Issued 5 May 2004

Long-term rainfall deficiencies persist, mainly in the east

The Bureau of Meteorology announced today that there was little change in the pattern of long-term (since mid-2002) rainfall deficiencies with the inclusion of the April rainfall data. With the exception of Tasmania, patches of rainfall deficits remain in all States and Territories, predominantly in NSW and Victoria.

22-month rainfall deficiencies

However, for the 22-month period from July 2002 to April 2004, rainfall deficiencies still persist along parts of the north Queensland coast between Townsville and Rockhampton, and in patches over inland eastern and southern Australia. The largest contiguous region persists in the southeast of the mainland and covers Gippsland, central and some of northeast Victoria, together with the southeast quarter of NSW and the ACT. There was some relief in the Sale-Bairnsdale region of Gippsland following above to very much above average rainfall during April. Nevertheless, some patches of record low falls for the 22-month July to April period are evident in East Gippsland and the NSW Southern Tablelands. The lows falls in the southeast of the country are notable in that this general region has experienced below normal rainfall for most of the past 8 years.

Because the deficiencies extend over such a long period, they’re likely to take some time to be removed. For example, around Orbost over 400 mm of rain (150 to 250% of normal) would be required over the next three months just to elevate the rainfall since July 2002 to the tenth percentile (top of decile range 1). Such a total would be near to, or above the record high May to July rainfall for this region!

In WA, long-term rainfall deficiencies are evident in a relatively small patch between Exmouth and Onslow (including some lowest on record falls), as well as in small areas near Shark Bay and Bunbury.

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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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