Seasonal Climate Outlook Message for May to August 2007
The bottom line
SOI worth watching in May
Dave McRae 07/05/07
Despite the fluctuations in value of the SOI during April there has not been any significant shift in rainfall probabilities. Based on historical rainfall records and a Consistently Near Zero SOI phase at the end of April there remains a 40 to 60% chance of getting median rainfall throughout Queensland for May through to the end of July.
It will be interesting to see what direction the SOI takes between now and the end of May. A return to consistently negative values would indicate a likely dry winter/spring. For there to be an overall improvement in seasonal conditions and a lift in rainfall probabilities, the development of consistently positive SOI values is needed. Daily updates on the SOI are available on (07) 46881439 or at www.longpaddock.qld.gov.au
The full story
SOI Neutral Dave McRae 07/05/07
Despite the fluctuations in value of the SOI during April there has not been any significant shift in rainfall probabilities. Based on historical rainfall records and a Consistently Near Zero SOI phase at the end of April there remains a 40 to 60% chance of getting median rainfall throughout Queensland for May through to the end of July.
Similar to Queensland, throughout much of the rest of Australia there is a 40 to 60% chance of getting median rainfall during May to July. The main exceptions are for north east NSW where there is a lower 30 to 40% chance of getting median rainfall and for central and north west Australia where there is a 60 to 70% chance of getting median rainfall during May to July.
It will be interesting to see what direction the SOI takes between now and the end of May. A return to consistently negative values would indicate a likely dry winter/spring. For there to be an overall improvement in seasonal conditions, the development of consistently positive SOI values certainly would help. Daily updates on the SOI are available on (07) 46881439 or at www.longpaddock.qld.gov.au
The MJO crossed northern Australia early May. It was associated with some rainfall during that period although the larger falls occurred largely in NSW and Victoria. Based on a timing of 40days it would be reasonable to next expect it in early to mid June. Widespread rain is still needed to improve soil moisture levels for the winter cropping season.
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 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%.
For more information refer to Rainman StreamFlow, www.dpi.qld.gov.au/climate or contact 132523.
Rainfall to date, the current soil water conditions and the seasonal climate outlook indicate a below average wheat yield during the 2007 wheat-growing season for most of Queensland. There are though the usual variations. For example central Queensland has a 30 to 50% of getting above long-term median shire wheat yields compared to southern Queensland where generally there is only a low chance (less than 30%) of getting above long term median shire wheat yields.
Obviously widespread above average rainfall is needed urgently to not only improve the wheat yield outlook but also provide planting opportunities.
The shire wheat yield outlook is based on the assumption of cropping after a summer fallow and does not take into account the effects of poor crop nutrition or damage due to pests, diseases or frosts. For more information on crop yields, contact Andries Potgieter on (07) 4688 1417 or 132523.
In the latest ENSO wrap-up available at www.bom.gov.au the Bureau of Meteorology state that sea-surface temperatures in the Pacific remain close to average following the breakdown of the 2006/07 El Niño event with trade winds and Pacific cloud patterns currently in a neutral pattern. The SOI did drop to strongly negative values during April. However while disconcerting there will be little impact if the SOI returns to near zero or better still strongly positive before the end of autumn.
Climate model output indicates at this stage the continuation of a neutral climate pattern is the most likely outcome although there is a slightly higher than normal chance of a La Nina climate pattern developing. The positive news is that while not impossible, there is only a low risk of a return to El Niño conditions in 2007.
While the end of the El Nino is usually associated with a return to more normal rainfall patterns, it should not be seen as an automatic start to drought-breaking rains. This particularly applies to eastern and southern Australia, which in some instances will require several years of good rainfall to recover.
When I'm asked about how climate and weather 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).
When using any of the number of weather internet sites available now, we strongly recommend that you have look at a number of them to develop a consensus view or find one that you believe works well for your area and stick with that. Do not troll through them all to find the one that says what you want to get and go with that.
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. The 'Climate Variability In Agriculture' (CVAP) research and development program 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. An interesting site http://www.managingclimate.gov.au/
