Tropical Climate Update

Northern Australia wet season highlights

The official end of Australia's northern wet season was 30 April. The dry season, which continues until the end of September, is a period of low rainfall and cooler conditions across tropical Australia, with a greatly reduced likelihood of tropical cyclone activity across the broader north Australian region.

Tropical cyclone (TC) activity was below the long-term average (since 1970–71) of 11 cyclones per season, and the more recent (since 2000–01) average number of 9 cyclones per season. The 2022–23 season total of 7 was the lowest since 2015–16, when only 3 TC were observed: the lowest count on record. Since 1970–71, only 9 other seasons have observed 7 or fewer total TC. While lower in number overall, the 2022–23 season had a higher number of stronger systems, with 5 out of the 7 TCs becoming severe tropical cyclones (category 3 or greater), and 3 systems reaching category 5 intensity (the highest intensity rating), the first time this many were recorded since season 2005–06. The highest seasonal number of category 5 TC observed in the Australian region, since accurate records commenced in the 1970s, was 4—last observed in season 1999–2000. When TC Ilsa crossed the Pilbara coast of Western Australia (WA) in April, it was the first category 5 system to make landfall in Australia since 2015, and the first for WA since 2009.

The wet season of 2022–23 was characterised by high rainfall and moderate to low temperatures. Averaged across northern Australia (north of 26°S, which is the NT–SA border), rainfall was 47% above the long-term average; this was the highest wet season total since 2010–11 and the sixth-highest on record. The averaged maximum temperature was 0.25 °C below the 1961–90 average, while the minimum temperature was 0.31 °C above the long-term average (both were the lowest since 2011–12).

Madden–Julian Oscillation to the north of Australia

A pulse of the Madden–Julian Oscillation (MJO) recently strengthened and moved into the Maritime Continent region, to the north of Australia. While this location typically favours above-average cloudiness and rainfall for the Australian tropics during the wet season, the MJO's influence on northern Australia reduces markedly at this time of the year. While parts of north-eastern Australia have a marginally increased likelihood of above-average rainfall, the MJO is expected to have little to no influence on most of northern Australia. However, the likelihood of above-average rainfall is increased for near-equatorial regions to the north of Australia in the coming fortnight, along with an increased tropical cyclone risk for the Bay of Bengal and the western North Pacific Ocean.

Read more about the Madden–Julian Oscillation and Climate Driver Update

Tropical activity focus continues to drift north

As dry season conditions become further established over northern Australia, seasonal changes act to shift the focus of tropical weather further north. In the coming month, monsoonal conditions are likely to develop close to the Indian subcontinent, in the lead-up to its annual wet season. Another significant change will be the increase in tropical cyclone activity over the western North Pacific Ocean, which typically has its peak period between July and October.