BOM's outlook suggests a wet summer. But never rule out fire

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Summer is set to be wet, according to the official outlook from the Bureau of Meteorology (BOM).

Despite it being relatively dry over the past few weeks the La Niña declared back in September is still strong, according to BOM senior climatologist Andrew Watkins.

At the moment, short-term climate drivers are conspiring to keep things dry, giving farmers a handy window to try and get the crop out.

But as the months play out, the continued presence of La Niña is expected to encourage far wetter conditions than we have seen over the past few years, with increased risk of floods and an average to above-average risk of tropical cyclones.

Climate driver dodgems

According to Dr Watkins, the Southern Annular Mode (SAM) being in neutral to the south and the Madden Julian Oscillation (MJO) sitting well away from Australia in the north have conspired to keep things dry in November.

“The mix of climate drivers has actually ended up with a drier pattern for many areas, except for south-west WA, of course, where they’ve had some good rain,” he said.

But the La Niña is still brooding over the Pacific.

Map of the Pacific ocean with a clockwise circle of arrows indicating strong air flow and increased convection over the westMap of the Pacific ocean with a clockwise circle of arrows indicating strong air flow and increased convection over the west
When there is a La Niña, the Walker circulation intensifies, bringing warm oceans and wet conditions to eastern Australia.(Supplied: BOM)

The La Niña is expected to continue to strengthen and peak in December or January before easing off towards the end of summer.

“We will be expecting things to start looking a more classic, La Niña-type rainfall pattern once we get into December or even January,” Dr Watkins said.

There is even the chance of the monsoon kicking in early.

The strong polar vortex circling Antarctica at the moment, positive SAM, warm waters over northern Australia, and impending arrival of the MJO in early December, are all expected to aid in bringing moisture over the continent this summer.

Heatwaves expected despite cooler temperatures

With the rain comes evaporative cooling and cloud cover that are expected to keep temperatures below average for central parts of the country.

But as we are about to experience this weekend, the La Niña is not going to stop it getting hot.

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“When we do see these heatwaves, as we get into the summer proper, they are likely to be a little longer than normal and possibly a little more humid than normal,” Dr Watkins said.

“Even if they don’t get to the extremes that we’ve seen in the last couple of years.”

Bushfire outlook

Even though it is looking wetter and cooler than recent summers, Dr Watkins warns there is still a risk of fire for southern Australia.

Rather than the large forest fires we saw early this year, the good spring rainfall means the grassfire risk is expected to be the concern this season.

“So possibly a milder, wetter summer. But it doesn’t mean, unfortunately, that the extremes have gone away,” Dr Watkins said.

Regions which suffered from high-intensity fires last season are at risk of flash flooding, erosion, and landslips if heavy falls do eventuate.

The race to harvest

Senior economist at the Australian Bureau of Agricultural and Resource Economics (ABARES), Peter Collins, said for some areas a lot of spring rainfall had slowed the harvest a little.

“But in a lot of areas, especially across New South Wales, the rainfall they have had has actually been beneficial,” he said.

A header harvesting wheat half way between Moree and Goondiwindi with rain in the background, October 2020. A header harvesting wheat half way between Moree and Goondiwindi with rain in the background, October 2020.
Farmers are racing to get their crops off before the rain.(Supplied: Chris Wright)

Farmer and agronomist Rohan Brill is one of the lucky ones who has been able to take advantage of the dry window over the past few weeks to get some of his crop in.

“We thought it was going to be a really nightmare harvest with the forecast that our headers would be getting bogged and our grain would be getting damaged by rainfall. But that hasn’t eventuated.”

In his neck of the woods in the central Riverina of New South Wales, Mr Brill said there had been a bit of frost damage but, overall, the near-average rainfall this year had been enough to set up a really good year.

It is not breaking records for individual paddock yields, but consistent across the board.

“So most of the farmers are just more and more relieved every day that it’s fine and sunny and grain is getting harvested and sold,” he said.

Mr Brill reckons most in his patch are “over the hump” and will need another week or so to finish up the harvest.

Grains of wheat running through a man's handGrains of wheat running through a man's hand
The crop doesn’t count until it’s out of the paddock and the money is in the bank.(ABC Esperance: Emma Field)

But there are still large parts of the country where they will be racing to harvest before the rains come.

Traditionally, the harvest moves later in the year the further south you go.

Mr Collins thinks there will still be people harvesting after Christmas.

“There’s a lot to get off this year, and in those regions where the harvest has been slowed that just means it will take longer to get what is a well-above-average crop off,” he said.

Fingers crossed they get it in, in time.