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<br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br /> <br /> <br />Figure 2 <br />Sub-Tropical Disturbances Affected Colorado <br />In the Monsoon Flow <br /> <br />Surface dew points in central and western Colorado were generally in the <br />upper 40s' and 50s (not shown) and the Surface to 500mb (~20,000 ft) <br />Precipitable Water Indices (PWI) ranged from 0.92" at Albuquerque to 1.00" at <br />Grand Junction at 600AM. These values were recomputed for the time of the <br />flash flood and approached 1.15 inches. The values for both the dew points and <br />the PWI are above average especially when one consider the elevation of many <br />of the individual stations at which the observations were taken. <br /> <br />Further evidence for this 'moisture surge' of moisture, commonly referred <br />to as the Mexican monsoon, can be found in the 700MB (~10,000ft) and 500MB <br />(N19,000ft.) analyses (Figures 3 and 4) shown for 1200 UTC (6:00 AM MDT) <br />on July 25th, 1999. The hatched area in these figures is indicative of very moist <br />dew points at these levels (> +SoC at 700MB and> -lSoC at 500MB). Excessive <br />mid-level moisture is one of the key ingredients necessary for Colorado Mountain <br />flash flooding. Dew points at 700MB of > SC have a high likelihood of producing <br />locally heavy rainfall. Note the narrow band of mid-level moisture flowing across <br />the state. Clearly this "river of monsoon moisture" established the possible <br />flooding locations by mid-morning. <br /> <br />4 <br />