefer to have the definitive voice on what I was trying to say and why. 

Spring 1917
Oil on wood panel 8 1/2 x 10 1/2 in. (21.6 x 26.7 cm)
Tom's Paint Box Size

Harris wrote "Save for Lawren Harris" on the back of this sketch. Apparently, Lawren saw something special in this weather observation as well. 

Tom's attention was always focused on the weather. Tom Thomson wrote to Dr. MacCallum on May 8th, 1917 that "the weather has been fine and warm". In Tom's last letter to MacCallum on July 7th, Tom complained that the weather "has been wet and cold all spring". As a true Canadian, Tom liked to talk about the weather but he painted it as well. This is the story of "Spring 1917" which was hidden in plain view with the deft strokes of Thomson's brush. 

Explanation of the Orange Sunrise and Red Sunset
Illumination Resulting from Diurnal Variations in
Atmospheric Particulates. 

Initially, one might scratch their head. Dawn was mentioned as the timing for this sketch. If only Tom had left a clue or two, that would have been helpful. The colour of the illumination was not strongly skewed to either the orange hues of sunrise or the reds of sunset. If anything, the clouds divulge a slight yellow tint so the timing of this sketch is likely early morning but not at the stroke of dawn. The "Belt of Venus" (see Tom Thomson's “A Northern Lake" Was the Belt of Venus Sunrise) was not evident as a result of the cloud cover. 

A narrow window in time and space allows the early morning sun 
to illuminate the scene before rising too high and thus becoming
blocked by the approaching and thickening cloud cover.
Note that I included the gravity waves of the wind waves and
the swells within the graphic deck of clouds.
Both are explained in more detail below. 

The distant hills were not yet illuminated so the sun was still rising but had not risen as high as the clouds. Later in the morning, the higher sun would be obscured by the thickening cloud deck. Tom had to be looking westerly early in the morning. 

The seasonal timing of spring is a certainty knowing where Tom was and what he was doing before the biting bugs emerged on May 24th, 1917. The leaves had not yet emerged and the landscape portion which was restricted to less than the lowest third of this panel was rather dark and drab. The front-lit colours of spring were not colourful as can be expected after a long winter. The birches alone revealed that the sunlight had to be on Tom's back. 

Tom was excited by the clouds and they were certainly the heroes of his scene. The altocumulus clouds were classic. If you hold your outstretched hand overhead, the convective elements of the altocumulus can be covered neatly by your thumb. This aptly named "rule of thumb" simply gauges how high (how far away) those cumulus elements are since convective bubbles are all about the same size in nature. The viewing distance is the only thing that changes the apparent scale of the convective elements. One can see that the overhead cumulus elements in Tom's painting are larger than those lower on the horizon. Tom accurately painted what he saw. 

Weather systems are swirls in the atmospheric ocean just like
 the swirls created by the stroke of the paddle in duckweed.
Tom was located at the gold star looking westward
(to the left in the above graphic). 

Cumuliform cloud shields are typical of an approaching warm conveyor belt during the convective seasons of the year (all seasons except winter). The conveyor belt conceptual model of mid-latitude weather systems is one that I have taught for several decades now. I keep trying to refine those methods and spread the joy of understanding the weather in terms of simple science. I do not give up easily.

The gravity waves superimposed on the altocumulus cloud elements reveal that the wind direction within that cloud deck was westerly. The waves on a lake respond to the wind in the very same way. The wavelength and amplitude of those gravity waves both increase with the wind speed. I used to teach the numerical correlation between the wind speed and the gravity cloud wavelength but I doubt if anyone does that anymore. 

Wave patterns are much easier to identify with backlit lighting. The alternating bands of light and dark clouds really stand out. The dark corresponds to thicker clouds associated with the updraft in the wave crest. The light bands identify thinner clouds with the downdraft flow of the wave trough. 

Dashed purple lines linking cumulus elements of roughly the
same size and brightness in an attempt to trace the updraft
region of the wind-induced gravity waves.

Front-lit gravity waves like those found in "Spring 1917" are much more challenging. The thicker cloud is brighter but marginally so compared to the thin cloud. Mie scattering of light from large particles throws most of the energy forward and away from the observer. Less energy returned to the observer through Mie scattering minimizes the contrast between thick and thin bands of the gravity wave clouds. If one links the adjacent, brighter altocumulus cloud elements, you can trace the wind wave crest and know that the wind in the atmospheric frame of reference must be perpendicular to that. 

Blue lines along the wave crests of longer wavelength
swells within the atmospheric ocean. 

