CWCB Wintertime Weather Mod Report

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2.6 Cloud Seeding Project Design It was concluded from the analyses, and based upon North American Weather Consultants' previous experience in designing and conducting similar winter orographic cloud seeding projects in other areas, that a program utilizing ground based silver iodide generators is feasible in Gunnison County. It was estimated that such a program can be expected to produce an average 10-20% increase in precipitation in the higher elevations of GunnIson County during operational periods. These statements are based upon the following considerations: . There are significant high elevation mountain barriers within Gunnison County which will produce substantial orographic lift of lower level atmospheric moisture during the passage of winter storms through the area. This lifting will produce __ _____frequent and sustained_periods of supercooled liquid water (water Qroplets 41 clouds that occur at temperatures colder than freezing) occurrences on the upwind slopes of these mountain barriers. The ~resence of supercooled cloud water droplets is a necessary ingredient for clouds to be seedable. --j . The supercooled liquid water droplets can be seeded using silver iodide to enhance the precipitation process in select periods during winter storm passages through the target area. . The heights of the mountain barriers in Gunnison County are very favorable for seeding, given the activity temperature threshold of the silver iodide seeding .' . material and the normal vertical structure of the atmosphere during winter storms. . Typical winter storm temperatures favor the use of manually operated, ground- based silver iodide generators which are comparatively inexpensive to operate. . Many prospective locations for siting of these generators appear to be available. 20 I I I I I I I I -- -~~ ---I~ I I I I I I I I I I