Seasonal Climate Outlook Message for August to November 2009
The bottom line
Mediocre outlook across Australia Dave McRae, Qld Climate Change Centre of Excellence, 10/08/09.
An analysis of historical rainfall records and a Consistently Near Zero SOI phase at the end of July indicates a 40 to 50% chance of getting above median rainfall throughout most of Queensland during August to October. This is a marginal improvement on the July to September seasonal outlook. The exception is for the region running from the central Queensland coast to the peninsular and adjacent inland area where there is a lower 20 to 40% chance of getting above median rainfall.
Similar rainfall probabilities can be found throughout the rest of Australia. The main exception is for the coastal strip of NSW where there is a 40 to 60% chance of getting above median rainfall for August to October.
Again it is worth noting that for northern Australia (including Queensland) we are in our 'dry season' and that August and September have the lowest median monthly rainfall totals for most locations in Queensland. Therefore significant or 'drought breaking' rain is not usual during this period regardless of the seasonal outlook.
The latest rainfall probability maps are available at www.longpaddock.qld.gov.au
According to the Bureau of Meteorology (www.bom.gov.au) monthly climate summary for Queensland, below average rainfall was recorded throughout most of Queensland for July. Area averaged across the state, July had the 5th lowest rainfall on record. Maximum temperatures for July were warmer than average (+1.19 degree C), while minimum temperatures were slightly below average (-0.11 degree C).
These warmer than average maximum temperatures are likely to continue. Currently there is an 80% chance of getting above the long term median maximum temperature during August to October throughout most of the southern half of Queensland. For the northern half of Queensland there is a 55 to 70% chance of getting above median maximum temperatures for August to October.
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%.
You can receive a text message with the latest SOI values sent to your mobile phone. To subscribe to this free service, call me on (07) 4688 1459 or e-mail david.mcrae@climatechange.qld.gov.au
The full story
SOI Remain in Near Zero Phase D McRae, QCCCE 17th August 2009.
Despite the value of the SOI fluctuating during the last few weeks, based on the shift in monthly value of the SOI from minus 2.8 for June to plus 2 for July, the SOI has remained in a "Consistently Near Zero" phase.
An analysis of historical rainfall and a Consistently Near Zero SOI phase at the end of July indicates a 40 to 50% chance of getting above median rainfall throughout most of Queensland during August to October. This is a marginal improvement on the July to September seasonal outlook. The exception is for the region running from the central Queensland coast to the peninsular and adjacent inland area where there is a lower 20 to 40% chance of getting above median rainfall. The latest rainfall probability maps are available at www.longpaddock.qld.gov.au
Similar rainfall probabilities can be found throughout the rest of Australia. The main exception is for the coastal strip of NSW where there is a 40 to 60% chance of getting above median rainfall for August to October.
Again it is worth noting that for northern Australia (including Queensland) we are in our 'dry season' and that August and September have the lowest median monthly rainfall totals for most locations in Queensland. Therefore significant or 'drought breaking' rain is not usual during this period regardless of the seasonal outlook.
For example median rainfall for August and September at Blackall is 9 mm and 6 mm, at Emerald is 11 mm and 9 mm, at Goondiwindi is 26 mm and 34 mm, at Toowoomba is 33 mm and 41 mm and Mareeba is 2 mm and 2 mm.
To follow the relationship between the SOI and rainfall patterns in more detail have a look at what happened in your area during August to October in the following years since 1930 that have had a 'Near Zero' SOI phase at the end of July; 1930, 1932, 1935, 1942, 1944, 1953, 1957, 1958, 1959, 1961, 1962, 1966, 1967, 1969, 1971, 1980, 1983, 1991, 2000, 2001, 2002, 2005, 2006 and 2008. For example at Dalby, well below median rainfall for August to October in those years was recorded 3 times, close to median rainfall was recorded 16 times and above median rainfall was recorded 5 times. Therefore rainfall at Dalby during August to October is more likely to be closer to the long term median than well above or below median. Refer to Rainman StreamFlow for more information.
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%.
According to the Bureau of Meteorology (www.bom.gov.au) monthly climate summary for Queensland, below average rainfall was recorded throughout most of the state for July. Area averaged across the state, July had the 5th lowest rainfall on record. Maximum temperatures for July were warmer than average (+1.19 degree C), while minimum temperatures were slightly below average (-0.11 degree C).
These warmer than average maximum temperatures are likely to continue. Currently there is an 80% chance of getting above the long term median maximum temperature during August to October throughout most of the southern half of Queensland. For the northern half of Queensland there is a 55 to 70% chance of getting above median maximum temperatures for August to October.
According to the latest ENSO Wrap-up from the Bureau of Meteorology www.bom.gov.au/climate/enso indictors are showing trends consistent with an El Nino climate pattern. Sea surface temperatures (SST's) are significantly warmer than the long term average throughout most of the tropical Pacific Ocean. SST's are above El Nino thresholds throughout the central and eastern equatorial Pacific. Warmer than normal sub-surface ocean temperatures are also evident, particularly throughout the eastern Pacific. This is a reversal of the La Nina like climate pattern that was evident during late 2008 and early 2009.
The 30day average of the SOI value is minus 3.9 as of the 17/08/09. Consistently negative SOI values are considered a feature of El Nino events.
This trend is also consistent with the output of the surveyed international climate models. Six of the seven leading climate models surveyed indicate an El Nino climate pattern is likely to persist for the remainder of 2009. None of the surveyed climate models are forecasting any potential return of La Nina or La Nina like conditions.
The message should not be "doom and gloom" another El Nino may be approaching. Rather this is an opportunity to take a risk management approach. Review your business, cropping, stocking, fodder, water use plans for the coming winter and spring, assess the seasonal conditions experienced in your area to date and the resources (soil moisture, grass, water, money, equipment) you have available, monitor changes in the seasonal climate outlook over coming months and adjust your plans if and as necessary.
Typically during an El Nino event, there is a lower chance of getting above median rainfall during winter, spring and early summer throughout southern and inland eastern Australia.
The next active phase of the Madden-Julian Oscillation or MJO is likely to cross northern Australia during late August/early September. 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 www.bom.gov.au
As at 30 June 2009, 35 percent of the land area of Queensland is drought declared under State processes. There are three Individually Droughted Properties (IDPs) in the North Burnett.
Drought declarations in Queensland are made following recommendations from the local drought committees to the minister. The local drought committees also make the recommendations to the minister for drought declarations to be revoked. This occurs when in their opinion there has been sufficient rainfall to promote enough pasture growth to permit stocking at 'near-normal' carrying capacities for the given time of year.
For a full list of drought declared regions and a seasonal conditions report go the Long Paddock internet site www.longpaddock.qld.gov.au Other information on the current drought situation and available financial assistance, drought planning advice, social, and community counselling services can be found at www.dpi.qld.gov.au/drought or through the DPI Call Centre on 132523.
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.
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.
