Fig. 6 indicates that the supermumeraries of the primary rainbow (for water droplets of radius r = 100 µm) require fairly uniform drops.  There is little difference between standard deviations of 1% and 5%, but the supernumeraries disappear for 10% and 20%.

Scattering angle (degrees)	Scattering angle (degrees)
Fig. 6   Primary rainbow: effects of disperse drop size (average radius = 100 µm, wavelength = 0.65 µm)