|Tas Seasonal Rainfall Outlook: probabilities for October to December 2006, issued 26th September 2006|
Below average falls indicated for Tasmania
There is a moderate to strong shift in the odds towards drier than normal conditions for the December quarter (October-December) over Tasmania, with the exception of the southwest, the Bureau of Meteorology announced today.
The pattern of seasonal rainfall odds across Tasmania 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.
For the total over the October to December period, the chances are between 30 and 40% for above median rainfall across most of Tasmania, with 25 to 30% chances in parts of the north (see map). Looking at the flip-side, these probabilities mean that BELOW median falls have about a 60 to 75% 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 over most of Tasmania, 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 over northwest and central Tasmania, but weakly consistent in the east and southwest (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 (EST) Monday to Friday by contacting the Climate and Consultancy section in the Bureau's Hobart Office: (03) 6221 2043.|
THE NEXT ISSUE OF THE SEASONAL OUTLOOK IS EXPECTED BY 26th OCTOBER 2006