Wet weather event to increase rainfall across Australia for next 4 months

It’s been a wetter than normal start to winter in Australia but these damp days are far from over with new predictions of above average rainfall until late November.

The Bureau of Meteorology has officially declared a so-called negative phase of the Indian Ocean Dipole (IOD), a climate phenomenon which was responsible for one of Australia’s wettest winters on record.

It means southern and eastern Australia should brace for a soaking in spring with lower than average temperatures and a late start to the fire season.

Supplied map of Australian rainfall data shows above average rain for large parts of Australia. Source: Bureau of Meteorology
Large parts of Australia have seen above average rainfall this year. Source: Bureau of Meteorology

Rainfall records broken last time similar pattern emerged

It’s the first negative dipole event since 2016, when Australia’s second wettest winter on record was declared.

That winter more than half of Australia received rainfall totals in the highest 10 per cent of historical records for the June to August period, contributing to extensive flooding including in inland NSW.

But this year’s IOD isn’t expected to be as strong.

Stock image of a pedestrian making their way through extreme weather and rain in Sydney, Australia. Source: Getty Images
The last time a negative dipole event was declared was in 2016, between June and September. Source: Getty Images

What is the Indian Ocean Dipole?

Bureau of Meteorology senior climatologist Felicity Gamble said the IOD weather phenomenon is driven by ocean patterns.

It's defined by the difference in sea surface temperature between two areas (or poles, hence a dipole) – a western pole in the Arabian Sea (western Indian Ocean) and an eastern pole in the eastern Indian Ocean south of Indonesia.

The IOD significantly impacts rainfall and temperatures in Australia and other countries that surround the Indian Ocean Basin, particularly during winter and spring.

"It typically beings wetter than average conditions to much of Australia," Ms Gamble said.

There are three phases of the IOD — positive, negative and neutral. On average, each phase lasts three to five years.

"A negative IOD typically develops in the winter months and persists into spring but by summer when the monsoon trough shifts into the southern hemisphere, that always brings an end to the Indian Ocean dipole."

Pictured is a map graphic showing how the Indian Ocean Dipole brings increased rain to Australia. Source: Bureau of Meteorology
A negative phase of the IOD can increase rainfall. Source: Bureau of Meteorology

Perth breaks rain record after weeks of wet weather

After 20 days of rain in a row, Perth has record its wettest July in two decades.

Consecutive cold fronts, powerful storms and heavy downpours have dumped more than 184 millimetres on the city this month, making it the wettest July since 2001, when 182mm was recorded..

But with little reprieve in sight, there's every chance this July could be declared the wettest on record for Perth.

The Bureau of Meteorology predicts widespread rainfall across southeast Western Australia and western South Australia today, which will continue to move further east into NSW and Victoria on Thursday and Friday.

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