NUMERICAL EXPERIMENTS TO THE SUBTROPICAL CYCLONE “ANITA” USING WRF MODEL

The Weather Research and Forecasting Model (WRF) were used to simulate the subtropical cyclone Anita, which occurred in March of 2010 over southwestern of South Atlantic Ocean. These cyclone instigated weather forecast centers around the world, since numerical models were indicating that it would atypically move to southwest. Therefore, numerical experiments with WRF were conducted in order to evaluate the sensitivity of Anita cyclone by changing different configurations/parameterization: (a) relaxation zone of the model (between 5 and 40 columns); (b) Betts-Miller-Janjic cumulus parameterization; (c) anticipation (24, 48, 72h). Simulations used a 25 km resolution grid, and boundary and initial conditions from FNL/NCEP (Final Analysis/National Centers for Environmental Prediction). Results were compared with the FNL/NCEP analyses and the Tropical Measuring Mission (TRMM). The relaxation zone conditions didn’t seemed to present a large impact in simulating the intensity and position of the cyclone. In general it is simulated a deeper than observed low pressure. In the experiments initiated with 72h before validation date tended to move the cyclone towards the continent, while the experiments initiated 24h before presented better agreement with observed cyclone path. The use of Betts-MillerJanjic cumulus parameterization provides results similar to the observed one, mainly for simulations initiated 72h before. The precipitation was, in general, overestimated in the experiments compared to the TRMM analyses.