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<br />the cloud where there was divergence. The downdrafts were induced in part by sublimation cooling of <br />solid (ice) precipitation falling from the altostratus. Only virga was observed and the radar echoes did <br />not reach the surface. <br /> <br />Stage Il[ was initially dominated by passage of a short-wave aloft. Drier air associated with the <br />short-wave led to complete evaporation of the altostratus of Stage I. The lower parts of the cloud <br />(<4.5 km MSL) eventually redeveloped into altocumulus. <br /> <br />Later ill Stage II, the wind veered more perpendicular to the mountains. Simultaneously, convergence <br />developed in the lower 900-1200 m of the atmosphere, and mesoscale updrafts of 0.1-0.2 m S-l were <br />calculated. Maxima in the water release rate were associated with the updrafts. <br /> <br />During Stage III, a passing cold front influenced the kinematics and cloud and precipitation. From prior <br />to frontal passage to a few hours afterward, the wind beneath the frontal surface veered from <br />southwesterly to northerly. There was strong convergence at low altitudes just upwind of the Tushar <br />Mountains. It was accompanied by strong, deep mesoscale updrafts extending from near the ground up <br />through the frontal surface and by water release maxima. <br /> <br />The stonn changed character after the wind at low altitudes had veered to northerly and had become <br />parallel to the Tushar Mountains. Convergence maxima continued to be present beneath the frontal <br />surface but weaker. They preceded by -0.5 h maxima in the convergence above the frontal surface. <br />Associated with these paired convergence features were updraft maxima located above the frontal <br />surface. Water release rates were generally lower than earlier in Stage III. The decrease was greatest at <br />low altitudes beneath the frontal surface where the wind had veered to northerly, where there was little <br />uplift by the Tushar Mountains, and where updrafts were weak. Above the frontal surface, the decrease <br />in water release rate was not as great inasmuch as lift by the frontal surface was still occurring. <br /> <br />The stonn dissipated in Stage IV. The axis of the longwave trough passed through the area, winds at <br />higher altitudes beneath the frontal surface veered more northerly, and there was substantial drying at all <br />altitudes above and below the frontal surface. The winds beneath the frontal surface were divergent, <br />indicative of subsidence, and mesoscale downdrafts were present. <br /> <br />Long, A. B., 1988: On the precipitation efficiency of a winter mountain stonn in Utah. Preprints, 11th <br />Conference on Weather Modification, Edmonton, Alberta, Canada, October 6-8, 1987. American <br />Meteorological Society, Boston, MA, 64-67. <br /> <br />No abstract. <br /> <br />Long, A. B., 1987: 1987 Field Operations Report-Utah/NOAA Cooperative Weather Modification Research <br />Program. For Utah Department of Natural Resources, Division of Water Resources. Atmospheric <br />Sciences Center, Desert Research Institute, Reno, NV, 133 pp. <br /> <br />No abstract. <br /> <br />Long, A. B., 1987: 1986 Field Operations and Analysis Plan-Utah/NOAA Cooperative Weather Modification <br />Research Program. For Utah Department of Natural Resources, Division of Water Resources. <br />Atmospheric Sciences Center, Desert Research Institute, Reno, NV, 78 pp. <br /> <br />No abstract. <br /> <br />48 <br />