Climatology of extreme rainfall and flooding from orographic thunderstorm systems in the upper Arkansas River basin

[1] Analyses of the spatial and temporal distribution of extreme rainfall in the Arkansas River basin above Pueblo, Colorado, are based on volume scan reflectivity observations from the Pueblo WSR-88D radar during the period 1995-2003. A storm catalog of 66 rainfall events during the 9-year period has been developed. Climatological analyses of extreme rainfall are carried out both from an Eulerian perspective, in which distributional aspects of rainfall at fixed locations are examined, and from a Lagrangian perspective, in which distributional aspects of rainfall are based on storm-tracking algorithms. Of particular interest is the spatial heterogeneity of extreme rainfall in the complex terrain of the upper Arkansas River basin. Lagrangian analyses are used to characterize the spatially varying distribution of storm initiation, storm motion, and storm structure. Climatological analyses indicate that convective rainfall in the Arkansas River basin above Canon City ( drainage area of 8070 km 2) does not contribute to the extreme flood response of the Arkansas River at Pueblo ( drainage area of 12,140 km 2). There is pronounced diurnal variation in warm season rainfall in the Arkansas River basin, and this feature of extreme rainfall is a key element of flood response in the upper Arkansas River basin. Climatological analyses of extreme rainfall in the upper Arkansas River basin are examined relative to the spatial and temporal properties of rainfall for extreme flood events that have occurred in the basin, including major flood episodes in June 1921 and June 1965.