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<br />, . <br /> <br />Task 3 <br /> <br />Page 6: <br /> <br />While agreeing on the "minimal impact" conclusion of the Saturated Storm Atmosphere <br />Assumption section, we disagree on the way in which it was reached. Studies in other <br />areas indicate that saturated pseudo-adiabatic conditions do exist in historic storms, See, <br />for example, Monthly Weather Review, November 1970, pp 851-859, especiallypp 855- <br />857. However even if saturated pseudo-adiabatic conditions are not always the case in <br />the historic storms, it does not follow that the PMP storm would be required to have less <br />water available for precipitation than would be the case in a saturated pseudo-adiabatic <br />atmosphere. <br /> <br />Pages 6-7, Maximum Storm Efficiency: <br /> <br />We agree that numerical models are not yet reliable tools for estimating PMP, <br /> <br />A storm that approaches the maximum efficiencv for rainfall production, such as is <br />referenced in the last sentence of the second paragraph, need not have produced <br />precipitation values close to PMP. <br /> <br />Page 7, Computed rainfall adjustments: <br /> <br />It should be noted that the sensitivity due to transposition varies according to the <br />elevation interval through which the transposition is made as well as with temperature <br />difference, This may be seen in a table of adjustment ratios below: <br /> <br />Temperature (OF) <br /> <br />Elevation Interval (ft) <br /> <br />70 <br /> <br />71 <br />0,717 <br />0.761 <br /> <br />4000- 7000 <br />4000-6500 <br /> <br />0.715 <br />0,754 <br /> <br />This example is based on full pseudo-adiabatic depletion over the complete elevation <br />interval. Different rules were followed in HMR 55A - see section 8.4.2.2, concerning <br />vertical transposition of in-place maximized storm depths of precipitation, <br /> <br />The approximate 5 percent adjustment for every degree of Fahrenheit change mentioned <br />works only if there is no change in elevation. Consensus rules for making adjustments in- <br />place and for vertical and horizontal transposition can be found in the Manual For <br />Estimation of Probable Maximum Precipitation, Operational Hydrology Report No.1, <br />World Meteorological Organization, 1986, sections 2.3 and 2,6. <br /> <br />7 <br />