A highlight of this sketch for me was noticing that there was another cyclic colour interval within Tom's sky. The darker purple/blue lines also appear at regular intervals. If one squints their eyes, this obvious wavelength becomes readily apparent and is unmasked from the details that Tom also recorded. These are gravity wave swells that have propagated great distances from where the atmospheric winds were stronger. The swell waves carry the characteristics of the source area where they were generated. These long wavelength waves were described in  "Wind Waves and Swells and Lines in the Sky" as well as in several other blog posts.

The wave pattern in the cloud is obvious but how can they be deciphered? The accompanying graphic attempts to illustrate small amplitude and short wavelength wind-driven waves superimposed on the larger amplitude and longer wavelength swells within the atmospheric ocean. The lifted condensation level for the air mass is described as Option 5 in the graphic so there is cloud everywhere even at the trough of the wind wave within the trough of the swell.  

The orientation of the swells compared to that of the wind waves must reveal the portion of the warm conveyor belt that was approaching Thomson. This in turn must reveal the progression of weather to expect. Using this bit of science was how I estimated Tom to be located at the gold star relative to the warm conveyor belt in the accompanying graphic as well as the above graphic - between the anticyclonic and cyclonic companions of the warm conveyor belt. 

The reality is that if you paint what you see, the science must always be correct. Tom was painting the bottom of the elevated warm frontal surface. If we estimate the height of that cloud above Tom and apply the standard slope of a warm frontal surface as being 200:1, Tom could have estimated how far to the southwest the surface warm front might have been. Most people do not care but Tom probably did. Those altocumulus clouds were probably nearly 12 thousand feet above Tom... the math is straightforward. That number of feet above the ground was about 2 miles so the surface warm front was approximately 2 times 200 or 400 miles away. By the way, please let me apologize for my reckless use of measures ranging from Metric to British to the size of your thumb - it reflects how I see the world.  

Spring 1917
Oil on wood panel 8 1/2 x 10 1/2 in. (21.6 x 26.7 cm)
Tom's Paint Box Size  

So the story behind "Spring" actually is more interesting than just a cloudy sky. Lawren obviously appreciated that story as well. 

Inscription verso (on the back): in graphite, This sketch was painted / in the spring of Thomson's drowning / J. MacCallum; in graphite, J + H (circled); in graphite, No. 3 Mrs. Harkness; in red, 21; in black paint, S.B.; in L. Harris's handwriting, under label, Save for (crossed out) lawren Harris (circled) Art Gallery of Ontario, Toronto (855). The back of this panel would be interesting to see! Lawren was overruled but by who? The inscriptions on the back of the panel might provide the answer to that mystery but it is a bit cryptic and one cannot be certain.

"Spring 1917" as it would have appeared in
Tom Thomson's paint box

Many panels by Tom Thomson bear the name "Spring 1917" or very similar variations. It was the most prolific period of his career. The provenance of this painting surprisingly does not include Lawren Harris. The painting went from the "Estate of the Artist" to Elizabeth, Tom Thomson’s eldest sister. Recall that Elizabeth's husband was Thomas “Tom” J. Harkness who was appointed by the Thomson family to look after the affairs of Tom’s estate. From Elizabeth, aka "Mrs. Harkness", the painting went to the Art Gallery of Ontario, Toronto (855), a Gift from the Reuben and Kate Leonard Canadian Fund, 1927. 

The story behind a painting can be as interesting as the art itself. 

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. 

Tom Thomson's "Cold Spring in Algonquin Park" 1917

Tom often did not need to travel very far before inspiration struck. I suspect that his view is from the front yard of the Mowat Lodge in the spring of 1917. The biting bugs emerged on the May 2- 4 weekend of that year. One can be certain that Tom stopped plein air painting then. 

Cold Spring in Algonquin Park Spring 1917
Oil on wood panel 8 1/2 x 10 1/2 in. (21.6 x 26.7 cm)
Tom's Paint Box Size 

The horizon is below the midpoint of this paint box panel. Tom was painting looking easterly in the mid-afternoon hours. The sun would have felt wonderful on his right shoulder. The mild southerly breezes would have made it a perfect time to be outside, enjoying life after a long winter in Toronto. But how do we know this? Please let me explain. 

The cumulus clouds were front-lit by the afternoon sun. Cumulus clouds of this size take some time to develop under the weaker illumination of the spring sun suggesting that the afternoon timing for the painting is accurate. The upwind flanks of these cumuli of various sizes were all angled upward and to the left. The geometry of the scene as depicted below only allows one orientation. The elongated north-south orientation of Canoe Lake favours wind directions along that axis. In this case, the winds had to be southerly. This analysis is supported by the drifting ice accumulating on the north-western shore of the lake. 

