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27 upwind, and this increases the time available for the seeding material to act. (2) The convection provides a region of relatively low ice crystal con- centrations. In cases where high ice crystal concentrations are falling into this 'area from above, the convection still provides regions where there are low ice crystal concentrations by lifting air parcels into which the high ice crystal concentrations have not fallen. The convection is therefore frequently associated with lower ice crYu~al concentrations, and the liquid water it contains may be seedable. (3) The convection provides a mechanism for transport of the AgI into the clouds. The convective/convergence zone is located approximately over the seeding generators, and provides a means for the AgI to reach the liquid ,.;rater clouds. Since this region is also the furthest upwind liquid water region, it appears that the seeding generators are ideally placed for un- stable storm stages such as 29 December 1974, flight 1. It appears that, if the more intense unstable storm stages are to be seeded, this convective region should be the target. However, in the neutral stages a different seeding technique would probably work better with the generators further upwind. Hobbs et al. (1975) concluded that the seeding generators should have been placed further upwind. We agree with this conclusion only for the neutral storm stages. For the unstable stages (which contain higher liquid water contents and generally have greater con- densation rates), the seeding generators seem ideally placed. They are located under the convecti,ve/ convergence zone which is also the furthest upwind liquid water region that could be seeded. Droplet spectra in these clouds are discussed in the individual case studies. In general, the droplet sizes at the upwind edge of the clouds ~~~-...- I I I I I I I I I I I I I I I I I, I I