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<br />Extraordinary storm dynamics were most likely involved in producing the precipitation <br />both at Cherry Creek and at Hale in May, 1935. Low level jets (as part ofthese <br />dynamics) were likely present at both locations. We speculate that in the hypothetical <br />PMP storm for the Cherry Creek Drainage, dust transported there from Texas, Oklahoma, <br />and Kansas could well be involved in the storm's microphysics. <br /> <br />Page 14, Storm positioning, paragraph 1: <br /> <br />Spatial distributions of basin centered cumulative PMP amounts as shown in Figures 2-5 <br />ofNWSl995 were achieved following guidelines in HMR 52 and are fully appropriate <br />for the Cherry Creek Drainage, <br /> <br />The answer to Question 2 in NWS1995 as well as answers to Questions 21 and 22 <br />address some of the concerns expressed in this section of IR# 1. <br /> <br />The NWS has no objection to a spatial distribution ofPMP average depths, such as those <br />found in Table 4 ofNWS1995, in which multiple isohyetal centers are present. While it <br />may be reassuring to use patterns that have been seen before, the patterns of Figures 2-5 <br />ofNWS 1995 are realistic in the setting of the Cherry Creek Drainage. We would caution <br />those who develop multiple isohyetal centered patterns within a basin not to exceed PMP <br />levels for subareas of the basin as specified by the depth-area-duration relations of section <br />11.3.3 ofHMR 55A along with the index values found in Plates Ib, IIb, illb, and !Vb. <br /> <br />IR# 1 refers to a "missing link" and to a "missing Cherry Creek storm", We agree that a <br />different orientation ofisohyets (from that seen in NWS1995) for the hypothetical PMP <br />storm could produce a lesser volume ofprecipitation in the Cherry Creek Drainage. <br />Procedures in HMR 52 for calculating basin averaged depths provide for such a situation, <br />However, nature is fully capable of producing in eastern Colorado isohyetal patterns like <br />lnose of Figures 2-5 ofNWS1995. <br /> <br />With regard to observation 1. on page 18: we do not agree that the "PMP event" is <br />volume-driven; rather the probable maximum flood resulting from a PMP event is <br />volume dependent. The basin centered average depths ofPMP for the Cherry Creek <br />drainage developed in NWS 1995 were done in such a way as to ensure the probable <br />largest volume of precipitation based on a PMP event. <br /> <br />Page 21, One percent chance storm rainfall: <br /> <br />In NWS 1995, 1 DO-year precipitation frequency analysis as modified to produce <br />orographic K-factors was used to modify POINT (emphasis is ours), non-orographic PMP <br />storm precipitation within the Cherry Creek basin and not to adjust "areal rainfall <br />patterns". Perhaps the authors were mistakenly recalling use of averaged K-factors by the <br /> <br />10 <br />