Tropical Climate Update

Heavy rainfall over Bangladesh, South East Asia and southern China

A vigorous monsoon flow continues across the northern Indian Ocean region, including the Indian subcontinent and parts of South East Asia. The highest rainfall totals of the week were observed in Bangladesh and northwest Myanmar. Heavy rainfall was observed across southern China and included daily totals in the order of 200 mm, leading to landslides and multiple fatalities. The high humidity in the atmosphere which moved over China with the monsoon was only partly responsible for the intense shower and thunderstorm activity over the region.  A persistent, near-stationary weather system called the Meiyu (or Baiu) front is an annual feature apparent in the northwest Pacific region at this time of the year. It can generate significant rainfall and lead to flooding episodes across China, Taiwan, Japan and the Korean Peninsula. In the last month or so, the Meiyu (Baiu) front has been active over southern China and contributed to extensive seasonal rains causing widespread flooding.

The Southwest Indian Monsoon is expected to continue its northwards progression over the Indian subcontinent. The northern limit of the monsoon is now near central India, slightly further south than its average position for this time of year. To follow the progress of the Southwest Monsoon, see the India Meteorological Department's monsoon page.

Madden–Julian Oscillation weakens

The Madden–Julian Oscillation (MJO) signal weakened last week while over tropical Africa. Unfortunately, there was no significant rainfall observed over eastern parts of the continent which are experiencing severe drought conditions.

International climate models generally indicate a weak or indiscernible MJO signal for the next few days to week, before the signal strengthens marginally and moves over the equatorial Indian Ocean. The models suggest that any strengthening is likely to be brief, and as such there is unlikely to be any significant effect on northern Australia in the coming week.

For more information on the MJO, see the Bureau's current MJO monitoring information.

El Niño Watch cancelled; ENSO-neutral likely for 2017

The Bureau's ENSO Outlook is now at INACTIVE, after an easing of climate model outlooks, and a reversal of the early autumn warming seen in the eastern tropical Pacific Ocean. In the last week the Southern Oscillation Index (SOI) decreased markedly, however this is a result of local factors and not indicative of development of a broadscale atmospheric circulation typical of El Niño. All eight international climate models surveyed by the Bureau of Meteorology now suggest tropical Pacific Ocean temperatures are likely to remain ENSO-neutral for the second half of 2017.

The Indian Ocean Dipole (IOD) remains neutral. Three out of six climate models suggest a positive IOD will develop during the Australian winter, with most other models approaching the positive IOD threshold, but remaining within neutral values. A positive IOD is typically associated with drier than average conditions over much of central Australia and parts of northern Australia during the build-up months of September to November.

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