Seasonal Climate Outlook Message for February to May 2002
The bottom line
SOI pattern continues to give mixed outlook. (Dated 04/02/02)
The monthly value of the Southern Oscillation Index (SOI) has risen from -11.2 at the end of December to +2.5 at the end of January. Based on this shift in the monthly value of the SOI over December/January, the SOI is now in a 'Rapidly Rising' phase. This shift in value continues the roller coaster ride the SOI has been on for most of the last 10-12 months.
The recent pattern of the SOI indicates the probability of above median rainfall for February to April will remain relatively positive (50-70%) for the strip running from Burke shire to the western side of Murweh shire for the time being (refer to map).
However, despite the rise in monthly SOI values over December to January, the probability of above median rainfall for February to April is relatively low (30-50%) for the far south west and most of the eastern half of the state. This area includes most of the north, central, south and south east of the state.
Given the recent publicity in the media about the potential development of an El Niño around autumn 2002 it must be stressed that it is still early days, especially given the volatility of climate patterns over autumn.
Our advice is to closely monitor information on SOI trends and sea surface temperature patterns over the next few months as some of the necessary pre-conditions required for the onset of an El Niño later this year are currently present.
The full story
SOI pattern continues to give mixed outlook. (Dated 04/02/02)
The monthly value of the Southern Oscillation Index (SOI) has risen from -11.2 at the end of December to +2.5 at the end of January. Based on this shift in the monthly value of the SOI over December/January, the SOI is now in a 'Rapidly Rising' phase. This shift in value continues the roller coaster ride the SOI has been on for most of the last 10-12 months.
The recent pattern of the SOI indicates the probability of above median rainfall for February to April will remain relatively positive (50-70%) for the strip running from Burke shire to the western side of Murweh shire for the time being (refer to map).
However, despite the rise in monthly SOI values over December to January, the probability of above median rainfall for February to April is relatively low (30-50%) for the far south west and most of the eastern half of the state. This area includes most of the north, central, south and south east of the state.
It is essential to remember that when dealing with probabilities the opposite always applies. For example there is only a low 35% chance of getting above the long term February to April median rainfall of 174 mm at Durong. Therefore there is a 65% chance of getting below the February to April median rainfall. Another way of looking at this is that in approximately one third of years with the current SOI pattern has above median February to April rainfall been recorded at Durong. Therefore at Durong in around two thirds of years with the current SOI pattern below median rainfall has been recorded for February to April.
For those who like to follow historical patterns more closely years in the past that had a "Rapidly Rising" SOI phase in December/January include 1996, 1986, 1982, 1980, 1977, 1968, 1967, 1963, 1954, 1953, 1940, 1937, 1935, 1931, 1930, 1920, 1902 and 1901. What was the rainfall like for January to March in your area for those years?
The 30-50 day oscillation is currently influencing our atmosphere. The timing of this phenomenon slowed considerably over January with its influence only becoming apparent across northern Australia over the last week. It is next expected in early/mid March. Although strictly speaking it is a tropical phenomenon, it also appears to influence the timing of rainfall events over southern and central parts of Queensland rather than the actual amount of rain.
Given the recent publicity in the media about the potential development of an El Niño around autumn 2002 it must be stressed that it is still early days, especially given the volatility of climate patterns over autumn.
Our advice is to closely monitor information on SOI trends and sea surface temperature patterns over the next few months as some of the necessary pre-conditions required for the onset of an El Niño later this year are currently present. We will continue to provide updated information on the likelihood of this occurring over the next 6 months.
It should also be noted that we do not have to have a 'classic' or 'strong' El Niño event to reduce rainfall in some parts of Queensland. 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 a classic El Niño in existence.
If anyone requires more climate related information contact the DPI Call Centre on 13 25 23.
