Tom Thomson's After the Sleet Storm, 1916

This is Tom’s “record” of freezing rain. It may not be a skyscape since the horizon is near the top third of the panel but the art is certainly all about the impacts of weather. Thomson painted "After the Sleet Storm" in his Shack Studio during the winter of 1915-16. It is unknown when Tom made the sketches in support of this decorative studio work but they were sufficiently representative in order to capture the reality of the event.  

After the Sleet Storm
Alternate title: Sleet Storm in the Cedar Bush Winter 1915–16
Oil on canvas 16 1/8 x 22 3/16 in. (40.9 x 56.3 cm)

The impacts of freezing rain can be quite severe.  Any coating of ice on surfaces makes travel extremely hazardous. Freezing rain typically lasts less than two hours but in those rare, extended events, the impacts can be severely extreme. I worked during the lead-up and duration of the Ice Storm of 1998 which has been called "The Worst Natural Disaster in Canadian History". Meteorology could accurately predict the occurrence but not prevent the impacts. 

The Back-lit Singleton Forest illustrates
the shimmering ice accumulations  similar 
to those that  Tom witnessed

Tom was certainly looking south when he composed the sketches.  Plein air artists rarely look toward the light anyway for the following reasons:

• the bright sunlight is damaging to your eyes
• the visible side of a backlit subject must be in shadow and lacking in colour and interest
• the painting surface and pallet are probably also in shadow making the colours difficult to discern

Perhaps this is why Tom based this studio work on quick sketches which he saved for some winter day when painting in front of the wood stove would be easier on the eyes and the body. I must also confess to doing the same thing in my Studio Shack more and more now. I am not forty years old anymore...

In any event, Tom was looking southward. The forests on the distant hillsides were all very dark in Tom’s painting. Tom was looking at the shadowed sides of those wintry slopes. The sunlight originated from the far side of the hills and Tom was certainly looking southerly. 

The accompanying graphic depicts the science of freezing rain following a snowflake from the top of the clouds through an above-freezing layer. The layer of warm air to the right of the white freezing isotherm in the accompanying graphic melts the snowflakes. The resulting water droplet then falls into a freezing layer near the ground and chills below freezing. Water droplets can happily exist below freezing without turning into ice. However, these supercooled water droplets will freeze on contact when they collide with a surface.

Given a southerly perspective, the icy tree tops would be haloed by the backlighting of the sun. From an artist’s perspective, it would have been the only view in order to record the interesting, brilliant light from the ice coating on the trees. The sky, although bright, was overcast with cirrostratus or thin altostratus. 

I am crediting Tom with being accurate with the weather even though the canvas was not a plein air creation. Cirrostratus is commonly associated with the warm conveyor belt over the warm sector of a winter storm. The sketches were completed after the freezing rain had ended and the surface warm front had moved northeast of Tom's location. Tom would have been sketching in the warm sector of the storm. Aside from looking into the bright light of the sun, it would have been a very pleasant sketching session. 

Observation of Supercooled water droplets freezing on the
windward side of a tree during a freezing rain event

Another important clue in Tom's direction of view can be found in the wind direction. It is very unlikely that all of the trees in Tom's painting were birches! By this, I mean that ice has coated what I believe to be the northeast sides of the trees in Tom's sketch and thus they appear white. This can only result in a freezing rain event if first, the trees are below freezing and second the prevailing wind during the extended period of freezing rain was northeasterly. Both of these statements are typically true in a freezing rain event where the cold conveyor belt of freezing air is a northeasterly wind being drawn into the approaching low-pressure area.  There will be no ice on the lee side of the tree trunks and thus that direction would also not be as appealing for Tom’s “record” of freezing rain if he wished to paint ice. The supercooled raindrops carried by the cold conveyor belt would freeze on contact coating the windward side of every tree with ice and transforming them into "white birches".