The bases of the cumulus clouds are not rigidly flat indicating that turbulent mixing with gusty winds also played an important role in lifting moist parcels of air from the ground up to the lifted condensation level of the air mass. There was probably abundant moisture on the ground given the precipitation that must have fallen with the passage of the warm front. 

The geometry of the painting including my
water-marked Canoe Lake Map on the right. 

The blue sky poking through the holes between the cumulus clouds allows some refinement in the story. The warm conveyor belt is often cloud-free far south of the warm front. Overcast layers of cloud can be expected ahead of the warm front. The lift required to produce such cloud layers is often missing further to the south within the warm sector of the storm. The absence of clouds suggests that the warm front of the conveyor belt conceptual model, was far to the north when Tom started to paint. The cold front had not yet arrived and could be minutes or hours to the west. Tom was enjoying the opportunity to paint within the storm's warm sector. 

The presence of ice chunks on the lawn in front of Mowat Lodge suggests that this was a rather large and slow-moving spring storm.  Those ice pieces could have been pushed onshore by strong easterly winds which are not typical given the shape and north-south orientation of Canoe Lake. The cold conveyor belt that would have been required to create such strong winds given the limited fetch, must have been strong. As a result, 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". Those easterly winds within the earth-frame of reference pushed those chunks of ice to the western shore of Canoe Lake. The southerly winds in the warm sector of the storm then started to shove the ice along the shore and up into Potter Creek for Tom to observe and paint. 

But there is more.. and thank you to my Thomson friend for encouraging the inclusion of some more science. I quite agree with the suggestion that the dark blue streak in the middle left was the ice-free current and outflow from Potter Creek. This fact points to another discovery that the rest of the surface of the lake that Tom painted had to be a layer of mushy ice, saturated with water - the kind of ice that you are guaranteed to fall through. The colour Tom used to depict that slushy surface was enough to deduce what was obvious at the time.  But also consider that if it was so windy as revealed by the clouds, why then were there no waves on the lake? The answer must be that, unlike the fast, open water of Potter Creek, Canoe Lake was ice covered! 

That slushy surface was still near freezing and had not warmed to that critical temperature of about plus 4 °C (39.2 °F) when water is most dense and actually sinks to the depths. Oxygen and nutrient-rich surface water sinks and is replaced by warmer water from below. The lake water flips and mixes and has a great positive impact on nature. The ice can vanish in a matter of hours during the flip. 

The strong southerly winds and the push from the ice pack are the forces that will shove that slushy ice up along the sloped shore. Water drains from the slush when it is heaped above the water line. The remaining crystals are actually quite reflective, bright and white - like diamonds. In fact, we observe this sequence of events every spring when the ice transforms and vanishes from Singleton Lake - signalling that the male loon would soon return and it was time to launch the nesting platform. 

Tom certainly knew what he was recording for prosperity when he stood on the lawn of Mowat Lodge! Spring was on the way. The buds were starting to swell on the saplings in the foreground.  Tom was revelling with the indications that spring had finally arrived. One can almost hear the arrival of the spring birds along with the warm conveyor belt of the storm.

The title assigned to this painting is a bit misleading as this particular day would have been relatively mild. The previous day would have been windy and chilly under the spell of the cold conveyor belt. This pleasant turn in the weather explains why Tom was painting en plein air after being confined to the interior of Mowat Lodge where he sometimes painted in the dining room.  Given the strength of the conveyor belt pattern, there could have still been a taste of winter to be delivered behind the approaching cold front and let's assume that justifies the name of the painting. 

Creative Scene Investigation really benefits from being able to visualize the weather in time and space. The process is like playing a movie in your mind and something that I have always daydreamt about especially when I was a Severe Weather Meteorologist. I could envision the forecast in my mind's eye.

"Cold Spring in Algonquin Park Spring 1917"
as it would have appeared in
Tom Thomson's paint box

The back of the panel has an inscription in ink: "Sketch by Tom Thomson / -1917- Consolidated Bathurst, Montreal".  I wonder what the back of the painting actually looks like? A picture can be worth a thousand words and a description of the annotations often just confuses me and probably others as well. 

The lower right on the front of the painting bears the inscription "TT". There is no indication of who put that mark there but that dark smudge on the lawn was unlikely to be the work of Tom. The front of the painting needs to remain the special domain of the artist. 

