Welcome to the Climate and Water Outlook for July to September 2016.
La Niña remains on the cards, but it's unlikely to be as strong as the 2010–12 event.
The strongest driver of Australia's climate in 2016 is likely to be the Indian Ocean,
which is fuelling the chance of a wetter and cooler year than 2015.
First, let's look at recent conditions.
Two East Coast Lows formed in June, carrying extra moisture from a record-warm Tasman Sea.
These brought significant rainfall to dry areas in the north of the Murray–Darling
Basin, western Queensland and Tasmania.
For instance, Longreach had more rain this June than it received in all of 2015 or 2014.
Tasmania, which had its driest ten months on record to April, then had its second-wettest
May–June period in 117 years of records.
These rains mean areas of rainfall deficiency have reduced.
In Tasmania, for instance, 14-month deficiencies (accumulated since May 2015) have all but
disappeared.
Lower-layer soil moisture is now higher than average across most of inland Australia and
Tasmania.
Since May, water storages in the Murray–Darling Basin, southwest Australia and Tasmania have
all risen.
Maximum temperatures across northern Australia were at record-high levels in June.
Bradshaw in the Northern Territory set a new national record for the warmest June day:
37.9°C on 7 June.
Nights also broke temperature records in the north:
Troughton Island off Western Australia broke the national record for highest minimum temperature
in June, five nights in a row, only getting down to 27.9°C.
And Darwin had its latest first night of the year below 20°C on record, on 21 June.
Northern Territory mango growers still haven’t had the five nights below 20°C they need
for good flowering.
So what's driving Australia’s climate right now?
The Indian Ocean is shaping up to be the strongest influence on our weather this winter and spring.
Warm sea surface temperatures south of Indonesia and easing of temperatures off Africa mean
a negative Indian Ocean Dipole, or IOD, is looking increasingly likely.
This typically increases rainfall in central and eastern Australia.
In the Pacific Ocean, El Niño ended quickly.
Most indicators have now moved towards La Niña, except for the trade winds in the tropical
Pacific, which have yet to become stronger than normal.
The chance of La Niña this year remains around 50 per cent, which is double the normal odds,
so our ENSO Outlook is still at La Niña WATCH.
If we do have a La Niña in 2016, our models show it is unlikely to be as strong as the
last La Niña from 2010 to 2012.
So what’s the rainfall outlook for July to September?
Above-average rainfall is likely across most of Australia, especially in the southeast.
Outlook accuracy is moderate at this time of year.
Turning to streamflows: By the end of May, flows were already returning
to more average conditions—with near-median or high flows forecast for two-thirds of locations.
We’re still analysing data from the heavy rainfall in June for our next seasonal streamflow
forecast, which will be available on 11 July at bom.gov.au/water/ssf.
Turning now to temperature: Outlooks suggest days will continue warmer
than average across the far north and in Tasmania, but cooler than average for the rest of the
country.
Nights are also looking warmer than average across the north, in Tasmania and in eastern
Victoria.
Accuracy for this outlook is moderate at this time of year.
So in summary:
We're watching for La Niña, but expect the Indian Ocean Dipole to dominate our climate
for the coming months.
Odds favour above-average rainfall for most of Australia, with temperatures warmer than
average across the north and in Tasmania but cooler elsewhere.
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 28 July.
For the Bureau of Meteorology, I’m Paul Feikema.