Seasonal Climate Outlook Message for August to November 2005

The bottom line

Climate Watch 01/08/05

SOI in Near Zero Phase

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.

Rainfall for the 3-month period May to July was average to above average for most of Queensland. The exception was for parts of northern Queensland where below average rainfall was recorded.

The higher totals during this period were recorded in June and provided relief in many areas. For example for the 15 months from March 2004 to May 2005, Kingaroy recorded 594 mm which was in the lowest 10% of rainfall recorded historically. This pattern was broken when a well above average 165 mm was received in June. More rain though is still required to catch up on the deficits of the last couple of years.

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? This will 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 only use climate information such as the long term monthly averages for your location.

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.