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<br />Effective Barrier Height: The height of a barrier determined from elevation analysis that <br />reflects the effect of the barrier on the precipitation process for a storm event. The actual barrier <br />height may be either higher or lower than the effective barrier height. <br /> <br />Envelopment: A process for selecting the largest value from any set of data. In estimating <br />PMP, the maximum and transposed rainfall data are plotted on graph paper, and a smooth curve <br />is drawn through the largest values. <br /> <br />Front: The interface or transition zone between two air masses of different parameters, The <br />parameters describing the air masses are temperature and dew point. <br /> <br />General storm: A storm event, which produces precipitation over areas in excess of 500 <br />square miles, has a duration longer than 6 hours, and is associated with a major synoptic weather <br />feature. <br /> <br />Hydrometeorological Report No.51 (HMR 51): Publication that provides Probable Maximum <br />Precipitation estimates for United States east of the IOSth meridian. <br /> <br />Hydrometeorological Report No.52 (HMR 52): Application manual for Probable Maximum <br />Precipitation for the United States east of the 105th meridian, <br /> <br />Hydrometeorological Report No.55A (HMR 55A): Probable Maximum Precipitation <br />estimates for United States between the Continental Divide and the 103cd meridian. <br /> <br />Hydrometeorological Report No.57 (HMR 57): Probable Maximum Precipitation for Pacific <br />northwest states, Columbia River (including portions of Canada), Snake River and Pacific <br />coastal drainages. <br /> <br />Isohyet: A line drawn through geographic points recording equal amounts of precipitation <br />during a given time period or for a particular storm. <br /> <br />Isohyetal map: Map depicting contours of equal precipitation amounts recorded during a <br />specific time period. <br /> <br />Isohyetal pattern: The pattern formed by the isohyets of an individual storm. This includes <br />shape, spatial dimensions and orientation of the isohyets on an isohyetal map. <br /> <br />K-factors: Orographic factors used to incorporate topographic effects on rainfall amounts. <br /> <br />Local storm: A storm event that occurs over a small area in a short time period. Precipitation <br />rarely exceeds 6 hours in duration and the area covered by precipitation is less than 500 square <br />miles, Frequently, local storms will last only I or 2 hours and precipitation will occur over areas <br />of up to 200 square miles. Precipitation from local storms will be isolated from general-storm <br />rainfall. Often these storms are thunderstorms. <br /> <br />XV1l1 <br /> <br />. <br />. <br />. <br />. <br />. <br />. <br />. <br />. <br />. <br />. <br />. <br />. <br />. <br />. <br />. <br />. <br />. <br />. <br />. <br />. <br />. <br />. <br />. <br />. <br />. <br />. <br />. <br />. <br />. <br />. <br />. <br />. <br />. <br />. <br />. <br />. <br />. <br />. <br />. <br />. <br />. <br />. <br />. <br />