CAPS Storm-Scale Ensemble Forecast Experiment in Supporting 2018 NOAA HWT SFE and HMT FFaIR

The Center for Analysis and Prediction of Storms (CAPS) at University of Oklahoma produced storm-scale ensemble forecasts (SSEF) at convection-allowing 3-km horizontal grid spacing from April 16 through June 1 to support the NOAA 2018 Hazardous Weather Testbed (HWT) Spring Forecasting Experiment (NOAA/HWT SFE2018), and from June 18 through July 20 to support the NOAA 2018 Hydrometeorological Testbed (HMT) Flash Flood and Intense Rainfall (FFaIR) Experiment (NOAA/HMT FFaIR2018). New in SFE2018 is a FV3 core storm-scale ensemble of 12 members of 84-h long at 3.5 km nested horizontal grid spacing over the CONUS domain, with different microphysics (Thompson, NSSL, GFDL), cumulus parameterization (Tiedtke, SA-SAS), and PBL (YSU, MYNN, both scale-aware and non-scale-aware, and EDMF) options, most of them implemented by CAPS. As in previous years, an experimental cycled GSI plus CAPS EnKF data assimilation was performed on the same 3-km CONUS grid, with a 40-member WRF ensemble initiated at 1800 UTC, assimilating the RAP/HRRR GSI data stream (without Mesonet1) hourly from 1900 to 0000 UTC and all WSR-88D radar data over a one hour period (2300-0000 UTC) at 15 minute intervals. The final cycle (0000 UTC) analyses were used to initiate a 10-member WRF SSEF ensemble of 48-h long. As part of a larger Community Leveraged Unified Ensemble (CLUE) effort in NOAA/HWT SFE2018, CAPS contributed a total 50 SSEF members consisting of five sub-ensemble groups including non-cycled 3DVAR based mixed-physics, single-physics, and stochastic-physics groups with ARW core, cycled GSI+EnKF ensemble group, and the multi-physics FV3 core ensemble, in an effort to provide guidance to the design of future operational SSEF systems. During FFaIR2018, CAPS contributed 15 SSEF members, consisting of 13 ARW and 2 FV3 members, with ensemble product including exceedance of Flash Flood guidance (FFG) and Recurrence Intervals (RIs) in a neighborhood framework with a 25-km radius. The NCEP Multi-Radar/Multi-Sensor (MRMS) QPE data will be used to evaluate CAPS SSEF QPFs and PQPFs. Ensemble spread and other deterministic and probabilistic scores will be examined in comparison among different ensemble groups.