Atmospheric processes associated with the September 2013 Colorado extreme rainfall and flooding

From 9-16 September 2013, extremely heavy rain fell over a large portion of northern Colorado, and especially in Boulder and Larimer Counties. This resulted in deadly and destructive flash flooding in many creeks and rivers in the foothills and mountains, and record flooding of the South Platte River on the Plains. This presentation will review the synoptic and mesoscale conditions typically associated with extreme rainfall along the Front Range of the Rockies, and will assess how the conditions during the September 2013 compare with those identified in past research. Inferences about the importance of a convectively generated mesoscale vortex and moist upslope flow to the rainfall totals will be presented based on synthesis of observations and the output from numerical model simulations. The predictive skill of operational and research-based numerical prediction models will also be assessed and connected to potential sources of errors in the precipitation forecasts. Finally, discussion will be initiated about the broader implications of this event and directions for research on this and similar events going forward.