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<br />, . <br /> <br />In making adjustments for differing saturated, pseudo-adiabatic conditions, the NWS uses <br />values closer to 40,000 feet than 20,000 feet. The differences in adjustment ratios <br />resulting from these choices are not trivial. Using a 1000mb, 12-hour persisting dew <br />point of70oP and transposing from 4,000 feet to 7,000 feet, a full depletion using the <br />NWS standard produces an adjustment ratio of 0.715, whereas an adjustment ratio of <br />0.679 is produced when a "ceiling" of 20,000 feet is used. The table and description in <br />IR#lleave the impression that HMR-55A goes up to only 20,000 feet whereas values up <br />to and above 40,000 feet are found in Appendix C ofHMR 55A. <br /> <br />Pages 7-8, paragraph 3 <br /> <br />Based on the "PWI-20" column, the decrease of 1 000 mb dew point from 700P to 600P <br />seems to result in a 37 percent, not 46 percent change in precipitable water. <br /> <br />We are not sure what purpose is served by the table on page 8. <br /> <br />Pages 9-12, Temporal distribution of hourly precipitation: <br /> <br />The temporal (as well as spatial) distribution of the precipitation developed in NWSI995 <br />was achieved following the rules stated in HMR 52, These rules are appropriate since the <br />Cherry Creek Drainage is located entirely east of the 105th meridian, See also the answers <br />to Questions 6 and 12 in NWS200 I. The rules governing temporal distributions are <br />found in section 2.3 ofHMR 52 (and in section 7.1,8,1-4 for the spatial distribution). <br />The rules developed in HMR 52 took historic storms into consideration, <br /> <br />As implied in several places in IR#I, scientists are still in the dark about some aspects of <br />extreme atmospheric behavior. Over time, typical characteristics of observed extreme <br />storms have been documented, However, it is a large step to take to insist that a storm <br />generated at the extreme upper limit of atmospheric probabilities must have the to-date <br />typical characteristics of already-observed storms, Recognizing this, HMR 52 permits the <br />user of developed basin averaged increments ofPMP considerable flexibility in <br />constructing a "storm" which will have the most significant of hydrological <br />consequences. The spatial and temporal distributions shown in Table 5 and Pigures 2-5 <br />ofNWS 1995, while not mimicking all aspects of certain, selected extreme storms, do <br />follow the guidelines established in HMR 52. <br /> <br />The temporal distribution of hourly increments of calculated 72-hour hypothetical PMP <br />storm basin-averaged depths are shown in Table 5 ofNWSI995, The arrangement of <br />these hourly amounts is simply one of many possibilities which were acknowledged as <br />permissible. The sequence of Table 5 was presented for use in hydrological applications, <br />A user of these increments could develop the hydrological consequences of having the <br />most intense 1 hour of precipitation occurring 22 hours after the beginning of <br />precipitation, but not necessarily at 10 PM local time, The use of the headings "Day 1, <br /> <br />8 <br />