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<br />..- <br /> <br />~,-",-.~--,.," <br /> <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 I <br />I <br />I <br />I <br />I <br />I <br />I <br /> <br />The initial review of the meteorological conditions suggests that the <br />following three factors may be useful in addition to standard criteria in predicting <br />Buffalo Creek basin flash flood watches by the National Weather Service: <br /> <br />1, PWI is greater than 1.00" and <br />2. Storm updraft warm layer is greater than 1.5 km and <br />3. Cloud layer winds favor movement less than 15 mph <br />4. Predicted peak 30-minute rain rate is greater than 1.00" <br /> <br />Based on the comparison of rainfall characteristics of the storms, HMS <br />suggests that the following quantitative characteristics of the storm's radar <br />signature could be used to assist in the issuance of flash flood warnings by the <br />National Weather Service: <br /> <br />1, When> 60 % of the basin will be covered by 5-level or greater radar <br />reflectivity capable of producing 0.50" of rain in 60 minutes or less <br /> <br />2. When> 30 % of the basin will be covered by 5-level or greater radar <br />reflectivity capable of producing 1.00" of rain in 60 minutes or less <br /> <br />The combination of the observed meteorological and radar conditions may <br />provide quantitative guidelines to the National Weather Service which will assist <br />in the issuance of flash flood watches and warnings in the basin. These <br />guidelines will have to be evaluated within the context of the results of basin <br />hydrological studies and the flexibility of NWS policy. <br /> <br />Finally, it is the opinion of HMS meteorologists that the Buffalo Creek flash <br />flood was primarily a product of coincident meteorological factors which <br />significantly overwhelm other possible weather-related impacts of the fire burn <br />area, The strong thunderstorms of July 12,1996 were the product of a very <br />volatile atmospheric structure which is repeated annually over eastern Colorado, <br />The co-incident arrival of the strong outflow boundary and the thunderstorm <br />complex from the west into the basin within the context of this atmospheric <br />structure is the dominant controlling factor on the cause of the flash flood, <br /> <br />28 <br />