Seasonal Climate Outlook Message for August to November 2004

The bottom line

SOI in "Consistently Negative" Phase 02/08/04

Based on the recent pattern of the SOI (minus 13.9 at the end of June and minus 6.4 at the end of July) it is more likely than not, that spring and early summer will be drier than normal.

Based on this consistently negative SOI pattern, for August to October there is only a low (10-40%) chance of getting above the long-term median rainfall across Queensland. Although technically we are not in an El Nino, the low SOI values are a result of a warm sea surface temperature pattern in the central Pacific. Such "El Nino" like conditions often suppress winter and spring rainfall in eastern Australia (eg 1992-1994).

The latest rainfall probability maps for Queensland, Australia and the world are at www.dpi.qld.gov.au/climate or www.longpaddock.qld.gov.au

The full story

SOI in "Consistently Negative" Phase

Based on the recent pattern of the SOI (minus 13.9 at the end of June and minus 6.4 at the end of July) it is more likely than not, that spring and early summer will be drier than normal.

Based on this consistently negative SOI pattern, for August to October there is only a low (10-40%) chance of getting above the long-term median rainfall across Queensland. For example Miles on the Darling Downs only has a 10% chance of getting at least its long term August to October median rainfall of 100mm. This means that there is a 90% chance of NOT getting at least 100mm through to the end of October.

Another way of looking at this is that in 1 year out of 10 (or one tenth of years) with the current SOI pattern, Miles has received at least 100mm for August to October. Therefore in 9 years out of 10 (or nine tenth of years), Miles has gotten less than 100mm for August to October. As rainfall probabilities and median rainfall levels vary between regions, we recommend referring to AUSTRALIAN RAINMAN for more specific rainfall data for your location. Otherwise call the DPI Call Centre on 13 25 23 or (07) 3404 6999 for more information.

Although technically we are not in an El Nino, the low SOI values are a result of a warm sea surface temperature pattern in the central Pacific. Such "El Nino" like conditions often suppress winter and spring rainfall in eastern Australia (eg 1992-1994).

The latest rainfall probability maps for Queensland, Australia and the world are at www.dpi.qld.gov.au/climate or www.longpaddock.qld.gov.au This forecast doesn't suggest or indicate the potential distribution or expected timing of rainfall over this period. The forecast is for a full 3 month period and doesn't say that any expected rain will fall evenly across these 3 months

For there to be an overall improvement in the seasonal outlook, the SOI needs to rise to a "Consistently Positive" pattern for a couple of months at least. The 30day average of the SOI as of the 2nd August is minus 6.4.

Many people like to follow the relationship between the SOI and rainfall patterns in more detail. To do that, have a look at what happened in your area over August to October in the following years; 1997, 1994, 1993, 1992, 1987, 1982, 1977, 1972, 1946, 1941, 1940, 1919, 1914, 1911 and 1905 and compare the rainfall recorded with your 'normal' rainfall for August to October.

For example at Dalby, historical records show that with this SOI pattern for August to October below average rainfall was recorded ten times, near average rainfall was recorded twice and above average rainfall was recorded three 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.

Given the intensifying dry conditions across most of Queensland, much interest will be shown in the next passage of the MJO. Unfortunately the last MJO at the end of July had little impact on our weather. If its timing remains current it would next be expected in early September.

The MJO is simply a band of low air pressure originating off the east coast of central Africa travelling eastward across the Indian Ocean and northern Australia roughly every 30 to 60 days. Research has shown the MJO to be a useful indicator of the timing of potential rainfall events across much of Queensland.

Given the growing interest in the MJO, and with funding from the DPI&F, GRDC and CRDC we have developed a site http://www.apsru.gov.au/mjo/> that will allow anyone interested to track its passage. However we are currently experiencing some difficulties in keeping this site correct because this experimental research is not operationally supported by CBOM. However we expect this issue to be resolved soon.

For more information contact us through the QDPI&F Call Centre on 13 25 23.