The misconception of Cloud-cloud collision is unable to show continuous triboelectric effect and charge differentiation of clouds. Rather, now charge exchange. Rather, wikipedia mentioned charge exchange between uprising supercooled water and ice droplets and Graupel (soft haill).
https://en.wikipedia.org/wiki/Lightning#Electrification
But both are nearly same material (water and ice)- why and do they exchange charge? even if they dow, how only state and crystallinity change of a material can change its triboelectric properties? Is there any structure-property justification of triboelectric series, anyway?