Seasonal Climate Outlook Message for March to June 2009
The bottom line
SOI falls in value. Dave McRae, Qld Climate Change Centre of Excellence, 30/03/09
The monthly value of the SOI has fallen from plus 15.2 for February to minus 1.3 for March. This is the lowest monthly value of the SOI since May 2008.
Based on historical rainfall records and a Rapidly Falling SOI phase at the end of March, there is a lower 30 to 50% chance of getting above median rainfall during April through to the end of June across most of Queensland.
For example Killarney has an 48% chance of getting above its April to June median rainfall of 122mm, Charters Towers has a 45% chance of getting above its April to June median rainfall of 65mm, Cooyar has a 40% chance of getting above its April to June median rainfall of 100mm, Augathella has a 40% chance of getting above its April to June median rainfall of 75mm, Longreach has a 35% chance of getting above its April to June median rainfall of 57mm, Rockhampton has a 35% chance of getting above its April to June median rainfall of 135mm, Goomeri has a 30% chance of getting above its April to June median rainfall of 116mm and Julia Creek has a 30% chance of getting above its April to June median rainfall of 25mm.
In terms of the seasonal outlook for winter and spring it would be worthwhile to watch SOI trends over coming months. For example, if the current fall in value of the SOI where to continue into strongly negative values and remain there through to the end of autumn, it would be a warning sign for a likely dry winter/spring.
For more information on historical rainfall data for your region try Rainman Streamflow, www.longpaddock.qld.gov.au 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 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.
As autumn is a key time for the establishment of climate phenomena such as El Nino and La Nina QCCCE climate staff will continue to closely monitor what happens over the next few months. 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.
