CNN CNN International March 27, 2015 05:53:00
Just like this. we look at mountainous terrain and any wind condition below 30 kilometers per hour, it just naturally flows over the mountains. when we look at winds in excess of 30 kilometers per hour, what we have in the forecast, we start to see some incredibly challenging flying conditions, especially for those helicopter pilots. basically you want to think of air flow over mountains like basically a river of water. as it moves up and over mountains and through very narrow ravines, the air or the water really starts to accelerate or decelerate, and that causes what is known as wind eddys. ...