Tom Thomson's Moonlight

Tom Thomson: Moonlight, 1913-14

Art is essentially about observing light and how it plays across the composition. Artists can also benefit from listening to what that light might be saying. Light contains a lot of science which seems deceptively simple... 

In Tom Thomson's Rainbow we investigated light refracting and reflecting from small, spherical rain drops to produce the multi-coloured rainbows. 

Refraction - Light is dispersed into its component wavelengths
as a result of differing transmission speeds in the different media

Refraction is the bending of a light when it travels at an angle from one medium into another. This refraction of light is caused by the difference in transmission speed in the other media. Refraction separates the white light, into its component colours sorted by wavelength. Short (violet) wavelengths bend by the most while long (red) wavelengths charge ahead on a straighter path.

Reflection  occurs when at least a part of the oncoming light remains in the initial medium at the boundary with another medium. 

Reflection from Surfaces Explained
Light reflected from a surface determines how we perceive it.
The accompanying graphic illuminates three different surfaces
with white light  - comprised of all of the colours of the rainbow.

The light in Tom's Moonlight took about 8 minutes and 20 seconds to get from the sun to the moon and another 1.3 seconds to reflect from the moon to his eye. How Tom saw and painted the moon was also  influenced by what was in the atmosphere. The moon is not a black body as it returns all wavelengths toward our eye - white light. The moon is the brightest object in Tom's skyscape. However, a broader area around the moon is also bright with light! How so? 

My friend, Professor Edward Lozowski directed me to an excellent site regarding atmospheric optics which I consulted extensively. I highly recommend it as well - the site contains days of scientific discovery...  including large sections on diffraction which is the bending of light around an obstacle or through an opening. We need to fully understand diffraction to appreciate Tom Thomson's Moonlight. 

Tom Thomson: Moonlight, 1913-14, 
Purchased 1914 by the National Gallery of Canada,
 Accession Number 943 52.9 x 77.1 cm
20.8 x 30.5 inches 

Diffraction refers to various phenomena that occur when a wave encounters an obstacle. Waves can bend around a corner or through an aperture into the region of the geometrical shadow of the obstruction. The diffracting object actually becomes a secondary source of the propagating wave. Italian scientist Francesco Maria Grimaldi first used the word "diffraction" in recording his observations of the phenomenon in 1660.  A deeper investigation into diffraction reveals the particle and wave dualities of light - electromagnetic radiation. This science is extremely interesting but we do not need to go there. 

Diffraction from Small Droplets

Diffraction occurs when light is scattered or bent by small particles having physical dimensions in the same order of magnitude as the wavelength of light. An everyday illustration is the spreading of automobile headlight beams by fog or fine dust particles. A canoeist might imagine a wave on a lake diffracting and bending into the sheltered cove behind an island. 

The waves of light scattering from the surface of the particles are independent of the particle interior - which could be water, ice or even coal. The waves diffracted by the host of particles mutually interfere to give regions of enhanced bright constructive interference and dark destructive interference. The shape of the particle is even unimportant - every particle diffracts energy. 

The angle of diffraction decreases as the particle size increases. Simply, small particles bend the light more than large particles. 

The amount of diffraction also increases with increasing wavelength. Longer, red wavelengths diffract more and can tint the outer fringes of the brighter area.

Diffraction of light produces the central white disk referred to as the aureole along with the colourful interference rings of a corona. If the particles are small and uniform, colourful corona rings the aureole with blue-violet on the inside and red on the outside. These coloured rings may repeat themselves in progressively fainter shades further from the light source. If the droplets vary in size, the interference pattern is simply a bright blur. 

What the science of diffraction reveals is that Tom Thomson observed what meteorologists refer to as a aureole. The colourful rings of the corona are are absent from Tom's painting. 

Areolas and coronae are circular, despite the fact that the moon is not a full circle. The circular symmetry is produced by the diffracting particles themselves and is independent of the shape of the source of light. The brightness of both increase with the number of particles. 

Classic corona ringing the central aureole within roughly ten degrees
of the light source formed by moonlight diffracting around
small, uniform particles - diffraction pattern also called an Airy disk.

Diffraction coronae differ from haloes which are formed by refraction from comparatively large ice crystals. The roughly 10° corona is much smaller than the 22° halo which can also ring the sun and moon.

