Climate Watch 8th August 05
SOI Remains Stable
The 30-day average of the SOI has remained relatively stable and as of the 8th August is minus 0.8. Based on the monthly values of the SOI at the end of June (plus 0.5) and the end of July (plus 1.6) most of Queensland has a 40 to 50% chance of getting above median rainfall for August to October. The exception is for the strip running from the central Queensland coast to the peninsular were there is a lower 20 to 40% chance of getting above median rainfall.
Therefore the chance of receiving well above average rainfall for August to October across Queensland is low with rainfall more likely to be below average to average.
Across most of the other states there is less than a 50% chance of getting median rainfall for August to October. The exception is for the north east corner of NSW and into the south east corner of Queensland where there is a 50 to 70% chance of getting above median rainfall.
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 over August to October in the following years; 2002, 2001, 2000, 1999, 1991, 1990, 1983, 1980, 1971, 1969, 1967, 1966, 1962, 1961, 1959, 1958, 1957 and 1953 and compare the rainfall recorded with your 'normal' rainfall for August to October.
For example at Rockhampton below median rainfall for August to October in those years was recorded 10 times, close to median rainfall was recorded 4 times and above median rainfall was recorded 4 times. Information on what rainfall patterns where like for August to October in those years can be found at www.longpaddock.qld.gov.au or in Australian Rainman.
As with any probability based system it is important to consider the opposite aspect. Springsure for example has a 75% chance of getting above 45 mm for August to October. This also means that there is a 25% chance of NOT getting 45 mm over August to October.
Another way of looking at this is that in around seven to eight years out of ten historically (or around three quarters) with the current SOI pattern, Springsure has received at least 45 mm over August to October. Therefore in two to three years out of ten historically (or around one quarter), Springsure has gotten less than 45 mm over August to October.
When looking at rainfall probabilities for your area it may make it easier to think of them in these terms:
1. Probabilities above 80% highlight a high chance 2. Probabilities above 60% highlight an above average chance 3. Probabilities below 40% highlight a below average chance 4. Probabilities below 20% have a low chance
Daily updates on the SOI are available on (07) 46881439. The latest rainfall probability maps are at www.dpi.qld.gov.au/climate or for more information call the DPI Call Centre on 13 25 23 or (07) 3404 6999.