Sensitivity to atmospheric forcings and WRF physical set-up forecast skill on the initiation of an intense thunderstorm in Córdoba

ALVAREZ IMAZ, MILAGROS; SALIO, PAOLA; DILLON, MARIA EUGENIA; FITA, LLUIS

CABA

Workshop; RELAMPAGO CACTI Data Analysis Workshop; 2019

The accurate determination of the location and timing of convective initiation (CI) is a crucial forecast task when contributing to the development of a correct warning system related to high impact weather events associated with deep convection. Central Argentina, particularly the Sierras de Córdoba (SDC), is characterized by the occurrence of deep convective cells that reach supercell characteristics producing large hail and occasionally tornadoes.In order to analyze the sensitivity of the CI over SDC, an ensemble of 12 simulations with the WRF model at convection-permitting resolution (3 km) was carried out to study a marginal supercell development in the area. The ensemble was built using 3 different microphysics (MP) parameterizations (WSM6, Thompson and Morrison) and 2 planetary boundary layer (PBL) parameterizations (Yonsei University and Mellor Yamada Janic). Also the sensitivity of initial and boundary conditions is considered by forcing the model with 2 different global analyses: the European Centre for Medium-Range Weather Forecast (ECMWF) model and the Global Data Assimilation System (GDAS). The single thunderstorm happened on October 17, 2017 19:23 UTC (16:23 LT) at SDC foothill with slow propagation to the east and two cell splittings.The two different forcing data show low-level moisture differences, which later modulate the life-cycle of the simulated cells. A tracking algorithm was used to capture the simulated cells life-cycle, and it was detected CI either at the hills and the plains. Simulations forced with ECMWF analysis tend to show better results with similar characteristics to the observed one such as: hill initiation, stronger cells and slow propagation. Within them, the best performance was obtained with the combination of Thompson MP and Yonsei University PBL schemes.