SOI Remains Near Zero 06/11/03
Across southern and western Queensland there remains a 30-50% chance of getting above the long term November to January median rainfall. Rainfall probabilities for the same period are marginally higher for eastern Queensland, reaching 60-70% for parts of the central and northern coastal strip. For example Gayndah has a 61% chance of getting above its long term November to January median rainfall of 290mm.
While these figures do represent a general improvement over this time last year, they are not high enough to guarantee immediate state wide drought breaking rain. For better chances of seasonal conditions improving, it would help if the SOI returned to more sustained positive values.
The 30day average of the SOI as of the 3rd November is minus 3.7. It is interesting to note that the SOI hasn't been in a 'Consistently Positive' phase since March 2001.
SOI Remains "Near Zero" 03/11/03
The monthly value of the SOI has remained stable from the end of September (minus 1.6) through to the end of October (minus 2.8). Based on the shift in value the SOI remains in a "Near Zero" (or neutral) phase.
For those interested in following historical SOI/rainfall patterns more closely, it can be useful to find out what rainfall and farming conditions where like in your area for November to January in the following years that also had a "Near Zero" phase at the end of October - 2001, 1995, 1990, 1985, 1980, 1979, 1978, 1968, 1967, 1961 and 1960.
Information on what rainfall patterns where like in those years can be found at www.longpaddock.qld.gov.au or in AUSTRALIAN RAINMAN.
More specifically, there is a 30 to 50% chance of getting above the long term November to January median rainfall across southern and western Queensland (refer to map). For example Quilpie has a 39% chance of getting above the long term November to January median rainfall of 90mm.
Rainfall probabilities are marginally higher for eastern Queensland, reaching 60-70% for parts of the north and central coastal strip. For example Gayndah has a 61% chance of getting above the long term November to January median rainfall of 290mm.
While these figures are a general improvement across most of Queensland over this time last year, they are not high enough to guarantee immediate state wide drought breaking rain at this stage. For better chances of seasonal conditions improving, it would help if the SOI returned to more sustained positive monthly values.
The 30day average of the SOI as of the 3rd November is minus 3.7. If you like to follow the fluctuations of the SOI, daily updates are available on (07) 46881439. It is interesting to note that the SOI hasn't been in a 'Consistently Positive' phase since March 2001.
When using probabilities or percentage chance of something occurring (eg amounts of rain in a period or race horses winning), it is important to consider the opposing view. For example, Dirranbandi has a 32% chance of getting above 180mm for November to January. This also means that there is a 68% chance of not getting above 180mm.
Another way of looking at this is that in 3 to 4 years out of 10 (or around one third of years) with the current SOI pattern, Dirranbandi has received more than 180mm for November to January. Therefore in 6 to 7 years out of 10 (or around two thirds), Dirranbandi has gotten less than 180mm for this period.
Many readers of this column like to follow the timing of the MJO (also know as the 40day wave). The MJO is simply a band of low atmospheric pressure originating off the east coast of central Africa travelling eastward across the Indian Ocean and northern Australia roughly every 30 to 50 days.
While it is a tropical phenomenon, it appears to indicate the timing of potential rainfall events (but unfortunately not rainfall amounts) over central and southern Queensland.
The last passage of the MJO influenced our weather in the first week of October producing some very patchy but useful rainfall totals especially across the south east quarter of Queensland. If it's timing remains current it would next be expected in the third week of November.
Research undertaken by the DPI has shown that with the current SOI pattern there is an increased chance (especially when compared with last year) for severe storm activity including hail and strong winds across southern Queensland and northern NSW for the rest of spring and summer.
Some interesting information recently sourced from ABARE highlighted the cost of the 2002/03 drought as $7 billion dollars and reduced Australian expected economic growth by 1%.
This forecast does not suggest or indicate the potential distribution or expected timing of rainfall over this period. The forecast is for the full 3 month period and does not suggest that expected rain will fall evenly across these 3 months.
Due to the size of the area covered, the information provided in this column is of a fairly broad nature. For those readers who require more specific climate information, try www.dpi.qld.gov.au/climate or contact us through the DPI Call Centre on 13 25 23.