Cyclone Arani occurred in March 2011 in the South Atlantic Ocean and was initially classified as a subtropical depression. When it reached winds above 34 knots, it passed to the subtropical storm category, and was named by the Brazilian Navy as Arani, which means furious weather in Tupi Guarani. This paper aimed to analyze the cyclone Arani through the Cyclone Phase Space, built with data from the European Centre for Medium-Range Weather Forecasts (ECMWF) ERA-interim reanalysis, with 0.7º spatial resolution, and also using synoptic fields and profiles with data from the Climate Forecast System Reanalysis (CFSR), with 0.5º resolution. Through the phase diagrams it was possible to identify the subtropical structure of cyclone Arani and the indication of an extratropical phase transition at the end of its life cycle. The results also indicated that the quality of the phase diagrams for cyclones with weak warm cores and small dimensions depends on adequate atmospheric models and therefore, the values obtained should be carefully analyzed when using global models. In this case, the qualitative study of the diagrams proved to be more useful than the purely quantitative analysis. Although disagrees with the information of an extratropical phase transition at the end of the cyclone Arani's life cycle, contained in the phase diagrams used in the study, the analysis of the fields and synoptic profiles contributed to the understanding of the cyclone's development and to the interpretation of the diagrams.