Seasonal Climate Outlook Message for March to June 2006

The bottom line

SOI Continues to Fluctuate 01/03/06

As expected an active phase of the MJO was evident in late February/early March. This coincided with some welcome rainfall with the larger totals mainly confined to the eastern half of the state. Information from the Bureau of Meteorology highlights that depending on location rainfall totals in excess of 50 mm to more than 600 mm are still needed before average falls for our normal "wet season" (October to April) are recorded.

The SOI has continued to fluctuate and shifted in value from plus 11.8 at the end of January to minus 0.5 as of the 28th February placing it in a "Rapidly Falling" phase. A return to sustained positive monthly SOI values would help provide the basis for a widespread improvement in seasonal conditions. For those looking out to the long term (>6 months) autumn is a key time to watch for developing trends in both the SOI and sea surface temperatures (SST).

Based the recent pattern of the SOI and historical rainfall records there is less than a 50% chance of getting above median rainfall during March to May across most of Queensland.

The lowest chance (20 to 40%) of getting above median rainfall can be found throughout central, northern and coastal regions. There is a higher 50 to 70% chance of getting above median rainfall during March to May for the western Darling Downs.

DPI&F is providing 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 4688 1236 neil.white@dpi.qld.gov.au and nominate the day(s).

The full story

SOI in Rapidly Falling Phase Dave McRae DPI&F 01/03/06

As expected an active phase of the MJO is currently evident (late February/early March). This coincided with some welcome rainfall with the larger totals mainly confined to the eastern half of the state. Information from the Bureau of Meteorology highlights that depending on location rainfall totals in excess of 50 mm to more than 600 mm are still needed before average falls for our normal "wet season" (October to April) are recorded. 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/ or http://www.bom.gov.au/climate/tropnote/tropnote.shtml

The SOI has continued to fluctuate and shifted in value from plus 11.8 at the end of January to minus 0.5 as of the 28th February placing it in a "Rapidly Falling" phase. A return to sustained positive monthly SOI values would help provide the basis for a widespread improvement in seasonal conditions. For those looking out to the long term (>6 months) autumn is a key time to watch for developing trends in both the SOI and sea surface temperatures (SST).

Based on a 'Rapidly Falling' SOI phase at the end of February and historical rainfall records there is less than a 50% chance of getting above median rainfall during March to May across most of Queensland. The lowest probabilities (20 to 40%) of above median rainfall can be found throughout northern and coastal regions. There is a higher 50 to 70% chance of getting above median rainfall during March to May for the western Darling Downs.

For example Charters Towers has a 20% chance of getting above its March to May median rainfall of 135mm while St George has a 50% chance of getting above its March to May median rainfall of 110mm. This doesn't mean there will be no rainfall recorded in those areas with the lower chance of above median rainfall - all it does mean is that rainfall recorded for March to May will more likely be below average to average than above average.

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 March to May in the following years since 1950 that have had a 'Rapidly Falling' SOI phase at the end of February; 2005, 2003, 1990, 1987, 1986, 1982, 1978, 1973, 1962, 1957, 1954 and 1953.

For example at Nebo well below median rainfall for March to May in those years was recorded five times, close to median rainfall was recorded five times and well above median rainfall was twice. At Talwood well below median rainfall for March to May in those years was recorded twice, close to median rainfall was recorded seven times and well above median rainfall was three times. Information on what rainfall patterns where like for March to May in those years can be found in Rainman StreamFlow.

Some features of a weak La Niña (namely cool SST in the eastern and central Pacific) are currently present in the Pacific. These cool sea surface temperatures have developed so late in the season that any impact on rainfall in Australia is highly uncertain. Based on most climate model outputs, this pattern is unlikely to persist past Autumn into Winter and Spring when the positive impacts for rainfall across Queensland would be greatest.

In terms of output from 12 surveyed reputable ocean or coupled ocean/atmosphere forecast models, all 12 are showing a continuing neutral SST pattern through to June. For more information on conditions in the Pacific try the US Climate Prediction Centre at www.cpc.ncep.noaa.gov/ or the Bureau of Meteorology at http://www.bom.gov.au/climate/ahead/ENSO-summary.shtml Warmer than normal sea surface temperatures can still be found around Australia's eastern and northern coastline. If this pattern persists it may have a positive influence on our expected rainfall.

Generally there is less than a 50% chance of getting above median rainfall during March to May across Australia with a marginally higher 50 to 70% chance of getting above median rainfall during March to May for parts of NSW. For more information on rainfall probabilities at your specific location 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, Charters Towers has a 20% chance of getting above its March to May median rainfall of 135mm. This also means that there is an 80% chance of NOT getting above 135mm during March to May.

Another way of looking at this is that in around three quarters of years with the current SOI pattern, Charters Towers has received less than 135mm during March to May. Therefore in one quarter of years with the current SOI pattern, Charters Towers has received more than 135mm over March to May.

When looking at rainfall probabilities 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

"Managing for Climate and Weather Workshop" at Mackay on the 6th March and Proserpine on the 7th March. Full day workshop starting at 9:00am and finishing at approx 4:00pm. Morning session has presenter from Bureau of Meteorology discussing what drives our weather and the basic of weather forecasting. Roger Stone from the QDPI&F will present the afternoon session and cover climate drivers, climate change, seasonal outlook etc. For more information contact Ross Ballin on 0407 739 210 or 4688 1468.

"Climate update and managing soil water workshop" at Clifton on Thursday 9th March starting at 8:30am. Half day workshop covering climate change, rainfall data, current outlook, raindrop characteristics, efficiency of rain entry into soil, impact of stubble cover etc. For more information contact Dave Gardiner at Central Downs Landcare on 0428 341 798.

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.