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<br />p. 12, first sentence: "In the standard approach to PMP outlined by the Wodd <br />Meteorological Organization, observed precipitation accumulations for extreme storms are used <br />as indicators of maximum values of convergence and precipitation efficiency." <br />p. 13, second paragraph, first sentence: "Notable controversy has also surrounded PMP <br />estimates for mountainous regions of the western United States. ... Orographic adjustment <br />procedures for PMP have been proposed for mountainous regions (see WMO 1986); however, <br />physical justification for these procedures has not been established clearly." <br />p. 13, third paragraph, first sentence: "It is important to distinguish site-specific from <br />national-scale generalized PMP estimates. ... One distinction between the two types ofPMP <br />estimates is that generalized PMP estimates entail an additional smoothing step in the objective <br />analysis procedure used to map local PMP estimates onto national (or regional) maps. <br />Generalized estimates ofPMP are determined by the higher values in a region to ensure that they <br />are sufficient for all points in a region, even though at specific points within the region <br />topographic features would lead to smaller PMP values from a site-specific analysis." <br /> <br />Introduction, fourth paragraph <br />The NWS comments state that" the NWS has a history of taking bold steps to revise <br />estimates when necessary. HMR 55 (1984) was completely withdrawn and entirely replaced by <br />HMR 55A (1988) after better ways were found (bold italicize added for emphasis) to estimate <br />PMP for short durations in small areas at higher elevations in Colorado." <br />HMR 55A states the following in the section titled "PREFACE TO REVISED <br />EDITION", section 2 on p. xvi: <br />"In HMR No. 55, the vertical moisture adjustment for local-storm PMP transposition <br />somewhat departed from past practice. Use of one-half the liquid water variation observed in <br />precipitable water tables (for a saturated pseudo-adiabatic atmosphere) considerably increased <br />the estimates pfPMP at higher elevation. The authors have changed this adjustment in HMR No. <br />55A to conform to previous studies (bold italicize added for emphasis) that allow for the full <br />moisture adjustment presented by the change in precipitable water with elevation." <br /> <br />Comment 1: <br />The NWS identified the omission of depth-area envelopment in the procedure used for <br />the Cherry Creek site-specific PMP study. They are correct. Depth-area envelopment will be <br />added to the A W A team procedure. Figure 2.10 in the WMO manual is for Depth-Duration <br />enveloping which previously was included in the A W A team procedure. Depth-Area <br />envelopment similar to that shown in Figures 2.11 and 2.12 will be added. <br /> <br />Comment 2: <br />The NWS list three storms that affect Colorado and would have led to an increase in <br />A W A estimates. <br />The Spring Brook, MT storm was not identified by the A W A team for consideration. <br />However, after transpositioning the storm to the Cherry Creek basin, rainfall values of 6.9" vs the <br />NWS 9.7" for the 6-hour/l,000 sq mi value and 10.5" vs the NWS 14.8" for the 24-hourll,000 <br />square mile value were computed. These values indicate that inclusion of the storm would not <br />have affected PMP values for the Cherry Creek study. <br />Both the Gibson Dam, MT storm and the Big Elk Meadows, CO storms occurred over <br />and west of the first upslopes and are not transpositionable to the Cherry Creek basin. HMR <br />