|#0839 "Cold Air Mass Cumulus" 8x10|
I would tend to dream on quiet night shifts playing thought experiments in my mind when examining satellite imagery. The simpler the explanation, the more likely it would be to bear fruit and to circulate among the team. Here is one of my favourites.
Imagine large pencils rolling along a table. I used colloured pencils a lot when working the forecast desk. Friction provided by the table and even a gentle push at the top gets the pencils rolling. In today's reinvention of that nightshift, we were making Chili during a snowstorm, so I used cans – same idea but tastier.
These hand waving thought experiments from night shift required both of my hands with me looking along the direction of the wind in the accompanying graphic. Bodies are biologically constrained so that the fingers must be curled in the same orientation as the rolling pencil or bean can.
|Two Cans Rolling on the Floor|
Now imagine any non-uniformity like a locally stronger push on one of the cans. That push is equivalent to a locally stronger wind. This situation is exactly analogous to what happens in the planetary boundary layer (PBL) of the atmosphere. Friction at the surface slows the wind while aloft, the stronger wind is never perfectly uniform.
|Venturi Meter and Bernoulli's Principle|
What happens when the stronger wind speed is applied to the rolling cans over a period of time?
|A Locally Stronger Wind|
Shouldered by Locally Weaker Winds