Were global numerical weather prediction systems capable of forecasting the extreme Colorado rainfall of 9-16 September 2013?

Abstract

From 9-16 September 2013 significant portions of Colorado experienced extreme precipitation and flooding resulting in large socioeconomic damages and fatalities. Here we investigate the ability of eight global state-of-the-art numerical weather prediction systems to forecast rainfall during the event. Forecasts were analyzed from initializations at 12 UTC 5 September to 12 UTC 12 September to determine when, and how well, the event was captured. Ensemble mean rainfall patterns initialized on 5 September (roughly 4+ day lead time) did not forecast the event's persistent nature; conversely, forecasts initialized on 9 September captured the rainfall patterns reasonably well, although with incorrect rainfall values. Accumulated rainfall forecasts improved when the region considered increased from a 0.5° area centered over Boulder to the entire state of Colorado. We conclude that the models provided guidance indicating a significant period of rainfall in Colorado from 9 September 2013, although not necessarily in the correct locations. ©2013. American Geophysical Union. All Rights Reserved.