MELBOURNE, Australia – Oceanic and atmospheric indicators reflect a mature La Niña with little variation over last fortnight, according to BOM’s Enso Outlook. Model outlooks suggest the event will peak at moderate levels during December, returning to a neutral phase during the late summer or autumn. The Southern Annular Mode (SAM) is expected to increase to strongly positive values over the coming week.
This is driven in part by the La Niña influence, and in part by a stronger than average polar vortex over Antarctica. Positive values are expected at least into early 2021, and typically increase the chance of rainfall in eastern Australia.
The Madden–Julian Oscillation (MJO) is relatively weak, and is currently over the Maritime Continent (Indonesia). It is forecast to move east and across Australian longitudes over the next fortnight. The MJO, in conjunction with other tropical influences, is looking favourable for monsoon onset and producing above-average rainfall over northern Australia.
Climate change is also influencing the Australian climate. Rainfall across northern Australia during its wet season (October–April) has increased since the late 1990’s, with a greater proportion of high intensity short duration rainfall events.
Climate outlooks, which include all climate drivers, indicate rainfall during December 2020 is likely to be above average over most of northern Australia while for January to March 2021, rainfall is likely to be above average for most of the northeastern half of the country.
