Issued on 6 December 2010

Australia's wettest spring but no relief for southwest WA

Australia recorded its wettest spring on record for the 2010 September to November period. The area averaged total of 163 mm beat the previous record by 23 mm. This was achieved despite the widespread above-average rainfall again missing the southwest corner of the country, which is experiencing its driest year-to-date on record. Northern and eastern parts of the country have continued to receive above to very much above average rainfall, with Queensland, New South Wales and the NT all recording their wettest spring on record. All states recorded above average rainfall for spring, with all states except Tasmania recording totals placing them in their ten wettest springs on record.

11-month rainfall deficiencies

For the 11-month period from January 2010 to November 2010, below average falls over the southwestern half of WA during November 2010 has maintained areas of rainfall deficiency as described in the previous drought statement and slightly increased areas of lowest on record. Some average to above average falls over inland areas of the Gascoyne and Pilbara districts have not been enough to clear the region of serious to severe rainfall deficiencies, with large areas still remaining. To relieve most areas of rainfall deficiency in WA, i.e. to just get above the tenth percentile, rainfall for December 2010 will have to be in the top 10% wettest Decembers on record. For the southwest corner (southwest of the line joining the points 30°S, 115°E and 35°S, 120°E) averaged as a whole, rainfall for 2010 will be the lowest on record unless rainfall for December is the second highest on record.

Whilst recent rains in eastern Australia have provided, in many cases, short-term relief, sustained periods of above-average rainfall are needed to remove very long-term deficiencies. This is especially true for the very long-term deficiency periods of 9 and 14 years (see the Special Climate Statement 22). Rainfall has been below average across much of southwest and southeast Australia since 1997, whilst central and southern parts of the Murray-Darling Basin have experienced below average rainfall since 2002. These long-term deficiencies have taken place against a background of well above average temperatures, including Australia's warmest decade on record. Further information on exceptional rainfall and temperature events across Australia can be found in the Special Climate Statements.

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Definitions

Lowest on record - lowest in the historical analysis, which runs from 1900.
Severe deficiency - rainfalls in the lowest 5% of historical totals.
Serious deficiency - rainfalls in the lowest 10% of historical totals, but not in the lowest 5%.

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.

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