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<br />Colorado Extreme Storm Precipitation Data Study <br /> <br />Introduction <br /> <br />This report summarizes the results of a nearly two-year study of extreme precipitation <br />characteristics in Colorado. The primary goal of this project was to identify and document <br />the heaviest storms that have occurred in or near the Rocky Mountains in Colorado. The <br />criterion used to define heavy storms was any storm that exceeded the l00-year storm <br />precipitation amounts for specified storm durations as published in the NOAA (National <br />Oceanic and Atmospheric Administration) Atlas 2, Precipitation-Frequency Atlas of the <br />Western United States, Volume ill - Colorado (1973). The critical properties of storms <br />that determine their potential for producing flooding are precipitation intensity, storm <br />duration and storm area. In many of the storms included in this study, particularly the <br />local intense summer thunderstorms, only a limited amount of information is known about <br />storm areas. However, because of the importance of area and duration, some storms with <br />large areas or long durations were considered even though they may not have exceeded <br />100-year thresholds at any individual point. <br /> <br />The format for this report is consistent with the outline of the original proposal submitted <br />to the State of Colorado, Department of Natural Resources Division of Water Resources <br />in the summer of 1994. Activities and accomplishments are presented in the order <br />described in the original proposal. Most of the work for this project was conducted by <br />personnel of the Colorado Climate Center, Department of Atmospheric Science, Colorado <br />State University. However, some tasks were performed with assistance of other <br />organizations. <br /> <br />Activities and Accomplishments <br /> <br />1) Compilation of hourly and daily precipitation data. <br /> <br />The starting point for this project was the careful scrutiny ofall archived National Weather <br />Service precipitation records back into the 1800s and up through 1993. For each station <br />and each month of record, the maximum observed precipitation for various durations was <br />determined. For many stations with data going back prior to 1948, this required manual <br />data processing and digitization. Maximum one, two and three-day precipitation totals <br />were determined for 598 official stations where precipitation has been measured on a daily <br />basis. For an additional 69 stations where precipitation has been measured hourly or more <br />frequently, maximum one-hour, two-hour, three-hour, six-hour, 24-hour, 48-hour and 72- <br />hour precipitation totals were determined for each month of record. <br /> <br />1 <br />