The Science Division of the Department of Science, Information Technology, Innovation and the Arts (DSITIA) considers that the probability of exceeding median rainfall during spring (September to November) is slightly below average for most of Queensland, whereas the probability of average to well-below average summer (November to March) rainfall remains higher than normal for much of the state. Read more (PDF, 284K, last updated 08:59AM, 16 September 2014)*
DSITIA’s rainfall outlooks for Queensland are based on the current and projected state of the El Niño–Southern Oscillation (ENSO) phenomenon and on factors which alter the impact of ENSO on Queensland rainfall (i.e. the more slowly changing extra-tropical sea surface temperature (SST) pattern in the Pacific Ocean).
At this time of year, and in the coming months, the prevailing ENSO pattern (as measured by indices such as the Southern Oscillation Index (SOI) or central equatorial Pacific Ocean SST anomalies) offers a useful basis for providing seasonal outlooks for spring and summer.
Although sea surface temperatures in the central equatorial Pacific remain below El Niño thresholds, the SOI, the key atmospheric measure of ENSO, fell to an extremely negative monthly value (-10.1) in August.
What if an El Niño event develops this year?
More than 75 per cent of Queensland remains drought declared under state government processes, including most inland regions and all of south-eastern Queensland. The possibility of an El Niño event developing, and with it the threat of another dry summer for some regions, poses a risk of current drought conditions becoming more protracted. This risk should be factored into decision- making and allocation of resources. In this context, DSITIA’s long-lead outlook for summer rainfall (next page) should be taken into consideration.
Outlook for summer rainfall
DSITIA scientists have shown that extra-tropical SST anomalies, when measured in specific regions of the Pacific Ocean in March, provide a useful basis for long-lead forecasting of summer rainfall in Queensland. This outlook can be modified, with increasing accuracy, as the monthly ENSO-related SST pattern is also taken into account from June to November.
This understanding has been incorporated in an experimental system known as SPOTA-1 (Seasonal Pacific Ocean Temperature Analysis version 1), which has been operationally evaluated by DSITIA scientists for over a decade.
Currently, DSITIA’s long-lead outlook for summer rainfall indicates a higher than normal probability of below-median rainfall for most of Queensland over the coming summer (November to March 2014/15) and, conversely, a low probability of widespread drought-breaking rainfall. This outlook will be updated monthly until November, with accuracy increasing each month.
In summary, it should be noted that:
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