The winter storm reconnaissance (WSR) program began in 1999 and has been operational at NCEP since 2001. Based on NCEP and ECWMF ensemble prediction products, Ensmemble Transform Kalman Filter (ETKF) technique has been used to identify the best flight tracks that might improve forecast to potential high impact U.S continental and Alaska weather events. Prior only to such significant weather events of interest, dropwinsonde observations are taken over the Northeastern Pacific by aircraft operated by NOAA Aircraft Operations Center (G-IV) and the US Air Force Reserve (C-130s). The past results have shown the program improved forecast in the 1-4 day lead-time range for high societal impact weather events by 10-20% reduction in the root mean square (RMS) errors in the verification regions.

We will evaluate the reduction of forecast RSM error over the verification regions by the NCEP Global forecast and assimilation system with the inclusion of the targeted observations during 2007 WSR period as compared with the exclusion of these data. Precipitation impact will also be addressed.