WA Seasonal Rainfall Outlook: probabilities for November 2003 to January 2004, issued 16th October 2003

Above average falls likely in north and west WA

The Bureau's rainfall outlook for the late spring to mid-summer period shows that above average seasonal falls are favoured in parts of northern and western WA. This outlook is largely the result of temperature patterns in the Indian Ocean.

For the November to January period, the chances of above median rainfall are between 60 and 70% over the Kimberley, and between 60 and 65% in the Pilbara and Gascoyne regions in the west of the State (see map). So with climate patterns like the current, about 6 or 7 seasons out of 10 are expected to be wetter than average in these parts of the State, with about 3 or 4 out of 10 being drier.

probability of exceeding median rainfall - click on the map for a larger version of the map

It is worth noting though, that heavy rain is uncommon in the area between Carnarvon and Kalbarri during the November to January period, with the notable exception of rare tropical cyclone impacts.

In remaining parts of the Western Australia, the odds for above average seasonal falls are in the 50 to 60% range.

Outlook confidence is related to the influence of Pacific and Indian Ocean temperatures on seasonal rainfall. During November to January, history shows this influence to be moderate in patches across in the far west and southwest of WA. Elsewhere in WA the influence is mainly weak or very weak so the outlook needs to be used with caution in those areas (see background information).

The tropical Indian Ocean is currently somewhat warmer than average, but has been cooling quite strongly. The Pacific is generally warmer than average, particularly in the west. For more detail see the El Niño Wrap-Up. The recent temperature changes in the Indian Ocean have had the dominant influence on the overall pattern of probabilities.

September's value of the Southern Oscillation Index (SOI) was –2, the same as that recorded in August. The approximate SOI for the 30 days ending 13th October was –1.


Click on the map above for a larger version of the map. Use the reload/refresh button to ensure the latest forecast map is displayed.

More information on this outlook is available from 9.00am to 5.00pm (WST) Monday to Friday by contacting the Climate and Consultancy section in the Bureau's Perth Office: (08) 9263 2222.


September 2003 rainfall in historical perspective

July to September 2003 rainfall in historical perspective


Background Information