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<br />3. CLIMATOLOGICAL CONTEXT OF 1987 WEATHER <br /> <br />D.A. Risch, D.A. Griffith, H.R. Swart, and J.R. Thompson (NAWC) <br />A.W. Huggins (DRI) <br /> <br />As in prior reports this section places the weather encountered <br />in the 1987 research program within the larger climatological <br />context and, when possible, compares the 1987 weather with that <br /> <br />which occurred in 1983 and 1985. <br /> <br />Synoptic patterns in 1987 are <br /> <br />compared to long-term historical distributions of those patterns. <br />Rawinsonde, surface temperature and precipitation data are also <br /> <br />compared to averages based on data from earlier years. <br /> <br />a. synoptic weather types <br />Elliott (1949, 1951) has developed a classification of synoptic <br /> <br />weather charts based on upper-level flow, surface pressure, and <br /> <br />outbreaks of polar air at the surface. <br /> <br />Figure 8 illustrates ten <br /> <br />weather types developed for the North American continent. These ten <br /> <br />weather types and three others have been used by Sutherland (1983) <br /> <br />to classify the winter weather in Utah. <br /> <br />Table 7 lists these <br /> <br />thirteen weather types, describes the prominent weather features <br /> <br />associated with each, and the typical weather in Utah. <br /> <br />Table 8 <br /> <br />lists the weather types observed during three-day periods in 1987. <br />On the basis of the list of weather types in Table 7 Sutherland <br />(1983) has classified the weather in Utah for drought and non- <br /> <br />drought periods. <br /> <br />The non-drought periods can be treated as a <br /> <br />"normal" against which the weather types of the 1987 field program <br />can be compared. Table 9 compares the weather types in 1987 with <br />the long-term "normal" distribution of types and with the types <br /> <br />observed in 1983 and 1985. <br /> <br />26 <br />