A Comparison of NAM CONUS Nest Failures and Successes to Regional 3-Km FV3 Runs with Different Microphysics Schemes.

EMC has developed a regional 3-km FV3 configuration that is currently being used to evaluate warm and cold season events. Cases that have been highlighted by forecast centers as examples of forecast failures and successes in the operational NAM CONUS nest were run in the 3-km FV3 configuration for comparison. One case presented is of a precipitation event from November 18 2017 for which the operational NAM CONUS nest over predicted precipitation over Alta, UT. Experimental 3-km NMMB runs also predicted higher precipitation amounts using the Ferrier-Aligo, WSM6, and Thompson microphysics, whereas much lower precipitation amounts were forecast in 3-km FV3 runs that used the GFDL, Thompson, and WSM6 schemes. These two sets of tests indicated that the microphysics did not play the primary role in the heavy precipitation bias in the NAM CONUS nest. Additional comparisons of FV3 with the NAM CONUS nest using the GFDL, Thompson, and WSM6 microphysics schemes will be shown for warm season cases.