Autumn Outlook. Dave McRae, Queensland Climate Change Centre of Excellence, 12/03/10.
Based on the shift in monthly SOI value from January to the end of February the SOI is in a "Rapidly Falling" phase. An analysis of this SOI phase and historical rainfall records indicates a 30 to 50% of getting above median rainfall throughout the northern half of Queensland for March through to the end of May.
Throughout the southern half of the state there is a 40 to 60 % (with a few locations up to 70%) chance of getting above median rainfall for March through to the end of May.
As the autumn predictability gap approaches it will be interesting to see what direction the SOI takes. At this a time of year consistently negative values are not a major concern. However if the SOI does not return to more positive values during autumn it would be a warning sign for a likely drier winter/spring.
As of the 11th March the 30 day average of the SOI is minus 9.3. Daily updates on the SOI are available at www.longpaddock.qld.gov.au or to receive the latest SOI values sent to your mobile phone call me on (07) 4688 1459 or e-mail firstname.lastname@example.org
SOI influence on climate varies across Australia (greatest skill is for eastern Australia) and between seasons (usually greatest skill is for winter, spring and early summer). Therefore users of the SOI and any other seasonal forecasts are urged to investigate skill level for their location by using such tools as Rainman StreamFlow.
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: 1953, 1954, 1957, 1962, 1973, 1978, 1982, 1986, 1987, 1990, 2003, 2005 and 2006. Work out your long term average rainfall for March to May and see how many times rainfall was well below, well above or close to average.
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 six 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 eight 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.
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 those looking for a potential rainfall trigger the next MJO event is expected to cross northern Australia during late March or early April. Currently the MJO is weak however it expected to reorganise and start to progress eastward across the Indian Ocean during the coming week.
The MJO is a band of low air pressure which originates off the east coast of central Africa. It travels eastward across the Indian Ocean and northern Australia roughly every 30 to 60 days. Because of the timing of the MJO the phenomenon is also known as the forty day wave. It can be used as an indicator for the timing of potential rainfall events.
The impact of the MJO on rainfall varies between the different seasons and location. For example the MJO has a greater influence on rainfall throughout northern Australia during summer and southern Australia during winter. For more information on the MJO go to http://cawcr.gov.au/bmrc/clfor/cfstaff/matw/maproom/RMM/phase.Last40days.html
According to the latest ENSO Wrap-up from the Bureau of Meteorology, while there is still a typical El Niño climate pattern present in the Pacific, the surveyed global climate models indicate a gradual breakdown of the EL Niño will occur during autumn with only a low chance of the El Niño redeveloping.
This expectation is reflected by a distinct cooling trend in sea surface temperatures (SST) throughout the eastern Pacific. There has also been a distinct warming trend in ocean temperatures around northern Australia. As autumn is the key transition time for the development and breakdown of El Niño and La Niña events we recommend monitoring SST and SOI values over the next couple of months. For more information go to the ENSO Wrap-up from the Bureau of Meteorology www.bom.gov.au/climate/enso
CSIRO have just released a new book titled 'Adapting Agriculture to Climate Change - Preparing Australian Agriculture, Forestry and Fisheries'. The book provides updated climate scenarios for Australia with the latest climate science. It includes chapters on adapting to climate variability and change, greenhouse gas emissions sources and sinks, as well as risks and priorities for the future. For more information go to www.publish.csiro.au
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.