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<br />3. GENERAL STORM PAtTERNS INFLUENCING THE SIERRA NEVADA <br /> <br />Synoptic patterns that brought weather to the central Sierra Nevada were <br />c'l ass ifi ed broadly into two groups Ibased on the prevail i rig f1 0\'1: those storms <br /> <br />that had a predominant zonal component, and those that had a predominant meridi- <br /> <br />ona1 component. Within each general group, storms were further organized based <br /> <br />on general synoptic scale characteristics and state of evolution as each storm <br /> <br />moved into the Sierra Nevada. The categorization presented includes all storms <br />which moved across the Sierra Nevada during the four field seasons beginning in <br /> <br />1983/84. Each category inc1udrj storms with similar synoptic characteristics, <br /> <br />such as storm trajectory, winr 10\'1, and cloud fields. The basis of the storm <br />. <br /> <br />categorization was cloud pattl ,s from satellite images and 500 mb flow fields. <br />Of the 63 storms that affected the project area 56 were found to fit into one of <br /> <br />five general categories. These categories are discussed below. <br /> <br />A. Storms with zonal flow characteristics <br /> <br />Storms originating in zonal flow over the eastern Pacific undergo continuous <br /> <br />changes as they develop, occlude and dissipate. The stage of evolution of the <br /> <br />storm often dictates the characteristics of supercooled water observed in the <br /> <br />storm during its passage over the Sierra Nevada. <br /> <br />1) Developing storm embedded in s!rong westerly or southwesterly flow <br /> <br />Fig. 3a shows a typical flow field, cloud pattern and trajl~ctory of the vor- <br />ticity maximum associated with the 500 mb trough in a developing storm embedded <br />in strong zonal flow. _ This type of storm system produced heavy, sustained pre- <br /> <br />cipitation in the Sierra Nevada. Th~se storms were often associated with <br /> <br />flooding. Typically, the surface circulation center was located between 45 and <br /> <br />6 <br />