Seasonal Climate Outlook Message for June to September 2006

The bottom line

SOI In Falling Phase 02/06/06 The 30 day average of the SOI has had a significant downward trend over the last few weeks to minus 8.7 as of the 2nd June. Based on this shift in value the SOI is now in a "Rapidly Falling" phase. This gives a mixed seasonal outlook for Queensland during June to August. Throughout much of the southern third of the state as well as along the central and northern coastal strip there is only a 20 to 40% chance of getting above median rainfall for June to August. For the rest of Queensland the chance of getting above the long term June to August median rainfall is generally between 40 to 60%. It is worth noting that if the SOI remains in a consistently negative pattern through to the end of June the chance of getting above median rainfall across Queensland will fall further. Analysis of climate models or forecasts from other agencies (Bureau of Meteorology, IRI, ECMWF) also indicate that the chance of getting well above average or "drought breaking" rainfall is low. 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

Some Warning Signs Present D McRae 02/06/06 The 30 day average of the SOI has had a significant downward trend over the last few weeks to minus 8.0 as of the 31st May. Based on this shift in value the SOI is now in a "Rapidly Falling" phase. This gives a mixed seasonal outlook for Queensland during June to August. Throughout much of the southern third of the state as well as along the central and northern coastal strip there is only a 20 to 40% chance of getting above median rainfall for June to August. For the rest of Queensland the chance of getting above the long term June to August median rainfall is generally between 40 to 60%. A Falling SOI phase at this time of year also increases the chance of getting below median minimum temperatures across most of Queensland during June to August. It is worth noting that if the SOI remains in a consistently negative pattern through to the end of June the chance of getting above median rainfall across Queensland will fall further. Analysis of climate models or forecasts from other agencies (Bureau of Meteorology, IRI, ECMWF) also indicate that the chance of getting well above average or "drought breaking" rainfall is low. 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 output from ocean and coupled ocean/atmosphere forecast models continues to reflect a neutral sea surface temperature (SST) pattern in the central Pacific over coming months although with a warming trend. This corresponds with the warming of both surface and sub-surface ocean temperatures in the key Nino 3.4 region of the central Pacific during May. If the warming trend in the central Pacific continues it may adversely affect winter, spring and early summer rainfall. Our recommendation therefore is to monitor SST trends over the next few weeks. Climate scientists consider this time of year critical in terms of climate patterns that may set in for the next 9 to 12 months. This is because the Pacific Ocean tends to 'lock-in' from one year to the autumn of the following year. For the coastal strip of NSW and Victoria there is a 50 to 70% chance of getting above median rainfall during June to August. For the rest of NSW and Victoria and throughout most of South Australia, Northern Territory and central Western Australia there is a lower 20 to 50% chance of getting above the long term June to August median rainfall. For more information refer to Rainman StreamFlow. This forecast does not indicate the potential distribution or expected timing of rainfall over this period. The forecast is for a full three-month period and does not suggest that any expected rain will fall evenly across these three months. As with any probability based forecast system it is important to consider the opposite aspect. For example, Roma has a 40% chance of getting its June to August median rainfall of 85 mm. This also means that there is a 60% chance of NOT getting at least its June to August median rainfall of 85 mm. Another way of looking at this is that in around 6 times out of 10 with the current SOI pattern, Roma has received less than 85 mm during June to August. Therefore around 4 times out of 10 with the current SOI pattern, Roma has received more than 85 mm over June to August. When looking at the chance of above median rainfall 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 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 June to August in the following years since 1900 that have had a 'Rapidly Falling' SOI phase at the end of May; 1911, 1925, 1928, 1929, 1934, 1935, 1947, 1953, 1957, 1958, 1972, 1999, 2001 and 2002. For example at Clermont, below median rainfall for June to August in those years was recorded 9 times, close to median rainfall was recorded twice and above median rainfall was 3 times. Therefore rainfall at Clermont during June to August is more likely to be below median than well above median. For more information refer to Rainman StreamFlow. 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. DPI&F provides free of charge a SMS text message of the SOI value and the MJO phase. To receive this message once or twice per week contact Neil White +61 7 4688 1236 and nominate the day(s). An additional message will be sent at the end of the month regardless of the days you nominate. For more information contact the DPI&F on 132523.