All that wind this week was the result of a visit from something called the jet stream. Ok, so what’s a jet stream?
The truth is that there are more than one, but when we talk about THE jet stream, we mean the north polar jet, the one that most directly impacts our weather here in North America. For us, the jet stream is the 100+ MPH river of wind that flows generally west to east, the core of which is 30 to 40 thousand feet above our heads.
If Earth were a perfect, smooth sphere with a uniform surface, and all other things were equal, there would be a jet stream. It would run in a never-ending counterclockwise circle, west to east, around the top of the globe at about 60 degrees of latitude, roughly up along the northern borders of the western Canadian provinces. It would be the result of various forces acting on air set in motion by temperature differences between the hot equator and the cold poles.
Here in the real world, the forces and moving air exist, but the Earth is not a perfectly uniform sphere, so the real-world jet stream is not a perfect circle but wavy. Seen from above the north pole (if you could somehow see the wind) it would be shaped more like a wide petaled daisy than a circle. And the petals would move too, not only rotating around but also moving slightly up and down. Heavier cold air tends to make the jet stream come closer to the surface in the winter.
Last week when it got so windy for days on end, it was because one of those petals had moved right over Idaho and also dropped down a little bit closer to the ground. The strongest wind was way up over our heads, but it was close enough to stir things up down here, too. Knocked my deck box right over. Again.
Several things can trigger wind events here in Teton Valley: outflow from storms, extreme differences in temperature or air pressure, a dust devil passing through, to name a few. It isn’t always the jet stream’s fault, but when the wind picks up and blows for days instead of hours, the jet stream is a likely suspect.