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<br />;;~ ~ <br /> <br />discussed in the WMO Manual, the maximization calculation effectively does not change if any <br />level at or above 400mb is used. A W A used the Table of Precipitable Water in HMR 55A, <br />Appendix C for precipitable water values. Thirty thousand feet was used as the height of the <br />300mb level. <br /> <br />For example, consider a storm that occurs at sea level with a storm representative 1000mb <br />dewpoint of70 F and a maximum 1000mb dewpoint of75 F. Using 300mb as the top ofthe <br />atmospheric moisture, the precipitable water associated with 70 F is 2.25 inches and with 75 F is <br />2.85 inches. These values produce a maximization factor of 2,85/2.25 = 1.267. If a higher level <br />in the atmosphere were used, say 200mb (approximately forty thousand feet), the precipitable <br />water associated with 70 F is 2.27 inches and with 75 F is 2.89 inches. These values produce a <br />maximization factor of 2.8912.27 = 1.273. Both of these calculations produce a maximization <br />factor of 1.27 when rounded to two significant digits. <br /> <br />To answer the Corps' question directly, the precipitable water above 300mb is not considered in <br />the A W A calculations consistent with the WMO Manual discussion, HMR 55A does not <br />provide any information on what level was used in HMR 55A calculations. <br /> <br />2. page 50. How was the storm center elevation of 5,000 feet determined? Note HMR 55A <br />lists a storm center elevation of 5,800 feet for the 1921 storm. <br /> <br />A W A response to Question 2. <br /> <br />The Storm Studies Pertinent Data Sheet for this storm, SW 1-23, shows the largest rainfall <br />observation at a location identified as No.3, Colorado, 12.0". The location for this location is <br />graphically shown on the storm isohyetal map from the NWS and is several miles northwest of <br />Pueblo. Coordinates hand written on the Storm Studies Sheet are 38020' N, 104041 W. This <br />location appears to be consistent with the plotted location on the NWS isohyetal map. A W A <br />produced a total storm isohyetal pattern using rainfall information from the NWS. The isohyetal <br />pattern is shown in Figure 4.2, page 51, of the report. The coordinates on the Storm Studies <br />Sheet fall within the maximum rainfall isohyetal in Figure 4.2. According to DeLorme Topo <br />USA mapping software, the elevation at thIS location is 4,960 feet. Additionally, a letter from <br />the Office of Hydrologic Director discussing the Design Storm Studies for the South Platte River <br />Basin, dated May 29, 1944, discusses the June 3-5, 1921 storm. This discussion states"... the <br />storm of June 1921 occurred at elevations of 5,000 feet.. ,." Using this information, an elevation <br />of 5,000 feet was used as the storm center elevation for the 1921 storm. <br /> <br />A W A could not find the reference in HMR 55A that lists a storm center elevation of 5,800 feet <br />for the 1921 storm. This elevation is probably associated with the rainfall center north of <br />Penrose. The area of large rainfall in this region was much smaller than the area northwest of <br />Pueblo and was associated with significant terrain upslope. A W A used the larger rainfall <br />volume associated with the region northwest of Pueblo for transpositioning to the Cherry Creek <br />drainage basin to be conservative, Hence, the elevation associated with this rainfall region was <br />used, <br />