Every cloud has a story to tell. This tale is from Monday July 4th, 2022. I was paddling with the family on Singleton Lake. The goal is to encourage others to take the time to look at those lines in the sky and to hear and understand what the clouds are saying.
The background explaining how a frame of reference attached to the mean flow in the atmosphere shapes the clouds can be found in Cloud Shapes and Lines in the Atmosphere. Additional blogs on similar topics can also be found. Trying to understand cloud shapes in a frame of reference attached to a spinning globe hides the actual simplicity behind patterns that form in fluids.
I will let the following images do most of the talking...
The cloud patterns were drifting toward the southeast revealing that the wind in the free atmosphere was northwesterly. The cloud bands were advancing slowly from the southwest with the warm conveyor belt (the warm orange arrow in the accompanying graphic).
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| Conveyor Belt Conceptual Model - COMET |
The sky to the southwest was filled with a thin veil of cirrostratus cloud. The warm and moist air was rising along the constant energy surfaces as it approached from the south. As is typical for eastern Ontario, the anticyclonic companion of the warm conveyor belt would arrive at Singleton Lake first. The col in the deformation zone pattern was far to the northwest.
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Looking southwest from the middle of Singleton Lake
midday July 4th, 2022
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A strong storm was developing west of the Great Lakes. The jet stream winds with this developing storm were sending out atmospheric swells. These large amplitude gravity waves were already reaching Singleton Lake a day ahead of the arrival of the storm. The crests of the swells contained thicker cirrostratus cloud in long bands. The troughs of those same swells looked clear but actually contained thinner cirrostratus. In the distance and low on the horizon, the swell crest band was less obvious and the associated cirrostratus cloud was exceedingly thin. The orientation of these bands could also be seen on the visible and water vapour imagery. Visible Satellite Imagery Left - Water Vapour Imagery Right
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 | Vertical Motion of Air Parcels Following the Wind Wave Added to the Swell.
I Distorted the Wind Wave to Follow the Swell. I included Five Options for the
Lifted Condensation Level within the Vertical Range of air parcel motions
following the combined Wind Wave and Swell.
Motions similar to these waves are area always occurring
regardless whether there is a cloud in the sky... |
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The somewhat, clumsy wave graphic above combines the vertical motion of air parcels following the large amplitude swell gravity waves with the vertical motions of the superimposed, locally produced wind waves. The visual appearance of the resultant cloud is determined by the location of the lifted condensation level within that range of air parcel vertical motion. Option 3 would explain what we were witnessing overhead. Option 2 is required to explain why only pieces of clouds were observed within the swell that is low on the horizon.
The local wind in the free atmosphere was generating wind waves that were superimposed on the swells. The graphics below summarize the larger scale process of swells and wind waves within the conceptual model of the warm conveyor belt. Together, these graphics actually explain the details of what we observed.
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The Wind Waves and Swells Explained
Using Atmospheric Frame of Reference Winds |
I have also written about these processes in
Keep an Open Mind and
Sunrise or Sunset - Seeing Even More Gravity Wave Clouds as well as elsewhere... (but I forget just where at the moment)
I do hope that this is clear and that I have not confused anyone... The bottom line of this weather story written in the clouds was that
cirrostratus was coming at us and it would begin raining overnight. The rain would continue for more than a day with 11.2 mm being measured at Singleton.
Warmest regards and keep your paddle in the water,
Phil the Forecaster Chadwick
