Seasonal Climate Outlook Message for October to January 2007
The bottom line
SOI Remains in Negative Phase Dave McRae 02/10/06
At the end of September the SOI has remained in a 'Consistently Negative' phase for the second month in a row. This is based on monthly SOI values of minus 14.1 for August and minus 4.6 for September.
Based on a Negative SOI Phase and historical rainfall data, the chance of getting above median rainfall for October through to the end of December is between 20 to 40% throughout central and northern Queensland. For southern Queensland there has been a slight improvement to the outlook with a 40 to 50% chance of getting above median rainfall for October to December.
For example Charter Towers has a low 25% chance of getting above its October to December median rainfall of 128 mm while Dalby has a 45% chance of getting above its October to December median rainfall of 215 mm. As always with probabilities it is important to consider the opposite aspect. Therefore at Charters Towers there is also a 75% chance of NOT getting its October to December median rainfall of 128 mm.
For those areas with a low chance of getting above median rainfall it does not mean there will be no rainfall. What it does mean is that rainfall will more likely be below median to median rather than well above median. As we are entering our spring/summer rainfall season there will still be a reasonable chance of getting some useful rain.
A Negative SOI phase at the end of September also increases the chance of getting above median maximum temperatures for October to December.
The 30day average of the SOI as of the 2nd October is minus 4.9. Daily updates on the SOI are available on (07) 46881439 and current rainfall probability maps are at www.dpi.qld.gov.au/climate or www.longpaddock.qld.gov.au For all other enquires thry the DPI&F Call Centre in 132523.
The full story
SOI remains in Negative Phase for second month 02/10/06
At the end of September the SOI has remained in a 'Consistently Negative' phase. This is based on monthly SOI values of minus 14.1 for August and minus 4.6 for September.
Based on a Consistently Negative SOI Phase and historical rainfall data, the chance of getting above median rainfall for October through to the end of December throughout central and northern Queensland is between 20 to 40%. For southern Queensland there has been a slight improvement with a 40 to 50% chance of getting above median rainfall for October to December.
Charter Towers for example, has a low 25% chance of getting above its October to December median rainfall of 128 mm while Dalby has a 45% chance of getting above its October to December median rainfall of 215 mm. As always with probabilities it is important to consider the opposite aspect. Therefore at Charters Towers there is also a 75% chance of NOT getting its October to December median rainfall of 128 mm.
For those regions with a low chance of getting above median rainfall it does not mean there will be no rainfall. What it does mean is that rainfall will more likely be below median to median rather than well above median. As we are entering our spring/summer rainfall season there will still be a reasonable chance of getting some useful rain.
To follow the relationship between the SOI and rainfall patterns in more detail have a look at what happened in your area during October to December in the following years that have had a 'Consistently Negative' SOI phase at the end of September; 1911, 1914, 1923, 1925, 1934, 1940, 1941, 1953, 1957, 1965, 1972, 1976, 1977, 1982, 1987, 1990, 1993, 1994, 1997 and 2002.
At Emerald, below average rainfall for October to December in those years was recorded 9 times, close to average rainfall was recorded 6 times with above average rainfall recorded 5 times. Therefore rainfall during October to December at Emerald is more likely to be below average to average than well above average. For more information refer to Rainman StreamFlow. Analysis of climate models or forecasts from other agencies also continue to indicate that the chance of getting state-wide well above average or "drought breaking" rainfall is low.
A Negative SOI phase at the end of September also increases the chance of getting above median maximum temperatures for October to December.
The latitude of the sub-tropical ridge of high pressure has remained further south than normal over the last 6 months. 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.
Information on ocean temperatures in the central Pacific (running eastward along the equator from the international dateline) continues to indicate a warming trend. As we have stated over the last few months, if this pattern persists it most likely will have a drying effect on our expected rainfall in spring and early summer (as it did in this winter) regardless of whether it is a 'classic' El Nino or not. Its effect (or impact on expected rainfall) is usually less noticeable in late summer.
Our recommendation for those businesses adversely affected by El Nino or "El Nino like" conditions in the central Pacific is to continue to monitor SST and SOI trends. Try the Bureau of Meteorology at http://www.bom.gov.au/climate/ahead/ for more information.
The last passage of the MJO occurred later than expected at the end of September. If a timing of approximately 30 to 35 days is maintained it would be reasonable to next expect it in early November. As we approach summer the sun will be over southern latitudes and stronger MJO signals can be expected.
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/
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.
SOI updates are available on (07) 46881439. For other enquires contact the DPI&F Information Centre on 132523.
