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<p>Cool season rainfall has declined in recent decades in many areas of the southern hemisphere subtropics and midlatitudes including parts of southern Australia. This has been partially linked to increases in sea level pressure and a decrease in extratropical fronts and lows. We use the ERA5 and JRA-3Q reanalyses to assess whether the trends near Australia between 1959 and 2022 can be characterised as a poleward shift in the latitude of the cool season storm tracks, analogous to previously identified shifts in the edge of the tropical Hadley Cell or the well-documented positive trend in the summer Southern Annular Mode. Using a range of metrics of the storm track we find indications of reducing storm activity near Australia in the low mid latitudes (particularly 35 to 45° S), coincident with rainfall declines during May–October. However, the core of the storm track has not materially changed in position across a range of metrics, and from this perspective cannot be said to be moving south in the observational record. Deeper analysis reveals that near-surface weather systems show a reduction in frequency at the northern edge of the storm track, which has implications for southern Australian rainfall. Thus, there is evidence that the storm track is changing, but we caution against a simple narrative of a poleward shift in its location.</p>

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Is the Australian storm track shifting south?

  • 期刊论文

  • 出版模式：

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  • 发表日期：

    2026年2月19日

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  • Acacia Pepler,
  • Irina Rudeva,
  • Ghyslaine Boschat,
  • Roseanna McKay,
  • Pandora Hope,
  • David Jones,
  • Joerg Henrichs

摘要

Cool season rainfall has declined in recent decades in many areas of the southern hemisphere subtropics and midlatitudes including parts of southern Australia. This has been partially linked to increases in sea level pressure and a decrease in extratropical fronts and lows. We use the ERA5 and JRA-3Q reanalyses to assess whether the trends near Australia between 1959 and 2022 can be characterised as a poleward shift in the latitude of the cool season storm tracks, analogous to previously identified shifts in the edge of the tropical Hadley Cell or the well-documented positive trend in the summer Southern Annular Mode. Using a range of metrics of the storm track we find indications of reducing storm activity near Australia in the low mid latitudes (particularly 35 to 45° S), coincident with rainfall declines during May–October. However, the core of the storm track has not materially changed in position across a range of metrics, and from this perspective cannot be said to be moving south in the observational record. Deeper analysis reveals that near-surface weather systems show a reduction in frequency at the northern edge of the storm track, which has implications for southern Australian rainfall. Thus, there is evidence that the storm track is changing, but we caution against a simple narrative of a poleward shift in its location.