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<br />from the onset of the cold frontal rainband to the dissipation of the orogr~phic <br />cloud. <br /> <br />. Di scus~ ion <br /> <br />The 22 December 1986 storm was one of 12 storms that impacted the Sierra <br />during the dissipation stages of weakening cyclones. The storms had many simi- <br />lar characteristics. Clouds and precipitation were associated with the passage <br />of weak cold fronts. The storms all moved into a mean long wave ridge located <br />over the western United States. Split flow at middle and upper levels of the <br />atmosphere was common. The parent occluded circulation centers. associated with <br />the cold fronti were typically located at 500 latitude or greater and were <br />dissipating. The storms all occurred during extremely dry months, based on an <br />89 year climatology. <br /> <br />No significant precipitation fell prior to the passage of the cold front in <br />any storm except 18 December 1986. On 18 December, light (0.5--1.0 mmh-1) pre- <br />cipitation fell for several hours prior to cold frontal passage. Maximum preci- <br />pitation rates in all storms (2-6 mmh-1)' were associated .with the cold frontal <br />passage. After cold frontal passage, orographic clouds typically formed. <br />Embedded convection may have been present within these clouds, but did not <br />appear to be very important to the precipitation processes, as evidenced by <br />steady precipitation rates (typica'lly < 1 mmh-1). Typical storm duration, based <br />on measurable precipitation at Kingvale, or the presence of supercooled water- <br />bearing clouds, ranged from 12-24 hours. <br /> <br />Complete radiometer data sets were available for five storms in this group. <br />In all five storms, supercooled water was present in the clouds throughout the <br />lifetime of the storms. The highest values were typically observed in the pre- <br /> <br />19 <br /> <br />J <br />