The Science Division of the Department of Science, Information Technology and Innovation (DSITI) considers that, for most of Queensland, there is an increased probability of below median summer (November to March 2015/16) rainfall. Read more (PDF, 352K, last updated 10:20AM, 13 November 2015)*
DSITI’s seasonal 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, 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 summer.
Associated with the current El Niño pattern, a strong SST gradient currently exists in the Pacific Ocean between eastern Australia and the central equatorial Pacific region. An index of this SST gradient (which is related to ENSO and Queensland summer rainfall), is incorporated in DSITI’s summer rainfall outlook.
Rainfall over the last six-month period (May to October) has been extremely low (less than the 10th percentile) across most of central, and parts of western, Queensland. However, for the same period, close to average rainfall has occurred in southern and southern-eastern parts of the state.
Currently, 80 per cent of Queensland remains drought declared under state government processes. The high probability of the current El Niño event continuing further over summer 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, DSITI’s outlook for summer rainfall (opposite page) should be taken into consideration.
Based on previous years when the SOI has been in a ‘Consistently Negative’ phase at the end of October, the probability of rainfall being above median for the next three-month period (November to January) is less than 30 per cent for most northern and eastern parts of Queensland (see map below). However, for most western and some southern parts of the state the probability of above median November to January rainfall is marginally higher (30 to 60 per cent).
DSITI scientists have shown that extra-tropical SST anomalies, when measured in specific regions of the Pacific Ocean in March each year, provide a useful basis for long-lead forecasting of summer (November to March) rainfall in Queensland. The accuracy of this outlook increases as the evolving ENSO-related SST pattern is also taken into account from May through to October. 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 DSITI scientists for over a decade.
As at 1 November 2015, DSITI’s final outlook for summer (November to March 2015/16) continues to indicate a lower than normal probability of exceeding median rainfall for most of Queensland, based on the evolving sea surface temperature pattern across the Pacific. The outlook for summer rainfall, which has been consistent since June this year, is closely related to the SST gradient across the South West Pacific Ocean measured in October, and is indicative of the current strong El Niño event.
It should be noted that:
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