Tropical Climate Update

Early wet season rains in tropical Australia continue

The early start to the northern wet season rains has continued over the Northern Territory and central Queensland. Rainfall in the last week continued the pattern seen during much of September (officially the last month of the dry season), when nearly all of northern Australia, apart from some areas in Western Australia, saw significantly above-average rainfall.

A strong and persistent negative Indian Ocean Dipole (IOD), combined with a La Niña–like pattern in ocean temperatures in the western tropical Pacific Ocean, and areas around Australia’s northern coastline,  is strongly influencing Australia’s climate. See the Climate Outlook for more information on what to expect in the coming months.

Climate models suggest the negative IOD is likely to return to neutral by the end of spring. In the tropical Pacific Ocean, the El Niño–Southern Oscillation (ENSO) remains neutral, though the Southern Oscillation Index (one ENSO indicator) has exceeded La Niña thresholds.  Most climate models surveyed by the Bureau indicate a neutral ENSO will persist for the remainder of 2016; however, La Niña-like impacts can still occur. During La Niña, northern Australia typically experiences above-average wet season rainfall, with the first rains of the season typically arriving earlier than normal.

See the Bureau’s ENSO Wrap-Up for official El Niño, La Niña and IOD information.

Indian monsoon withdraws

The southwest monsoon began to withdraw on 15 September from parts of Rajasthan, in India, and continued to move south. This is a slightly later-than-average withdrawal—typically the southwest monsoon will have withdrawn to be near Madhya Pradesh by this time of year. The monsoon is forecast to continue its slow southward migration over the coming week.  The Indian monsoon has so far yielded close-to-average rainfall across the sub-continent.

In the last week, the Madden–Julian Oscillation (MJO) weakened as it exited the Indian Ocean and crossed the Maritime Continent. Typically, when the MJO is over the Maritime Continent at this time of the year, there is an increase in cloudiness and rainfall over South-East Asia. Some international climate models predict that the MJO may strengthen slightly over the Maritime Continent before moving into the western Pacific. If this occurs then it may aid in the withdrawal of the southwest monsoon, as there is typically a reduction in cloudiness over India as the MJO moves in to the western Pacific.

See the Bureau's MJO Monitoring for current MJO information.

Typhoon activity in northwest Pacific

Typhoon Malakas made landfall over the southern Japanese island of Kyushu last week, generating significant flooding in mainland Japan, and causing widespread disruption across Taiwan.

More recently, Megi has reached typhoon strength and is predicted to make landfall today over Taiwan as a very strong typhoon, with maximum sustained winds of 90 knots, before tracking west towards southeast China. Warnings and information on Megi are available from the Japanese Meteorological Agency.