Forecast

Issue Notes - Issued Apr 2

ENSO status: El Niño, breaking down. IOD status: Neutral. SAM status: Positive, trending slightly positive. The El Niño Southern Oscillation (ENSO) is in an El Niño and is breaking down. All international models indicate neutral conditions should return by late April or early May. The Southern Oscillation Index (SOI) is varying significantly with tropical activity over Australia and the Pacific. Waters in the Coral Sea are far warmer than normal, especially for an El Niño, and are offsetting the effects of this event. El Niño only has a small effect during autumn, typically increasing rainfall over the Nullarbor and SA, but having little effect elsewhere. The Indian Ocean Dipole (IOD) is in a neutral phase. Ocean temperatures are high across most of the Indian Ocean. The IOD index is spiking in response to hot waters near Africa, more-so than the average temperatures near Indonesia and WA. The IOD has little to no effect during autumn. The Southern Annular Mode (SAM) is positive and will slightlyfavour a positive phase during April and May, and possibly into winter. A positive SAM increases easterly winds, increasing rainfall and thunderstorm activity in the east. As we go closer to winter, a positive SAM also reduces cold fronts and rainfall over southern Australia. The reverse occurs with a positive SAM, with more frequent cold fronts crossing the south. Rainfall outlooks are predicting average rainfall for the vast majority of Australia throughout autumn. There are some weak signals that southwest WA could be slightly drier than normal in April, and eastern Qld and northeast NSW could be slightly wetter during May, but otherwise near average.