22 Degree Halo resulting from refraction of the 
moonlight within relatively large ice crystals. The cirrostratus 
is full of billions of these large ice crystals - enough so that a few 
will be oriented perfectly to refract light at 22 degrees to your eye -
thus forming the ring around the moon and alerting us to the 
approach of the warm conveyor belt and a weather system.  

PowerPoint slide from my Tom Thomson Was a Weatherman
presentation. I always used the line that the effect of the colourful
interference pattern of the corona could also be achieved using 
the Mexican beer but that the science was very different.

When I view such a phenomenon, I always use the phrase "cirrostratus coming at us" to describe a storm on the way. Cirrostratus composed of large ice crystals is more likely to be marked by the refractive, 22 degree halo. The concept of the approach of the warm conveyor belt of a weather system applies regardless whether the cloud is composed of large ice crystals or small, uniform diffractive crystals. A aureole, corona or a halo tell similar weather stories. The 10 degree aureole produced by smaller ice crystals provides longer lead time for the approaching system. 

Now for the CSI (Creative Scene Investigation)! Let’s assume that this is the evening. I believe that it is easier to stay awake in the evening than it is to get up hours before dawn.  

This summer moon is waxing - the shadowed side of the moon is on the left. In another week it will be a full moon rising in the east just as the sun sets to the west. Thus Tom is certainly looking in eastward on that summer evening probably later in the season after the biting bugs had subsided. A correlation with the eastern horizon from some shoreline should be possible given the amount of accurate detail Tom that typically put into the profile of the terrain.

There is also quite a bit of wave action indicated by the spreading out of the reflection of the moon and aureole. This wave action is more likely in the evening hours after a windy day. The planetary boundary layer is unstable during the day and the winds at the top of the boundary layer are mixed down to the surface. After a night of radiational cooling and air mass stabilization, this transfer of wind is much less likely. Of course there are always exceptions to any rule and a well-developed low pressure area nearby could produce a strong wind at any time of the day. 

The wind creating the choppy waves was likely near 10 knots and described as something between a gentle and moderate breeze in the Beaufort Scale. 

The reflection of the moon across the water is spread out by wave action. Each wave is essentially a mirror twisting and turning with the wind. With distance from the viewer, the water surface area which subtends the viewing angle increases dramatically. Countless more reflective wave mirrors can by chance direct light toward the viewer. The noticeable, bright water surface actually get larger with distance - a triangular wedge of reflected light. 

The small and uniform particles required for diffraction and the aureole, halo effect are most commonly provided by cirrostratus cloud. These high, ice crystal clouds are the advance messenger ahead of a low pressure area. The warm conveyor belt portion of the low pressure area rises higher on constant energy, isentropic surfaces. The thin, cirrostratus cloud is at the very leading edge of the warm conveyor belt. It would be cloudier to the southwest on that summer evening.

As a result, the aureole around the half-moon is advance notice of an approaching low pressure area.  Those winds rippling the Canoe Lake surface are possibly from the east and within the cold conveyor belt being drawn into the low. Tom would be looking easterly into that chilly wind.

Tom Thomson worked on this painting with the assistance of his friend A.Y. Jackson. Tom Thomson shared Studio 1 with Jackson for the first twelve months after the Studio Building was completed in January 1914. "Moonlight" was completed on Thomson's studio easel as I recreated in the accompanying image, more or less to scale. 

The Studio Building financed primarily by Lawren Harris who had a studio on the top floor. He liked to listen to music while he painted and his records could be heard blasting throughout the building. 

A.Y. Jackson in Studio 1 photographed
as he was packing up to leave for WW1

When Jackson left for World War 1 and Lawren Harris departed to be a gunnery instructor at Camp Borden, Thomson moved in to share a studio with Franklin Carmichael. When Carmichael married and left a few months later Thomson, could not afford the $22 monthly studio rental fee. Tom never really enjoyed working in the city anyway.

Tom's studio work lacks the direct interpretation, immediacy and reality that comes with the Plein Air experience. Many prefer Tom's 8.5 by 10.5 inch sketch box creations completed spontaneously while surrounded by nature. Both approaches have important parts to play in the development of of every artist on their individual journeys.

