An analysis of the synoptic forcings of the 28 April 2001 severe storm generating a tornado at Resistencia

TORRES BRIZUELA, MARCELA; NICOLINI, MATILDE; CERNE, BIBIANA; POSSIA, NORMA; GARCIA SKABAR, YANINA

Foz do Iguaçu, Brazil

Conferencia; 8th International Conference on Southern Hemisphere Meteorology and Oceanography; 2006

American Meteorological Society

A thunderstorm generating a tornado F2 (Fujita scale), developed during the afternoon of 28 April 2001 over the area of Resistencia (27°27’ S, 59°03’ W), Province of Chaco, Argentina. On this day strong damages occurred in the area around Resistencia city, but also strong winds were detected at Corrientes city located in the other side of the Paraná river. In order to identify the synoptic-scale forcings of this strong convective event a detailed analysis of the atmospheric patterns is addressed in this paper. Advections of temperature and water vapor and different components of the ageostrophic winds are analized. A dynamic factor that has contributed to the relative vertical vorticity concentration to generate the tornado is related to the increasing synoptic scale vertical vorticity during the day of the event. The hypothesis is that this enhanced vertical vorticity contributed by the cyclonic shear to the west of the low-level jet as it progressed toward the east (forced by the cold air incursion), finally becomes located in the Resistencia area where the presence of convergence have concentrated the relative vertical vorticity by stretching, just in time for the occurrence of the tornadogenesis in a convective scale.