Originally Posted by Zacnlinc

I was on my LAX-HKG-LAX flights 3 weeks ago and experienced moderate turbulence indeed. It just so happened that on the HKG-LAX leg, after deplaning at the remote station the pilots were seated adjacent to me. At some point, a passenger asked the pilots why was it so turbulent. There came a hush in the bus as everyone was eager to hear the reply.

Long story short, the senior pilot says that March and November are the times when the polar winds change into three (Witch?) belts and it's the transiting of the plane between them that causes such turbulence. Something about the tilting of the earth during the change of seasons makes this phenomenon occur off the coasts of Japan and North America.

Let's just say that the turbulence was bad enough that I was wishing the plane would land and I'd be happy being on the ground for a while.