Seasonal Climate Outlook Message for September to December 2006

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Climate Watch Dave McRae Qld Dept of Primary Industries and Fisheries 04/09/06

SOI Remains Negative

Based on a monthly value of minus 14.1 for August the SOI is now in a 'Consistently Negative' phase. For most of Queensland the chance of getting above the long-term median rainfall for September to November is 20 to 40%.

For example Toowoomba has a 25% chance of getting above its long term September to November median rainfall of 195 mm. As always with probabilities it is important to consider the opposite aspect. Therefore at Toowoomba there is also a 75% chance of NOT getting its September to November median rainfall of 195 mm. The low rainfall probabilities do not mean there will be no rainfall during September to November. What it does mean is that rainfall across Queensland will more likely be below median to median rather than well above median.

A Negative SOI phase at the end of August also increases the chance of getting above median maximum temperatures for September to November especially across the southern two thirds of the state.

Over the last couple of months the latitude of the sub-tropical ridge of high pressure has remained further south than normal. This has contributed to rain and shower activity through increased flow of moist easterly winds. Its effect has been most noticeable across northern and coastal regions of Queensland.

The 30day average of the SOI as of the 4th September is minus 11.5. Daily updates on the SOI are available on (07) 46881439. Current rainfall probability maps are at www.dpi.qld.gov.au/climate or www.longpaddock.qld.gov.au and SOI updates are available on (07) 46881439.

The full story

Climate Watch Dave McRae 04/09/06

SOI in Negative Phase

The low rainfall probabilities do not mean there will be no rainfall during September to November. What it does mean is that rainfall will more likely be below median to median rather than well above median. Analysis of climate models or forecasts from other agencies also indicate that the chance of getting widespread well above average or "drought breaking" rainfall remains low.

The latest information on conditions in the Pacific continues to indicate a warming trend of ocean temperatures in the central Pacific running eastward along the equator from the international dateline. If this pattern persists it most likely will have a drying effect on our expected rainfall in spring and early summer regardless of whether it is a 'classic' El Nino or not. For more on conditions in the Pacific try the Bureau of Meteorology at www.bom.gov.au/climate/ahead/

The latitude of the sub-tropical ridge of high pressure has remained further south than normal for this time of year. This has contributed to rain and shower activity through increased flow of moist easterly winds with its effect most noticeable during the last couple of months across the northern and coastal regions of Queensland.

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 that have had a 'Consistently Negative' SOI phase at the end of August; 1905, 1911, 1914, 1918, 1919, 1923, 1925, 1940, 1941, 1946, 1951, 1965, 1972, 1976, 1977, 1982, 1987, 1993 and 1994.

For example at Miles, below average rainfall for September to November in those years was recorded 10 times and close to average rainfall was recorded 6 times with well above average rainfall was recorded twice. Therefore rainfall during September to November at Miles is more likely to be below average to average than well above average.

Based on a Consistently Negative SOI phase at the end of August there is also a low 20 to 40% chance of getting above median rainfall during September to November throughout most of NSW, South Australia, the Northern Territory, Tasmania and Victoria.

During winter a synoptic feature such as a north-west cloud band or frontal trough system is usually required in conjunction with the MJO to result in MJO associated rain across Queensland. The next passage of the MJO is expected in mid September.

The MJO is 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 (but not amounts). For more information try www.apsru.gov.au/mjo

The latest probability maps are at http://www.dpi.qld.gov.au/climate or http://www.longpaddock.qld.gov.au and daily updates on the SOI are available on (07) 46881439. For more on rainfall probabilities, monthly medians or medians for your location refer to Rainman StreamFlow or contact 132523 or (07) 3404 6999.

* Cloud Seeding

For those interested in cloud seeding there is an interesting report from CSIRO available at http://www.cmar.csiro.au/e-print/open/cloud.htm It is a better source of information to quote or believe than some of the recent media articles on this topic.

* Climate Workshops

There are none planned currently. If you are interested in having a Managing for Climate and Weather Workshop run in your area let me know.

* Key Points To Consider When Using Climate Information

When I'm asked about how climate information can be used I refer to a couple of key points developed from client feedback. Key points include that management decisions should never be based entirely on one factor such as a climate or weather forecast. As always, everything that could impact of the outcome of a decision (soil moisture, pasture type/availability, crop and commodity prices, machinery, finance, costs etc) should be considered. For example, the level of soil moisture at planting is the major factor influencing crop yield or success.

A simple cost benefit analysis when making a major decision may also be useful. For example what will I gain if I get the desired outcome? What will I lose (sleep, money, family relationships) if I do not get the desired outcome and what other options (risk neutral) are there? A PART OF THIS PROCESS IS TO HELP MANAGERS TO BE CAREFUL NOT TO CHANGE FROM NORMAL RISK MANAGEMENT TO HIGH LEVEL RISK TAKING BASED ON A PIECE OF INFORMATION (SUCH AS A CLIMATE FORECAST).

Forecasts as well do not always give a strong signal as to likely conditions for your location. In assessing climate forecasts as a management tool consider the level of signal for the key decision times in your location. Rainman StreamFlow is a useful tool for this.

An interesting site http://www.managingclimate.gov.au/ from the 'Climate Variability In Agriculture' (CVAP) research and development program is well worth looking at. It highlights some case studies on how producers and businesses have used (to varying levels of success) climate and weather information in their decision-making processes.

Last updated: 3 September 2006

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