Tropical Climate Update

Rare severe tropical cyclone hits central Western Australia coastline

One of the most intense tropical cyclones to impact Western Australia's central coast made landfall just south of Kalbarri on the evening of 11 April. Severe tropical cyclone Seroja made landfall at category 3 strength, generating wind gusts up to 170 km/h near Kalbarri. Seroja was the southern-most severe tropical cyclone (category 3 or higher) to cross the Western Australia coast in the satellite era (approximately from the early 1970s). Seroja experienced what is known as the Fujiwhara Effect, which is a phenomenon where two tropical lows in close proximity interact with each other. Seroja passed close to another tropical low (which briefly developed into tropical cyclone Odette), and this interaction contributed to Seroja taking a track that was more southerly than what it otherwise would have been. Additionally, very warm sea surface temperatures off Western Australia's west coast persist in the region (associated with the La Niña of 2020–21), helping Seroja maintain its strength as it moved further south.

Locations south of Kalbarri, including Geraldton and Northampton, observed wind gusts of 120-140 km/h. Widespread damage was reported around Kalbarri, with homes destroyed and power outages. Because Seroja was moving very rapidly along its south-easterly track, rainfall totals were relatively modest, although a reading of 166.8 mm was observed near Kalbarri.

Another tropical cyclone also developed off the Western Australian coast during the past week. Tropical cyclone Odette became the 8^th tropical cyclone of the season when it formed on 9 April. Odette was short-lived, however, and had no influence on the WA coast after it interacted with and was 'absorbed' by Seroja.

Read more about tropical cyclone information and outlooks

Madden–Julian Oscillation moves into Western Pacific

A pulse of the Madden–Julian Oscillation (MJO) which tracked eastwards across the Maritime Continent to Australia's north, and contributed to the recent tropical cyclone activity, moved into the Western Pacific region. At this time of the year, as an MJO pulse moves across the tropical Western Pacific, its influence on rainfall patterns over northern Australia move from an enhancing effect to a suppressing effect. Based on current climate model forecasts, the MJO's location in the coming days will increase the likelihood of below average rain for much of northern Australia.

As the MJO moves away from the Australian region in the coming week, the risk of tropical low and tropical cyclone development becomes low.

Read more about the Madden–Julian Oscillation

Widespread rainfall across northern Australia unlikely for remainder of April

As the influence of the Madden–Julian Oscillation and other short-term tropical climate drivers lessens, the chance of above-average rainfall across northern Australia decreases markedly for the remainder of the northern Australian wet season (October–April). While some parts of northern Australia with east-facing coastlines may see significant rainfall for the next month or so, the remainder of northern Australia looks to be entering a sustained dry period.