After decades of flying, pilot Stuart Walker says turbulence isn’t entirely predictable. But there are different types of turbulence pilots watch for. Walker explains each one and what pilots do to avoid a bumpy ride. Illustration: Alex Kuzoian for The Wall Street Journal More from the Wall Street Journal: Visit WSJ.com: http://www.wsj.com Visit the WSJ Video Center: https://wsj.com/video On Facebook: https://www.facebook.com/pg/wsj/videos/ On Twitter: https://twitter.com/WSJ On Snapchat: https://on.wsj.com/2ratjSM #WSJ #Aviation #Turbulence