Weekly Tropical Climate Note

Significant rainfall over Bangladesh

The past week saw a strengthening in southwesterly monsoon flow over Bangladesh and western Myanmar, delivering large rainfall totals. The active monsoon conditions became more intense with a tropical low, which sat near Bangladesh for much of the past week. Rangamati, a hilly district in Bangladesh's southeast, was particularly affected, with 343 mm recorded over 24 hours to the morning of Tuesday 13 June, more than half their June monthly average rainfall in a single day. This heavy rain triggered multiple landslides across the southeast of the country, with loss of life and damage to infrastructure recorded.

Meanwhile, the Southwest Monsoon continued its northward progression over India. The northern limit of the monsoon is now over the central districts, slightly further south than its average position for this time of year. The focus of last week’s rainfall over the Indian subcontinent was in central and northeastern regions, associated with a trough and tropical low. Follow the progress of the Southwest Monsoon on the India Meteorological Department's monsoon page.

Madden–Julian Oscillation maintains strength over western hemisphere

The Madden–Julian Oscillation (MJO) signal maintained moderate strength as it moved over the western hemisphere and Africa over the past week. This has seen increased cloudiness and rainfall over central and western Africa. Impacts over eastern Africa, where the MJO signal is usually best defined, have been minimal, with no break in the severe drought affecting the region.

Most international climate models forecast the MJO to rapidly weaken over coming days as it moves eastward, while others forecast it to maintain at moderate strength as it moves over the Indian Ocean. If the MJO maintains its strength over the western Indian Ocean, rainfall would typically be enhanced over parts of the Indian subcontinent. There would also be an increased chance of tropical cyclone development in the area.

With the MJO over the far western Indian Ocean, there is typically little effect for northern Australia at this time of the year. However if the MJO maintains moderate strength while moving further east across the Indian Ocean, there is an increased chance of onshore flow along the north Queensland coast and thus enhanced rainfall.

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

El Niño WATCH cancelled; ENSO neutral likely for 2017

The Bureau's ENSO Outlook has been downgraded from El Niño WATCH to INACTIVE, after an easing of climate model outlooks, and a reversal of the early autumn warming seen in the eastern tropical Pacific Ocean. 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, compared to seven of eight models that were forecasting a possible El Niño event in April.

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

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

Product code: IDCKGEW000

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