Tropical Climate Update

Record-setting dry season ends for northern Australia

Rainfall in northern Australia (north of 26 °S) during the dry season months of May to September was the highest since records commenced in 1900. All individual months since May saw significantly above-average rainfall totals, most significantly in September when northern Australia observed nearly five times its average rainfall. A significant proportion of southwestern and central Queensland, an area which had been enduring a prolonged drought prior to the dry season, as well as the Top End of the Northern Territory, had their highest rainfall on record in the five-month period.

Widespread warmth was also a feature during the dry season. The mean temperature was the second highest since records commenced in 1910, only eclipsed by 2013. No individual month during the May to September period saw below average mean maximum or mean minimum temperatures. Overnight temperatures were the equal highest on record, tying the mark set in 1973.

Strong negative Indian Ocean Dipole continues to dominate

The strong negative Indian Ocean Dipole (IOD), combined with warm ocean temperatures to the north of Australia, remain the major drivers of Australia’s climate. During a negative IOD rainfall across northern Australia is typically above average in September to November, with warmer daytime and night-time temperatures usually observed.

The pattern of warm waters to Australia’s north resembles that which is typically observed during La Niña, although the El Niño–Southern Oscillation (ENSO) state is currently neutral. In the atmosphere, there has been less than usual cloudiness near the Date Line and a Southern Oscillation Index value above 8 for the last three weeks - both indicators that are typical of La Niña. Hence the (ENSO) Outlook remains at La Niña WATCH.

Climate models indicate the IOD will return to neutral levels by the end of spring, while the Pacific is likely to remain at ENSO-neutral levels through to the end of 2016, though one international model suggests that La Niña late in the year is possible. 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.

Typhoon activity continues in northwest Pacific

Typhoon Megi (Helen) made landfall over central Taiwan last Tuesday, with sustained winds estimated at near 200 km/h.  Torrential rainfall, including a reported 945 mm in less than 24 hours at Taipingshan in northeastern Taiwan, resulted in flooding, landslides and widespread power failures.

Another very strong tropical system, typhoon Chaba (Igme), is located between Taiwan and southern Japan. Chaba (Igme) has already brought intense wind and rainfall to the Japanese islands of Kumejima and Okinawa and is expected to produce heavy rain and high winds on Japan’s mainland in the next day or two. Warnings and information on Chaba (Igme) are available from the Japanese Meteorological Agency. Since the start of September, thirteen tropical storms or typhoons have affected the northwest Pacific region, compared with the average number for September to October of between eight and nine.

In the last few days, the Madden–Julian Oscillation (MJO) has strengthened over 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 and the northwest Pacific Ocean. Most international climate models predict that the MJO will weaken in the coming week.

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