|NSW Seasonal Rainfall Outlook: probabilities for Spring 2006, issued 23rd August 2006|
Mainly neutral spring rainfall outlook in NSW
Although below normal spring (Sep-Nov) rainfall is favoured by the outlook over much of Queensland, the latest seasonal rainfall odds are mainly neutral over NSW, the Bureau of Meteorology announced today. So the chances are generally close to 50% for accumulating at least median rainfall over September to November.
The pattern of seasonal rainfall odds across Australia is a result of higher than average temperatures in both the Pacific and Indian Oceans, the latter of which has been warming strongly in recent months.
For the September to November period, the chances of above median rainfall are mostly between 40 and 55% over NSW, dropping a little below 40% in the far northwest corner of the State near the borders with Queensland and SA (see map).
So in years with ocean patterns like the current, about five or six springs out of ten are expected to be drier than average in NSW, with about four or five of ten being wetter.
Outlook confidence is related to how consistently the Pacific and Indian Oceans affect Australian rainfall. During spring, history shows this effect to be moderately consistent across most of NSW (see background information).
The Southern Oscillation Index (SOI) was negative for the third straight month in July with a value of −9. This came after readings of −6 in June and −10 in May. The approximate SOI for the 30 days ending 20th August was −16. If history is any guide, the SOI will probably stay negative for the rest of the year.
Although a late-developing El Niño event is still a possibility this year, especially considering the SOI, the consensus from computer models is for continued neutral ENSO conditions for the remainder of 2006, but on the warm side of average. Continued Pacific warmth and negative SOI values are generally associated with increased likelihood of below average rainfall in eastern and northern Australia. 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 (EST) Monday to Friday by contacting the NSW Climate Services section in the Bureau's Sydney Office: (02) 9296 1610 or (02) 9296 1525.|
THE NEXT ISSUE OF THE SEASONAL OUTLOOK IS EXPECTED BY 26th SEPTEMBER 2006