Question highlights the formation of graupel through riming (i.e., the immediate freezing of supercooled droplets on contact with larger ice particles). The three photos depict this process, starting on the left with a stellar plate that has grown large enough to descend with respect to supercooled droplets and accrete a dense coat of rime. The middle photo shows the same stellar plate after accreting even more rime. The photo on the right shows conical graupel. Graupel is the stage of riming when the embryo (a stellar plate in this case) can no longer be discerned. Note that riming is a positive feedback mechanism: as an ice particle accretes rime, its radius and fall speed increases and it collides with a larger number of supercooled droplets per unit time. Graupel becomes hail when supercooled droplets no longer freeze immediately upon collision (due to latent heat of freezing, the graupel surface warms). Hail normally accretes supercooled droplets in both wet and dry growth modes.