Seasonal Climate Outlook Message for August to November 2002
The bottom line
OUTLOOK REMAINS CAUSE FOR CONCERN (DATED 06/08/02)
The seasonal outlook remains a cause for concern. Based on the recent pattern of the SOI, the probability of receiving or getting above the long term median rainfall for August to October remains relatively low (30-50%) across most of Queensland.
Currently an El Nino SST pattern exists in the central Pacific Ocean. Normally this type of pattern once developed will last until the following autumn before breaking down.
Therefore at this stage, rainfall probabilities based on the SOI would be expected to remain relatively low until early to mid summer. Rainfall probabilities would then usually rise marginally due to increasing storm activity. However, as most readers would be aware storm activity is usually patchy and may provide limited relief rain only.
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.
For those who like to follow historical patterns more closely some of the years in the past that had a "consistently Near Zero" SOI Phase at the end of July include 2001, 2000, 1991, 1990, 1983, 1980, 1978, 1971, 1969, 1967, 1966 and 1962. What were the rainfall and/or farming conditions like for August to October in your area for those years?
The full story
OUTLOOK REMAINS CAUSE FOR CONCERN (Dated 06/08/02)
The seasonal outlook remains a cause for concern. Based on the recent pattern of the SOI, the probability of receiving or getting above the long term median rainfall for August to October remains relatively low (30-50%) across most of Queensland.
As always, when dealing with probabilities it is essential to consider the additional information that probabilities provide. For example based on the recent pattern of the SOI there is only a 32% chance of getting the long term August to October median rainfall of 36mm at Charters Towers. Therefore there is a 68% chance of not getting the long term August to October median rainfall.
Another way of looking at this is that in approximately one third of years (3 years out of 10) with the current SOI pattern has Charters Towers received its long term median August to October rainfall. Therefore in around two thirds of years (7 years out of 10) with the current SOI pattern below median rainfall has been recorded at Charters Towers for August to October.
It is also worth taking into account that August and September are historically the two driest months across most of Queensland.
For the specific rainfall probabilities for your location refer to Australian Rainman.
The monthly value of the SOI for June was -6.8 and July was -7.1. Based on this shift in value over June and July the SOI is now in a "Consistently Near Zero" phase.
Currently an El Nino SST pattern exists in the central Pacific Ocean. Normally this type of pattern once developed will last until the following autumn before breaking down.
Therefore, at this stage rainfall probabilities are expected to remain relatively low until early to mid summer. Rainfall probabilities may then rise marginally due to increasing storm activity in mid to late summer. However, as most readers would be aware, storm activity is generally patchy and may provide limited relief rain only.
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.
It is worth noting that each El Nino event is unique with respect to rainfall patterns and areas affected by dry conditions. The Bureau of Meteorology has an interesting site www.bom.gov.au/climate/ahead that provides a good summary of the rainfall patterns that have occurred in previous El Nino years.
For those who like to follow historical patterns more closely some of the years in the past that had a "consistently Near Zero" SOI Phase at the end of July include 2001, 2000, 1991, 1990, 1983, 1980, 1978, 1971, 1969, 1967, 1966 and 1962. What were the rainfall and/or farming conditions like for August to October in your area for those years?
Unfortunately the previous passage of the 30-50day intra-seasonal oscillation (also known as the MJO) did not help induce any significant rainfall events across Queensland. It is next expected to influence our weather in mid to late August.
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 especially across southern and central Queensland. Given the overall dry conditions that have existed for most of the year across Queensland, many producers will be waiting to see if the next passage of this phenomenon helps create some state-wide relief rainfall.
Our strong advice as always remains to closely monitor SOI trends and sea surface temperature patterns. As an El Nino event is occurring we encourage readers to consider what any repercussions and/or benefits an El Nino could mean to their businesses.
For more information contact the DPI Call Centre on 13 25 23. Alternatively try the DPI climate web site www.dpi.qld.gov.au/climate on which the 'Climate Note" can be found.
