|WA Seasonal Rainfall Outlook: probabilities for February to April 2008, issued 24th January 2008|
Wetter conditions favoured in western WA
The Western Australian outlook for late summer to mid-autumn rainfall (February to April), shows a moderate to strong chance of exceeding the seasonal median in western WA.
The pattern of seasonal rainfall odds across WA 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 February to April are between 60 and 75% in a line running approximately from Port Hedland to east of Esperance (see map). So for every ten years with ocean patterns like the current, about six or seven February to April periods are expected to be wetter than average in this part of the State, while about three or four are drier.
Over the rest of the WA, 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.
Outlook confidence is related to how consistently the Pacific and Indian Oceans affect Australian rainfall. During the February to April period, history shows the effect to be moderately consistent through most of WA, especially in the south. In the north of the State around and to the south of Fitzroy Crossing, and in the extreme southwest corner, the effect is only weakly or very weakly consistent (see background information).
A La Niña event is in progress across the Pacific Basin and computer models indicate it will persist at least until autumn. The 30-day value of the Southern Oscillation Index (SOI) was +18 as at 21st January. For routine updates and comprehensive discussion on any developments please see the ENSO Wrap-Up.
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 8.30am to 4.30pm (WDST) Monday to Friday by contacting the Climate Services Centre in the Bureau's Perth Office: (08) 9263 2222.|
THE NEXT ISSUE OF THE SEASONAL OUTLOOK IS EXPECTED BY 26th February 2008