Investigation with Increased Horizontal Resolution and Ensemble Size for Future GEFS

The NCEP Global Ensemble Forecast System (GEFS - V11.0) will increase the horizontal resolution from about 55 km (T254) to 34km (TL574) in April 2015 after NCEP GFS was upgraded to 13km (TL1534) in January 2015. A very high horizontal resolution GEFS is much possible with a rapid increasing of computational resource in NCEP in the next few years. The impact of the horizontal resolution increased from TL574 to TL1534 is investigated with convective based stochastic physics scheme by comparing the predictability of several heavy rainfall events over North American.

On the other hand, in past 10 years, NCEP GEFS used all increased computation resources to improve model horizontal and vertical resolutions without changing membership. In this study, a set of experiments and objective evaluation will be taken to assess the benefits/costs by using different ensemble size. The experiments are conducted by using latest GEFS configuration (V11.0 - TL574) with 20, 40, 60 and 80 ensemble members.