Record warmth off NSW coast enough to 'support' a tropical cyclone

Ocean temperatures off the coast of Sydney and New South Wales are high enough that they could theoretically support a tropical cyclone.

A cyclone is not expected to form - other factors needed to develop such a storm are not in place - but the temperatures have topped records.

Weatherzone reported that sea surface temperatures off the NSW coast had been two to more than three degrees higher than usual in recent weeks for this time of year.

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"These temperature anomalies would be exceptional in any month, but in early autumn, which is typically the warmest time of year in the western Tasman Sea, they represent record-breaking warmth," Weatherzone said.

A sea surface temperature of 27 degrees was recorded off the coast of Forster on the Central Coast on March 8, more than two degrees above average.

Further south, off Sydney's Northern Beaches, temperatures of 26.75 degrees on March 8 and March 9 - the highest on record for that buoy in records going back to the early 1990s, Weatherzone said.

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And temperatures of more than 26 degrees have been detected further down the coast this month, even reaching south of Sydney.

In theory, ocean temperatures at or above 26.5 degrees can provide enough energy to support tropical cyclone development.

However, a more likely development is that the warm water will fuel low pressure systems that could see heavy rain sweep westward over the coast.

Weatherzone reported that sea surface temperatures had been more than 1.5 degrees above average over parts of the Coral Sea recently, and more than three degrees warmer than usual south of Victoria and east of Tasmania.