Brazilian Northeast Jet Stream: association with synoptic-scale systems

Abstract

The association of the Brazilian Northeast Jet Stream (BNEJS) with synoptic-scale systems was analysed over 16 years (1994–2009) using reanalysis data from the National Center for Environmental Prediction – National Center for Atmospheric Research (NCEP-NCAR). BNEJS events were divided into three groups, which show the location of the jet stream between synoptic systems at high levels: Type I, a southerly BNEJS between the Bolivian High and upper tropospheric cyclonic vortexes (UTCVs) and/or the trough (UTT) over the ocean; Type II, a northerly BNEJS between the South Atlantic Subtropical High (SASH) and the UTCV (and/or the UTT) over the continent; and Type III, a westerly BNEJS between the UTCV in the Northern Hemisphere and a UTT in the Southern Hemisphere. Throughout the year depending on the characteristics of the BNEJS, three distinct meteorological features were observed. A dry period from December to February in the coastal region was characterized by a relatively small number of fast BNEJSs with a low wind speed in the core, with a dominant southeast direction and with the BNEJS's location between the UTCV and the Bolivian High. A period between April and October (a rainy period and the transition to a dry season in the coastal region) was characterized by a rather high number of fast BNEJSs, with high wind speed in the core, a predominant northwesterly direction, and the location of the BNEJS between the UTT and the SASH. Transitional periods (March and November) have a moderate number of BNEJSs without a high wind speed in the core, with a predominant southwesterly direction, and the BNEJS's position between the UTT and the Bolivian High.