Mid-air Collision
This is one for the natural sciences afficionados.
This photo of Mauna Kea taken from the Kohala Road above Waimea shows two colliding air masses. Notice that the area underneath the clouds on the right side of the photo is hazy. That haze is VOG, wrapping around the south side of Big Island and blowing up toward Waikoloa.
If you look closely at the VOG area, you can see a distinct near vertical line where the air is hazy to the right and clear to the left; that vertical line aligns precisely with the vertical front of the puffy clouds.
That vertical haze line and the vertical cloud front mark the collision of the southern VOG air with NE trade winds blowing over the island from the Hamakua coast through Waimea. The two air masses are not mixing; at the time I took the photo they were each pushing against each other in almost a perfect standoff. At the collision point, both air masses were suddenly being pushed upward with little mixing. It looks as if the dewpoint in the VOG air mass is about 2500 feet; as the VOG air is forced above that level moisture condenses and clouds form. If you watched the clouds there was actually pretty violent churning on that vertical face and you could see the moisture condensing out of the air to form clouds. Somewhere around 8000 feet it appears that the NE trade winds begin to overwhelm the VOG air, and the trade wind air starts overrunning the VOG air, shearing off the tops of the clouds that have formed over the VOG air.
Driving over the Kohala Mountains, you could see the colliding air and churning clouds almost all of the way from Waimea to Hawi. Much of the time the collision was directly over the highway. If you looked to the east the views were sparkling and clear; to the right the scenery was hazy and had a brownish tint.
