Wet spring ahead: Australia braces for more rain as BoM declares negative Indian Ocean dipole

Meteorologist says it is the first time since reliable weather records began that negative IOD events have occurred in back-to-back years

A negative Indian Ocean dipole event has been declared, increasing the chances of above-average rainfall over much of Australia during the rest of winter and spring.

It is believed to be the first time since reliable records began in 1960 that negative Indian Ocean dipole events have occurred two years in a row.

The Indian Ocean dipole is determined by sea surface temperature differences between the eastern and western Indian Ocean. The climate phenomenon affects rainfall and usually begins in late autumn or winter.

BREAKING: A negative Indian Ocean Dipole (IOD) has just been declared, increasing the likelihood of above-average rain over large areas of Australia in the coming months. This is the first time we have seen back-to-back negative IOD years since reliable records began in 1960. pic.twitter.com/vCCsPosRss

— Ben Domensino (@Ben_Domensino) August 2, 2022

In a negative dipole event, warmer water concentrates in the eastern Indian Ocean and moisture-rich air flows towards Australia.

The last negative Indian Ocean dipole began in July 2021, the first in five years.

Ben Domensino, a meteorologist with Weatherzone, said the event increased the likelihood of above-average rain over parts of Australia for the next three to four months and has prompted concerns after so much rain already in the country’s east this year.

“When we have a negative Indian Ocean dipole in place, typically southern and south-eastern inland Australia have a high chance of seeing above-average rain, and most other areas of central, eastern and southern Australia are also more likely to be wet,” Domensino said.

“One thing that a lot of people are concerned about with this IOD declared is that Sydney just had a record wet year to date.”

He said there was still an expectation of above average rain in eastern New South Wales but the influence from the negative dipole is more pronounced to the west of the Great Dividing Range.

“So this will more influence rainfall for the Murray-Darling basin rather than the eastern seaboard,” he said.

“The IOD doesn’t have much of an influence on rainfall in south-western WA, or Tasmania and far north Queensland.”

He said the declaration on Tuesday is “confirmation that we’ve been in a negative Indian Ocean dipole pattern for the last eight weeks”.

The Bureau of Meteorology said in a statement that “all five international climate models surveyed … anticipate a negative IOD is likely to persist through to November” and that “it also increases the chances of warmer days and nights for northern Australia”.

Domensino said the BoM had reliable records of these events dating back to 1960. “In that time, including this year’s, there have been 13 negative Indian Ocean dipole events,” he said.

In addition to the two negative Indian Ocean dipoles, there have been two consecutive La Niña events, in 2020-21 and 2021-22. “This is very rare, to have these consecutive years of wet phase climate drivers,” Domensino said.

Some models suggest that another La Niña event may occur later this year.


Donna Lu

The GuardianTramp

Related Content

Article image
Cold weather, rain and damaging winds to slam south-eastern Australia
Wintry blast pushing through South Australia expected to reach Victoria, Tasmania and NSW on Wednesday, with possible snow flurries in Queensland on Saturday

Lisa Cox

18, Aug, 2020 @9:26 AM

Article image
Flood warnings downgraded after heavy rain in south-east Australia
Steady rainfall that has dumped more than 200mm in some catchments gradually begins to ease

Calla Wahlquist

02, Dec, 2017 @11:07 PM

Article image
Wind change fans blazes as Sydney hit by hazardous air quality – as it happened
Almost 3,000 firefighters deployed across New South Wales as more than 80 bushfires continue to burn.

Naaman Zhou (now), Helen Davidson and Michael McGowan (earlier)

10, Dec, 2019 @9:04 AM

Article image
New South Wales state of emergency declared as 17 missing in Victoria – as it happened
At least nine people have died since Christmas Day, with more dangerous conditions predicted for the weekend. This blog is now closed.

Helen Davidson (now) and Luke Henriques-Gomes and Amy Remeikis (earlier)

02, Jan, 2020 @9:17 AM

Article image
Thousands of Sydney homes still without power after heavy rain – as it happened
Evacuation orders are in place for several areas around Sydney, with thousands of homes still without power after Sunday’s rainfall. This blog is now closed

Shelley Hepworth, Lisa Cox, Naaman Zhou, Calla Wahlquist andJosh Taylor

10, Feb, 2020 @6:36 AM

Article image
Firefighters battle Boxing Day bushfires ahead of looming heatwave
Temperatures forecast to reach the mid-40s again as heat moves from South Australia to New South Wales by Monday

Calla Wahlquist

26, Dec, 2019 @2:05 AM

Article image
Australia breaks weather records with hottest ever summer
2018-19 season tops temperature highs across the country, exceeding previous record set six years ago

Naaman Zhou

28, Feb, 2019 @5:53 AM

Article image
Australia offers assistance to tsunami-hit Tonga after undersea volcano eruption
Minister for the Pacific says a surveillance aircraft would help gather information about the extent of the damage

Australian Associated Press

16, Jan, 2022 @7:29 AM

Article image
NSW ‘primed’ for more flooding as heavy rain expected over eastern Australia this weekend
With catchments and dams already saturated, flood warnings have been issued for a number of rivers across the state

Mostafa Rachwani

11, Aug, 2022 @5:30 PM

Article image
Victoria braces for severe weather after another day of heavy rain soaks NSW and Queensland
Bureau of Meteorology says catchments are already saturated and more heavy rain is forecast on Friday night

Josh Taylor with Australian Associated Press

12, Nov, 2021 @8:38 AM