MJO late and disappointing Dave McRae 09/10/06
The last passage of the MJO occurred later than expected at the end of September. It produced a generally poor rainfall signal with only patchy rainfall over southern Queensland and northern NSW. If a timing of approximately 30 to 35 days is maintained it would be reasonable to next expect it in the first half of November. As we approach summer stronger MJO signals can be expected.
The MJO is a band of low air pressure originating off the east coast of central Africa travelling eastward across the Indian Ocean and northern Australia roughly every 30 to 60 days. Research has shown the MJO to be a useful indicator of the timing of potential rainfall events (but not amounts). For more information try http://www.apsru.gov.au/mjo/
The latitude of the sub-tropical ridge of high pressure has remained further south than normal over the last 6 months contributing to rain and shower activity through increased flow of moist easterly winds. Its effect has been most noticeable across northern and coastal regions of Queensland where in many areas unseasonably large falls of rain have been recorded. It will start to lose its influence on our climate patterns over spring and summer hopefully allowing cane harvesting to be finished.
Information on ocean temperatures in the central Pacific (running eastward along the equator from the international dateline) continues to indicate a warming trend. As we have stated over the last few months, if this pattern persists it most likely will have a drying effect on our expected rainfall in spring and early summer (as it did this winter over much of eastern Australia) regardless of whether it is a 'classic' El Nino or not. A common feature of an El Nino SST pattern is a later than normal start to the northern wet season. Its effect (or impact on expected rainfall) is usually less noticeable in late summer. For more on conditions in the Pacific try the Bureau of Meteorology at http://www.bom.gov.au/climate/ahead/
The 30day average of the SOI has fallen since the start of the month to minus 8.9 as of the 9th October. Current rainfall probability maps are at www.dpi.qld.gov.au/climate or www.longpaddock.qld.gov.au and SOI updates are available on (07) 46881439. For other enquires contact the DPI&F Information Centre on 132523.