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File: PMPtopics799summary2.doc July 22, 1999 Creek drainage basin. What analysis (i.e. analysis vs opinion) has been performed to demonstrate the HMR 52 is appropriate for use for the non-orographic component of PMP for the Cherry Creek location? (Tomlinson) The group did not reach consensus. The NWS will examine a way to verify this assumption. 7. The most recent storm included in HMR 55A analyses is 1978. Was a review of more recent storms conducted to identifY significant rainfall events which could influence the site- specific PMP study? (Tomlinson) The NWS reviews stonn events after they occur to detennine if an event would have a significant impact on the regional study. As of 1995, no stonns were identified that would alter HMR 55A. 8. Table 14 in HMR 52 provides a list of the storms used to develop the withinlwithout curves. Averages of values from these 29 storms were used and smoothed. It is stated that the authors of HMR 52 chose not to consider any regional variation that may exist in these storm ratios. They additionally state that they consider this conclusion (i.e. not to consider regional variations) to be justified at this time (1982) but add "..., however, future study should investigate regional variation in depth-area relations." In the HMR 55A discussions related to Depth-Area-Duration Relations (Section 11), it states that ".. .DAD relationships in the non-orographic regions west of the HMR No. 51 region should decrease with increasing area size at an even faster rate than they do within the HMR No. 51 region." In light of these identified variations west of the HMR 51 region and the suggestion that future studies should investigate regional variations in depth-area relations, why were not regional variations in the withinlwithout curves considered in the site-specific PMP study for Cherry Creek? (Tomlinson) The group did not reach consensus. The NWS will examine a way to verify this assumption. 9. Among storm K-factors were applied to the within storm rainfall values to account for orographic effects, in agreement with the HMR 52 recommendation that additional modification to the distribution of PMP brought about by terrain effects be considered (Section 5.1, p43). However, HMR 52 states that these local modifications should modifY or warp the pattern in the direction of major storm patterns that have been observed in the drainage. Does the application of the among storm K-factors modifY the pattern in the direction of major storm patterns that have been observed in the drainage? Please provide examples. (Tomlinson) The group did not reach consensus. The NWS opinion is that any additional study results will have a minimal impact on results and there will be no further examination of this issue at this time. 10. The barrier elevation map in HMR 55A was used to adjust the raster fields of "non- 2 Topics and summary of 21 July 1999 Technical Meeting