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BOM says signs of wetter months ahead as South Australia reels from dry July

By Malcolm Sutton, Wednesday August 5, 2020 - 06:28 EST
ABC licensed image
Satellite imagery on Tuesday shows a low pressure system moving towards SA from the west. - ABC licensed

South Australians appear to have a fair chance of receiving average rainfall for the next two months, despite a near record-breaking dry July prompting recommendations for people to water their gardens.



Bureau of Meteorology (BOM) climatologist Naomi Benger said there was an average chance of exceeding the state's median rainfall in the southern agricultural areas during August and September.

Districts further north had an "elevated chance", she said.

"That includes the eastern Eyre Peninsula and the northern Mid-North districts, and up into the southern part of the Flinders district as well."

Dr Benger said the state's north had the strongest chance of significantly wet weather thanks to the cooling of the central and eastern tropical Pacific Ocean, which is likely to .

The La Nina atmospheric-oceanic climate cycle typically brings wetter weather and cooler daytime temperatures south of the tropics.

"But the influence of Pacific waters is more for eastern Australia, so while northern parts of SA might benefit, it's less likely to really influence the rainfall in southern parts of the state," Dr Benger said.

"There, we're looking at possibly around average rainfall, or possibly a little drier on some of the southern fringes, and it will be similar in September as well."



SAM causes dry July

South Australia dried out through July due to a positive Southern Annular Mode (SAM), which resulted in the planet's southern belt of westerly winds — known as the roaring 40s or the furious 50s — to push even lower towards Antarctica.

This meant the cold fronts and rain-bearing systems that usually pass over parts of South Australia did not make landfall.



"For SA's entire agricultural districts, the last couple of months have been dry," Dr Benger said.

"July had some areas, particularly on Kangaroo Island and in the lower South-East and some patches in the north as well, where it was pretty close to the driest July on record."

Rainfall was 67 per cent below average for the state as a whole — the lowest since 1997.

"A lot of the agricultural areas would be really feeling it, really struggling," Dr Benger said.

"In May, the southern areas east of the Mount Lofty Ranges and down to the south there received pretty good rainfall, but unfortunately many other areas haven't seen that."

BOM does not single out weather events as being attributed to climate change, but Dr Benger said the conditions reflected a trend over several decades for increasingly frequent dry periods in SA.

"Even if we do have the climate drivers [such as La Nina] supporting more moisture in the air, we haven't had the frontal systems come through to be able to deliver the systems that bring the rainfall," she said.

Gardens need water



A over the next fortnight is expected to bring some rain to agricultural areas in SA, but nothing like the drenching seen in May.

Gardening Australia presenter Sophie Thompson reminded listeners to water their gardens and not be lulled into a "false sense of security" because it was winter.

"Even though it might be green on top, it's a dry green," she told .

"Check the soil, particularly vegetable gardens, pot plants and fruit trees.

"They say we're going to get rain later in the week in Adelaide, but when I look at how much rain is expected, there's not much there.

"They're saying it's going to be higher in the rural areas, which is where they desperately need it, so we pray that it does come."


- ABC

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