If I am permitted to guess, I suspect that the "TT" was added by J.E.H. MacDonald in the spring of 1918 when he and Lawren Harris met in the Studio Building. Tom's paintings from the Shack had been stacked in the Studio Building. Harris and MacDonald planned to sort through Tom's art, make comments on the back and distribute what they felt were the best examples of his genius. MacDonald might have been experimenting with how best to identify and authenticate a Thomson painting. MacDonald designed the Estate Stamp that was later used to distinguish Thomson's unsigned art. The stylized "TT" inscribed on "Cold Spring in Algonquin Park Spring 1917" bears a remarkable resemblance to the design of the Estate Stamp. 

The Tom Thomson Estate Stamp designed
by J.E.H. MacDonald and bequeathed to the
National Gallery of Canada by Dr. James MacCallum in 1944

You might notice that I use "front" and "back" to describe the faces of my art. The front is the pictorial brushwork story told in tones, shapes and pigments. I typically sign my name inconspicuously in the lower right. I have been using toothpicks and nails to scratch my name in the wet oils and I dot the "i" with red. The back of the painting is where I record the name of the work and some of the story behind its creation along with my complete signature. Simple yet complete with no ambiguity.

"Front" and "back" are really simple terms using English, the language of science around the globe and the "new Latin". I was always impressed during my travels with COMET and NOMEK how meteorologists could flip to English during presentations and I wished that I could speak Swedish, Finnish, Icelandic and a host of other languages, especially outside the classroom. I took math and physics in High School and unfortunately, there was no time for the Latin class in that schedule. I can still very much appreciate how and why art curators prefer to use the more cryptic "recto" and "verso" borrowed from Latin. The front or face of a single sheet of paper or the right-hand page of an open book is called the recto. The back or underside of a single sheet of paper or the left-hand page of an open book is known as the verso. 

Cold Spring in Algonquin Park Spring 1917
Oil on wood panel 8 1/2 x 10 1/2 in. (21.6 x 26.7 cm)
Tom's Paint Box Size 

But I digress... This painting did indeed go to Elizabeth, Tom Thomson’s eldest sister upon his passing. Elizabeth's husband was Thomas “Tom” J. Harkness who was appointed by the Thomson family to look after the affairs of Tom’s estate. T. J. and Elizabeth lived in Annan, Ontario, just east of Owen Sound. The painting was then passed to Gardner Thomson and then into a private collection in Toronto. That collector passed the painting on to Consolidated Bathurst of Montreal and that is where it can possibly be viewed but only by the privileged few. 

I include a photo of the back of each painting in my catalogue raisonné. There is nothing hidden or cryptic in the details written on the back of each painting. Sometimes I record the key elements of the story behind the painting. Often I include some weather details if I feel that they are important. I have even scraped some paint from my palette as a temporary cache left on the stretcher bars just in case I might need it. The information about where the paintings go is also included with the story of each. Of course, that information can only be completed up to the current time. All of these details are also included in a numbered and chronological web page which is the modern version of the "recipe cards" that I used when I started oils in 1967. Technology can be a good thing. 

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. 

Tom Thomson's "Woods in Winter" 1917

Sometimes the Creative Scene Investigative (CSI) solution is as simple as sketching some lines on a piece of paper and thinking about the obvious facts recorded in the painting. Tom Thomson's "Woods in Winter" painted in the early spring of 1917 is just such an observation of nature. 

Thomson arrived at Mowat Lodge in early April 1917. Winter conditions can be observed in Algonquin right up into May so an observation of snow in April at Mowat was not a rarity. The timing for this weather observation was definitely spring although the conditions certainly looked like winter.

Woods in Winter, Spring 1917
Oil on wood 5 11/16 x 7 7/8 in. (14.5 x 20 cm)
Smaller than Tom's Paint Box Size (8.5 x 10.5 in.)
Tom Thomson Art Gallery, Owen Sound 

The horizon on this painting was at the upper third of the panel but there is still a weather element to the painting. 

The long shadows crawling across the snow banks tell some of the story. The particularly long shadows in the foreground trail across the entire image and do not reveal whether the sunlight was originating from either the right or the left. 

PowerPoint slide from "Tom Thomson Was A Weatherman" 

The limbless pine standing tall at the right third of the panel comes to our rescue. The shadow must start at the base of the pine and that shade stretches to the left. The light clearly must originate from the right with the sun shining on Tom's right shoulder. The many shadows behind that towering pine reveal that the forest was thicker to the right as well. 

As is typical for plein air work, the scene is entirely front-lit. Artists can go blind painting looking into the radiation of the sun, especially over a reflective snowy surface. The illuminated spring vegetation displayed rich and vibrant colours. The opaque clouds were quite bright, and white as well. 

I use the following, simple geometry looking down on the human body to diagnose the illumination of plein air scenes. Thankfully, artists' heads do not swivel like those of an owl. 

This is not rocket science. A simple consideration of the visual clues in the painting can reveal a lot. 

