Seasonal Climate Outlook Message for February to May 2009
The bottom line
Neutral SST Pattern Persists. Dave McRae, Qld Climate Change Centre of Excellence, 17/02/09.
According to the latest Bureau of Meteorology ENSO Wrap-Up (available at www.bom.gov.au/climate/enso) a neutral sea surface temperature (SST) pattern continues to persist in the Pacific Ocean.
This is despite some atmospheric indicators such as south east trade winds and SOI indicating borderline La Nina conditions over recent months. For example, the south east trade winds have been stronger than normal across the western half of the equatorial Pacific. This has contributed to the SOI remaining in positive values and the inflow of warm moist air across the eastern Australian coastline.
Also subsurface ocean temperatures stretching from the central to eastern Pacific have also been cooler than normal. This would normally be considered as an early indicator for a developing La Nina SST pattern.
Historically however, our climate year runs from autumn to autumn and it would be unusual for a La Nina (or for that matter an El Nino) to develop at this time of year. In terms of SST patterns for the rest of 2009 a key time to watch for the potential development of an El Nino will be over autumn.
This is reflected in the output from the reviewed dynamic climate models with the majority forecasting a neutral SST pattern to persist through to the end of the 08/09 summer.
The Madden-Julian Oscillation or MJO crossed northern Australia over the last couple of weeks helping to trigger recent rainfall events. If its timing remains consistent, the next passage of the MJO is likely to occur during mid March. Interestingly a key time to watch for the potential development of cyclones is after summer passages of the MJO.
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.
The 8th Australian Tropical Pastures Conference is on the 18th to 19th March, 2009 at Goondiwindi. The theme is Pastures for Production, Soil Health and Carbon Sequestration. For more information on the conference contact Ian Partridge on (07) 46881375 or try the web site at www.tropicalgrasslands.asn.au
The 30 day average of the SOI as of 16 February is plus 12.7. You can receive a text message with the latest SOI values sent to your mobile phone. To subscribe to this free service, call (07) 4688 1459.
The full story
SOI Remains Consistently Positive Dave McRae, QCCCE, 17/02/09.
The monthly value of the SOI for December was plus 11.6 and for January was plus 8.2. This places the SOI in a Consistently Positive phase for the 5th month in a row.
Based on historical rainfall records and a Consistently Positive SOI phase at the end of January, there is a reasonable 50 to 70% chance of getting above median rainfall during February through to the end of April across most of Queensland. For example Atherton has an 70% chance of getting above its February to April median rainfall of 595mm, Aramac has a 67% chance of getting above its February to April median rainfall of 132mm, Charters Towers has a 65% chance of getting above its February to April median rainfall of 253mm, Birdsville has a 60% chance of getting above its February to April median rainfall of 36mm, Esk has a 60% chance of getting above its February to April median rainfall of 270mm, Goondiwindi has a 60% chance of getting above its February to April median rainfall of 150mm and Roma has a 50% chance of getting above its February to April median rainfall of 155mm.
For more information on historical rainfall data for your region try Rainman Streamflow or www.bom.gov.au
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%.
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 to mid 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 February to April in the following years since 1950 that have had a Consistently Positive SOI phase at the end of January; 1950, 1951, 1956, 1957, 1962, 1974, 1975, 1989, 1997, 1999, 2000, 2001 and 2008. Find out your average rainfall for February to April and see how many times rainfall was well below, well above or close to average during February to April in the listed years.
According to the Bureau of Meteorology monthly climate summary for January (www.bom.gov.au) there were dramatic regional differences in the weather and climate experienced across Australia.
Due to the strong onset of the monsoon season most of the tropical northern Australia experienced a very wet and cool January. This is in stark comparison to southern Australia where temperatures were well above average and rainfall well below.
Throughout Queensland similar regional differences can be found. For example most of the Gulf Country, Northwest, Northern Goldfields, Herbert and Lower Burdekin, Northern Tropical Coast, Tablelands and western Channel Country have recorded above average rainfall. This is in contrast to the northern Peninsula and southern half of the state, most of which recorded well below average rainfall for January. For example, Ballandean on the Darling Downs received its lowest total January rainfall on record (14mm recorded, average 97mm). Coincidently, many locations in these regions have recorded only 40 to 80% of their long term average rainfall for the northern wet season to date.
According to the latest Bureau of Meteorology ENSO Wrap-Up (available at www.bom.gov.au/climate/enso) a neutral sea surface temperature (SST) pattern continues to persist in the Pacific Ocean.
This is despite some atmospheric indicators such as south east trade winds and SOI indicating borderline La Nina conditions over recent months. For example, the south east trade winds have been stronger than normal across the western half of the equatorial Pacific. This has contributed to the SOI remaining in positive values and the inflow of warm moist air across the eastern Australian coastline. Also subsurface ocean temperatures stretching from the central to eastern Pacific have also been cooler than normal. This would normally be considered as an early indicator for a developing La Nina SST pattern.
Historically however, our climate year runs from autumn to autumn and it would be unusual for a La Nina (or for that matter an El Nino) to develop at this time of year. In terms of SST patterns for the rest of 2009 a key time to watch for the potential development of an El Nino will be over autumn. This is reflected in the output from the reviewed dynamic climate models with the majority forecasting a neutral SST pattern to persist through to the end of the 08/09 summer.
The Madden-Julian Oscillation or MJO crossed northern Australia over the last couple of weeks helping to trigger recent rainfall events. If its timing remains consistent, the next passage of the MJO is likely to occur during mid March. Interestingly a key time to watch for the potential development of cyclones is after summer passages of the MJO.
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.
The 8th Australian Tropical Pastures Conference is on the 18th to 19th March, 2009 at Goondiwindi. The theme is Pastures for Production, Soil Health and Carbon Sequestration. For more information on the conference contact Ian Partridge on (07) 46881375 or try the web site at www.tropicalgrasslands.asn.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.
The 30 day average of the SOI as of 16 February is plus 12.7. You can receive a text message with the latest SOI values sent to your mobile phone. To subscribe to this free service, call (07) 4688 1459.
