Seasonal Climate Outlook Message for November 2009 to February 2010
The bottom line
El Niño pattern persists Dave McRae, Queensland Climate Change Centre of Excellence, 16/11/09.
According to the latest ENSO Wrap-up from the Bureau of Meteorology www.bom.gov.au/climate/enso a typical El Niño sea surface temperature pattern is clearly present in the tropical Pacific Ocean. Sea surface temperatures have continued to warm in the central and eastern Pacific Ocean to a level that has not been observed since the 2002 El Niño event.
Sub-surface sea temperatures (to a depth of 300 plus metres) throughout the central and eastern tropical Pacific have also continued to warm, with temperatures as much as 6 degrees C above normal in some regions. Rainfall patterns over eastern Australia for the past three months have also broadly been in keeping with the impact of an El Niño event.
Five of the six international climate models surveyed forecast sea surface temperatures to remain above El Niño threshold levels throughout summer. None of the surveyed climate models are forecasting any potential return of La Niña like conditions. Given that El Niño events (and La Niña's) tend to persist from autumn to autumn, this is not a surprise.
Recently there has been a lot of media coverage of a report released by the Federal Government on the likely impacts of climate change on coastal communities at risk from sea level rise, inundation and coastal instability. It is the first continental scale mapping of residential buildings at risk from climate change and details risks to coastal infrastructure, services and industry. For a copy of the report go to www.climatechange.gov.au
The Bureau of Meteorology also provides information on our highly variable and changing climate including rainfall and temperature trends. Go to www.bom.gov.au/climate/change/
The full story
SOI in Falling Phase Dave McRae, Queensland Climate Change Centre of Excellence, 16/11/09.
Based on a Rapidly Falling SOI phase at the end of October and historical rainfall records, there is a 30 to 60% chance of getting above median rainfall throughout southern and western Queensland for November through to the end of January. However, the chance of getting above median rainfall throughout central and northern Queensland is lower and varies between 20 to 40%.
For example Ayr has an 25% chance of getting above its November to January median rainfall of 360mm, Mackay has a 33% chance of getting above its November to January median rainfall of 510mm, Wyandra has a 50% chance of getting above its November to January median rainfall of 105mm, Gatton-Lawes has a 50% chance of getting above its November to January median rainfall of 270 mm, Mount Isa has a 50% chance of getting above its November to January median rainfall of 160mm and Talwood has a 58% chance of getting its November to January median rainfall of 185mm.
It is worth noting that even for those areas with a lower chance of getting above median rainfall, that as we are entering our spring/summer rainfall season there is still a reasonable chance of getting some useful relief rain.
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 November to January in the following years that have had a 'Rapidly Falling' SOI phase at the end of October; 1915, 1920, 1925, 1941, 1944, 1947, 1963, 1978, 1981, 1992 and 2006. It can be useful to find out what rainfall and farming conditions where like in your area for September to November in those years. Information on what rainfall patterns where like in those years is available at www.longpaddock.qld.gov.au or 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%.
According to the latest ENSO Wrap-up from the Bureau of Meteorology www.bom.gov.au/climate/enso a typical El Niño sea surface temperature pattern is clearly present in the tropical Pacific Ocean. Sea surface temperatures have continued to warm in the central and eastern Pacific Ocean to a level that has not been observed since the 2002 El Niño event. Sub-surface sea temperatures (to a depth of 300 plus metres) throughout the central and eastern tropical Pacific have also continued to warm, with temperatures as much as 6 degrees C above normal in some regions. Rainfall patterns over eastern Australia for the past three months have also broadly been in keeping with the impact of an El Niño event.
Negative SOI values (say below minus 5) are normally associated with El Niño events. Typically during an El Niño event, there is a lower chance of getting above median rainfall during winter, spring and early summer throughout southern and inland eastern Australia. Therefore there will be much interest in which direction SOI values take as the summer rainfall season approaches.
Five of six international models surveyed, forecast sea surface temperatures to remain above El Niño threshold levels throughout summer. None of the surveyed climate models are forecasting any potential return of La Niña like conditions. Given that El Niño events (and La Niña's) tend to persist from autumn to autumn, this is not a surprise.
Recently there has been a lot of media coverage of a report released by the Federal Government on the likely impacts of climate change on coastal communities at risk from sea level rise, inundation and coastal instability. It is the first continental scale mapping of residential buildings at risk from climate change and details risks to coastal infrastructure, services and industry. For a copy of the report go to www.climatechange.gov.au
The Bureau of Meteorology also provides information on our highly variable and changing climate including rainfall and temperature trends. Go to www.bom.gov.au/climate/change/
Based on soil water conditions at the end of October and the seasonal rainfall outlook for November to January, there is only a low chance of getting above median sorghum yields at a regional council level during the 2009/2010 summer growing season for Queensland. For example, throughout central Queensland there is less than a 30% chance of getting above the long term medium sorghum yield. Throughout southern Queensland there is a marginally higher 20 to 40% chance of getting above the long term median sorghum yield.
It is worth remembering however that it is early in the growing season and any widespread rainfall events have the potential to improve the general summer crop outlook. The regional sorghum crop outlook is based on the assumption of cropping after winter fallow and does not take into account effects of poor crop nutrition or damage due to pests, diseases, heat or frosts. For more information on the seasonal crop outlook contact Andries Potgieter on (07) 4688 1417 or www.dpi.qld.gov.au
For those looking for a potential rainfall trigger the next MJO event is expected to cross northern Australia during mid November. Currently there a band of enhanced convection developing in the western and central Indian Ocean which is indicative of an active MJO. Therefore the MJO is likely to cross northern Australia within the next fortnight.
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
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.
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
