• Wind is stronger up higher and weaker close to ground
• indicates strong wind speed, hear w/ height
• one vortex that was going as a horizontal roll and a strong updraft comes and forces it up and now you have 2 vortices that are tilted vertically, stretched it, and vorticity increases
o think of ice skaters rotating on ice
• vertical wind speed shear, wind simply getting stronger w/ height just off ground—answer to what causes it!