Tom sketched looking southerly toward the sun
within the warm sector of the winter storm under
the cirrostratus skies of the warm conveyor belt (WCB) 

After the Sleet Storm

The ice storm that Tom sketched was quite a significant event judging by the tree limbs being weighed down by accumulated ice. Such an event would require a chilly and persistent cold conveyor belt (blue arrow labelled CCB in the above graphic) with the flow backed to blow more from the northeast than the east. In modern meteorology, I use Doppler radar to diagnose this backing of the wind in order to anticipate more significant icing situations. We can deduce that Tom’s view would be looking southerly to southwesterly from within the warm sector of the winter storm. The freezing rain would have moved well to the northeast ahead of the warm front by the time Tom completed his sketches in support of the painting. 

PowerPoint Slide from "Tom Thomson Was A Weatherman"

As an aside, “sleet” is an American term for a mix of freezing rain and ice pellets. The term “sleet” is not used by the Meteorological Service of Canada where the phenomenon is referred to as a “mix of freezing rain and ice pellets” (the audience always chuckled at this). The event that Tom recorded was mainly a freezing rain event as ice pellets bounce and cannot stick to surfaces. 

Freezing rain is typically associated with a warm or nearly stationary frontal situation. The warm front provides the required layer of above-freezing air aloft. The cold conveyor belt is necessary for the below-freezing temperatures near the surface. If the layer of freezing air is too thick, the melted snowflakes are refrozen into ice pellets (Type A).  If the freezing layer is too thin, only the smaller melted snowflakes are chilled enough to become supercooled. Freezing rain requires a Goldilocks cold conveyor belt which is just right - neither too thick nor thin. This makes the accurate prediction of extended periods of freezing rain especially challenging. Doppler and more recently, dual polarization radars have been instrumental in the prediction of freezing rain as well as other precipitation types. 

Freezing rain is also more probable with slow-moving weather systems which encourage a vigorous cold conveyor belt (see "Weather Lessons for Everyone from the Cold Conveyor Belt Wizard" for an explanation of why this is true). Slow-moving systems are becoming more common with the climate change weakening of the jet stream. The increased likelihood of split flows also results from the meandering flow of a weaker jet stream. Split flows are very conducive to freezing rain. 

In addition, cold air often gets trapped at the surface by terrain features which can result in extended periods of freezing rain. The Ottawa River Valley can trap cold air as well as regions north of the Oak Ridges Moraine which includes the Algonquin Highlands. Meteorological friends of mine at Environment Canada produced the accompanying freezing precipitation climatology in the early 1990s before the tragic ice storm of 1998.  

Freezing precipitation in Canada

View of my Brother's Burritt's Rapids Forest, 

east of Merrickville, January 1998

The 1998 Ice Storm was a highlight of my career. The dedicated operational team at the Weather Centres provided accurate predictions of a very rare event that unfortunately, is certain to happen again. The meteorological clues were apparent a week in advance that something historic beyond anyone's personal experience was about to occur.  That message did not get much attention - not even from my Brother who refused to purchase a backup generator upon my early advice. One of my "Pictorial Technical Discussions" from before the event depicted 50 mm of ice accretions over a large area of eastern Ontario and western Quebec - including my Brother's home and acreage. That prognosis raised more than a few eyebrows although people knew that I could be boldly extreme in my science. Those early maps were hand drawn and faxed to some media and clients of the Weather Centre. Being an artist, it was often better to communicate with pictures instead of thousands of words and I tried to make those discussions attractive as well as scientifically informative and accurate. I wish that I had that particular Technical Discussion map now. I can still see it in my mind's eye ... a copy might survive somewhere but goodness knows where. 

Ice Accretions from January 1998

This studio canvas was unsigned by Tom and upon his death, passed into the possession of his older brother George and eventually from there to the Mellors-Laing Galleries, Toronto in 1941. The painting passed through a few more hands before finding a permanent home with the Art Gallery of Ontario. An alternate title for this work that was authenticated by George is "Sleet Storm in the Cedar Bush" which is another clue that these trees were not birches. 

The ice associated with freezing might be as beautiful as a Tom Thomson painting but please, avoid all travel when it threatens. Stay home and stay safe...

Warmest regards and keep your paddle in the water,

Phil Chadwick

PS: It is not coincident that these memories were published in time for early 2023. I remember very well where I was and what I was doing a quarter of a century before. 

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