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Class C3: Cloud systems associated with a tropical air mass moving over Morocco from the south and consisting mainly of altocumulus and altostratus. Class C2: Relatively isolated convective clouds that are generally associated with post frontal storm events and consist mainly of cumulus congestus. Class C1: Stratiform cloud system associated with either westerly or northwesterly flow, and possibly containing embedded convection. Figure 5. Frequency of occurrence of cloud category classifications. storms are the major cloud and precipitation producers for Morocco, and are the most likely situations when sel~dable conditions are pre- sent. The cloud physics analysis suggests that the post frontal clouds are the most likely to have seedable conditions. More cases, how- ever, are needed to "erify this trend. 5. DISCUSSION Using 21 cases, the analysis shows a mi- crophysical distinction between the three cat- egories of clouds initially subdivided according to their stability and air mass characteristics. The clouds in category C2 associated with un- stable air have a relatively high frequency of occurrence of high liquid water. and a low fre- quency of high ice particle concentration. This suggests that this category likely contains clouds which have good seedability. Category C3. on the other hand, probably does not have good seedability. Category Cl clouds have moderate seedability, and may benefit from further subdivision to make a clearer distinction between seedable and unseedable portions of these stomlS. In general, the highest water contents and lowest ice particle concentrations were found in the convective clouds (cumulus congestus) of class C2. When the stonn moves in from the south or southwest (Case C3), the flow tends to parallel the mountain barrier and does not seem to receive enough orographic lifting to produce, significant levels of supercooled water. Flow from the west or northwest (Class Cl), on the other hand. will generally have a significant cross-barrier component to the flow and was often found to produce significant quantities of supercooled water contents. In order for these results to be more gen- el~al1y applicable, the frequency of occurrence of each of these cloud categories was also de- umnined (see Figure 5). Class C1 occurred most frequently, 67% of the cases; while class C2 occurred 23% of the time. Fortunately, the le,ast seedable case C3 occurred only 10% of the time. This study is ongoing, and will be updated al; more data are collected. These initial rElsults, however, suggest that the cloud sys- tEims occurring over Morocco are likely to be good candidates for seeding in most cases. Further study needs to be done to extend the sample size and to determine the areal extent and duration of each of these cloud categories. REFERENCES Baddour, O. and R. M. Rasmussen, 1988: :Microphysical observations over the Atlas mountains in Morocco. Tenth International Cloud Physics Conference, Bad Homburg, F'RG,IUGG, 15-20 August 1988,356-358. Bensari, et aI., 1989: Programme AI Ghait _ Design and evaluation of a weather modifi- cation program in Morocco. Fifth WMO Scien- ti.fic Conference on Weather Modification and Applied Cloud Physics, World Meteorological Organization, Geneva. (this volume) Vall, G.. R. Koenig. and T. Yoksas, 1988: Esti- mate of precipitation enhancement potential for the Duero Basin in Spain. J. AppI. Meteor.. 27,829-850.