Tropical Climate Update

Two severe tropical cyclones in Australian region

During the past week two severe (category 3 or stronger) tropical cyclones impacted parts of northern Australia. Tropical cyclone Trevor first made landfall on the Cape York Peninsula in northern Queensland on 19 March as a category 3 storm, causing extensive vegetation damage and some damage to buildings. More than 300 mm of rain fell in 24 hours at Lockhart River, near the landfall site. Trevor then moved over the Gulf of Carpentaria, making a second landfall east of Boroloola, in the Northern Territory, as a category 4 system on Saturday 23 March. Gales were recorded at Boroloola for several hours while a wind gust of 139 km/h was recorded at nearby Centre Island, the highest gust associated with the Northern Territory landfall of Trevor. Peak 24-hour rainfall for the Northern Territory was 150 mm near the McArthur River Mine station. The low which was formerly Trevor tracked across a large section of the eastern Northern Territory, bringing significant rainfall to areas that were experiencing low wet season rainfall. The low is expected to maintain its structure and move further into eastern Australia, potentially generating widespread rainfall in parts of Queensland in the next few days.

In Western Australia, tropical cyclone Veronica became very slow moving as it approached the Pilbara coast between Port Hedland and Roebourne on 24 March. Despite not crossing the coast, Veronica steadily weakened from its peak intensity of category 4 as atmospheric conditions became less favourable. Due to its slow movement, locations near the cyclone's centre experienced gale force winds for many hours, including Roebourne, which endured gales for over 30 hours. The peak wind gust recorded was 158 km/h at Legendre Island, on the Dampier Archipelago. Several sites in the Pilbara district recorded 24-hour rainfall totals of more than 200 mm, with a peak daily rainfall of 360 mm at a station southeast of Port Hedland. This heavy rainfall brought widespread flooding around Port Hedland and nearby inland parts. Veronica weakened below tropical cyclone intensity on the morning of 26 March.

Australian monsoon may redevelop

Tropical cyclones Trevor and Veronica both formed from tropical lows which developed along a monsoon trough which was active across northern Australia last week. As these lows moved south, the monsoon trough in which they were embedded became separated from the cross-equatorial flow to the north, an essential element of monsoonal conditions. As a result, the monsoon trough broke down along much of its length. However, some weather models suggest a strengthening flow from the northern Pacific Ocean may move to Australian latitudes and lead to the redevelopment of a weak monsoon trough to Australia's north in the coming week. If a monsoon trough does develop, the likelihood of tropical low formation typically increases. Widespread rainfall could also be a feature if the monsoon trough moves over land.

Madden–Julian Oscillation remains weak

The pulse of the Madden–Julian Oscillation (MJO) which was active in the Australian region in recent weeks, and helped initiate the recent monsoonal episode, has become indiscernible. Climate models show no indication that the MJO will strengthen significantly in the coming fortnight. As a result, any lingering influence the MJO was having with regard to enhancing tropical rainfall in the Australian region is expected to become negligible in the coming week or two.

Read more about the Bureau's current MJO monitoring.

Further tropical cyclone activity across Indian Ocean

Tropical cyclone activity has again been a feature in the southern Indian Ocean during the past seven days. After the devastating impacts associated with tropical cyclone Idai, which made landfall along the Mozambique coast, another very strong storm has developed near southern Africa. Tropical cyclone Joaninha, equivalent in intensity to an Australian category 4 storm, is currently well east of Madagascar. It lies over open water, but may pass very close to Rodrigues, a populated island east of Mauritius.

Further information on Joaninha is available from the Meteo-France centre at La Réunion.