Townsville weather: La Nina likely, increasing chance of cyclones

Early indications of a La Nina pattern have started to form, increasing the chances of tropical cyclones and heavy rain.

THE chances of cyclones and heavy rain this summer have grown as early indications of a La Nina pattern have started to form.

Weatherwatch meteorologist Anthony Cornelius said a series of high-pressure systems were expected to link together over the Pacific Ocean this week, generating easterly winds.

“The result will be a big (and unusually early) increase in moisture across eastern Australia late next week, which is a classic La Nina pattern,” he said.

“We need several months of La Nina patterns for this year to officially be called a ‘La Nina year’ but that’s looking very likely, and ... has been something we’ve been talking about (for) five months now.”

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Mr Cornelius explained the increase in moisture would likely combine with an approaching surface low and upper trough to bring showers, rain and storm activity across a large part of eastern Australia.

He said rainfall in North Queensland, however, would likely be more patchy due to the greater distance from the upper system.

“Nonetheless, September is one of the driest periods of the year, so to see this occur so early is probably a bit of a sign of things to come in the next few months,” he said.

The Bureau of Meteorology said the shift towards La Nina was continuing in its weekly tropical note.

“The cooling trend in the tropical Pacific Ocean continued during the past week,” it said. “Water temperatures in the central Pacific Ocean are edging closer to La Nina thresholds, while there is mounting evidence that the atmosphere is responding to the water temperature patterns.

“A mature La Nina is characterised by both the pattern of sea surface temperature across the equatorial Pacific Ocean and changes in the atmospheric circulation overlying the region.”

The bureau’s La Nina Alert remains, meaning the chance of a La Nina occurring this year is 70 per cent – roughly three times the normal likelihood.

Bureau manager of climate operations Dr Andrew Watkins said La Nina normally resulted in above-average winter rainfall for North Queensland, however, rainfall in Townsville had been below average.

“It typically also brings cooler and cloudier days, more tropical cyclones and an earlier onset of the first rains of the wet season across the North,” Dr Watkins said.

Originally published as Townsville weather: La Nina likely, increasing chance of cyclones