Seasonal Climate Outlook Message for March to June 2002

The bottom line

Low rainfall probabilities for south and south east continue (Dated 05/03/02. Next Update 13/03/02.)

Despite the continued rise in the Southern Oscillation Index (SOI) over the last 2 months, the probability of above median rainfall for the March to May period across most of the south and south east of Queensland remains relatively low (refer to map).

For the area bordered by the Miriam Vale, Taroom, Murilla, Rosalie, Jondaryan and Boonah shires there is only a low 30-40% probability of getting above the long term March to May median rainfall. Relatively low rainfall probabilities of only 40-50% also exist for most of the remaining regions of southern and south eastern Queensland. This area of lower rainfall probabilities extends into western Queensland and includes parts of the Winton and Boulia shires.

Across the north of the state however, the probability of getting above median rainfall for March to May, is higher at around 50-80% depending on location.

It is essential to remember that when dealing with probabilities the opposite also applies. For example there is only a low 36% chance of getting above the long term March to May median rainfall of 145 mm at Proston in the Burnett region of south eastern Queensland. Therefore there is a 64% chance of getting below the March to May median rainfall.

Another way of looking at this is that in approximately one third of years (approximately 3 to 4 years out of 10) with the current SOI pattern has above median March to May rainfall been recorded at Proston. Therefore in around two thirds of years (6-7 years out of 10) with the current SOI pattern below median rainfall has been recorded for March to May.

The monthly value of the SOI rose from +2.5 at the end of January to +7.1 at the end of February. Based on this shift in the monthly value of the SOI over January/February, the SOI is now in a 'Rapidly Rising' phase.

The 30-50 day oscillation influence was last apparent in the first and second week of February. It is next expected around mid to late March. It is important to remember that while it is a tropical phenomenon it also appears to influence the potential timing of rainfall events across central and southern Queensland (rather than the actual amount of rain).

For those who like to follow historical patterns more closely years in the past that had a "Rapidly Rising" SOI phase in March to May include 2000, 1997, 1985, 1984, 1978, 1977, 1975, 1971, 1968, 1965, 1961, 1955, 1950, 1949, 1946, and 1944. What was the rainfall like for March to May in your area for those years? Maps of the rainfall in those years can be found at the 'Long Paddock' internet site www.nrm.qld.gov.au/longpdk or in Australian Rainman.

If anyone requires more climate related information contact the DPI Call Centre on 13 25 23.

The full story

Low rainfall probabilities for south and south east continue (Dated 05/03/02)

Despite the continued rise in the Southern Oscillation Index (SOI) over the last 2 months, the probability of above median rainfall for the March to May period across most of the south and south east of Queensland remains relatively low (refer to map).

For the area bordered by the Miriam Vale, Taroom, Murilla, Rosalie, Jondaryan and Boonah shires there is only a low 30-40% probability of getting above the long term March to May median rainfall. Relatively low rainfall probabilities of only 40-50% also exist for most of the remaining regions of southern and south eastern Queensland. This area of lower rainfall probabilities extends into western Queensland and includes parts of the Winton and Boulia shires.

Across the north of the state however, the probability of getting above median rainfall for March to May, is higher at around 50-80% depending on location.

It is essential to remember that when dealing with probabilities the opposite also applies. For example there is only a low 36% chance of getting above the long term March to May median rainfall of 145 mm at Proston in the Burnett region of south eastern Queensland. Therefore there is a 64% chance of getting below the March to May median rainfall.

Another way of looking at this is that in approximately one third of years (approximately 3 to 4 years out of 10) with the current SOI pattern has above median March to May rainfall been recorded at Proston. Therefore in around two thirds of years (6-7 years out of 10) with the current SOI pattern below median rainfall has been recorded for March to May.

The monthly value of the SOI rose from +2.5 at the end of January to +7.1 at the end of February. Based on this shift in the monthly value of the SOI over January/February, the SOI is now in a 'Rapidly Rising' phase.

The 30-50 day oscillation influence was last apparent in the first and second week of February. It is next expected around mid to late March. It is important to remember that while it is a tropical phenomenon it also appears to influence the potential timing of rainfall events across central and southern Queensland (rather than the actual amount of rain).

For those who like to follow historical patterns more closely years in the past that had a "Rapidly Rising" SOI phase in March to May include 2000, 1997, 1985, 1984, 1978, 1977, 1975, 1971, 1968, 1965, 1961, 1955, 1950, 1949, 1946, and 1944. What was the rainfall like for March to May in your area for those years? Maps of the rainfall in those years can be found at the 'Long Paddock' internet site www.nrm.qld.gov.au/longpdk or in Australian Rainman.

There is evidence that the impetus for an El Niño event later this year continues to strengthen. Much of this evidence is based on sub-surface sea temperatures and the recent re-occurrence of strong westerly wind bursts in the equatorial Pacific Ocean.

The Climate Prediction Centre in the United States has a very useful internet site at www.cpc.ncep.noaa.gov/ for monitoring sea temperature and westerly wind burst patterns in the Pacific. Information from this site indicates that warmer than normal sub-surface water has continued to expand eastward over the last month. It will be interesting to see to what extent this warming continues to and what ramification this will have on Queenslands expected rainfall.

However more definitive information will not be available until later in autumn due to the variability that exists in equatorial patterns, especially sea surface temperature patterns over the next few months.

As we are concerned about the likelihood of this occurring we will continue to monitor the situation and provide updated information regularly. Our strong advice therefore is to closely monitor information on SOI trends and sea surface temperature patterns. A dramatic drop in SOI values between March and May would, for example, further substantiate the potential for reduced rainfall in many districts.

Readers should also be aware of comments in the general media such as "strong" or "weak" when used to describe El Niño or La Niña events. This refers to the level of intensity of sea surface temperature patterns rather than the impact on expected rainfall.

It is worth remembering that in Queensland and much of eastern Australia a 'classic' El Niño event is not needed to reduce rainfall. A warmer than normal sea-surface temperature pattern in the central equatorial Pacific (and coexisting negative SOI pattern) can form and negatively influence our rainfall patterns without there being an El Niño in existence.

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. A recorded message with the 30day average of the SOI is also available on 46881439.