Investigating an extreme meteo-oceanographic event in the southern Brazil from in situ observations and modeling results

In March 2016, the passage of a cold front on the southern coast of Brazil generated extreme meteo-oceanographic conditions along the southern Brazilian coast. This work investigates the wave field evolution during this period from in situ observations and numerical modeling. The observations were obtained from high-frequency measurements performed in four sites along the coastline (Santos, Tramandaí, Rio Grande, and Cassino). The wavefield simulations were performed by coupling the Global Forecast System (GFS) reanalysis and the WAVEWATCH-III (WW3) ocean wave model. In a synoptic analysis was observed that not only the cold front caused the high wave in the area, but the interaction between the front post-high-pressure center and a low-pressure center generated a substantial pressure gradient area along the Brazilian coast with winds between 17.1 and 20.7 m s−1 reaching up to 24.4 m s−1. Model estimates confirm the presence of high waves between 6.0 and 6.5 m on the Southern coast of Brazil. Also, in the adjacent deep waters of the South Atlantic Ocean, highly simulated waves reached significant wave heights of 9 m. An analysis of the model input wind indicates that the GFS winds represented very well the trends and evolution of the wind registered by ocean buoys, with a small phase error. The t-test shows no significant differences in any buoys, with p-value = 0.73 and p-value = 0.78, with a significance level of 0.05.