Seasonal Climate Outlook Message for August to November 2005

The full story

SOI In Near Zero Phase 02/08/05

The monthly value of the SOI remained relatively stable from the end of June (plus 0.5) to the end of July (plus 1.6) putting the SOI in a 'Near Zero' phase. Based on this phase and historical rainfall records for August to October most of Queensland has a 40 to 50% chance of getting above median rainfall. The exception is for the strip running from the central Queensland coast to the peninsular were there is a lower 20 to 40% chance of getting above median rainfall.

It is worth noting that we are in our 'dry season' with August and September having the lowest median monthly rainfall for most locations in Queensland. For example the long term historical median rainfall for August and September at Blackall is 9 mm and 6 mm, at Charters Towers is 2 mm and 3 mm, at Emerald is 11 mm and 9 mm, at Miles is 29 mm and 31 mm, Goondiwindi is 26 mm and 34 mm and at Morven is 15 mm and 11 mm.

Similar to Queensland there is less than a 50% chance of getting median rainfall across the rest of Australia. The main exception is for north east corner of NSW and into the extreme south east corner of Queensland where there is a 50 to 70% chance of getting above median rainfall.

For more on rainfall probabilities, monthly averages or medians for your location refer to Rainman Streamflow or contact me on 132523 or (07) 3404 6999 and I'll send you any information I have.

Many people like to follow the relationship between the SOI and rainfall patterns in more detail. To do that, have a look at what happened in your area over August to October in the following years; 2002, 2001, 2000, 1999, 1991, 1990, 1983, 1980, 1971, 1969, 1967, 1966, 1962, 1961, 1959, 1958, 1957 and 1953 and compare the rainfall recorded with your 'normal' rainfall for August to October.

For example at Rockhampton below median rainfall for August to October in those years was recorded 10 times, close to median rainfall was recorded 4 times and above median rainfall was recorded 4 times. Information on what rainfall patterns where like for August to October in those years can be found at www.longpaddock.qld.gov.au or in Australian Rainman.

Based on the current seasonal outlook and soil moisture levels at the end of July there is a 30 to 50% chance of getting above median shire wheat yields for the eastern Darling Downs. Due to rain events in June lifting soil moisture profiles the chance of getting above median shire wheat yields across most of the rest of the wheat growing regions of Queensland and northern NSW is between 70 to 90%.

The APSRU/DPI&F wheat yield outlook is based on a shire scale. It does not take into account crop area planted and is purely a yield forecast. It 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. It should be noted that forecast quality of the crop outlook improves as the season progresses.

For more information on the regional wheat crop outlook contact Andries Potgieter on (07) 46881417 or try www.dpi.qld.gov.au/climate where a full copy the wheat crop outlook can be found.

Currently the MJO is somewhat hard to discern due to strong monsoon activity over India and SE Asia as well as convection over the South China Sea. It is also the time of year when it has less influence on our region.

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) across much of Queensland. For more information on the MJO including its location try www.apsru.gov.au/mjo/ or try www.bom.gov.au/climate/tropnote/tropnote.shtml

I've developed a list of key points from client feedback for those interested in using climate information. Key points include that management decisions should never be based entirely on one factor such as a climate or weather forecast. As always, everything that could impact of the outcome of a decision (soil moisture, pasture type/availability, crop and commodity prices, machinery, finance etc) should be considered.

Doing a simple cost benefit analysis when making a major decision may also be useful. For example what will I gain if I get the desired outcome? What will I lose (sleep, money, family relationships) if I do not get the desired outcome from this decision and what other options are there? A part of this process is to help managers to be careful not to change from normal risk management to high level risk taking based on a piece of information (such as a climate forecast).

Forecasts as well do not always give a strong signal as to likely conditions for your location. In assessing climate forecasts as a management tool consider the level of signal for the key decision times in your location.

A key point to remember with any probability based forecasts is that they are just that - probabilities and not definitive forecasts. Therefore the opposite always applies eg 70-30; 30-70. So if you are not 'comfortable' with probability based forecasts don't use them. Only use climate information such as the long term monthly averages for your location.

According to information from the Bureau of Meteorology "El Niño wrap up" at www.bom.gov.au/ key indicators in the Pacific suggest that the likelihood of a classic El Niño event developing this year has continued to recede and is now low.

The key region to watch for the development of El Niño or La Niña events runs east along the equator from the international dateline to South America. If sea surface temperatures (SST) in this region remain warmer than normal it is often associated with below median rainfall for much of eastern Australia.

The reason for the concern about the potential for an El Niño or borderline El Niño to develop over the last few months has been that SST in the central Pacific have remained slightly warmer than normal. This is similar to the SST pattern that could be found for much of the second half of 2004 and early 2005 and as readers would be aware rainfall for this period was below average for most of eastern Australia.

In terms of output from 12 surveyed reputable ocean or coupled ocean/atmosphere forecast models, 8 are showing a neutral SST pattern through to December with 3 showing an El Niño SST pattern and 1 showing a La Niña pattern. For more information on conditions in the Pacific try the IRI for Climate Prediction at http://iri.ldeo.columbia.edu/ or the US Climate Prediction Centre at www.cpc.ncep.noaa.gov/