Showing all posts tagged: climate

Tropical cyclones may return to Sydney coastal region

24 November 2022

For about thirty years, until the mid-seventies, tropical cyclones were relatively regular weather events in the Sydney region, but now meteorologists are concerned they may return. But climate change is not behind their possible re-emergence, rather changes in the Interdecadal Pacific Oscillation (IPO):

The inordinate frequency of cyclones from the 40s to the 70s and the disappearance in recent decades is not random variability. A 2020 report in the Journal of Southern Hemisphere Earth Systems links NSW cyclone activity with changes in the Interdecadal Pacific Oscillation (IPO). The current state of the IPO and other cyclone influences has rapidly shifted in the past three years to resemble the 1950s. Meaning, the current phase of the Pacific is conducive to tropical cyclones impacting NSW.

While more often see in northern regions of Australia, tropical cyclones haven’t reached Sydney in decades, but they have impacted some parts of NSW, bringing flooding and storm damage with them.


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A spring of Sam (Southern Annular Mode) and La Nina summer?

5 September 2022
Rainy evening, photo by John Lampard

Image courtesy of disassociated.

While there’s a slim chance regions of Australia may yet be spared a third consecutive wet, rainy, La Niña weather event this summer, the outlook for spring is not so promising.

The Bureau of Meteorology advised last week parts of eastern Australian can expect higher than usual rainfalls, thanks to another meteorological phenomenon, a positive Southern Annular Mode, or Sam, for short:

Further, Dr Bettio said a positive Southern Annular Mode (SAM) is also likely, which pushes weather systems south, bringing wetter easterly winds to NSW and fewer cold fronts to western Tasmania. Dr Bettio said parts of Western Australia and western Tasmania are likely to experience below average rainfall this spring. Almost all of Australia is likely to experience warmer than average nights, while cooler days are likely for large parts of the mainland except the tropical north.


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Australia on alert for a third La Nina event this summer

18 August 2022

Another wet summer may be on the cards for parts of Australia, after the Bureau of Meteorology moved the ENSO Outlook to a La Niña alert status.

This status change follows a renewal of cooling in the tropical Pacific Ocean towards La Niña thresholds over recent weeks, as well as the persistence of the Southern Oscillation Index (SOI) at La Niña levels and strengthened trade winds at La Niña levels. Climate models indicate further cooling is likely, with four of seven models suggesting La Ni Niña a could return by early-to-mid southern hemisphere spring.

If another La Niña eventuates this summer, it will be the third in a row.


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