Brazilian Northeast Jet Stream: association with synoptic‐scale systems

Abstract

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.