SOI continues to rise Dave McRae, Qld Climate Change Centre of Excellence, 13/04/10.
The 30day average of the SOI has continued to maintain the upward trend of the last couple of weeks and is plus 7.0 as of the 13th April. This is up from minus 18.2 for February and minus 10.8 for March.
It will be worth watching to see if these positive values are maintained over coming months. At this a time of year, a return to consistently negative values would be a warning sign for a likely dry winter/spring. In terms of a continued improvement in seasonal conditions and outlook, the development of consistently positive SOI values and even a La Nina would help.
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 couple of months. More information on the development of these climate patterns can be found at www.bom.gov.au/climate/enso or www.cpc.ncep.noaa.gov
Convection associated with a weak MJO became evident in the Indian Ocean during mid-March and travelled eastward across Australian longitudes during the end of March/early April. This coincided with the development of Tropical Cyclone Paul in the Gulf of Carpentaria.
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 try the Bureau of Meteorology at www.bom.gov.au
In the mean time based on a "Consistently Negative" SOI phase at the end of March there is a lower 20 to 40% chance of getting above the long term April to June median rainfall throughout the far north west and peninsular region of Queensland. This is in contrast to the outlook across most of the rest of the state where there is a higher 50 to 70% chance of getting above median rainfall during April to June. For the latest outlook map go to www.longpaddock.qld.gov.au