  A central problem in cloud physics is understanding the kinetics of the
growth of water droplets. It is believed that there exists a
'condensation-coalescence bottleneck' in the growth of intermediate size
droplets. Here the Lifshitz-Slezov theory of Ostwald ripening is applied to the
kinetics of the growth of rain drops. The analysis shows that kinetic barriers
to rain initiation are not significant. It is also shown that Ostwald ripening
can greatly enhance the apparent collision efficiency of droplets falling under
gravity.
