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Show 4. 5. 4. 1. 3 Seeding Schedule Ground seeding from Mt. Harris was done from 0715 to 0815 MST with the period 0700-1000 designated as the seeded precipitation block for analysis in AP. No. 5. The Queen Air dropped pyrotechnics from 1600 MST to near 1700 MST. Verey pistol flares were fired at one minute intervals along a pre-determined 8 mile long track. Three repeated seeding runs were made along this track. The period 1600-1900 MST was designated as the seeded precipitation block on AP No. 6. 4. 5. 4. 1. 4 Experimental Area 3 -Hourly Precipitat~on Totals Isohyetal maps were drawn for each three-hour period of AP' s 5 and 6 (Figures 136-139) using all _a vailable weighing bucket data. The most interesting feature of these maps is the light amount of snow at Buffalo Pass, particularly in Figures 136-138. The pattern here is just reversed from the seasonal normal pattern according to 5 years .of snow course water equivalent data normalized to Buffalo Pass. The implications of these patterns are discussed later. 4. 5. 4. 1. 5 Computed Seeded Precipitation Fallout Area~ and Percent of SixHour Precipitation Occurring in Three-Hour Seeded Precipitation Period Calculations of seeded snow crystal fallout trajectories were made, and the interception of trajectories with the ground are noted in Figures 140 and 141. An envelope enclosing all ·these interceptions yields the estimated seeded precipitation zone for the -prevailing wind regime used in the calculation. The Mt. Harris vertical wind profiles used in the computations are shown in Figure 142. In Figure 140, the seeded precipitation fallout zone is based on the 0749 MST Mt. Harris winds aloft observation; by 1012 MST, winds had veered and would have turned the trajectory toward Rabbit Ears and False Top. Surface wind reports at Mt. Harris and Thunderhead indicated this wind shift likely occurred near 0900 MST. Ground-based seeding effects should have been noted around Fish Creek, Buffalo Pass, Lodwick and Emerald Mountain within approximately 50-60 minutes from first seeding release, and should have occurred most strongly from 0810 to about 0910 MST. Following the wind shift near 0900 MST, the AgI remaining in lower levels should have been shifted southward to affect the southern portion of the area around Rabbit Ears, False Top, Valley View, and Walton Peak. Thus, a seeding effect could be expected to reach these locations after 0900 MST and be mostly over by·1100 MST (unless low level winds were too light around Mt. Harris during the _0 715-0815 MST Agl release). These predicted seeding effects are compared to hourly weighing bucket totals and Lodwick vertical pointing radar in Section 4. 5. 4. 1. 6. 221 |