Tom's patron, Dr. MacCallum spent $176 (big money in those days) to refurbish the workmen's shed on the east side of the Studio Building. Tom  rented that shack for $1 a month. Thomson spent the summers in Algonquin Park as a guide, ranger and fire-fighter although those occupations got in the way of his plein air painting. Tom spent his last two winters Glamping in "Thomson's Shack" creating his studio master works based on his favourite plein air sketches.

"Tom did not want a studio in the building. It was altogether too pretentious for him… There was a dilapidated old shack on the back of the property… We fixed it up…and he [Tom] lived in that place as he would a cabin in the north." Lawren Harris

A.Y. Jackson apparently inherited that studio easel after Tom passed in July 1917. Tom would have liked that. 

If you paint that you see, the science of nature must be basically correct. Tom did that and these blogs attempt to explain that science, placing the art within the context that it was created. Sometimes that science is deceivingly complex. 

Thank you to my friend Professor Edward Lozowski for his guidance in constructing this post. 

Warmest regards and keep your paddle in the water,

Phil the Forecaster 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”

 

Tom Thomson's Rainbow

After every storm there is always a “silver lining” and in Tom’s case, that tempest had all the colours of the rainbow.  

Rainbow -1916 Oil on wood 8 1/8 x 10 1/4 in. (20.6 x 26 cm)
Inscription verso: Snow-Covered Trees, oil on wood,
Vincent Massey Bequest to the National Gallery of Canada in 1968 

The optics of the rainbow require that the sun be on the back of the observer and that the sunlight is unobstructed to reach a collection of spherical raindrops. Perfect conditions for the plein air artist!  Raindrops are most spherical when they are small. As the size of the raindrop increases, they become distorted into an oblate spheroid – a flattened bun-like drop .. a Big Mac. Large drops are not effective refractors or reflectors of sunlight and create clumsy rainbows if at all. 

I prefer graphics rather than words to explain natural wonders.
Here parallel rays of sunlight encounter a host of small water
droplets. Refraction is when light passes from one medium into another
 and the colours are separated - shorter wavelengths bend more than longer
wavelengths. The single internal reflection (within a medium)
from the back of the raindrop returns some of that light at roughly
40 (violet) to 42 (red) degrees from the incident light rays.

It is unusual to have rainbows in the morning since convection and the associated rain showers are less likely in the morning. More importantly with the morning sun in the east, the cloud producing the raindrops will typically also obscure the necessary sunlight. Rainbows appearing in the western sky in the morning light are rare. 

It is much more typical to have a rainbow in the afternoon with the sun in the west. The convection that produced the raindrops would be moving away toward the east and followed by clearing. This clearing is vital since it allows the sunlight to fully illuminate the last drops as the rain tapers off and the clouds move away with the prevailing winds of the westerly jet stream. This gentler precipitation on the back edge of the heavier rain area is typically comprised of smaller, more spherical drops which are perfect for producing rainbows. 

Note that there can be no rainbow at noon… midday rainbows would have to be viewed between the observer and the ground. Rainbow effects can happen at noon but it involves a water hose and probably washing your car. 

The following text is from the first draft of "Rainbow". That interpretation of "Rainbow" was playing the meteorological odds but in this case, gambling did not pay!

"As a result, it is safe to say that Tom was looking eastward in the late afternoon after a band of showers had moved across his vantage point. This is another excellent example of Tom recording his observation of a weather phenomenon in oils. He was probably anxious to get back to painting again after having his plein air session temporarily rained out."

The real story emerges with boots on the ground! Terrain matching has located the painting location for "Rainbow". Thomson was actually looking toward the west-northwest from the cliff overlooking Tarn Lake in the summer of 1916 (Latitude 45.799988 Longitude -77.697180). That story is told below. Recall that Tom was working as a fire ranger and must have been quite surprised to see a mid-morning rainbow. There was not much cloud in the eastern sky so this was a line of convection along a cold front approaching Tarn Lake. The sunlight refracted in the small raindrops that were about to make Tom wet.

The black arrows on the upwind flanks of the cumulus and cumulus fractus clouds indicate that the wind direction at cloud level had a southerly component. Tom would have been in the southerly winds of the warm conveyor belt with a cold front on the way. 

