I pulled over on the interstate to take this photo. What you’re looking at is a phenomenon called a Kelvin-Helmholtz instability. The ridgeline directly ahead had been cloaked in heavy fog all morning, and as a cold front came through, it sent strong, laminar winds above and along the ridge. This resulted in lower pressure just above the fog layer. The fog was lifted off the mountain and “rolled forward” in the distinctive way you see by encountering the laminar flow aloft.
This was really, really cool to see. At its peak, there were 7 well-formed waves lined up down the ridge. This is a phenomenon you see fairly commonly in cloud layers, but I’ve never, ever seen it on the ground.
Associated goodness: I have posted commentary on a local weather blog, and have attracted the unwanted attentions of a chemtrail conspiracy theorist who seems to be convinced that the K-H waves are evidence of the government experimenting on the good citizens of our country.
Somebody shoot me. The chemtrail “activists” are all over that weather blog now (either that, or one person with multiple socks) talking about the TRUTH of government geo-engineering, and how they have thousands of activists, and how it can’t be a natural phenomenon, because it looks all weird and shit.
Stupid, haunted, superstitious cretins. These would be the same idiots accusing their neighbors of being witches in the old days.
Well no. They might be the descendants of the idiots who accused their neighbors of witchcraft in the old days. But they could be the same idiots accusing their neighbors of being witches now-a-days though.
Nah, I read the thread title, said “cool!” as well, and then started wondering if I could work out stuff about the instability from the picture. And then realized that not only had turbulent flows taken over my work life, they were just taking over my life.
Yeah well, this is how much of a nature/weather/science geek I am: I’m pretty sure I was the first person in the city to identify it as a K-H instability. We were driving on the interstate, and I saw the fog (really a very low cloud layer) start to destabilize in places. As we were passing into the downtown area, I saw the beginnings of telltale “peaks” in the fog spaced at regular intervals. Right then, before any distinctive wave forms were discernible, I shouted “Kelvin-Helmholtz!” I can’t really imagine that anybody else on the planet beat me to the punch on that one.
I broke off in the middle of a conversation with my wife about Christopher Hitchens, and she momentarily thought I’d lost my mind. Within just a couple of minutes, the waves were fully formed, and we stopped on the side of the road to take photos.