The truth is still out there: will conditions improve? by Dave McRae, QDPI Centre for Climate Applications
GroundCover™ Issue: 46
THE SOUTHERN Oscillation Index (SOI) slowly rose from the end of June (minus 13.2) through to the end of July (plus 3.2). Based on this shift in value, the SOI is now in a 'rapidly rising' phase.
For those interested in historical rainfall patterns, some of the years that have had the same SOI pattern at the end of July include 1999, 1998, 1988, 1985, 1984, 1979, 1974, 1963, 1960, 1954, 1949, 1948, 1947, 1943, 1939, 1936 and 1933.
It can be useful to find out what rainfall and farming conditions were like in your area for August- October in those years.
Information on what rainfall patterns were like in those years is available at www.longpaddock.qld.gov.au
August-October rainfall probabilities for much of Queensland's grainbelt are an improvement over the situation this time last year. Currently there is a 50-80 per cent chance of getting the long-term August-October median rainfall or more across most of the southern two-thirds of Queensland (refer to map). Rainfall probabilities across the rest of the state remain patchy.
However, it is worth remembering that August and September are normally the two driest months of the year across northern Australia and that high rainfall totals are not common during this period. For the central and north-west of NSW, central SA and north-west WA, there is a 50-70 per cent chance of getting the long-term August-October median rainfall or better. Rainfall probabilities across the rest of Australia though are lower at 30-50 per cent.
Sea surface temperatures and SOI - looking ahead
While this pattern is an improvement from the last 12 months, SSTs have not changed significantly enough to guarantee a large improvement in overall conditions (e.g. widespread drought-breaking rain). For there to be increased confidence in the longer-term outlook (through to summer), SOI monthly values will need to become more positive over the coming months.
Due to the national perspective of this column, the information provided is of a fairly broad nature. For those readers who require more specific climate information, we recommend referring to Australian Rainman, the latest 'Climate Note' at www.dpi.qld.gov.au/climate or contact us on 07 4688 1459.