Climate and Water Outlook, August–October 2019

Climate and Water Outlook, August–October 2019

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Welcome to the Climate and Water Outlook for
August to October 2019. Drier and warmer-than-average conditions are
likely to continue at least into October. And fire potential this season is higher than
usual for parts of southern Queensland. But first, let’s look at recent conditions. The first half of the year was very dry, this
has extended the drought in many areas. But July saw timely rains in parts of Western
Australia and the southeast. Western Tasmania in particular, had above-average
rainfall for the month. Mid-July also brought strong winds and snow
to southeastern Australia. However, temperatures for our coolest month
of the year remained above average in most areas. Nights in inland Western Australia and across
the Top End were colder than usual. Southern Australia was warmer overall, but
some nights still brought winter fog and frost. With warm and mostly dry conditions continuing
in the east and southwest, soil moisture remains below average for many key agricultural regions. Mid-winter is the time of year when we’d normally
see southern water storages filling. But there’s been little change in overall
storage levels in the southeastern mainland over the past month. Levels in the northern Murray–Darling Basin
are still at just 7 per cent. So, what will influence our climate over the
next few months? El Niño now looks unlikely to form in the
Pacific Ocean this year. The Indian Ocean is the dominant influence
on the outlook, with climate models favouring a positive Indian Ocean Dipole. This is typically associated with drier conditions
over central and southern Australia during winter and spring, and an early start to the
southern bushfire season. Another, shorter-term climate driver has also
been affecting us in July—a northward shift of cold fronts—called a negative Southern
Annular Mode, or SAM—brought the wild weather and rains to southeastern Australia. However, this negative SAM period is now coming
to an end. So, what does all that mean for our August
to October outlook? Average to drier-than-average conditions are
likely for much of Australia, largely due to the influence of the positive Indian Ocean
Dipole. Streamflow forecasts for July to September
suggest low flows are likely to continue for nearly two thirds of locations across Australia. Near-median and high flows are more likely
in regions such as northeastern Queensland, that had above-average rainfall earlier in
the year. Turning to temperatures for August to October: Days are very likely to be warmer than average
for most of Australia. Clear nights and dry soils in southern inland
areas will raise the risk of frost. It’s now fire season in the north. Parts of southern Queensland have higher than
usual fire potential. This is the result of vegetation that has
dried out since the start of the year. For the remainder of northern Australia fire
potential is likely to be normal for the season. For more details, visit the Bushfire and Natural
Hazards CRC website. We’ve already seen bushfires in southeastern
New South Wales, due to dry conditions. So take care with those winter burnoffs, particularly
on windy days. In summary, for much of the country:
we’re expecting an average to drier-than-average August to October;
temperatures are likely to be higher than average;
low streamflows are likely at most locations; and there’s an increased risk of bushfires
in parts of southern Queensland. For more details, visit bom.gov.au/climate/ahead. Our first look at likely conditions for spring
will be available on Thursday the 15th of August.

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