SOI remains in a "Consistently Near Zero" phase 28th September 2004
The 30day average of the SOI as of the 28th September is minus 3.3. This means the SOI has remained in a "Consistently Near Zero" phase for the second month in a row.
Based on a "Consistently Near Zero" SOI phase and the available historical rainfall records for Queensland there is a 40 to 50% chance of getting above median rainfall through to the end of December across most of Queensland. However there are some areas especially in the north and west of the state that have a lower 30 to 40% chance of getting above median rainfall through to the end of December.
For more specific rainfall probabilities, median rainfall levels and significance tests for different locations, we recommend referring to AUSTRALIAN RAINMAN. The latest rainfall probability maps are available at www.dpi.qld.gov.au/climate or www.longpaddock.qld.gov.au
While these rainfall probabilities are an improvement on what would have been the case if the SOI had remained in a "Consistently Negative" SOI phase, given ongoing dry conditions across the state they are not as high as many would want. For there to be an overall improvement in the seasonal outlook for Queensland, it would help if the SOI rose to a "Consistently Positive" pattern for a couple of months at least.
As with any probability based forecast system it is important to consider the opposite aspect. For example Barcaldine currently has a 30% chance of getting above its long term October to December median rainfall of 115mm. This also means that there is a 70% chance of NOT getting above the 115mm through to the end of December.
Another way of looking at this is that in 3 years out of 10 (or around one third) with the current SOI pattern, Barcaldine has received at least or above 115mm for October to December. Therefore in 7 years out of 10 (or around two thirds), Barcaldine has gotten less than 115mm for October to December.
Sea surface temperatures (SST) in the central Pacific from the international dateline running east towards South America remain warmer than normal (+0.5 to 1.5oC). This pattern can be described as a "border line El Nino". It is worth noting that the USA Climate Prediction Centre www.cpc.ncep.noaa.gov/ expect this pattern to continue into early 2005.
While the current SST pattern is not usually as serious as the El Nino such as occurred between 2002 and 2003, it can still have major impact on Queensland rainfall and water supply, especially if the SOI where to return to a "Consistently Negative SOI Phase". As an example, we had a borderline El Nino state in 1992 and 1993, both years producing below average rainfall for large parts of Queensland but not to the extent of the 2002/2003 event. The Bureau of Meteorology "El Nino wrap up" www.bom.gov.au/climate/enso/ is a good starting point to find out more on conditions in the Pacific.
Daily updates on the SOI are available on (07) 46881439. Or if you want to receive the SOI update by text to your mobile phone, send me an e-mail or call 13 25 23.