El Niño year, but the inland is flooding

Strong El Niño, wet inland, Murray near flood

Here is the short version, the El Niño headline numbers are extreme and the inland south keeps getting wet anyway.

The Bureau of Meteorology's 11 August update put the relative Niño3.4 index at +2.20C for the week ending 9 August, well past the +0.80C El Niño threshold.

The 30-day Southern Oscillation Index to 8 August sat at -25.6 against a threshold of -7, and July's average of -29.1 was the most negative July on record.

The event is expected to hang around into autumn 2027, with models pointing at a peak in late spring or summer.

"A strong El Niño signal in the Niño3.4 region does not necessarily mean strong impacts on Australia's climate; ENSO is only one of many factors," the Bureau said.

The Murray is the one to watch

BOM issued a minor flood warning for the Murray River at 1:56pm Friday 21 August, the fourth warning in the sequence.

Barham was sitting at 5.47m and steady at 1:00pm Friday, with the minor flood level at 5.50m and a possible exceedance overnight into Saturday.

Upstream flows plus Goulburn flood water are driving it, and further rises are possible next week.

Other Friday heights were Albury 1.11m, Tocumwal 3.84m, Torrumbarry Weir 6.72m, Swan Hill 3.48m, Wentworth Lock 10 3.81m and the Edward River at Deniliquin 3.07m.

Far West NSW copped it too

Broken Hill Airport picked up 11.6mm across the Monday and Tuesday of the week of 17 and 18 August, in country that rarely sees winter rain.

BOM senior meteorologist Angus Hines called that rain "pretty uncommon for winter in the region".

"The average in Broken Hill for August rainfall is about 18 millimetres, but we've had already two pretty solid dumps of rain just in the past couple of weeks, which have well and truly exceeded that monthly average."

The Mundi Mundi Bash near Silverton wore the consequences, after organisers said a 42mm rain event on 8 and 9 August, then more rain during roll-in.

Thirty per cent of the site was unsuitable for camping and Wilangee Road dropped back to 4WD only.

Founder Greg Donovan called limiting access "the most gut-wrenching decision".

Mildura's Lincoln Dalla Santa summed up the mood: "What nature dishes out, we just gotta live with that."

Rain totals that do not read like El Niño

Arkaroola in the northern Flinders has logged 96.9mm from 1 to 21 August, against a long-term August mean of 14.0mm across 1938 to 2026.

The bulk arrived in three hits: 43.0mm on Sunday 9 August, 30.8mm on Tuesday 18 August and 10.6mm on Friday 21 August.

Cape Borda on Kangaroo Island has recorded 65.6mm to 21 August.

Meanwhile Queensland's east and inland remain in drought, with the Balonne no longer running.

Warm water is doing the heavy lifting

Australian coastal sea surface temperatures for the week to 9 August were especially warm off southern NSW and eastern and southern Tasmania, peaking 2 to 3C above average.

July global sea surface temperatures ran 0.57C above the 1991 to 2020 average, the warmest July on record since 1900.

BOM climatology discussion has Indian Ocean waters well above average.

BOM senior climatologist Zhi-Weng Chua explained the mechanism: "Warmer waters can increase atmospheric moisture, providing favourable conditions for rainfall-producing weather systems such as north-west cloud bands and frontal systems that can draw tropical moisture across inland Australia."

Chua also noted El Niño typically favours warmer-than-average conditions across the southern two-thirds of Australia, and that exceptionally warm surrounding oceans may enhance that warmth signal.

The IOD is the wildcard

The Indian Ocean Dipole is neutral, but the weekly index hit +0.41C on 9 August, a third straight week at the +0.4C positive threshold.

Models suggest a positive IOD may develop, which would start choking off the moisture supply feeding these cloudbands.

What it means, plainly

The same El Niño drying the Balonne country is not shutting off the Southern Ocean and Indian Ocean moisture tap into the inland south.

Niño3.4 strength is not proportional to Australian rainfall impact, so a record index does not buy you a record dry.

Heat, though, will follow the El Niño script even if the rain does not.

Next week's setup

A north-west cloudband is dragging tropical moisture off the Indian Ocean, with patchy rain across WA this weekend and into South Australia on Monday 24 August.

The eastern states get their turn on Tuesday and Wednesday, 25 and 26 August.

A second band may push out of south-west WA on Wednesday and reach the east next weekend.

Forecast totals sit at 15 to 50mm for most of south-east Australia and parts of WA before month end, and that is a forecast, not money in the bank.

On the water

The Murray is the main game, and rising water at Barham, Swan Hill and Wentworth means debris, dirty plumes and snags sitting just under the surface.

Ramps that were fine a fortnight ago can be closed, silted or plain sketchy, so walk the ramp before you back the trailer down.

Trailer-boat owners on the Edward at Deniliquin and around Torrumbarry should expect faster current and floating timber mid-channel.

If the Darling and Menindee start to run, dirty water and debris will push on downstream toward Wentworth.

Fishing follows the usual pattern, with bites holding on the clean edge of the plume for a few days, then shutting down once the water turns to soup.

Divers and snorkellers off southern NSW, Victoria and South Australia will lose visibility once the next cloudband tips runoff into the bays and estuaries.

Bar crossings from Bermagui down to the Coorong get uglier when river flow pushes out against swell, so give them a day or two to settle.

Right now the Eden Coast is under a gale warning issued at 4:00am Saturday, meaning sustained winds of 34 knots (63 km/h) or more.

Kiters will find plenty of wind down there, but a Far South Coast gale with a flood plume running is not a beginner's day out.

Rain is not finished with the inland south and the Murray has more water coming, so keep the NSW warnings page open as the next band crosses.

Line up your next session on Seabreeze tides before you hook up the trailer.