In this work a synoptic/dynamic analysis of atmospheric conditions associated with the cyclone development occurred between 2008 September 12 and 19 is presented, aiming to highlight differences and similarities to the environment of Catarina event in March 2004. The main similarities were found in the synoptic patterns: occurrence of a pattern typical of dipole blocking associated with the potential vorticity anomaly at upper levels; a trough at middle levels with westward slope; the presence of a column of cyclonic vorticity from surface to lower stratosphere; and on the surface, the pattern of a higher pressure to the south of a lower pressure. Despite these similarities, differences that influence the intensity of the systems were found: the Catarina occurred in lower latitudes compared to the 2008 September case; the blocking pattern associated with September 2008 case was a day and a half long, while the Catarina lasted three days; the configuration of temperature advection in the 1000-500 hPa layer favored the displacement of the September 2008 event from eastward/southeastward, in contrast to Catarina, in which the warm advection to the east of the cyclone was suppressed and the local tendency of geopotential height was positive, which hinder the displacement of the system eastward; in the case of 2008 September the pattern of the meridional temperature gradient inversion on the -2.0 units of potential vorticity (UPV) surface was characterized by the incursion of an elongated region of warm air from the equator toward the south and cold air from the south toward the equator, while in the Catarina that inversion occurred by the isolation of a cold air bubble to the north and a warm air bubble to the south, which may have contributed to increase the duration of the dipole blocking pattern in this case, because the dissipation gets harder. Systems such as Catarina may be rare in the South Atlantic Ocean, but this does not occur for the synoptic environment which formed the Catarina. In order to better understand the atmospheric processes that led to the formation of Catarina it is necessary to perform numerical experiments of sensitivity to the 2008 September case with the objective of verifying the possibility of becoming a tropical cyclone.
dipole blocking; tropical transition; Catarina; blocking index
