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<br />Recommendations - Data collection needed to improve future <br />estimates of extreme precipitation in the Colorado mountains, <br /> <br />Despite this intensive study of observed extreme precipitation in Colorado, there will <br />continue to be debate and uncertainty concerning just how heavy high elevation rains <br />could conceivably be. Some of this uncertainty is well justified considering the sparsity of <br />long-term precipitation records at elevations above about 9,000 feet in Colorado. <br />Figure 7 shows the maximum observed one-day precipitation amounts for Colorado <br />weather stations as a function of elevation. This figure is intended to give a visual <br />perspective of the variation of rain with elevation although some data points in Fig. 7 <br />could be snow. A set oflarge one-day amounts which may be in other reports but are not <br />included in Fig. 7 are given in Table 6 with the appropriate explanation of the occurrence <br />of snow or an error of including two-day precipitation totals. The 8.05" at Gladstone on <br />October 5, 1911 is questionable but it was a large rainstorm and has not been rejected for <br />this figure. Except for the SNOTEL data, very little long-term data have existed at high <br />elevations. Only a few of the SNOTEL data points include IS years of data, and no <br />SNOTEL sites in Colorado include daily observations prior to 1978. Due to this lack of <br />observations in critical high-elevation locations, it is imperative that ongoing efforts be <br />made to detect and describe extreme rainfall events at high elevations. Streamflow <br />records exist for high elevation watersheds, and these records along with paleoflood <br />evidence continue to point to a lack of extreme events, or more accurately, lower <br />magnitude extreme events at high elevations above 7,500-8,000 feet in Colorado. <br />However, with little corroborative meteorological evidence, uncertainty remains. <br />Therefore, it is imperative that additional data be collected now and into the future ifwe <br />wish to improve the confidence and widespread acceptance in the estimates of probable <br />maximum precipitation in the Rocky Mountains. <br /> <br />A set of recommendations follow which suggest a variety of strategies and data collection <br />activities that, iffollowed, would result in data that would greatly enhance and provide <br />more confidence in future estimates and analysis of extreme precipitation. <br /> <br />1) Recently deployed National Weather Service WSR-88D meteorological radar <br />installations near Denver, Pueblo, Grand Junction and Cheyenne, Wyoming offer <br />better coverage of Colorado including most mountain areas and better remote rainfall <br />estimation potential than at any time in history. Quantitative precipitation estimates <br />may still be problematic, but radar reflectivity patterns will permit much improved <br />analysis of storm areas and durations. These variables may hold the key to <br />understanding high elevation storm characteristics. Therefore, NWS radar data should <br />be collected and archived, and research efforts should be initiated to investigate storm <br />characteristics over the mountains and how storm properties vary as a function of <br />ground elevation near the storm areas. Particular emphasis should be made to assure <br />radar data collection for the true extreme storm events comparable to those listed on <br />Table 5. <br /> <br />29 <br />