From the orientation of the rainbow as it hits the ground, one can also estimate the sun’s elevation and thus the time of day. A steep arc to the ground occurs right at sunset when the sun is at its lowest elevation but still able to illuminate the raindrops. The rainbow that Tom painted had a shallower slope to the ground so his observation was probably made at least two hours from either sunrise or sunset.

PowerPoint Slide from my "Tom Was a Weatherman Presentation"
I knew the time and thus the hours until sunset in those rainbow
images I took to calibrate the rainbow angle and time to sunset. 

In addition, the colours in the sky are not those of sunset. Although the sun was low on the horizon, there was still possibly as long as three hours after the sun rose or until it would set. If the sun was indeed lower on the horizon, the colour of the setting sun would have been more orange as illustrated in the accompanying graphic - top left rainbow at sunset. This is especially true given the May 22nd, 1915 eruption of Lassen Peak in north-central California. Volcanic aerosols from that eruption just over a year previous to "Rainbow" would still be lingering in the stratosphere (exponential decay time of approximately 1.5–2 years) and thus colouring the sunrise and sunset skies. 

The path between the rain and the observer is the adjacent base used for the 42-degree rainbow. The longer this line, the higher and larger the rainbow must appear in the sky. The tangent (tan) of the 42-degree angle must always be the same as adjacent base (a) increases, the height (o) must also increase - simple trigonometry. The density of the small, spherical raindrops and thus the intensity of the rainfall must both increase in order to see a rainbow distinctly as this baseline (a) distance increases. The rain-producing Tom's large rainbow was quite a distance away!

The physics of internal refraction and reflection within a raindrop surrounded by air is also very interesting. On each internal reflection, some of the light energy is lost due to refraction as it is transmitted into the other media. That is why the secondary rainbow… is secondary… plus it requires two internal reflections. Each of these internal reflections within the raindrop loses a bit of light energy to refraction. A double internal reflection within exceptionally spherical raindrops can produce a secondary rainbow based on a 51-degree reflection. Tom did not see and thus did not paint the faint secondary rainbow on that late convective afternoon in 1916. 

Tom carefully and correctly matched the colours of the rainbow. This chromatic feat belies his dexterity in handling his oils and brushes. If you are in doubt of Tom's prowess, try it yourself. I have many times. I always make time to enjoy a rainbow - as Tom obviously did. 

A photo I took of primary and secondary rainbows at sunset on Foley Mountain looking east.
The sky between the primary and secondary bows is noticeably darker and this effect was first described in 200 AD by Alexander of Aphrodisias. “Alexander’s Band” is darker since light rays undergoing a single internal reflection brighten the sky inside the primary rainbow. Light reflected twice deviated to form the secondary bow and brighten the sky outside. Raindrops along the lines of sight between the two rainbows cannot send light to your eye and so the sky is darker there. 
There is a considerable amount more of science and optics in this image but I will leave
that detailed information to the textbooks. 

The Tom Thomson blogs are always a work in progress - striving to complete the story behind each painting. These investigations have evolved from being purely about the weather and science to include more historical background behind each work. Since the efforts started in the early 1980s, the circle of Thomson friends who have contributed to these efforts keeps getting bigger and bigger. That is a great thing! The wealth of knowledge from these individuals adds considerably to the history. 

One Thomson friend introduced me to a trio of new Thomson enthusiasts in May 2024. Scott Rodgers, Mark Rubino and Mark Scarlett completed an epic trip in May 2015 and at the urging of my Thomson friend were persuaded to visit the Tarn Lake cliff. They were armed with prints of some Tom Thomson paintings that might have been completed in that area. They were very successful and did indeed follow in the footsteps of Tom Thomson. Maps by Jeff Maps by Jeff  V4 showed a historic trail from Upper Pine to Grasspink with a dogleg southwest of ZigZag. As the canoeists recall:

"we turned back at the beaver pond as we had run out of flagging and, sadly, after lunch we had nothing left to use for bread crumbs to finish the job. These are some shots of what we found, with a white line beside the trail we were following."

The following photo looking west-northwest from the cliff reveals a terrific match in the terrain depicted in Thomson's painting. Tom did not make stuff up - clearly, he painted what he saw. Somehow Tom also included what he felt in those brush strokes and therein lies the magic of the artist. 

