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Ocean trends point to wet spring

Indian Ocean temperatures and a La Nina-like pattern in the Pacific Ocean are strongly influencing Australia’s climate, with the two features typically a cause of wet spring weather in the eastern states.

A negative Indian Ocean Dipole (IOD) has strengthened after easing last month and is close to record values observed in July, the Bureau of Meteorology says in an update.

The IOD measures temperature differences between the west and east tropical Indian Ocean. In a negative event, much of eastern Australia tends to experience above-average spring rainfall.

In the Pacific Ocean, a La Nina watch remains in place because some climate models indicate a late and weak La Nina is possible, although the bureau says thresholds are yet to be met.

Northern and eastern Australia typically experience above-average spring rainfall during La Nina, with the first rains of the wet season arriving earlier than normal.

“At present, warmer-than-average seas surrounding Australia – which more typically occur during La Nina – mean some La Nina-like impacts may occur even if thresholds are not exceeded,” the bureau says.

Climate models suggest the IOD will weaken in coming months, returning to neutral values before the end of the year.