Australia
is the driest habitable continent on earth, and as a continent is subject
to many different weather areas. The arid zone covers over 70% of the
inland and is made up of many microclimates. Climatologists agree that
the arid zone is set by isohyets ( the contours of areas of equal rainfall).
This is 400mm in wet dry tropical northern Australia, 150mm in the colder
and drier east and south, and 200mm in the west. There are some basic
rules to the weather. Summer is HOT. Winter is mild. It doesn’t rain
very often. It can rain at any time of year. It can also choose to rain
regularly, or not at all. There are no averages. Sometimes no rain
falls for years. Only in the wet dry tropics is there a wet and a dry
season. Australia’s deserts are climactically capricious.
This page contains climate information that is relevant to the southern
half of Outback Australia including Eastern New South Wales, Northern
South Australia, Eastern Western Australia, the southern regions of the
Northern Territory, and Western Queensland. I also contains links to current
weather information.
If
you need any further information on Outback Australia,
e-mail
us and we will be happy to help
Seasonal
variations in wind patterns are controlled by shifts in the position of
the high-pressure belt (which forms part of the global sub-tropical ridge),
from the southern portions of the continent in summer to the latitudes of
central Australia in winter. During the warmer half of the year (October
– March), the ridge is located in the south of the area; most of the
prevailing winds are from the southeast quadrant. During autumn the mean
position of the ridge moves north and remains over the centre of the continent
for the cooler months (April to September), and winds tend to be lighter.
Gale force winds (in excess of 61kph) are uncommon, being most frequent
from October to December when they are observed on average one day per month
Rainfall
variability in the Outback is among the highest in Australia, and average
annual totals are amongst the lowest. In effect there is no real seasonality.
The principle synoptic influences on rainfall are of tropical origin, taking
the form of moist tropical airmass incursions, rain and monsoon depressions
and thunderstorms. Even so, mid latitude influences together with frontal
activities produce rain. In other words, the tail ends of tropical cyclones
can come down from the north and deluge the country in summer, as can the
tips of cold frontal systems from the south in winter. The northern half
of South Australia lies on the northern or southern end of these systems,
and therefore is the driest place in Australia. The driest recorded place
in Australia is Mulka Station on the Birdsville Track, where rainfall is
below 120mm per annum.
Evaporation
is dependent on sunshine, temperature, humidity and wind, and is measured
as a potential value, assuming an unlimited water supply. Average evaporation
rates in the Outback are greater than 3,400 mm. In the Simpson Desert they
are estimated to be 3,800 – 4,000mm.
Drought refers to an acute water shortage. It implies that rainfall for
a given period is less than a certain threshold. In Oodnadatta, years with
rainfall in the first decile (ie. The lowest 10% of falls on record) since
1900 were 1900, 1915, 1918, 1928, 1929, 1934, 1937, 1940, 1944, 1951, 1959,
1960, 1961, 1965, 1967, 1970, 1972 and 1990.
Maximum
temperatures average 36-39°C in summer and 18-24°C in winter. Temperatures
are cooler in the Flinders Ranges and the Central Australian Ranges. July
is generally the coolest month. In winter the temperature can drop well
below freezing with frosts occurring up to 50% of mornings during July and
August. Temperatures in the sand hills are often hotter than the plains,
rising to the high 50°C range. The gibber stones heat to 80°C.
The
bureau of Meteorology only records events where horizontal visibility is
reduced to below 1,000 metres. At Oodnadatta, 5 storms are recorded on average
per annum. The frequency of dust storms is relative to ground cover or lack
of it. After the rabbit plagues and periods of drought, horrendous storms
are recorded. The banner at the top of this page shows a duststorm we encountered
at 4pm. on 8th. October 1999 near Gosses Springs at Lake Eyre South.
For
the latest information on Australian weather, click
here
The
morning was clear and fine, with a moderate southerly wind and the temperature
in the high twenties. You could tell it was going to be a hot day. We departed
our camp on the Rig Road in the Simpson Desert and headed east. The wind
was constantly picking up, and dust was lifting off the ground. We stopped
for lunch in a corkwood grove, the wind was now howling, and the sky was
a murky brown. Visibility was down to 500 metres. The temperature was 40°C.
We continued on through the afternoon, at least in the vehicles we were
sheltered. Trees were being uprooted. Sand was blowing across the ground.
At 6pm the storm appeared to be abating. We pulled into a grove of gidgee
trees and set up camp. We buried the tents in sand so they wouldn’t
blow away. Just as we sat down for dinner we could hear a roaring in the
south. The wind swung, and blew with an even greater ferocity. Tables and
chairs went flying. We closed everything up and battened down for the evening.
The most extraordinary thing was the wind. I had never heard wind roaring
at such a volume. I zipped up my swag and managed to fall asleep. I woke
at 6am. There was sand in my eyes and up my nose. There were several shovel
loads in my swag. The light was golden, the wind was over and the storm
had gone. The air was clear, cool and crisp.”
And
further:
Don't be fooled by the glossy travel brochures. The far north of Australia
is under the influence of monsoonal troughs from November until April,
the weather is hot and humid with lots of rain. At this time the beaches
of Victoria, South Australia, Tasmania, Southern New South Wales and Southern
Western Australia are magnificent, but the big international tourism investment
is in the north of the continent, so their advertising drives international
visitors to the wet north. Take a careful look at the Australian Bureau
of Meteorology before planning your holiday. Travelling in the Outback
between November and March you will experience extreme heat. Diamantina
choose to visit the Outback during the cooler months, when temperatures
are ideal.
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