|SA Seasonal Rainfall Outlook: probabilities for October to December 2006, issued 26th September 2006|
Below average falls indicated for southern SA
There is a moderate shift in the odds towards drier than normal conditions for the December quarter (October-December) over the agricultural areas of South Australia, the Bureau of Meteorology announced today. Across the rest of the State, the chances are generally close to 50% for accumulating at least median rainfall during the coming three months.
The pattern of seasonal rainfall odds across SA is a result of higher than average temperatures in both the Pacific and Indian Oceans, the former of which has been warming strongly in the past few months.
Across southern SA, including southern parts of the Eyre Peninsula (see map), the chances of the accumulated rainfall totals exceeding median rainfall for the period October to December are between 30 and 40%. Looking at the flip-side, these probabilities mean that BELOW median falls have about a 60 to 70% chance of occurring.
So in years with ocean patterns like the current, about six or seven December quarters out of ten are expected to be drier than average in these parts of the State, with about three or four out of ten being wetter.
Outlook confidence is related to how consistently the Pacific and Indian Oceans affect Australian rainfall. During the December quarter, history shows this effect to be moderately consistent across the eastern half of SA, but only weakly consistent in the west (see background information).
The Southern Oscillation Index (SOI), negative for the fourth straight month, dropped from −9 in July to a low −16 in August. The approximate SOI for the 30 days ending 19th September was −4.
In addition to the low SOI, the equatorial Pacific has been warming and the Trade Winds have been weak. These ENSO indicators are all consistent with the development phase of an El Niño event, the likelihood of which has risen strongly in the past month. For routine updates and comprehensive discussion on the latest data relating to ENSO, 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 (CST) Monday to Friday by contacting the Climate and Consultancy section in the Bureau's Adelaide Office: (08) 8366 2664.|
THE NEXT ISSUE OF THE SEASONAL OUTLOOK IS EXPECTED BY 26th OCTOBER 2006