Tropical Climate Note

Widespread rainfall expected for north-eastern Australia in coming week

While the influence of the Madden–Julian Oscillation currently favours below-average rainfall broadly across northern Australia, a more localised influence is expected to lead to continued widespread heavy rain across parts of Australia's north-east during much of the next fortnight. A slow-moving weather pattern, with a strengthening high-pressure ridge across southern Australia, is expected to dominate the Australian region for at least the next week. This pattern will see a moist onshore flow directed onto Australia's tropical east coast, with high rainfall totals likely. Rainfall totals in the region are likely to be enhanced due to locally high sea surface temperatures in the Coral Sea. Along with Queensland's tropical north-east, parts of eastern Arnhem Land in the Northern Territory may experience periods of above-average rainfall.

Apart from tropical north-east Queensland and the far north-east of the Northern Territory, northern Australia is likely to see dry conditions in the coming fortnight. From 1 May, Australia's dry season officially commences across the tropical north. Low rainfall totals are typically a feature of northern Australia during the dry season months of May to October, although some east-facing coastlines, particularly along Queensland's tropical east coast, receive significant rainfall at times due to onshore winds which can direct available moisture onto near-coastal locations.

Madden–Julian Oscillation approaches tropical Americas

A moderate to strong pulse of the Madden–Julian Oscillation (MJO) has tracked eastwards across the Pacific Ocean during the past week and is expected to approach American longitudes in the coming days. Current climate forecasts indicate this pulse will maintain a similar strength as it moves further east towards Africa in the following week. At this time of the year, an MJO pulse near tropical America or Africa typically acts to suppress rainfall across northern Australia and the Maritime Continent.

Read more about the Madden–Julian Oscillation

First typhoon of 2021 forms over western North Pacific Ocean

Typhoon Surigae (Bising), currently located to the east of the Philippines, is the first typhoon for 2021 and the strongest April typhoon on record. Typhoons in April are relatively uncommon, but Surigae is most notable for its intensity. It peaked at the equivalent intensity of an Australian category 5 storm, with peak mean winds estimated at 215 km/h and peak gusts of 295 km/h.  

Surigae (Bising) is currently located just east of Luzon (northern Philippines) but is not expected to make landfall on the island group. Over the next few days, Surigae is forecast to gradually weaken and track to the northeast, remaining over open waters, well south of Japan.

Tropical cyclone warnings and information for western North Pacific region