Tropical Climate Update

Fifth tropical cyclone for 2017-18

Tropical cyclone Joyce was the fifth in the Australian region for the 2017-18 tropical cyclone season, and the second to make landfall. Cyclone season continues until 30 April 2018. All five tropical cyclones have been confined to the Western Region. The first two cyclones of the season (Cempaka and Dahlia) moved southwest from south of Indonesia towards northwest Australia, while the three subsequent systems (Hilda, Irving and Joyce) formed, and remained within the Western Region. The start of the current season has been much more active than that of 2016-17, when only one tropical cyclone (Yvette) formed prior to February 2017.

Joyce was the second tropical cyclone to affect Western Australia's Kimberley region within three weeks. Joyce began as a tropical low which developed off the far northern Kimberley coast on 7 January, and then intensified to tropical cyclone strength on the morning of 11 January.  Tropical cyclone Joyce moved over land during the afternoon of 12 January before it strengthened beyond category 1. As a result, wind damage was limited; heavy rainfall and flooding were the main impacts associated with the system. Some coastal locations in the southwest Kimberley observed rainfall totals in excess of 250 mm.

Weak monsoon trough to Australia's northwest

A monsoon trough has been over Australia's northwest (predominantly offshore) since the beginning of January and remains active, but relatively weak. Forecast models suggest the trough will remain over waters to Australia's northwest but is not expected to strengthen significantly in the coming week.

International climate models predict the Madden–Julian Oscillation (MJO), currently over the Indian Ocean, will move into the western Maritime Continent in the coming week. The MJO in this region would typically assist in invigorating a pre-existing monsoon trough over northwest Australia, however, the broadscale weather pattern in the region is currently not favourable for this to occur. This is primarily due to an out-of-season tropical low which is currently located off the north coast of Borneo. This low is drawing in the energy associated with a surge of winds from the South China Sea which might otherwise cross the equator and energise the monsoon trough in the Australian region. The presence of tropical lows in the northern Indian Ocean during the austral summer has been a recurring theme during the current Australian wet season, and has played a significant role in the lack of monsoonal activity across northern Australia to date.

See the Bureau's current MJO monitoring for more information.

Weak La Niña in the tropical Pacific Ocean

Weak La Niña conditions persist in the tropical Pacific. Climate models suggest this La Niña will decay in the southern autumn of 2018. La Niña typically brings above average rainfall to eastern Australia parts of northern Australia during summer. However, weak events typically mean a weaker influence on Australian rainfall.

See the Bureau's current ENSO Wrap-Up for more information.