#2433 "Tomorrow’s Snow"

The Tuesday sunset told the entire weather story. The deformation zone and the accompanying cloud features placed Singleton Lake under the anticyclonic companion of the approaching system. The calm surface of the lake also followed the old saying about winds before a storm. Snow would arrive before dawn but it would not be too heavy. 

The sunset sky was telling the truth as one would expect. The clouds never lie. I have written about these signatures many times before but I will give it one more try with the graphics applied to this actual sky. The right hand rule is the key. Orienting the fingers of your right hand to point in the direction of the wind shaping the gravity waves, forces your thumb to point downward. This requires that the col in the deformation zone which is the centre of the stretching action, must be further to the north. This in turn places Singleton Lake under the anticyclonic companion of the approaching system. It is typical for the gravity waves to slant downwind along a deformation zone with the stronger winds on the clear air side of the moisture boundary. This was especially evident in the sunset sky. These downwind slanted gravity waves indicate significant horizontal wind shear. The implications about the approaching weather also follow. The anticyclonic flow is less of a weather producer that its cyclonic companion. The stories in the sky are really this simple and interesting. 

This is the material that I had hoped to teach in the Training Branch of the Atmospheric Environment Service in the mid eighties. I could not get past teaching the very the basics. The physics of sun glint threw all of the students into a tizzy. The beauty of the right hand simulation of the flow and atmospheric vorticity is that you can direct your fingers in the orientation of the flow and your thumb gives you the accepted convention of the meteorological vorticity. Of course the smoke ring is three dimensional but meteoroligists prefer a plus vorticity that points upward. You can look doward at your right hand to represent the satellite view of the weather or looking up to envision the circulation from the ground. The circulation and the atmospheric flow as represented by your right hand does not change. Only your perspective of the circulation changes. This allows you to fully understand the conveyor belt conceptual model and the atmospheric frame of reference. We live at the bottom of the atmospheric ocean of air but the satellite view from space can be more revealing. I was lucky enough to start my meteorological career at the same time that satellite remote sensing was coming available. I embraced that new satellite data and everything that it was revealing about how the atmosphere really worked. 

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