Seasonal Climate Outlook Message for March to June 2005

The bottom line

SOI takes big fall. Dave McRae Qld Dept of Primary Industries and Fisheries 1st March 05

Based on the SOI trend over January and February chances for average to above average rain over the next three months (March to May) across most of Queensland is less than 50%. This does not mean there will be no rainfall at all for the 3-month period. What it does means though, is that rainfall recorded for March to the end of May in the affected areas will, more likely than not, be below average for this time of year.

The main exception is for an area running from central NSW into the western regions of southern Queensland where there is a 50 to 70% chance of getting average to above average rain over the next three months. The latest rainfall probability maps for Queensland, Australia and the world are at www.dpi.qld.gov.au/climate or www.longpaddock.qld.gov.au

Of much interest is the quite a fall in value the monthly value of the SOI has taken from plus 1.2 at the end of January to a remarkable minus 29.5 at the end of February. This drop in value and some press coverage has left many wondering if another El Niño event is developing.

At present there are a number of 'warning signs' including the drop in value of the SOI that suggests this is a possibility. These include the recent strong westerly wind bursts in the central Pacific (driven by the development of 3 tropical cyclones east of the dateline) which can trigger the changes in ocean and atmospheric patterns needed for an El Niño event.

While the borderline El Niño sea surface temperature pattern that has persisted over the last 6 to 9 months has weakened, there has been a marked increase in sub-surface sea temperatures in the key areas of in the central Pacific. This again highlights the potential risk of the return of a more 'classic' El Niño event.

There remains however, a large amount of uncertainty about the development of an El Niño this year. For a start it is only early March. El Niño events usually develop in mid to late autumn so there is still plenty of time for conditions in the Pacific to change.

It is also unlikely that the current westerly wind bursts will be sufficient to trigger an El Niño event. So there will most likely need to be some more westerly wind bursts over the next few months in the Pacific especially during late autumn if an El Niño is likely to develop. As well, historically the monthly value of the SOI for February has been below minus 27 on only 2 other occasions. That was in 1978 and 1983. In the second half of both those years the SOI returned to more positive values.

So, we will key an eye on this situation over the next few months and pass on information as it becomes relevant. And to borrow a phrase, 'be alert but not alarmed' about changes in patterns in the Pacific.

For more information call the DPI Call Centre on 13 25 23 or (07) 3404 6999.

The full story

Is an El Niño on the cards for 2005? Dave McRae Qld Dept of Primary Industries and Fisheries 1st March 05

The monthly value of the SOI has taken quite a fall in value from plus 1.2 at the end of January to a remarkable minus 29.5 at the end of February. This drop in value and some press coverage has left many wondering if another El Niño event is developing.

As well, historically the monthly value of the SOI for February has been below minus 27 on only 2 other occasions. That was in 1978 and 1983. In the second half of both those years the SOI returned to more positive values.

If you would like to find out more try the Bureau of Meteorology "El Niño wrap up" at www.bom.gov.au/climate/enso/ or the IRI for Climate Prediction at http://iri.ldeo.columbia.edu/news/monthlyproduct.html or the US Climate Prediction Centre at www.cpc.ncep.noaa.gov/ For the latest sea surface temperature maps have a look at www.cpc.ncep.noaa.gov/products/ or at www.longpaddock.qld.gov.au/

In the mean time based on the SOI trend over January and February chances for average to above average rain over the next three months (March to May) across most of Queensland is less than 50%. This does not mean there will be no rainfall at all for the 3-month period. What it does means though, is that rainfall recorded for March to the end of May in the affected areas will, more likely than not, be below average for this time of year.

Similar to Queensland, for the rest of Australia the chance for average to above average rain over the next three months (March to May) is less than 50%. Because rainfall probabilities and median rainfall levels vary between regions, we recommend referring to Rainman StreamFlow for more specific information. Otherwise call the DPI Call Centre on 13 25 23 or (07) 3404 6999.

This forecast doesn't indicate the potential distribution or expected timing of rainfall over this period. The forecast is for a full 3-month period and doesn't suggest that any expected rain will fall evenly across these 3 months.

As with any probability based forecast system it is important to consider the opposite aspect. For example, Jericho has around a 30% chance of getting above its normal March to May rainfall of 90 mm. This also means that there is a 70% chance of NOT getting the 90 mm over March to May.

Another way of looking at this is that in around 3 years out of 10 historically (or around one third) with the current SOI pattern, Jericho has received at least 90 mm over March to May. Therefore in 7 years out of 10 historically (or around two thirds), Jericho has gotten less than its normal 90 mm over March to May.

When looking at rainfall probabilities for your area it may make it easier to think of them in these terms:

1. Probabilities above 80% highlight a high chance 2. Probabilities above 60% highlight an above average chance 3. Probabilities below 40% highlight a below average chance 4. Probabilities below 20% have a low chance

After a period when the amplitude or signal of the MJO (40-day wave) has been very weak and difficult to locate, convection activity is apparent in the central Indian Ocean. So for those looking for some more rain a renewed active phase of the MJO over northern Australia should occur in a couple of weeks. Very warm sea surface temperatures in the central and western Pacific appear to be continuing to disrupt the typical MJO progression.

The MJO is simply 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 across much of Queensland.

For more information on the MJO including it's location try www.apsru.gov.au/mjo/ or for more technical blurb try www.bom.gov.au/climate/tropnote/tropnote.shtml

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 March to May in the following years; 2003, 1990, 1987, 1986, 1982, 1978, 1973, 1962, 1957, 1954, 1953, 1937, 1935, 1931, 1926, 1916, 1912, 1905 and 1902 compare the rainfall recorded with your 'normal' rainfall for March to May.

Information on what rainfall patterns where like for March to May in those years can be found at www.longpaddock.qld.gov.au or in Australian Rainman.

When incorporating climate forecasts into management decisions, it could be worthwhile to consider some of the following general rules of thumb developed from feedback from climate users.

1. Be sure of your source of information and what it is actually suggesting. Do not take a quick grab of information from any source including radio, TV or the internet and assume what you heard/saw/read applies to your location.

2. Decisions should never be based entirely on one factor (such as a weather or climate forecast). As always, all factors that could impact of the outcome of a decision (such as soil moisture/type, crop, pasture type/availability, commodity prices, machinery, work force, transport, finance, costs, seasonal outlook etc) should be considered.

3. Access local information or at least be aware of the long-term median for your location so you can correctly interpret the forecast.

4. Do a cost benefit analysis of any decision with a climate risk factor eg What will I gain if I get the desired outcome from this decision? What will I lose if I don't get the desired outcome from this decision? What other cost neutral options do I have if any?

An interesting site http://www.cvap.gov.au/mastersoftheclimate/ from the 'Climate Variability In Agriculture' (CVAP) research and development program is well worth looking at. It highlights some case studies on how producers and businesses have used (to varying levels of success) climate and weather information in their decision making processes.

For more information call the DPI Call Centre on 13 25 23 or (07) 3404 6999.

Last updated: 1 March 2005

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