Seasonal Climate Outlook Message for July to October 2002
The bottom line
SOI Remains Negative (Dated 02/07/02)
Based on the recent pattern of the SOI over May and June, the probability of receiving or getting above median rainfall for June to September is low for most of Queensland. Currently there is only a 10-30% chance of receiving or getting above the long term median rainfall for July to September for most of the state.
The monthly value of the SOI at the end of May was -13.8 and at the end of June was -6.8 . Based on this shift in the value of the SOI over May and June, the SOI is now in a "Consistently Negative" Phase. A daily updated recorded message with the 30day average of the SOI is also available on (07) 46881439.
It is essential to remember that when dealing with probabilities to also consider the additional information that probabilities provide. For example, based on the recent pattern of the SOI there is only a 9% chance of getting the long term July to September median rainfall of 96 mm at Kingaroy. Therefore there is a 91% chance of not getting the July to September median rainfall.
Another way of looking at this is that in approximately one tenth of years (approximately 1 year out of 10) with the current SOI pattern has Kingaroy received its long term median July to September rainfall.
Therefore in around nine tenths of years (9 years out of 10) with the current SOI pattern below median rainfall has been recorded at Kingaroy for July to September. For more information on the specific rainfall probabilities for your area refer to Australian Rainman.
If anyone requires more climate related information contact the DPI Call Centre on 13 25 23.
The full story
SOI "Consistently Negative" (Dated 02/07/02)
Based on the recent pattern of the SOI over May and June, there is only a 10-30% chance of receiving or getting above the long term median rainfall for July to September for most of Queensland. The only exception to these low rainfall probabilities is in one section of the north west of the state where the probability of getting above median rainfall is between 60-70%.
However it is important to remember that the long term median rainfall for July to September is quite low in this area (eg 9mm at Richmond). Therefore high rainfall totals are not required to get above median rainfall for that part of the state.
The monthly value of the SOI at the end of May was -13.8 and at the end of June was -6.8. Based on this shift in the value of the SOI over May and June, the SOI is now in a "Consistently Negative" Phase.
The outlook for later this year (eg. August to October) will depend on just how the currently changing ENSO pattern continues to develop. If the SOI remains negative we would expect these low rainfall probability values to continue.
It is essential to remember that when dealing with probabilities to also consider the additional information that probabilities provide. For example, based on the recent pattern of the SOI there is only a 9% chance of getting the long term July to September median rainfall of 96 mm at Kingaroy. Therefore there is a 91% chance of not getting the July to September median rainfall.
Another way of looking at this is that in approximately one tenth of years (approximately 1 year out of 10) with the current SOI pattern has Kingaroy received its long term median July to September rainfall.
Therefore in around nine tenths of years (9 years out of 10) with the current SOI pattern below median rainfall has been recorded at Kingaroy for July to September. For more information on the specific rainfall probabilities for your area refer to Australian Rainman.
For those who like to follow historical patterns more closely, years in the past that had a "Consistently Negative" SOI phase at the end of June include 1997, 1994, 1993, 1987, 1977, 1972, 1946, 1940, 1914, 1912, 1911 and 1905. What were the rainfall and/or farming conditions like for July to September in your area for those years?
The previous passage in mid-June of the 30-50day intra-seasonal oscillation (also known as the MJO) was evident with the rise of the 30day average of the SOI and some scattered rainfall events. The MJO is next expected to influence our weather in mid to late July.
The timing of this phenomenon can alter and it is worth remembering that it is an indicator as to the potential timing of rainfall events rather than an indicator as to potential rainfall amounts.
Recent sea surface and sub-surface temperature data sourced from both the Climate Prediction Centre in the United States www.cpc.ncep.noaa.gov/ and the Bureau of Meteorology www.bom.gov.au highlight 'warm' sea temperature anomalies in the Niño 3 and 4 regions of the equatorial Pacific.
It is believed that this 'warming' trend was enhanced by the recently recorded strong westerly wind burst activity in the same region. These westerly wind bursts were strengthened by the last MJO. It will be interesting to see if this 'warming' trend in the central Pacific develops into an El Nino SST pattern.
While El Nino SST patterns are usually associated with below average rainfall it should be remembered that for most of eastern Australia low rainfall probabilities often exist without the presence of an El Nino.
References to 'weak' or strong' El Niño events can be misleading as these refer to the magnitude of sea-surface temperature anomalies and not the impacts of an El Niño. For example, many of the sea temperature anomaly patterns observed in the Pacific during 1991 to 1994 were regarded as 'very weak' El Niño events yet the impact on Queensland rainfall was considerable. The current ENSO pattern is somewhat similar to what happened in 1993/1994.
Due to the increased likelihood of some type of El Nino event occurring it may be a suitable time for readers to consider what any repercussions and/or benefits an El Nino could mean to their businesses.
If anyone requires more climate related information contact the DPI Call Centre on 13 25 23. Alternatively try the DPI's climate web site www.dpi.qld.gov.au/climate on which the "Climate Note" can be found.