There are five distinct possibilities for illuminating any scene as governed by the passage of time and the apparent sundial movement of the sun. The Earth makes a revolution every day while it orbits the centre of the solar system about 150 million km away. It took a long time for Copernicus and Galileo Galilei to get those concepts accepted. 

The constraints of the front-lit scene, the shadows stretching from right to left and the sun on Tom's right shoulder quickly eliminate two of the five choices (mid-afternoon and sunset). The shadows are very long making the "noon" view unlikely. At midday, the sun is at its highest elevation in the sky and cast the shortest shadows. The sunrise option does not fit the colour of the light illuminating the scene. The direct beam from the rising sun is Rayleigh filtered by a long path through the atmosphere resulting in a yellow hue to the light at dawn. The conclusion is that only a mid-morning time for this painting satisfies all of the constraints. Tom was looking northeasterly around 10 am.

Another bit of CSI deduction relates to the cloud. Even disorganized pieces of opaque altostratus reveal gentle ascending air in the free atmosphere. Rising air is also associated with falling pressures at the surface - a well-known fact to any weather enthusiast with a barometer. Weather systems are always on the move and a low-pressure area was approaching Mowat on that winter-like spring day in 1917. The weather situation was remarkably similar to another painting from April of 1917, Tom Thomson's "Early Spring". In fact, weather can connect one painting to another and perhaps even several others - weather can be the missing link! 

I do not believe this to be a coincidence but rather a typical experience for a plein air artist on a creative roll. It is common for a plein air artist to knock off more than five paintings in a day with each documenting an orientation of the sunlight as displayed in the above diurnal graphic, like the "Stations of the Cross". Even fourteen plein air paintings in a day are easily achievable. I strongly suspect that "Woods in Winter" was painted just before "Early Spring" on the same day, under identical weather conditions. Recall that "Early Spring" was completed around midday. If Tom just stayed in one place, the weather conditions recorded by "Woods in Winter" would have morphed into those of  "Early Spring" by the inevitable approach of the low-pressure area. 

Tom Thomson's painting locations with respect to the weather
associated with the conveyor belt conceptual model for 
"Woods in Winter" at location yellow Star 1
and "Early Spring" at yellow location Star 2. 
Tom did not move while the weather advanced above him.
 “After the Sleet Storm”  might have even been observed
within the warm sector of this storm. 

Upon his death during that summer of 1917, Tom Thomson's "Woods in Winter" passed from his estate to his older sister Louise. Louise was born in 1873 four years before Tom in 1877. Louise related some interesting tales about her younger brother Tom in a letter to Blodwen Davies in 1931. Blodwen Davies (1897-1966) was a Canadian advocate for the Group of Seven and an important biographer for Tom Thomson. Her research preserves some very interesting and authentic insights into the man, his art and his times. (see Louise Henry, Letter to Blodwen Davies, Mar. 11, 1931)

Louise became Mrs. J.G. Henry of Guernsey and then Saskatoon in Saskatchewan but she wanted the art of her brother to return home. "Woods in Winter" was gifted to the Tom Thomson Art Gallery, Owen Sound (967.056) in 1967. 

The smaller than typical paint box size of this painting also asks a question - Why? The sketch is smaller than 6 by 8 inches which is significantly smaller than his typical paint box size of 8.5 by 10.5 inches. Were art supplies in that final spring of 1917 in such severe shortage or was that selection intentional? How did Tom hold that tiny panel in his paint box while he worked on it? Without seeing the original panel, I wonder if this was just a scrap of wood from a packing crate that Tom had at his disposal. I have painted on scraps of wood many times but I reveal the reason why.  I do not have those answers for Tom's art story. Maybe someone does. 

"Tom Thomson Was
A Weatherman
 Summary As of Now"
QR Code

As one can see, there is always a story behind the art hanging on the wall of a gallery. With the invention of the world-wide-web and innovative communication technology, these stories can be readily available by scanning a QR Code. The black and white pixel patterns of the QR Code can link to information from any site within the web (even this one), The instantly available background story can supplement the art on the wall. Modern devices can even play that story into your earphones should you be wearing any at the time. I have done this for my own art when it was hung in galleries. In addition to names, my paintings are also numbered sequentially and the weather is an important part of each story. As a result, the weather linkage between consecutive paintings is easily deciphered within my own catalogue raisonné and not open to the conjecture like that proposed above. 

Sometimes it is just as revealing and enjoyable to simply gaze at the pigments and listen to what the brush strokes of the artist have to say.  You do not need to be an art historian or a meteorologist to really appreciate art! Sometimes it helps to appreciate the background story though. 

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. 

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.