Under what circumstances do you see this wind arc like this?
Every puff hits the water with this shape. On a grander scale even the sea breeze has shape to the wind arc.
There are 2 different scenarios for favored course.
1) The course is not layed out square and 1 side is then a shorter distance to sail.
2) There is greater wind pressure on 1 side vs the other. In this case for sure both up and down, it is favorable to stay on the same side with the better pressure.
