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<br />. <br /> <br />. <br /> <br />. <br /> <br />NWS 11 May 2001 <br /> <br />2. Primary overall concern with this PMP is the "storm area" and, to a lesser extent, the storm <br />centering in light of the southeasterly surface winds needed to advect the quantity of moisture <br />associated with such an extreme storm. (Doesken) <br /> <br />The group did not reach consensus. The NWS will examine a way to verify this <br />assumption. <br /> <br />Answer 2 (and 3). <br /> <br />The creation of a strong synoptic low, or "cyclone", to the south or east of <br />the Palmer Ridge can produce a precipitation maximum north of the <br />Palmer Ridge, as evident from the Plum Creek Storm of 1965 and the <br />Cherry Creek Storm of 1935. The circulation from such a low would be <br />enhanced by upslope, and the large-scale moisture source would be from <br />the southeast, that is, the Gulf of Mexico. The resulting precipitation <br />would maximize north of the Palmer Divide, and would show a <br />precipitation pattern over the Basin similar to Figures 2 through 5 of The <br />Study. The pattern of the PMP storm precipitation for the Cherry Creek <br />drainage was developed following the procedures of HMR 52. HMR 52 <br />procedures are applicable to that amount of total precipitation which is <br />attributable to non-orographic processes, occurring east of the 105lh <br />meridian. Guidance from HMR 52 required that non-orographic PMP be <br />created for the storm area size as close as possible to that of the Cherry <br />Creek drainage, with lesser amounts for storm area sizes above and below <br />that of the drainage. The HMR 52 procedures also required that the <br />isohyets of non-orographic PMP be oriented in such a way as to produce a <br />maximum volume in the drainage. This required orientation was north to <br />south. The orientation of the 1935 Cherry Creek storm isohyets was <br />south-southwest to north-northeast (isohyets as drawn by the Corps of <br />Engineers in 1943). The orientation of the Plum Creek storm isohyets was <br />north to south (Figure 3-6 of HMR 44 and Figure 2.19 of HMR 55A). <br />These observed orientations support the orientation shown in Figures 2 <br />through 5 of The Study. <br /> <br />6 <br />