Pacific and Indian oceans likely to remain neutral this winter, but tropical Pacific Ocean warming
VFF update Thursday 7 June 2018
Two of Victoria's major climate drivers, the El Niño–Southern Oscillation (ENSO) and the Indian Ocean Dipole (IOD) are currently neutral, meaning they are unlikely to have a strong influence on winter rainfall.
ENSO is currently neutral, but the tropical Pacific is slowly warming, and climate models suggest the trend will continue in the coming months. The amount of forecast warming varies, with some models indicating temperatures close to the long-term average, but three of the eight models exceed El Niño thresholds in October.
Figure 1 showing three models exceed El Niño thresholds in October in the central Pacific Ocean (NINO3.4). Model outlooks provided by: BoM (Bureau of Meteorology), CanSIPS (Canadian Seasonal to Interannual Prediction System), ECMWF (European Centre for Medium-Range Weather Forecasts), JMA (Japan Meteorological Agency), Météo France, NASA (National Aeronautics and Space Administration), NOAA (National Oceanic and Atmospheric Administration), and the UKMO (United Kingdom Met Office).
The IOD is currently neutral and all six of the international models surveyed by the Bureau forecast the IOD will remain so over winter. Beyond winter, one model predicts a negative IOD in October.
Figure 2 showing most international model outlooks for the IOD sea surface temperature index remain neutral in October. Model outlooks provided by: BoM (Bureau of Meteorology), CanSIPS (Canadian Seasonal to Interannual Prediction System), ECMWF (European Centre for Medium-Range Weather Forecasts), Météo France, NASA (National Aeronautics and Space Administration), and the UKMO (United Kingdom Met Office).
When the IOD and ENSO are neutral, other climate drivers can have a greater influence on Australian rainfall and temperature patterns. Also, long-term trends, such as the drying during the cool season (April-October) in southern Australia, and the increasing global atmospheric and ocean temperatures, can be more obvious without a contribution from IOD or ENSO events.
Read the ENSO Wrap-Up for more details about the current state of the Pacific and Indian Oceans.
See the Climate Model Summary for a comparison of the international model forecasts for June and August.