TURBULENCE AND CLOUD SHAPES. “Turbulence is thought to modify the collision efficiency of droplets in one of three ways: 1. By modifying the flow field around the droplets; 2. By generating spatial inhomogeneities in the droplet concentration field; 3. By modifying (generally increasing) the relative velocities between droplets.”
http://www.mpimet.mpg.de/fileadmin/staff/stevensbjorn/teaching/skript-5.pdf