POWERING SMARTER WEATHER DECISIONS
Search

Wet spring still on the horizon, despite recent lapse in IOD

 

Around two-thirds of Australia are tipped to see above-average rain this spring, with cool days and warm nights also on the cards with wet spring still on the horizon, despite recent lapse in IOD.

As winter draws to a close in the southern hemisphere, Australia finds itself surrounded by abnormally warm waters.  

These warm sea surface temperatures have already contributed to several decent rainfall events over the last few months and will likely cause more useful rain in spring. 

Current state of climate drivers 

The Indian Ocean has been in a pattern called a negative Indian Ocean Dipole (IOD) since May this year. This occurs when abnormally warm water sits to the northwest of Australia and abnormally cool water lies near the Horn of Africa.A negative IOD typically increases rainfall and causes cooler-than-average days and warmer-than-average nights over large areas of Australia. 

While the IOD recently returned to neutral values during August, most forecast models suggest it will remain in an overall negative phase through the southern hemisphere’s spring. IOD events typically come to an end by the start of summer, which is expected to be the case this year. 

Meanwhile, the central Pacific Ocean has been gradually cooling over the last two months, showing signs of an emerging La Niña-like pattern. While most models are not expecting this cooling to develop into a fully-fledged La Niña event, it may still enhance rainfall over northern and eastern Australia during spring and possibly early summer. 

So, how will these climate drivers influence Australia’s weather during spring and early summer? 

Rain 

The combined influence of the negative IOD, a La Nina-like pattern in the Pacific and above average sea surface temperatures near northern Australia increase the odds of above average rain over the eastern two-thirds of Australia in spring.

Above-average spring rainfall over areas of southern and southeastern Australia that saw decent winter rain would increase the likelihood of flooding. 

Temperature 

The anticipated mix of climate drives also favors below-average daytime temperatures and above average overnight temperatures across much of the country during spring. 

La Nina also typically reduces the amount of extreme heat days in summer but increases the frequency of heatwaves, particularly in southern Australia. However, it’s difficult to know how much the Pacific will influence Australia’s weather in the months ahead, given the La Nina signal is quite weak in the outlooks. 

Tropical Cyclones 

Warmer-than-average seas to the north of Australia are also conducive to increased tropical cyclone activity from November onwards. We will have more details on Australia’s tropical cyclone outlook for the 2021/22 season in October. 

Bushfires 

Parts of eastern Australia are coming into spring with an abundance of grass and crop growth, following healthy winter rain. As temperatures increase throughout spring and summer, this grass is likely to dry out and provide fuel for fires. 

A broad area from central Queensland down to northern and central inland NSW is expected to have an above-normal risk of grassfires during spring and summer. 

Thunderstorms 

Negative IOD events have been shown to increase thunderstorm activity across northern Australia and decrease storm activity in southern Australia.  

Northern Rainfall Onset 

Models also suggest that northern Australia’s first wet season rains will arrive earlier than usual this year, as a result of the negative IOD and La Niña-like pattern. 

The impacts listed above are expected during spring and early summer. By late summer, the IOD will have broken down and the Pacific Ocean should be in a neutral phase. This means that typical weather conditions for that time of year are most likely. 

For detailed seasonal information and forecasts, please contact us at business@weatherzone.com.au 

 

Cover image source: @nardoodigram

Latest news

Satisfy your weather obsession with these news headlines from around the nation, and the world.

Wind farms facing potential cut outs

  Fierce winds are expected to lash parts of Vic, Tas, the ACT and NSW early next week, bringing the risk of wind farm cut outs in the region.  A low-pressure system should develop early next week near Vic and NSW as a cold front interacts with tropical moisture.  This cold front will sweep across SA […]

Exceptionally warm, dry March for parts of SA

Soaring temperatures and abundantly clear skies have just caused one of the warmest and driest Marches on record in parts of South Australia. Abnormally high pressure near southern Australia this month has kept rain-bearing systems away from SA, leading to plenty of warm and dry weather across the state. Image: Clear skies over SA on […]

Easter deluge possible as tropical moisture moves south

The tropical moisture that caused significant flooding in the NT and Qld is set to move southeast over Easter, bringing heavy rainfall, thunderstorms and possible flooding and damaging winds with it.  The map below shows the massive rainfall totals that fell across the southern NT and parts of Qld over the last week.  Image: The […]

Smoke from WA bushfires seen from space

  Several fires are burning across southwest WA this week, with smoke plumes seen from 36,000km above the surface.   A previously out-of-control bushfire in Perth’s southwest is now under control, after burning 3000 hectares of land and damaging property.  As of 10am WST On Tuesday, March 26, four other fires are burning in the […]