Drought Statement - Issued 4th February 2003


drought_text.html

Statement on Drought for the 10 and 14-month periods ending 31st January 2003
ISSUED 4th FEBRUARY 2003

Rainfall deficiencies intensify

Widespread dry conditions throughout eastern Australia in January intensified rainfall deficiencies, the Bureau of Meteorology announced today. Furthermore, the situation was exacerbated by continuing well above average temperatures. One area that did experience relief was around the Gulf of Carpentaria, particularly in the NT, where heavy monsoonal rain ended periods of rainfall deficiencies.

For the ten-month period from April to January, serious to severe rainfall deficiencies covered the vast majority of Queensland, NSW and Victoria, more than half of South Australia, much of the southern NT, significant areas in southwest WA and the far east of Tasmania. A large area through central Queensland and northern NSW has had record low rainfall for the April to January period, with records dating from 1900.

For the fourteen-month period from December 2001 to January 2003, some additional areas between Cooktown and Townsville in far north Queensland, and in the southeast of the State from Rockhampton to the NSW border have also experienced serious to severe rainfall deficiencies.

The period to the end of March remains the most likely time for a significant change in Australia’s rainfall patterns. This relates to the end of the current El Nino event, which is now showing clear signs of decay. These changed rainfall patterns, which usually mark the beginning of the end of drought conditions, can take various forms ranging from a succession of moderately wetter than average months, to a widespread deluge that heralds several months of significantly above average rainfall.

It is not possible for the Bureau to say just how or when this current period of rainfall deficiencies will end, but because they are so widespread, the breakdown is unlikely to be uniform in either space or time. Furthermore, different industries are impacted by different lengths of periods of rainfall deficiencies and for example, it may take water supply storages longer to recover from a period of rainfall deficiency than a farming or grazing activity.

Comparisons with other dry spells

A frequently asked question is "how does the current drought compare with other notable ones from the past?" It should be noted that the Commonwealth Department of Agriculture Fisheries and Forestry - Australia (AFFA) takes the lead on drought impact issues at the national level, and official drought declarations are the responsibility of the State and Territory Governments. The Bureau of Meteorology advises AFFA on all aspects of climate conditions.

The Bureau’s National Climate Centre monitors Australian rainfall patterns on a range of time-scales from days to years, including analyses of rainfall deficiency that form the basis for statements like those above. To reiterate, rainfall is said to be deficient if it is within the lowest 10% of historical totals (decile range 1 or below the 10th percentile) for the period in question (3 months or longer).

The National Climate Centre has analysed the historical rainfall record back to 1900 looking at both the extent of areas below the 10th percentile, as well as the mean Australian percentile ranking. The 10-month period from April to January is compared to all ten-month periods of previous Australian droughts with the results tabulated below. Note that for long droughts with multiple overlapping 10-month periods, only the most intense period is shown in the table.

Rank 10-month period % of Australia
below the 10th
percentile
Rank 10-month period Mean Australian
percentile value
1. Nov 1901 - Aug 1902 61.2 1. May 1982 - Feb 1983 16.2
2. May 1982 - Feb 1983 60.3 2. March - Dec 1940 17.5
3. Apr 2002 - Jan 2003 53.8 3. March - Dec 1994 18.3
4. Feb - Nov 1940 51.0 4. Feb - Nov 1902 18.9
5. July 1951 - Apr 1952 45.2 5. Apr 2002 - Jan 2003 19.0
6. May 1928 - Feb 1929 45.0 6. Apr 1946 - Jan 1947 19.2
7. Apr 1946 - Jan 1947 45.0 7. March - Dec 1938 19.7
8. Oct 1964 - July 1965 43.6 8. July 1951 - Apr 1952 20.9
9. March - Dec 1994 42.1 9. Apr 1928 - Jan 1929 22.2
10. March - Dec 1918 39.9 10. Nov 1969 - Aug 1970 22.5

So in an Australia-wide sense, the current drought is among the worst on record, as far as relatively short to medium-duration events are concerned, being remarkable for both its spatial extent of rainfall deficiencies, and average level of "dryness". Even outside of the rainfall deficient areas, the past ten months were mainly drier than average with very few regions experiencing average or above average totals. The main exception is around the southern Gulf of Carpentaria where recent very heavy rain has produced the wettest April to January period on record!

Ultimately it will only be at the conclusion of the current event that its true historical context can be calculated.


Rainfall deficiency maps for standard periods (3, 6, 9, 12, 18, 24 and 36 months) are updated monthly on the Bureau's web site.

Note: The terms used to describe rainfall in these Drought Statements have the following meanings -

Well 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%
Well above average - rainfalls in the highest 10% of historical totals
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


For more information regarding this rainfall deficiencies statement, please contact the following climate meteorologists in the National Climate Centre:

Blair Trewin on (03) 9669 4603
Grant Beard on (03) 9669 4527



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