Australian rainfall Projections March to May 2008

Map: Bureau of Metereology rainfall projections February to April 2008.

Continuing my climate series, the Bureau of Metereology has released its latest rolling three month projections on the probablities of rain across Australia.

According to the Bureau. the projections show a mixed autumn rainfall outlook: a wetter than normal season is favoured in northern Queensland and in parts of NSW and SA, while below-normal falls are more likely in parts of Victoria and Tasmania.

The pattern of seasonal rainfall odds across Australia is a result of cooler than average waters across the equatorial Pacific in association with La Niña, and continuing higher than average temperatures in the central to southeastern Indian Ocean.

The chances of exceeding the median rainfall over March to May are between 60 and 70% over most of north Queensland, and between 60 and 65% in a band extending from central SA to the far west of NSW (see map). So for every ten years with ocean patterns like the current, about six or seven autumns are expected to be wetter than average in these parts of the country, while about three or four are drier.

In contrast, areas in northern and central Tasmania together with parts of Victoria's coastal fringe have a 35 to 40% chance of exceeding the autumn median. This means that a drier than normal autumn is a 60 to 65% chance in these regions.

Over the rest of the country, the chances of exceeding the three-month median rainfall are between 40 and 60%. So the chances of being wetter than normal are about the same as the chances of being drier