Study of High Resolution Ensemble and Extend Range (Week 3 and 4) in the NCEP Global Ensemble Forecast System

The horizontal resolution of the NCEP Global Ensemble Forecast System (GEFS) will increase from about 55 km (T254) to 34km (TL574) in the next implementation after NCEP GFS was upgraded to 13km (TL1534) in January 2015. A higher horizontal resolution for GEFS is possible with a rapid increasing of computational resource in NOAA in the next few years. In this study, the impact of the high horizontal resolution on several weather and hurricanes is investigated for future update based on latest version of GFS. Another effort in the NCEP ensemble group is to extend the GEFS forecast to week 3-4. In a short term, the GEFS will remain an atmosphere model only system. As a result, the experiments for the extended forecast do not use the coupled model although the variance of the ocean generally becomes more important in the extended range. The predictability of the week 3-4 forecast is explored by using different SST forcing for the operational purpose.