29 July 2008
SOI settles to near zero values
The monthly SOI has held its own staying more or less steady at plus 2.9 in June and plus 2.7 for July as of the 29th of July. This places the SOI in a "Consistently Near Zero" or neutral phase for July.
Based on this phase and historical rainfall data there is a 30 to 50% chance of getting more than the median rainfall throughout most of Queensland during August to October. For example Cloncurry has a 50% chance of getting above its August to October median rainfall of 16 mm, Emerald has a 45% chance of getting above their August to October median rainfall of 74mm and Gympie has a 56% chance of getting above its August to October median rainfall of 148 mm.
The exception is for the north of the state where there is a lower 20 to 40% chance of getting median rainfall for August to October. While rainfall probabilities for the north are not as high as the rest of the state it is worth noting that especially for northern Queensland we are in our 'dry season'. Therefore significant or 'drought breaking' rain is not usual during this period regardless of the seasonal outlook.
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 August to October in the following years since 1950: 1953, 1957, 1958, 1959, 1961, 1962, 1966, 1967, 1969, 1971, 1978, 1980, 1983, 1990, 1991, 2000, 2001, 2002, 2005, 2006. Find out your average rainfall for August to October and see how many times rainfall was well below, well above or close to average in the listed years.
As always when using a climate forecast you should remember that the probability or percent chance of something occurring is just that - a probability. For example if there is a 70% chance of recording more than 100 mm there is also a 30% chance of recording less than 100 mm i.e. 70-30; 30-70. It does not mean that you will get 70% more than 100 mm or 100 mm plus another 70%.
Neutral sea surface temperatures remain across the tropical Pacific Ocean, with an associated neutral ENSO state. Most models forecast that neutral conditions will continue throughout 2008, although the tropical Pacific will continue to become slightly warmer.
For more information on the SOI or rainfall outlook maps, or sea surface temperature maps, try www.longpaddock.qld.gov.au http://www.longpaddock.qld.gov.au/> . To find more information on rainfall probabilities rainfall figures for your area use Rainman Streamflow. Daily updates on the SOI are available on (07) 46881439.