The McElroys had already visited Tarn Lake in 2012 and chronicled that experience in "The Cliff at Tarn Lake". Their exploits always make for an interesting read. Positive experiences, learning and exploration never get old. It takes a circle of open minds to really learn and discover the truth.

The information from this image helped to reveal the true story of Thomson's "Rainbow". That required a bit of a rewrite as noted above but most text was left unchanged. I was playing the safe weather bet of a departing shower moving toward the east producing a rainbow with the sun in the western sky. The odds were in my favour but it was still a losing gamble. 

The following graphic depicts the updated truth behind Tom's weather observation. For mid-summer (arbitrarily picked as July 15th), the painting would have been done just after 9 am about 3.5 hours after sunrise. Tom painted pretty much exactly what he witnessed but this timing does put a lot of emphasis on the azimuth angle to the sun. I believe that Tom was that particular about what he painted! The sun would have been about 22 degrees above the eastern horizon and Rayleigh scattering would not have been sufficient to cast a reddish hue to the illumination. The facts all fit together nicely. 

Note that as the date of the painting deviates from the above July 15th guess to an earlier time approaching summer solstice on June 22nd, the time of the observation gets slowly later to around 9:19 am with the solar declination maxing out at 23.45 degrees. The earliest sunrise for Tarn Lake Cliff at summer solstice was 5:21 am. 

As the painting date gets later than July 15th, the sunrise of course gets later and the observation time gets gradually earlier. A September 1st painting date would require Tom to be painting around 8 am and the solar declination would be only 8 degrees above the horizon. By the summer equinox on September 22nd, the sun would rise at 6:55 am and Tom would have to be painting by 7:30 am. The solar declination would be barely above the eastern horizon. 

Clearly, the plane of the rainbow and the intersection with the earth is determined by the solar declination. The angle to the sun above the horizon then reveals the date Tom painted the rainbow. I am still tinkering with that estimate but expect the date to be around July 1st. It is safe to say that Tom was painting by 9 am on that summer morning. This post will be updated only when I have a convincing estimate that I am satisfied with...

There is some additional meteorology for the weather enthusiasts. The convective clouds producing the raindrops that created Thomson's rainbow were actually ahead of the surface position of the approaching cold front. The split cold front pattern where the cold air aloft gets ahead of the surface front is quite common. Southerly winds were still evident in the clouds to Tom's west but the cold front had already produced weather overhead. Such a cold front is also termed as being active or anabatic. In contrast, the weather with an inactive or katabatic front is found behind the frontal passage. The col in the deformation zone which is the cold front, separates the anabatic portions associated with the cyclonic companion from the katabatic and anticyclonic companion. These facts further place Thomson within the weather pattern of the summer morning at Tarn Lake. The following graphic summarizes these considerations. This material will not be on any exam... See "Finishing The Dry Conveyor Belt" for more details.

Tom Thomson did not autograph this weather observation - just like he rarely signed any of his artistic records.  A very cursory look at the art reveals 1916 written in the upper left corner of the panel - probably in pencil. The Tom Thomson Estate Stamp was pressed in the lower right. After Tom passed in 1917, his friend and future charter member of the Group of Seven, J.E.H. MacDonald designed a stamp that was made in both metal and rubber. The Estate Stamp was pressed into the paintings that Thomson had left behind in his Shack beside the Studio Building in Toronto. Apparently, both stamps have been locked in the National Gallery for decades and I have not yet seen them in person. Tragically, the estate stamp caused some damage to a few of these paintings. 

Tom Thomson had some very good friends including these two Jims.

Tom Thomson pushed away from the Mowat Dock at 12:35 pm on Sunday, July 8th. He paddled southward remaining on the east side of Little Wapomeo Island on that hot and muggy summer afternoon. Tom passed out of sight between Little Wapomeo and Big Wapomeo Islands. There his body would surface from the depths of Canoe Lake eight days later on Monday, July 16th, 1917. He was born on Sunday, August 5th, 1877. Tom's brilliant painting career ended mere days shy of his 40th birthday. He was just discovering his wings as an artist. 

