'BOW' WAVE?

Whether this is a 'true' wave (or even whether it exists) is controversial in some pilots' minds, but only those who've not experienced it, read about it in technical publications or seen our photographs of lenticular clouds stacked miles UPwind of the mountains.Visualize the air piling up similar to river water on the upstream side of a bridge pier.  Because bow waves are typically weak, you work such lift by facing the wind and hovering, nearly stationary relative to the hillside, rather than tacking along it.  Bow waves may remain steady all day, but usually flow through with the wind and then break.  When one does, penetrate upwind and look for a new pulse of lift there.  If you find zero sink, you can circle in it (or figure-eight) while drifting back to where the lift was previously.   Your original lift may return in cyclic fashion.Also, if the mountain is large and steep enough, and presents a wide obstruction to the wind, there might be more wave-like lift further upwind, well away from the hill, like harmonics of a ‘classic’ wave in reverse.