Welcome to the Climate and Water Outlook for Spring 2015.
El Niño continues to strengthen, and is likely to stay with us until early 2016, leading
to some colourful headlines.
But while typical impacts are starting to be felt around the world, the impacts we'd
normally expect to see in Australia are being eased by a record warm Indian Ocean.
But first, let’s look at how our climate fared over winter.
While northern Australia is normally dry, for southern Australia winter is the time
when soils wet up and water storages start to fill.
And while El Niño may typically bring a dry winter, this year, moisture from the warm
Indian Ocean has brought above-average rainfall to some areas.
Southern parts of Western Australia had a slow start, but received good rains late in
the season.
Inland eastern Australia has also had timely periods of good rain;
however, Western Victoria and neighbouring parts of South Australia had some very dry
months … … extending the short-term rainfall deficiencies
in those areas.
Long-term deficiencies continue in central Queensland and northern New South Wales.
These areas get their rain in the northern wet season, so it's unlikely there will be
any significant change until later in the year.
Deep soils remain dry across many areas, absorbing rainfall and reducing surface runoff into
storages.
Winter inflows to Perth’s catchments were the lowest since 1911, leaving water storages
in southwest Western Australia only 37 per cent full.
In the South Australian Gulf and the Murray–Darling Basin, storages are only half full.
In terms of temperature, the southeast had several cold snaps over winter, with average
to cooler-than-average conditions overall.
In contrast, much of northern and western Australia was warmer than average.
So what may drive our climate over spring?
Well, the 2015 El Niño has matured, with the Pacific Ocean and atmosphere now clearly
reinforcing each other.
This is likely to lock the event in until at least early 2016.
Climate models suggest temperatures in the Pacific Ocean may rival the big 1972, ’82
or even ’97 El Niño events.
Normally, El Niño brings drier and warmer conditions across southern and eastern Australia.
But while typical impacts are being felt elsewhere around the globe, the impacts we'd normally
see in Australia are being eased by a record warm Indian Ocean.
This may continue to feed more moisture than normal over Australia during spring.
However, three out of the five climate models we survey suggest the northeast Indian Ocean
could cool, reducing the feed of moisture from the west, and reinforcing El Niño’s
drying influence on Australia.
We'll be watching the Indian Ocean very closely.
So what's the outlook for spring?
Well odds favour above-normal rainfall for western and central Australia, as the Indian
Ocean moderates El Niño impacts.
Our rainfall outlook has high accuracy at this time of year.
In northern Australia, the first rains of the wet season are keenly anticipated.
They usually arrive in October for eastern Queensland, and by February in parts of WA.
But these dates do vary.
Our new northern rainfall onset service shows the chances of an early start to the northern
rains.
For example, green areas on the map, such as in central Australia, may get an earlier-than-usual
start to the wet season rains this year.
Turning to streamflows, our August–October forecast shows low flows are expected at 81
locations, mostly where soils are dry.
Near-median flows are forecast at 39 locations, with high flows more likely at only 10.
Accuracy for our streamflow forecasts is high at this time of year.
In terms of temperature, clear skies mean warmer-than-average days for coastal parts
of Queensland and northern New South Wales.
Cooler-than-average days are likely in the north of WA and western Victoria.
Accuracy for this outlook is high at this time of year.
Nights are likely to be warmer than average across most of the country.
El Niño can bring severe frosts in early spring, due to clear night skies.
Later in the season, dry soils and vegetation can raise the risk of early heatwaves and
bushfires.
So in summary: El Niño has matured, but the Indian Ocean
remains at record warm levels.
This may take the edge off El Niño's influence for some parts of Australia.
Still, frosts may come early in the season, with heatwaves and bushfires possible later.
Spring may be wetter than average in western and central Australia, while low streamflows
are likely to continue in many areas.
For more details, head to our website at bom.gov.au/climate/ahead You can also follow us on Facebook and Twitter.
Our next video will be released on Thursday 24 September.
For the Bureau of Meteorology, I’m Andrew Watkins.