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For the 3, 4 and 12-month
period ending 31st August 2007
Very dry since late autumn in parts of southern Australia
LINKS:
rainfall deficiencies definition
3-month rainfall deficiencies
4-month rainfall deficiencies
12-month rainfall deficiencies
The late autumn and winter has been very dry over parts of southern Australia,
particularly in Western Australia and South Australia. For some areas it is
the second rainfall deficient winter in successive years, with winter rains
being suppressed in 2006 by an El Niño event. At the yearly time-scale,
rainfall deficiencies are evident in all states and territories, with the
exception of the Northern Territory. As August 2007 was generally wetter than
August 2006 in the areas with twelve-month rainfall deficiencies, there was a
slight easing of these deficits compared with the situation at the end of July.
For the 3-month period from June to August 2007, an area of serious to severe
rainfall deficiencies covered much of SA, the far southwest corner of
Queensland, far western NSW and parts of northwest Victoria. Also affected
were parts of southwest WA, western Victoria and north-central Tasmania.
Several regions had record low winter totals, the most notable being near
Ceduna on SA’s west coast.
Rainfall deficiencies for the 4-month period from May to August 2007 were
widespread across the southwest of Western Australia. In South Australia they
were evident along and inland of the west coast and Eyre Peninsula, as well
as in a narrow zone extending from Port Pirie to near the SA/NSW/VIC tri-state
border.
For the 12-month period from September 2006 to August 2007, zones or regions
of rainfall deficits existed near the southwest and west coasts of WA
(generally south of Shark Bay), along parts of coastal SA, in northern
Tasmania, in a band from south-central Victoria to the tablelands and western
slopes in southeastern NSW, and in southeast Queensland. Rainfall deficiencies
at this time-scale were eased or removed in southeast Queensland as a result
of above to very much above average August rainfall. Record low falls for
this particular 12-month period were recorded just to the east and southeast
of Melbourne, and along WA’s west coast between Shark Bay and Geraldton.
Despite the rapid demise of the 2006 El Niño event, the Murray-Darling
Basin (MDB) is still to see a sustained period of above average rainfall
in the intervening period. This is the first time in the record dating
from 1900 that an El Niño-drought in the MDB has not been followed by at
least one three-month period with above normal rainfall (basin average) by
the end of the following winter. Almost the entire basin shows well below
average rainfall for periods starting in 2006.
The deficiencies discussed above have occurred against a backdrop of
multi-year rainfall deficits and record high temperatures that have severely
stressed water supplies in the east and southwest of the country. Several
years of above average rainfall are required to remove the very long-term
deficits. Furthermore, the combination of heat and drought during the past
five to ten years over the MDB and southeastern Australia, is outside the
typical range of variability experienced during the previous 100 years.
Rainfall
deficiency maps for standard periods out to three years are
available.
Note: The terms used to describe rainfall in these
Drought Statements have the following meanings -
Serious deficiency
- rainfalls in the lowest 10% of historical totals,
but not in the lowest 5%
Severe deficiency
- rainfalls in the lowest 5% of historical totals
Lowest on record
- lowest since at least 1900 when the data analysed begin
Very much below average
- rainfalls in the lowest 10% of historical totals
Below average
- rainfalls in the lowest 30% of historical totals,
but not in the lowest 10%
Average
- rainfalls in the middle 40% of historical totals
Above average
- rainfalls in the highest 30% of historical totals,
but not in the highest 10%
Very much above average
- rainfalls in the highest 10% of historical totals
For more information regarding this rainfall
deficiencies statement, please contact the following
climate meteorologists in the National Climate Centre:
Grant Beard on (03) 9669 4527
Blair Trewin on (03) 9669 4623
David Jones on (03) 9669 4085
External Sites Relating to Drought
The Bureau of Meteorology does not make formal drought declarations
as these are done by either the relevant State Governments or by the
Australian Government. The Australian Government Program is called
Exceptional Circumstances
and it is administered by the Federal Department of Agriculture,
Fisheries and Forestry (DAFF). General information about Australian
Government drought assistance is available at
http://www.daff.gov.au/droughtassist.
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