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r.ll. ~"':: 3. page 50. What does the "1.50(a)" mean for the in-place Maximization factor? A W A response to Question 3. A W A concurs with the NWS conclusion that there should be upper limits place on in-place maximization factors. The basis for this conclusion is that the maximization procedure assumes that a storm's efficiency in converting atmospheric moisture to rainfall remains unchanged during the maximization process, i.e. atmospheric moisture can be added up to the maximum value used in the maximization process without changing the storm efficiency. Adding moisture to the atmosphere associated with a rainfall event can and does have an effect on storm efficiency and at some point the assumption that additional moisture has no effect on the storm's efficiency is no longer valid. NWS has adopted upper limits to storm maximization. HMR 51 applied a limitation of 1,50 to the maximization factor (HMR 51, Section 3.2,2, page 28), HMR 55A, Section 8.4,1.1, page 131, provides some discussion on limitations to in-place maximization adjustment. HMR 55A adopted the 1,50 limit for the nonorographic region east of the Orographic Separation Line (OSL) (HMR 55A, Section 5.4, page 88). Both HMR 55A and the newer HMR 57 apply a limitation of 1.70 in orographic regions. This limit was adopted to allow for inadequacies of the storm sample in orographic regions (HMR 55A, Section 8.4,1.1, page 131; HMR 57, Section 7.2, page 66). A W A used the limitation of 1,50 for Cherry Creek and annotated when it was applied with "1.50(a)", indicating that the adopted value of 1.50 was used instead ofthe higher calculated in-place maximization value for the storm. 4. page 50, How was the Elevation Adjustment Factor Computed? Note: it appears that a direct ratio of precipitable water was used for the Elevation Adjustment factor. HMR 55A uses one-half of the ratio and excludes the first 1,000 feet of elevation difference. A W A response to Question 4. It is correct that a direct ratio of precipitable water depletions based on either elevation or upwind barriers (which ever was higher) was applied, For example, for an elevation adjustment made to 5,000 feet, the precipitable water from the 1000mb level to the 300mb level would be adjusted by subtracting the precipitable water from 1000mb to 5,000 feet from the total precipitable water value (1000mb to 30,000 feet), For a storm representative dewpoint or maximum dewpoint of70F, the total precipitable water is 2,25 inches and the precipitable water between 1000mb and 5,000 feet is 0,52 inches (determined using the tables in HMR 55A, Appendix C), Hence an elevation adjusted value of 2.25 - 0,92 = 1.33 would be used. There are two other issues involved in this question. The first is the use of the full moisture adjustment using the change in precipitable water with elevation. HMR 55 did use one-halfthe liquid water variations observed in the precipitable water tables. This was one of the three areas where alternate decisions were incorporated into HMR 55A from those used in HMR 55. Quoting from the Preface to Revised Edition in HMR 55A, page xvi, "The authors have changed this adjustment (use of one-half the liquid water variation) in HMR 55A to conform to the previous studies that allow for the full moisture adjustments presented by the change in precipitable water with elevation." None of the subsequent HMRs have used the one-half liquid water variations.