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number of visual cloud observations made in Durango and around the Target area ar.ld cloud top estimates made from the many rawinsonde observations indicated that fre~- quent vertical fluctuations of the cloud top over several thousands of ~eet occurred during many of the storm periods. Several aircraft plume tracking flights have both verified the transport of seedi.ng material from the generator sites into the Target area during seeding operations and also the prolonged residence of the seeding material under certain meteorological conditions. This information should lead to improved operational designs for future programs. One of the more important findings associated with the Pilot Project developed by EG&G Inc. project personnel was the technique to stratify cloud profiles as observed on plotted adiabatic soundings by cloud types. This stratification would be accom- plished prior to the evaluation of the response that each cloud type has to seedi.ng. This diagnostic evaluation technique allows clouds of the same type to be compared individually to determine their augmentation potential and the favorable seeding range of their observed meteorological parameters. The cloud types f~om the first four operating seasons that responded most favorably to the existing ground based seeding network are as follows (Figure 2): 1) Orographic clouds with a stable lid top which have no higher clouds above the orographic cloud and have 14,000 feet MSL wind speeds of 35 knots or less and a cloud top or 500 mb temperature of -30C or warmer (whichever is colder). 2) Orographic clouds. with a stable lid top which have middle clouds and/or cirrus above the orographic cloud and have 14,000 ft MSL wind speeds of 30 knots or less and a cloud top temperature of -23C or warmer or a 500 mb temperature of -26C (whichever is colder). 3) An orographic cloud with an unstable ambient lapse rate above the oro- graphic cloud with or without higher clouds and 14,000 ft MSL wind speeds of 27 knots or less and an orographic clouo top temperature of -23C or warmer or a 500 mb temper- ,ature of -26C or warmer (whichever is colder). 4) A deep cloud type usually associated with large synopic storms with 14,000 ft MSL wind speeds of 27 knots or less and a 500 mb temperature of -26C or warmer. The average seed/no-seed ratio of the precipitation data across the Target area for these favorable cloud types is 1. 65. The initial results of this diagnostic study look very promising as a means of identi- fying cloud systems with positive modification potential and of evaluating the seeding effectiveness of the Colorado River Basin Pilot Project. Data for the fifth operating season is presently being gathered for analysis. The results of this five season evaluation and its statistical strength will be included in EGEG Inc.'s Final Report on the Pilot Project. " I \ 8