Verification of WRF-ARW convective-resolving forecasts over Southeastern South America

Abstract

During November-December 2012, high-resolution (4 km-38 vertical levels), convection-allowing 48 hours WRF-ARW forecasts were produced at the National Weather Service of Argentina. The aim of this paper is to evaluate hourly quantitative precipitation forecasts to assess the model performance on representing its location, intensity, spatial variability and diurnal cycle. The focus is on the central-east region of Argentina and south of Brazil. The study is based on a combination of visual comparison of forecasted and estimates accumulated precipitation fields and objective scores calculated employing 8-km resolution CMORPH (CPC MORPHing technique) satellite rainfall estimations. Additional insight is gained by examining an organized convective event occurred during 6th and 7th December, 2012. As a complement, radar data is considered to evaluate convective features using simulated model reflectivity. Results show that WRF model forecast captures quite well the position and timing of the major convective events, even though the magnitude of events was underestimated. Total amounts averaged over the verification domain are underestimated as well as the areal coverage for small thresholds. In general, results suggest that convection-allowing WRF-ARW model has the potential to improve short range forecasts over the region although it should be evaluated over a longer period of time.