Welcome to the Climate and Water Outlook for May to July 2016.
The northern wet season has been one of the hottest on record, and many areas have been
far drier than normal. But El Niño could be in its final month, and chances have risen
for La Niña later in the year. Odds now favour above-average rainfall over
the next three months. But first, let's look at recent conditions.
While most areas have had a very dry couple of months, much of southwestern WA enjoyed
a long, steady soak in April. The northern wet season, from October to April,
had only three brief monsoon bursts, with little significant rain since the start of
the year. The poor wet hasn’t been helped by the record
low number of tropical cyclones—just three in our region this season, compared with the
average of 11. This wet season has also been one of the hottest
on record. Short and long-term rainfall deficiencies
remain in all States and Territories. Despite rain in some parts of western Queensland,
high temperatures and evaporation mean most drought affected areas are still very dry.
For many in northern Australia, it's been the fourth poor wet season in a row.
Lower-layer soil moisture is now below average in many agricultural areas, particularly across
the Murray–Darling Basin. With little rain and low soil moisture, some
farmers in western Victoria have been dry sowing as they wait for a late autumn break.
Water storages across Australia are now around 10 per cent lower than at this time last year—and
many are likely to fall further. So what's driving Australia’s climate right
now? El Niño is declining rapidly, and is likely
to be gone before winter. We've already seen the first signs of cooler
water off the South American coast. In the Indian Ocean, temperatures are still
at record warm levels. Combined with favourable weather patterns, this contributed to that
extra rainfall in southwestern WA. For the Great Barrier Reef, the good news
is that sea surface temperatures are finally starting to cool.
But off the coast of Western Australia ocean temperatures have increased, and coral bleaching
has already been observed. The demise of El Niño, coupled with international
model outlooks, has increased the chance of La Niña in 2016 to around 50 per cent. That's
double the normal odds. That means our ENSO Outlook has moved to La
Niña WATCH. If La Niña forms, it would typically bring
above-average winter–spring rainfall over central and eastern Australia.
If ENSO returns to neutral, other climate drivers will play a greater role.
One of these is the Indian Ocean Dipole, or IOD.
Models suggest the IOD could turn negative by late winter or spring, raising the chance
of good rainfall for southern Australia. In contrast to last year, the outlooks for
ENSO and IOD both now favour above-average rainfall.
So what’s the rainfall outlook for May to July? A late break is expected for southern Australia,
but odds favour above-average rainfall for the first three months of the southern cropping
season. Outlook accuracy is low to moderate at this
time of year. Turning to the streamflow forecast for April–June:
Low flows are likely at most locations, with dry soils soaking up the first rains.
Near-median flows are forecast for 26 locations, and high flows for 7.
Accuracy for these streamflow forecasts is moderate at this time of year.
Looking at temperature: Outlooks show warmer-than-average days for
northern and far southern Australia. Nights are very likely to be warmer than average
across the country. Accuracy for this outlook is moderate at this
time of year. So in summary:
El Niño continues to decline, with a La Niña WATCH in place for the coming months.
Odds favour above-average rainfall for most of Australia, but low streamflows 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
26 May. For the Bureau of Meteorology, I’m Andrew
Watkins.