SOI Remains Near Zero Dave McRae 08/09/03
Based on the recent pattern of the SOI, the current outlook across Queensland is mixed. For September to November there is a 30 to 50% probability of getting above the long term median rainfall for northern, central and western Queensland. For the south east quarter of the state, the probability of getting above the long-term median rainfall for the same period is marginally higher at 50-60%.
The current outlook for Queensland is a slight improvement on this time last year. However based on these probabilities this forecast would not normally be regarded as providing or indicating a high chance of the much needed well above average state wide 'drought-breaking' rain.
It is also worth remembering that September is normally one of the drier months of the year.
For increased confidence in seasonal conditions improving in the longer term (through to summer) the SOI needs to return to more positive monthly values. As of the 8th September the 30day average of the SOI was minus 2.2. For who like to follow the SOI, updates are also available at (07) 46881439.
Patchy Outlook For Australia Dave McRae Qld Dept of Primary Industries 08/09/03
Generally speaking, the current outlook across Australia is patchy. For September to November there is a 30 to 50% probability of getting above the long term median rainfall for northern, central and western Queensland.
For the south east quarter of the state, the probability of getting above the long-term median rainfall for the same period is marginally higher at 50-60%.
Across most of Australia there is a 30-50% chance of getting or getting above the long term September to November median rainfall. Rainfall probabilities though are marginally higher at 50-60% for parts of central and coastal NSW, south west WA, southern Victoria and Tasmania.
Overall for Queensland the current outlook is a slight improvement on this time last year. However based on these probabilities this forecast would not normally be regarded as providing or indicating a high chance of getting the much needed well above average Queensland wide 'drought-breaking' rain.
It is worth remembering that September is normally one of the drier months of the year.
For increased confidence in seasonal conditions improving in the longer term (through to summer) the SOI needs to return to more positive monthly values. As of the 8th September the 30day average of the SOI was minus 2.2. For who like to follow the SOI, updates are available at (07) 46881439.
The current rainfall probability maps are also available at www.dpi.qld.gov.au/climate or at www.longpaddock.qld.gov.au
As always when using any probability based forecast system, it is important to consider the alternate view. For example, St George currently has approximately a 70% chance of getting above 70mm for September to November. This also means that there is a 30% chance of not getting above 70mm.
Another way of looking at this is that in 7 years out of 10 (or slightly less than three quarters) with the current SOI pattern, St George has received more than 70mm for September to November. Therefore in 3 years out of 10 (slightly more than one quarter), St George has gotten less than 70mm for this period.
Remember that this forecast does not suggest the potential distribution or timing of rainfall for this period. The forecast is for the full 3 month period and does not suggest that 70mm will fall evenly across 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 next passage of the MJO is expected to influence our weather in early October.
The monthly value of the SOI dropped slightly from the end of July (plus 3.2) through to the end of August (minus 1.1). Based on this shift in value the SOI is now in a "Near Zero" (or neutral) phase.
For those interested in following historical patterns more closely, some of the years that have had the same SOI pattern at the end of August include 2001, 1999, 1995, 1992, 1990, 1984, 1980, 1878, 1969, 1968, 1963, 1961, 1959 and 1952.
It can be useful to find out what rainfall and farming conditions where like in your area for September to November in those years. Information on what rainfall patterns where like in those years is available at www.longpaddock.qld.gov.au
According to the United States Climate Prediction Centre www.cpc.ncep.noaa.gov/ and the Bureau of Meteorology www.bom.gov.au/ a neutral sea temperature pattern continues in the tropical Pacific Ocean.
The sub-surface warming trend in the central and eastern Pacific highlighted last month has slowed with a slight cooling trend developing over the last fortnight. However a large area of warmer than normal water can still be found in the Pacific near the international dateline.
Overall though, sea-surface temperatures remain close to average across most of the equatorial Pacific (temperature anomalies of -1 to +1oC). The south east trade winds while varying have been generally near normal over recent weeks.
It is interesting to look at the latest output from the ocean and coupled ocean/atmosphere forecast models (GCMs'). Of 12 models that forecast out to December 2003, 9 indicate the development of a neutral sea temperature pattern and 3 indicate the potential development of a La Nina sea temperature pattern.
Of the 10 models that forecast out to March 2004, all of them indicate the development of a neutral sea temperature pattern. While it is positive news that the majority of these models show the development of a neutral SST pattern rather than an El Nino SST pattern, we recommend a cautious approach when considering the longer term outlook.
For more information on GCMs' try the Bureau of Meteorology site www.bom.gov.au/climate/ahead
At the end of July, crop conditions and the seasonal rainfall outlook indicated a near average chance of above median wheat yield at the state level during the 2003 wheat growing season. However at the shire scale the chance of getting above the long term median wheat yield varies greatly.
Average to above average shire wheat yield probabilities (60-90%) are forecast for most of the cropping areas in southern Darling Downs (eg Jondaryan), western Darling Downs (eg Murilla) and the far south west (eg Balonne).
In contrast, areas in the Dawson Callide show slightly below average chances (30-50%) of exceeding the long-term median while areas in the Central Highlands (eg Emerald, Bauhinia) show a much-reduced chance (i.e. 10-30%) of exceeding the long-term median yield.
The likely range of yield outcomes has narrowed and the forecasted state median is 1.26 t/ha. This range will narrow further over the next few months as the outlook is updated.
Rainfall recorded for May to July was near average for most of the southern areas of Queensland's cropping region, which helped planting opportunities and consequently near average wheat yield expectations in most of these areas.
In contrast, below average rainfall was recorded for almost all cropping areas in Central Queensland. This further depleted subsoil moisture levels and consequently, poor crop yields are expected for these cropping areas. With the planting window for wheat now closed, above average rainfall is needed around flowering for the current state wheat outlook to improve.
This outlook is based on a shire scale and does not take into account individual property circumstances or the effects and damage from poor crop nutrition, pests, diseases, frosts and distribution of planting rain within a shire.
For more information on the APSRU/QCCA regional wheat crop outlook contact Andries Potgieter on 46881417.
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, we recommend referring to Australian Rainman, the latest 'Climate Note' at www.dpi.qld.gov.au/climate the Long paddock site www.longpaddock.qld.gov.au or contact us through the DPI Call Centre on 13 25 23.