Seasonal Climate Outlook Message for January to April 2002

The bottom line

Dated 4th January 2002

The monthly value of the Southern Oscillation Index (SOI) has fallen from +8.9 at the end of November to -11.19 at the end of December. Based on this shift in the monthly value of the SOI over November/December, the SOI is now in a 'Rapidly Falling' phase. This shift in value continues the roller coaster ride the SOI has been on for most of 2001.

Despite the fall in the monthly SOI value, rainfall probabilities for the rest of the state remain relatively high for the time being, especially across western and central Queensland.

The down side of this rapid drop in monthly SOI values is that rainfall probabilities for the January to March period have fallen once again across south east Queensland. This area includes the eastern Darling Downs and Burnett regions.

Given this drop in the value of the SOI and the potential development of an El Niño sometime around autumn 2002, we recommend viewers keep track of the sea surface temperature patterns and any shifts in the monthly value of the SOI over the next few months.

The 30day average of the SOI as of the 4th January 2002 is -9.8.

The full story

SOI In 'Rapidly Falling' Phase (Dated 04/01/02)

The monthly value of the Southern Oscillation Index (SOI) has fallen from +8.9 at the end of November to -11.19 at the end of December. Based on this shift in the monthly value of the SOI over November/December, the SOI is now in a 'Rapidly Falling' phase. This shift in value continues the roller coaster ride the SOI has been on for most of 2001.

Despite the fall in monthly SOI value, rainfall probabilities for a large part of the state remain relatively high for the time being, especially across western and central Queensland.

Regions of the state that have relatively high probabilities (60% to 90%) of getting above median rainfall for January to March include a strip running from Cairns, Douglas and Cook shires through to Carpentaria shire and from Bourke and the western half of Dalrymple shires through to the Barcoo, Quilpie and Bulloo shires in the south west of the state.

Other areas of relatively high rainfall probabilities also exist in the Paroo, Murweh, Mitchell, Balonne, Waroo, Bungil and Yuleba shires. An increase in rainfall probabilities (to 60-70%) in the Broadsound and eastern half of the Belyando shires indicate the potential for some relief rain for these dry areas.

The down side of this rapid drop in monthly SOI values is that rainfall probabilities for the January to March period have fallen once again across south east Queensland. This area includes the eastern Darling Downs and Burnett regions. A large part of this area suffered a remarkably dry winter in 2001.

For those who like to follow historical patterns more closely years in the past that had a "Rapidly Falling" SOI phase in November/December include 1908, 1912, 1918, 1934, 1935, 1940, 1943, 1948, 1952, 1972, 1976, 1991 and 1995. What was the rainfall like for January to March in your area following those years? Maps of the rainfall in those years can be found at the 'Long Paddock' internet site www.nrm.qld.gov.au/longpdk

The 30-50 day oscillation is next expected to influence our atmosphere in the third week of January. 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.

Most oceanic and atmospheric models continue to reflect ENSO-neutral conditions in the short term. However, there are indications of a slow evolution towards a 'warm' (El Niño like) episode. Since mid 2001 sea surface temperatures have been slowly warming in the central equatorial Pacific ocean. During the same period, subsurface temperatures have also warmed in the same region. This pattern has previously been observed prior to the onset of past 'warm' or El Niño episodes.

Also of interest in the longer term is information that has been sourced from the United States Climate Prediction Centre at www.cpc.ncep.noaa.gov/ During mid-October significant westerly wind bursts were recorded over the western equatorial Pacific ocean. Strong westerly wind bursts in that region have in the past assisted in the development of the necessary pre-conditions required for an El Niño event.

It will be interesting to see to if the warming in the central Pacific reaches El Niño proportions in autumn 2002 and what impact, if any, the recently recorded westerly wind bursts will have.

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. The climate note contains more detailed information including rainfall probability maps, SST information, world forecasts and detailed regional rainfall probabilities etc. A recorded message with the 30day average of the SOI is also available on 46881439.