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Persisting dew point: The dewpoint value at a station that has been equaled or exceeded <br />throughout a period. Durations of 3, 12 or 24 hours are commonly used, though other <br />durations may be used at times. <br />Probable maximum precipitation (PMP): Theoretically, the greatest depth of <br />precipitation for a given duration that is physically possible over a given size storm area <br />at a particular geographic location at a certain time of the year. <br />Rainshadow: The region, on the lee side of a mountain or mountain range, where the <br />precipitation is noticeably less than on the windward side. <br />Saturation: Upper limit of water -vapor content in a given space; solely a function of <br />temperature. <br />Storm transposition: The hypothetical transfer or relocation of storms from the location <br />where they occurred to other areas where they could occur. The transfer and the <br />mathematical adjustment of storm rainfall amounts from the storm site to another location <br />is termed "explicit transposition." The areal, durational, and regional smoothing done to <br />obtain comprehensive individual drainage estimates and generalized PMP studies is <br />termed "implicit transposition" (WMO, 1986). <br />Synoptic: Showing the distribution of meteorological elements over an area at a given <br />time, e.g., a synoptic chart. Use in this report also means a weather system that is large <br />enough to be a major feature on large -scale maps (e.g., of the continental U.S.). <br />Temporal distribution: The time order in which incremental PMP amounts are arranged <br />within a PMP storm. <br />Tropical Storm: A cyclone of tropical origin that derives its energy from the ocean <br />surface. <br />Total storm area and total storm duration: The largest area size and longest duration <br />for which depth - area - duration data are available in the records of a major storm rainfall. <br />Transposition limits: The outer boundaries of the region surrounding an actual storm <br />location that has similar, but not identical, climatic and topographic characteristics <br />throughout. The storm can be transpositioned within the transposition limits with only <br />relatively minor modifications to the observed storm rainfall amounts. <br />Warm front: Front where relatively warmer air replaces colder air. <br />Warm sector: Sector of warm air bounded on two sides by the cold and warm fronts <br />extending from a center of low pressure. <br />1 0 <br />