SOI MESSAGE 25th October 2000
The average SOI over the previous 30 days remains ' strongly' positive at +11.8. For the first time in about two years rainfall probability values have risen to comparatively high levels over most of Queensland. The probabilities of getting or exceeding the long-term median rainfall during the total October-December period are now 60-80% in most regions in Queensland, except for parts of southern Qld and the far central-west where they remain comparatively low at about 50%.
Review of Climate Forecasts and Information
As mentioned in previous releases, the dry conditions experienced over much of Qld (especially southern areas) have been due to the sub-tropical high-pressure ridge tracking further north than usual this year. This pattern would not normally be expected to persist beyond spring, suggesting some easing of the dry conditions are possible by the end of November.
Climate pattern and SOI 'phase'. The latest SOI 'phase' analysis suggests reasonably high probabilities of exceeding the long-term median rainfall during the October-December period for many areas of Queensland. For example, the probabilities for most of eastern Qld are between 60% and 80%. Similarly, the probabilities for most inland parts of central and southern NSW are 60% to 70%. Note that a 70% probability of exceeding the long-term median for a location also means there is a 30% probability of not exceeding the median for that location. These probability values are simply statements of fact referring to the history of rainfall events for particular locations over the past 100 years.
In contrast, over parts of southern Qld (particularly from the western Maranoa westwards) and northern NSW the probabilities remain comparatively low at close to 50%.
Sea-surface temperatures. Sea-surface temperatures in the Pacific and Indian Oceans are generally close to 'average' at the moment, although there are patches of cooler-than-normal water in the far eastern equatorial Pacific. Some general circulation models are suggesting the potential for warming in the eastern equatorial Pacific Ocean over the next 6-9 months. We will watch the situation closely to determine any potential for El Niño development, or otherwise, in 2001. We suggest close monitoring of sea-surface temperature patterns over the next six months.
Pasture Growth forecasts. The probabilities of obtaining median pasture growth or better during the October to December period are 'above-average' over most of Qld. However notable exceptions are parts of the south-east of the State where the probabilities are only 10% to 30% due to poor soil moisture conditions.
30- to 50-Day Oscillation. The next passage of the 30- to 50-Day Oscillation over Qld is expected about the third week in November.