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<br />weather stations and the District ALERT weather station at Evergreen to <br />calculate and assign a radar-rainfall relationships to the Buffalo Creek basin. <br /> <br />Figure 3 shows the HMS-plotted surface weather observations for the <br />PROFS mesonet for 805PM PM (0205Z) on July 12. Note the strong moist, <br />northeasterly winds flowing into Jefferson County, Next, HMS plotted the <br />surface weather station observations from the meso net on a Skew-T, Log P <br />thermodynamic diagram (Figure 4) on which the evening Denver upper air <br />sounding had already been plotted. The vertical plotting of the surface weather <br />observations is called by HMS a mesosound and is used as a means of <br />calculating the changes in the stability and moisture content of the air over the <br />District. <br /> <br />Note on Figure 4 points A and B. Point A is where the cloud base has <br />been calculated using the surface weather observations from the meso net and <br />point B is the point where the thunderstorm updraft cools to OC. The calculated <br />PWI is 1.31" adjusted for an elevation of 7,000 feet while the depth of the warm <br />updraft layer is point B (5.4km) minus point A (2.6 km) or 2.8 km. The next <br />step is to solve Equations 2 to 4 for the peak rainfall rates. <br /> <br />Next insert the values for PWI (1.31") and the depth of the warm layer (2,8 <br />km) into Equation 2 and solve for the peak 60-minute rainfall rate which is 4.90", <br />Using this value in Equation 3 and solving the equation, the peak 30-minute <br />rainfall rate is calculated to be 3.43 inches, These rainfall rates are assigned to <br />the grid squares covered by radar reflectivity values of 5 level or greater. The <br />rainfall rates assigned to lower reflectivity values are found in Table 1. Note that <br />the peak 10-minute rain rates are not calculated to allow for the reduction of <br />rainfall by hail production in the storm. <br /> <br />Table 1 <br /> <br />Relationship between peak 50-minute and peak <br />3D-minute rainfall rates and radar reflectivity levels. <br /> <br /> <br />0.10"/5min <br />0.22"/5min <br />0.30"/5min <br />0.40"/5min <br />0.40"/5min <br /> <br />0.22"/5min <br />0.30"/5min <br />0.41 "/5min <br />0.57"/5min <br />0.57"/5min <br /> <br />* Hail <br />* Hail <br /> <br />HMS routinely archives 6 minute radar observations from the National <br />Weather Service (NWS) WSR-88D located at Watkins, Colorado. This radar is <br />located less than 60 miles from the Buffalo Creek basin and provides very <br />accurate radar reflectivity observations, The resolution of tlhe radar reflectivity <br /> <br />6 <br />