Study of three days duration coupling between jets in South América

Abstract

It can be understood by coupling between jets when Upper-Level Jet (ULJ) superimposes the Low-Level Jet (L LJ). The literature shows that such couplings tend to generate or intensify surface instabilities. Thus, the objective of this study was to analyze the synoptic configuration and the coupling between the jets associated with storms during the period of October 28-30, 2019, when instabilities hit southern Brazil causing intense precipitation and several damages. This work was carried out through the analysis of meteorological fields employing ERA5 reanalysis data and GOES-16 satellite imagery. The coupling between jets was verified in the three days of study. Upward vertical movements at 500 hPa was observed in the same area of occurrence of the upper level difluent flow, as well as an intense 850 hPa northerly flow, a large amount of moisture due to the action of the Northwestern Argentinean Low, and the presence of a frontal system between Uruguay and RS, except on the first day. Storms developed east (downstream) of the area where the coupling took place. The coupling was observed before and during the development of the mesoscale convective systems, and its dissipation occurred simultaneously with the storm. However, on the 30th, the peak of coupling did not occur together with the most intense phase of the system, it occurred before.