Weekly Tropical Climate Note

Tropical convection increases in the northern hemisphere

Over the past week, tropical convection has increased over parts of the northern hemisphere. Satellite imagery depicts widespread and active convection, and a change in the wind-flow pattern, over much of the Indian Ocean in the northern hemisphere. This can be seen in recent gradient wind analyses over the region.

The cross-equatorial wind-flow over the northern hemisphere Indian Ocean apparent in the last fortnight signals the development of the Indian Southwest Monsoon, and is a return to a more northern-hemisphere summer pattern.

The Southwest Monsoon currently lies to the southeast of Sri Lanka, near to its average location for this time of the year. Based on recent progress, it is expected that the Indian Monsoon onset at Kerala, in southern India, will occur in the first week of June – close to the climatological average onset date. The Indian Meteorological Department recently forecast near-average rainfall for India this monsoon season.

Madden–Julian Oscillation currently weak

After tracking eastward over the Indian Ocean, the Madden–Julian Oscillation (MJO) was weak for most of the past week. International climate models suggest that the MJO will strengthen and move over the eastern Indian Ocean, and then eastwards towards the western Maritime Continent, in the coming fortnight. A strengthening MJO in the eastern Indian Ocean would likely enhance the development of monsoonal conditions across the Indian subcontinent.

Typically, an MJO event in the eastern Indian Ocean at this time of the year brings enhanced rainfall along the Queensland coast. If the MJO strengthens and continues to move east into the western Maritime Continent, rainfall across Queensland, far northern Australia and much of the Maritime Continent is typically above average.

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

El Niño WATCH continues

Although atmospheric and oceanic indicators indicate a neutral El Niño–Southern Oscillation (ENSO) state in the Pacific Ocean, there remains a possibility that El Niño could develop during the second half of 2017. The Bureau's ENSO Outlook remains at El Niño WATCH. This means the likelihood of El Niño forming in 2017 is approximately 50%, which is about twice the climatological average.

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

Product code: IDCKGEW000

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