1 September 2008
There was a marginal improvement in the monthly SOI value from July (plus 2.3) to August (plus 8.0). This places the SOI in a "Rapidly Rising Phase".
Based on this phase and historical rainfall data there is a 40 to 70% chance of getting median spring rainfall throughout most of Queensland during July to September. The exception is an area in the south west of the state with a lower 20 to 50% chance of exceeding their median rainfall.
Further analysis indicates that the September to November rainfall is likely to be close to or above average (middle to upper third) rather than below normal (lower third). This represents a slight shift in the odds towards wetter conditions compared with last months outlook.
For example Longreach has a 70% chance of getting above its September to November median rainfall of 42 mm, and Emerald and Gympie have a 55% chance of getting above their September to November median rainfall of 111 mm and 196 mm respectively. Roma has a 48% chance of getting above its September to November median rainfall of 124 mm while Charter Towers has a 73% chance of getting above its September to November median rainfall of 63 mm.
For those who like to follow the relationship between the SOI and rainfall patterns in more detail have a look at what happened in your area during September to November in the following years since 1950: 1954, 1962, 1964, 1966, 1967, 1970, 1971, 1983, 1985, 2000 and 2007. Find out your average rainfall for July to September and see how many times rainfall was well below, well above or close to average during September to November in the listed years.
The question remains though as to whether this upward trend of the SOI will continue or is just a short-term fluctuation. As stated regularly, to increase the chance of an overall improvement in seasonal conditions across eastern Australia especially leading into spring and summer, it helps if the SOI has moved into consistently positive values for a couple of months at least.