Tom Thomson has been called the Canadian Vincent van Gogh. Indeed there are similarities of artistic genius passing tragically and inexplicably way too young - 37 years old in the case of Vincent. Some people, including members of his own family, felt that the mystery of Tom's death was essential to his legacy. I respectfully disagree with that opinion. Understanding why Tom painted what he did and listening to what he was saying with his oils and brushes, are the essential ingredients to appreciating his art. Herein lies the motivation for these blogs in an attempt to place his art within the context that they were created and that they deserve. There are many more Blog entries to come. Thank you for reading!

Warmest regards and keep your paddle in the water, 

Phil the Forecaster Chadwick

Tom Thomson Post 11

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”

Tom Thomson's Squall Line Thunderstorms - Evening Summer-1915

 

Evening from the summer 1915

Tom painted what he saw! Here is what we know. The low horizon indicates this is another of Tom’s skyscapes. The art and the story are all about the weather. 

• This back lit cloud is clearly based in the low etage - near the ground. The air mass is very moist as the lifted condensation level is so low that the cloud bases are hidden by the landforms on the horizon. 
• There is a “white line” on the distant lake shore indicating that Tom was looking toward the light source – the sun. That bright line is caused by the sunlight glinting off the waves.
• The air mass is also very unstable with gusty surface winds from the left to right – southerly to southwesterly. These winds were fuelling the clouds with heat and moisture energy.
• White caps begin to appear at 8-10 knots and become more frequent above 15 knots. The absence of numerous white caps suggest a wind speed of perhaps 10 knots or around 18 kilometres per hour. That is enough wind to keep the mosquitoes from being too annoying. 

Evening, Alternate title: Evening Clouds,
Summer 1915, Oil on composite wood-pulp board,
8 1/2 x 10 1/2 in. (21.6 x 26.7 cm)

• The stronger illumination of the left flanks of the clouds indicates that Tom was turned a bit toward the northwest. 
• The clouds are towering cumuli also known as cumulus congestus that were transitioning into cumulonimbus – thunderstorms. Note the thunderstorm anvils developing as the updrafts near the stable tropopause and the top of the layer of the atmosphere that contains most of our weather. 
• The thunderstorm anvils were being directed by the northwesterly winds at the highest levels of the atmosphere. 
• The sketch is certainly late in the day due to the colouration of the atmosphere. The word “evening” in the title was not really needed to make this deduction. A squall line of developing thunderstorms such as this would be a rare event in the morning!
• There are perhaps some low cloud pieces between Tom and the line of developing thunderstorms which would indicate a wind direction along the elongated edges of these clouds. I could make a case for these clouds to be stratocumulus streets being drawn into the convection along a southerly breeze ahead of the approaching line of convection. If so, that would explain why the northern cell to the right was more developed than the southern cells. Note that there would be enhanced convergence, wind shear (helicity) and moisture advection along those stratocumulus streets that feed into the convection. The subtle cloud rolls in the painting appear to be pointed toward the more northern convective tower.  
• The rich orange colours in the clouds and sky were also influenced by the May 22nd, 1915 eruption of Lassen Peak in north central California. The Lassen Peak eruption was tiny compared to the major eruption of Mount St. Helens in 1980 but the effects on the sky were still noticed by the artists in Algonquin - and after all, they painted what they saw. 

  

  Sulphur dioxide spewed from volcanoes reacts in the atmosphere to form sulphate aerosols (aerosols are tiny, suspended particles in the air). Rayleigh scattering by volcanic ash and aerosols preferentially scatter the shorter blue wavelengths out of the sun's direct beam. The direct beam passes through a long path of atmosphere at sunrise and sunset leaving only
  longer wavelengths of orange and red to illuminate the scene.

PowerPoint slide from my presentation. The yellow circle is
intended to represent the sun's position. The red block arrows
denote the updraft locations and their relative strengths.
The black arrow is the atmospheric frame wind directing
the thunderstorm anvils at the tropopause.

The Creative Scene Investigation (CSI) Solution

Tom was looking west-northwesterly. A south to north line of thunderstorms was approaching Tom’s camp during the evening of a warm and moist summer day. Southerly breezes would shift dramatically to the west with the passage of these thunderstorms in about an hours time. Damaging downbursts and hail would be a distinct possibility and it would be getting dark when these arrived. 

The thunderstorms were probably associated with a cold front and the following day would be cooler and drier with brisk northwest winds likely. Angling would not be very good as it had been in the warm sector of the system (ahead of the cold front). Fish tend to become sluggish and stop biting behind a cold front. Tom's time would be better spent using the paint box on the day following the passage of this squall line. 

