|WA Seasonal Rainfall Outlook: probabilities for February to April 2007, issued 23rd January 2007|
Increased late summer to mid-autumn rains in northwestern to central WA
The outlook for total February to April rainfall, shows a moderate to strong shift in the odds towards above average falls in northwest to central WA. The pattern of seasonal rainfall odds across WA is a result of higher than average temperatures in the Pacific Ocean (because of El Niño) and also in the Indian Ocean. More influence has come from the Indian.
The chances of exceeding the median rainfall for the coming three months are between 60 and 75% in a broad zone extending over northwestern and central WA (see map). So in years with ocean patterns like the current, about six or seven February to April periods out of ten are wetter than average and three or four out of ten are drier in this large region with elevated odds.
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 (see background information).
December was the second successive month when the Southern Oscillation Index (SOI) was only slightly negative, with a monthly value of −3 following the −1 in November. A link to 30-day SOI values is available in the ENSO Wrap-Up (see next paragraph).
The neutral SOI is one of a few indicators which show that the current Pacific El Niño pattern is beginning to weaken. For routine updates and comprehensive discussion on the latest data relating to El Niño, together with details on what the phenomenon is and how it has affected Australia in the past, 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 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.|
THE NEXT ISSUE OF THE SEASONAL OUTLOOK IS EXPECTED BY 22nd FEBRUARY 2007