Cyclonicity and thermal conditions for precipitation occurrence over Argentina

The underlying dynamics of synoptic-scale vertical motion and precipitation at middle and subtropical latitudes east of the Andes is examined through cyclonicity conditions and 500/1000 hPa thickness anomalies for the Southamerican region. Patterns of anomalously cyclonic and anticyclonic 500 hPa relative vorticity associated with precipitation occurrence at stations located from 25 degrees S to 55 degrees S are remarkably different. This indicates the preferential positions of cyclonicity anomalies to occur for favoring rainfall at distinct places of Argentina. The results also highlight the importance of the position, extension and propagation direction of the upper-level trough for estimating local precipitation probabilities. The thermal behavior of the migratory systems which produce precipitation can be inferred from the patterns of 500/1000 hPa thickness anomalies in relation to precipitation occurrence. It may be clearly seen that, in general, There exist a negative correlation (i. e., negative anomalies) to the west of the precipitation area and a positive one to the east evidencing the frontal nature of rainfall in most cases for different regions of Argentina.