The Great Southern Sling

Throughout June, Antarctic ridging helped launch storms into Australia's south-east — but can July keep the recoil going?

June delivered more than most expected, even with no influence from ENSO or the IOD. A brief pulse of the MJO early in the month likely nudged the SAM negative, but the real driver appeared to be a strong anomaly in the Amundsen Sea Low (ASL). This helped anchor a wavenumber-2 pattern around the pole, reinforcing Antarctic ridging and bending the jet in Australia’s favour.

This setup didn't just shape storm tracks — it helped define the broader polar energy flow. With semi-permanent ridges holding over the Weddell Sea and the western Ross/West Pacific sectors, a blocking effect developed near the Antarctic shelf. That, in turn, diverted storm systems equatorward, guiding cold air and moisture straight into the mid-latitudes — and into Australia’s snowfields.

NOAA’s reanalysis tool helps depict mean sea level pressure anomalies (left) and the 500mb upper-level anomalies, which presented last month. The Amunsen Sea Low (ASL) has been strengthening and the red circle on the image to the right has been added to highlight the dominant coupling of these diametrically opposing lows. Source: NOAA

Instead of slipping harmlessly south, systems have been stretched and steered north (aided by the ridging near the Antarctic shelf), boosting the season’s early snowfall and cold bias. It’s a complex pattern, but the big question now is whether this polar-driven rhythm can hold through July.