The accompanying photo of a cold frontal squall line compares very closely to Tom’s painting. The setting sun was in the photo so the west-northwest direction of view for that summer evening was well established. The multiple thunderstorm anvils guided by the northwesterly upper level winds are almost identical to Tom’s anvils. Those pouch-like cloud structures on the underside of the anvils are mammatus clouds. Mammatus clouds are an example of clouds in sinking air. They require strong updrafts to carry large concentrations of precipitation particles into the highest levels of the atmosphere. The moisture laden air is heavier than the surrounding air and must sink back to earth. Over time, the cloud droplets eventually evaporate and the mammatus dissolve. The slow vertical motion of mammatus cloud droplets results from a balancing of warming in sinking air and evapourative cooling. The mammatus pouches just hang around... The photo proves that squall lines similar to the one that Tom recorded certainly do exist. 

Two Very Different Photographs of the Tom's "Evening Clouds"

Photographing art can be challenging. Even the professionals at the major galleries must find it difficult to accurately represent the actual art. The differences in these two images are striking. The bold brush strokes are more crisp on the left image. The colours are dramatically different. The tone in the right image is far darker while some colours are more vivid. Perhaps the official image of the painting comes down to the personal choices and preferences of the photographer. Nothing is ever quite as good as the original. 

The right hand image does a better job of showing the scraping that occurs when the panel is slid into the sketch box upon completion. Tom was probably canoeing and certainly not staying at Mowat Lodge when he painted "Evening". 

I take great effort to match the official, high resolution  image
of my art with the original. Professional Studio lighting and even 
covering the reflective camera tripod makes the image the best it
can be... but each painting is different so careful experimentation
 with the lighting umbrellas is also important. My computer controls
the camera remotely so there is not even light bouncing off my body
that could influence the image of the painting... The pegboard grid  
ensures that the camera is aligned perfectly with the centre of each
painting. The goal is to honestly match the image with the original.

This fine painting was in the Laidlaw family of Toronto from 1922 to 1965 when it was gifted to the McMichael Canadian Art Collection, Kleinburg (1966.15.20). Tom Thomson did not autograph this weather observation either. 

Warmest regards and keep your paddle in the water,

Phil the Forecaster 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”

Tom Thomson’s Last Weather Observation

Tom Thomson disappeared  midday on Sunday July 8th, 1917 but his art and influence on Canadian culture continues more than a century later.  I have an opinion about his passing but I choose to focus instead on his life, art and science. This is the story of that final sketch "After the Storm". This is also about a May supercell and I thought I would post it a few days before the 105th anniversary of his death. 

After the Storm, Alternate title: Sketch in Green, Oil on wood
8 7/16 x 10 1/4 in. (21.5 x 26 cm)
Sold to Private Collector Nov 27, 2015 $1.1 million

Thomson's patron, Dr. James MacCallum probably gave that name to Tom's final weather observation. He certainly influenced the alternate title.  Dr. MacCallum  scrawled on the back of the panel "This sketch was done by Tom Thomson in the late spring of the year in which / he was drowned. It is one of the few done in green. When the foliage had / come on [southly?] he usually gave up sketching and took to fishing / and canoeing until the fall color appeared. / J.M"

Tom wrote to MacCallum in a letter dated July 7, 1917 (the day before his disappearance): 

Mowat P. O., July 7, 1917

Dear Sir:

I am still around Frasers and have not done any sketching since the flies started. The weather has been wet and cold all spring and the flies and mosquitos much worse than I have seen them any year and the fly dope doesn’t have any effect on them. This however is the second warm day we have had this year and another day or so like this will finish them. Will send my winter sketches down in a day or two and have every intention of making some more but it has been almost impossible lately. [...] Have done some guiding this spring and will have some other trips this month and next with probably sketching in between. [...]

Yours truly

Tom Thomson

In the spring of 1917 Mark Robinson, Algonquin Park Ranger recalled that his friend Tom Thomson told him that he had done a series of 62 sketches that spring. Tom had asked Mark if he might hang these works in the Ranger’s cabin in order to see them all together at one time. Thomson referred to these particular paintings as  “records” intending that the series would provide an observation of the unfolding of spring in Algonquin Park. Tom said to Mark:

“I have something unique in art that no other artist has ever attempted … I have a record of the weather for 62 days, rain or shine, or snow, dark or bright, I have a record of the day in a sketch.”

