Monthly Climate Statement for January 2024
The Department of Environment, Science and Innovation (DESI) monitors sea-surface temperature (SST) anomalies in key regions of the Pacific Ocean over autumn, winter and spring and provides objective outlooks for summer (November to March) rainfall on this basis. Based on the evolving SST pattern in the Pacific Ocean leading up to summer, the Science Division of DESI considered that the probability of exceeding median summer (November to March) rainfall was lower than normal for much of Queensland.
The most closely monitored driver of Queensland rainfall is the El Niño-Southern Oscillation (ENSO) phenomenon. Climate scientists monitor several ENSO indices, including the atmospheric Southern Oscillation Index (SOI) and SST anomalies in the central equatorial Pacific Ocean.
The average SST* anomaly in the central equatorial Pacific over the last three-month period (October to December) is +1.8°C, which falls well within the ‘El Niño’ range (>+0.5°C as recognised by DESI). The average value of the SOI** over the last three-month period is -6.3, which also falls well within the ‘El Niño’ range (<-5.0 as recognised by DESI). International climate models indicate that the current El Niño pattern is likely to persist through summer and weaken over autumn.
Sea-surface temperature anomalies in the central equatorial Pacific tend to ‘lock in’ over the winter, spring and summer seasons, and this persistence provides a basis for seasonal forecasting. The DESI outlook for summer rainfall in Queensland, issued at the beginning of November, is based on an objective analysis of SST anomalies measured in key regions of the Pacific Ocean, including those regions related to ENSO. On this basis, the Science Division of DESI considered that the probability of exceeding median summer (November to March) rainfall was less than 30 per cent for much of Queensland (see map in PDF).
The northern Australian wet season extends from October to April. By the end of December, parts of tropical north Queensland had received record high rainfall for the October to December part of the season (see map in PDF), due to the impact of tropical cyclone Jasper. Whilst rainfall over the October to December period was also well-above-average in parts of central and southern Queensland, the distribution of above-average wet season rainfall has been patchy so far.
Tropical cyclone Jasper formed near the Solomon Islands on 5 December and made landfall near Wujal Wujal, south of Cooktown, on 13 December - a period when the Madden Julian Oscillation (MJO) was active in Australian longitudes. Associated high rainfall occurred over several days on the tropical east coast between Cape Melville and Ingham. Under ‘El Niño’ conditions, a landfalling tropical cyclone is a rare occurrence in Queensland that early during the tropical cyclone season, which lasts from 1 November to 30 April. The MJO is currently (as at 22 January) active again in Australian longitudes, enhancing the northern Australian monsoon.
Readers are reminded that seasonal outlooks are expressed in terms of probabilities. The probabilities shown on the rainfall outlook map are based on an objective analysis of historical data and show the summer rainfall outcome in years when SST conditions were closest to the current year. An analysis may, for example, indicate that below-median summer rainfall occurred in most of those years. However, this also means that summer rainfall was at, or above, the long-term median in some of those years. Therefore, an outlook which states that there is ‘an 80 per cent probability of below-median rainfall’ should also be interpreted as there being ‘a 20 per cent probability of median or above-median rainfall’.
For more information, please contact Stuart Burgess at: stuart.burgess@des.qld.gov.au
* www.cpc.ncep.noaa.gov/data/indices (monthly OISST.v2.1 NINO3.4 1991-2020 base period)
** www.longpaddock.qld.gov.au/soi/soi-data-files (monthly SOI 1887-1989 base period)
