Evaluating the Boundary Layer Environment and Convective Storm Evolution from 3 km, Limited-Area FV3 Simulations at the 2019 Hazardous Weather Testbed

The National Centers for Environmental Prediction (NCEP) is currently in the process of transitioning its entire modeling suite to the Finite-Volume Cubed-Sphere (FV3) dynamical core, with the overarching goal of unifying its operational production suite. As a first step in this transition, the Global Forecast System (GFS) model, the primary global forecast model maintained by NCEP, underwent a major upgrade on 12 June 2019 with the implementation of GFSv15, which utilizes the FV3 core. In the coming years, all operational models run at NCEP, including the regional and high-resolution systems, will be transitioned to the FV3 dynamical core.

To enhance regional modeling efforts using the FV3 core, a limited area or stand-alone regional (SAR) capability was developed at the NCEP/Environmental Modeling Center (EMC). A 3-km horizontal resolution, convection-allowing FV3SAR configuration centered over the continental U.S. is currently being developed for a planned operational implementation soon. The FV3SAR configuration run at EMC during Spring 2019 inherited the planetary boundary layer (PBL) scheme from the GFS. This scheme has a documented bias of overmixing the PBL, which reduces boundary layer moisture and thus instability.

FV3SAR forecasts will be compared against observations within pre-convective environments of several high-impact severe weather events during May 2019 over the South Plains, Southeast and Northeast U.S. regions. Analysis will heavily involve evaluation of model soundings utilizing the SHARPpy and MetPy packages in Python, with a focus on thermodynamic characteristics of the boundary layer and free atmosphere. Results detailing the impact of the GFS PBL scheme on FV3SAR forecasts of the pre-convective environment and convective initiation, mode and evolution will be presented.