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<br />events may be different than those of PMP precipitation events and because of a <br />poorly defined precipitation climatology for the Mason Reservoir high elevation <br />site, <br /> <br />The transposition of historical storms took care to adhere to the HMR 55A <br />protocols as much as possible, The steps followed are summarized below: <br /> <br />1. In place moisture maximization involved the determination and use of <br />both the 12-hour storm representative and thl~ maximum persisting dew <br />points. <br /> <br />2. Transposition considered comparative dew points along the moisture <br />inflow vectors at both the original and the transposed storm locations. <br /> <br />3. Elevation-related moisture adjustmlmts followed HMR 55A guidcllnce for <br />local storms which relies on the adjustment for elevation based on <br />Figure 14.3 in HMR 55A (p 219) and the maximum 12-hour persisting <br />1000 mb dew point. <br /> <br />4. The pseudo-adiabatic method was llsed to reduce moisture for e,ffective <br />barrier heights in general stormS. This methc)d uses tables of <br />precipitable water as a function of height, assuming the presence of a <br />saturated atmosphere. The location of the Mason Reservo,ir relative to <br />important moisture inflow negated this correction. <br /> <br />5. Since all the historic storms had significant o,rographic influenclls to <br />their precipitation patterns, no attempt was made to separate thE~ <br />orographic and convergence components of precipitation. <br /> <br />6. Local terrain was considered for its orographic lift relative to the <br />placement of both local storm and general storm isohyetal patterns. <br />Transposed storm center locations were determined using guidance <br />provided in HMR's 55A and 49. <br /> <br />The next two sections of this report will present the local and general storm <br />PMP's prepared using the standard HMR 5!5A site-specific storm methodologies, <br /> <br />25 <br />