Evidently even Tom himself admitted to being a weather enthusiast. The word “record” could be easily replaced by the modern meteorological equivalent terminology “observation”. Tom made a point of stressing that the weather was of prime importance in those 62 sketches.

There is more evidence and it is overwhelming. Dr. James MacCallum, Tom’s benefactor and friend said that Tom “never painted anything he had not seen.” Apparently Tom painted and saw lots of weather. J.E.H MacDonald's son, Thoreau was just a boy when he hung around his father’s friend. Remembering those days spent with Tom, Thoreau said “some competent critic … should be familiar, not only with every phase of his work, but with the .. weather; have them in his bones … “. 

"After the Storm" Diagnosis from my PowerPoint Presentation

I wish to leave the final word on whether he was a “weatherman” to Tom himself. Tom didn’t leave behind many words. He communicated best with bold strokes, texture and colour in oil on small surfaces. Tom’s very last plein air sketch, unbeknownst of course to him at the time, was “After the Storm”. This sketch was completed before the Algonquin black flies emerged that year. They started biting on May 24th in 1917. Tom’s motivation to “record” this particular event was to observe the impacts of a severe supercell thunderstorm. It must have been a violent thunderstorm to catch Tom’s attention. Tom was looking eastward at the retreating flank of the thunderstorm after emerging from the shelter he would have had to take. 

Note the chaotic sky which reveals the turbulent wind. In Tom’s painting it is difficult to be certain about wind direction but the longest cloud edges appear to be rising from left to right which would be consistent with a northwesterly wind in the wake of a convective storm. It was certainly windy at ground level and this would have helped to keep all the insects down - especially the weakly flying mosquitoes that Tom mentioned. 

My presentation includes an image of the rear flank of an actual supercell. The diagnosis of that image is included in the accompanying graphic. 

Wind, heat and water are energy for thunderstorms and this storm must have had a lot of power thus encouraging Tom to record its aftermath. The La Niña event that developed in the spring of 1916 and lasted until the spring of 1918 was the 13th strongest of the ‘classic’ La Niña events. My meteorological research revealed that the La Niña phase of ENSO (El Niño-Southern Oscillation) was conducive for supercells over Ontario. This helps to explains their prevalence in the last year of Tom's art. 

Tom was looking eastward at the rear flank of the
supercell thunderstorm
with the emerging sun on his back. 

Most of Tom's sketches were weather observations. They were not even art to him and not worth signing. Tom did not sign "After the Storm". This is quite a contradiction at a time when Tom was just reaching his stride as an artist. That Tom was a weatherman should now be clear. He could have been a meteorologist except that vocation didn’t really exist in 1917. It would have been a great career choice for Tom. Meteorology certainly worked well for me starting in 1976. I am still teaching and researching weather and climate and making a positive difference. Life is good! 

You do not have to be a meteorologist to understand the art of Tom Thomson or his motivation to record what he did... but it does help. Admirers of Tom’s work must to be careful that they do not project their own vision and experiences on those of Tom’s. I am possibly as guilty of this as others who have been inspired by Tom but I tried to give the last word to Tom and the people who knew him personally. 

Persistence is an acceptable forecast technique. A weather forecast that the future weather will be the same as the current conditions is an example of persistence forecasting. Persistence works really well if nothing much changes. Forecasting a change is much more challenging and prone to errors. Many meteorologists forecast a change incorrectly many times until it happens – if in fact it does happen at all. In this situation I would certainly apply persistence to estimate where Tom was headed with his art and it was not abstraction. Tom himself said it best in his July 7, 1917 letter to his patron Dr. James MacCallum posted a day before he died, 

“will send my winter sketches down in a day or two and have every intention of making some more”.

Tom was planning on painting more of what he saw... focussing on the weather. Nature and the weather might look like abstract art but it is real - especially if you study nature and know what is saying.

It is a tragedy in Canadian art and Canadian society that Tom never got the chance “of making some more”. I wonder what he might have created. 

Warmest regards and keep your paddle in the water,

Phil the Forecaster 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”