Weekly Tropical Climate Note

Issued on Tuesday 18 November 2014

First tropical cyclone for the season develops over the southwest Indian Ocean

Tropical convection this past week has been below average over much of South–East Asia and slightly elevated over parts of the southwest Indian Ocean. Severe tropical storm Adjali, which developed near Diego Garcia in the southwest Indian Ocean in recent days, has become the first named storm for the season in the Indian Ocean, south of the equator. Tropical storm Adjali is predicted to move south then southwest, slightly intensifying over the coming day before weakening as it moves over cooler waters.

An active Madden—Julian Oscillation

This past week, a Madden—Julian Oscillation (MJO) signal strengthened over Africa before weakening. Hence, it is possible the recent MJO activity contributed to the development of tropical storm Adjali and the recent supressed conditions over tropical parts of South–East Asia and the western Pacific Ocean.

Climate models indicate the MJO will move east over the Indian Ocean this week, however, there are a range of predictions of the MJO's likely strength. Some models suggest a clear signal, while others suggest the signal will be weak or indiscernible and unlikely to influence tropical weather. When the MJO is active over the Indian Ocean, it typically enhances convection over the Indian Ocean, while suppressing convection over tropical parts of South–East Asia, northern Australia and the western Pacific Ocean.

If the MJO continues to move east and remains active, there is a chance that it will enhance tropical convection in the Australian region from the end of November or start of December. However, MJO outlooks beyond a fortnight should be treated with considerable caution, as there is significant uncertainty surrounding the predicted strength and speed of movement of this current MJO signal.

See the Bureau's MJO Monitoring for more information.

Tropical Pacific Ocean moves closer towards El Niño

The Pacific Ocean has shown some renewed signs of El Niño development. International climate models expect this situation to persist, with most models predicting values near El Niño thresholds for the next two to three months. The latest NINO3.4 sea surface temperature anomaly is +0.9 °C and the 30-day Southern Oscillation Index value to 16 November is −10.9.

Regardless of whether or not El Niño fully develops, some El Niño–like impacts remain likely. For northern Australia, this means an increased likelihood of drier than usual conditions over the coming months, including an increased chance of the monsoon commencing later than usual.

See the Bureau's ENSO Wrap up for official El Niño information.

Next update expected by 25 November 2014 | Product Code IDCKGEW000

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