On Wednesday, January 24, 2018 at 1:51:47 PM UTC-7, wrote:
But what does the green line intersecting a gray line with the dark marker at the intersection mean?

The green line is of great interest to glider pilots because it represents a bubble of air warmed by the sun hitting the ground. Once the bubble breaks away from the surface it starts to cool. The green line represents the temperature of the air as it rises. As long as the green line in to the right of the red line, the bubble will continue to rise. The red line of course represents the temperature of the ambient air as you go up in altitude. Where the green line crosses the red line the bubble is the same temperature as the ambient air at that altitude. So buoyancy is neutral. But the rising bubble has mass, so it has momentum and that carries it above the altitude of the crossing point.

So the rising bubble of air is followed by another rising bubble of air and that creates what we call a thermal or an updraft. If you're a glider pilot you can climb until the bubble stops rising. If you're a power pilot you will experience turbulence below the altitude where the bubble stops rising.

Now this bubble started out at surface air with a specific dewpoint when it was at the surface. This dewpoint is where the blue line intersects the ground. The dark grey line shows the dewpoint of the bubble as it rises. Where it intersects the green line, the temperature of the bubble at that altitude equals it's dewpoint. A cloud forms. The little horizontal dash marks the cloudbase. There is a corresponding dash on the altitude scale to the right, so that you can read an altitude number off the scale.


And what does moving the spot marker off of the temp line accomplish? It defines a grayed area in sort of a triangle but I haven't figured out what it's telling me.

The only grey area that I see is on the wind speed vs. altitude graph to the right of the skew-t. Dragging the cloudbash hashmark just pans the skew-t I think.