Antarctic atmospheric circulation anomalies and explosive cyclogenesis in the spring of 2016

This work examines teleconnections between extratropical explosive cyclogenesis and the Antarctic region and its relationship with the Southern Annular Mode (SAM) and with the zonal wave three (ZW3) pattern at the end of October 2016. From 26 to 28 October, an explosive extratropical cyclone developed on the Brazilian southern coast. Then, from the 29th to the 31st, southern Australia, including Tasmania, was hit by an explosive extratropical cyclone originating in the Indian Ocean. Both events caused damages. The year 2016 also stands out as the warmest in the recorded record, both globally and in the Southern Hemisphere; further, in 2016, the smallest Antarctic sea ice extent (SIE) was recorded since 1979. This SIE reduction has been attributed to positive sea surface temperature anomalies, the ZW3 and a SAM negative phase. We reconstructed the geopotential height fields, wind vectors, zonal wind, and temperature using the ERA-Interim reanalysis data. These fields, associated to wave and tidal and wind records, denote that negative SAM and ZW3 influenced both events. This association favored intense cyclogenesis, which included a baroclinic increase in both cases, with well-organized vertical structure; thus, this combination formed meteorological “bombs” as a response to the tropic-pole temperature contrast, and an exceptional atmospheric circulation was observed between subtropical and polar latitudes in 2016.