Weekly Tropical Climate Note

Issued on Tuesday 23 September 2014

Tropical activity suppressed

Tropical activity was generally suppressed over much of the Australasian region this past week (including the Indian sub-continent), except countries surrounding the South China Sea and East China Sea (including the Philippines, Taiwan and the southeast coast of China). These countries were impacted by severe tropical storm Fung-Wong (Mario), which developed in the South China Sea on the 17 September and moved north and north-eastwards into the East China Sea during the weekend. Recent days have also seen an intensification of tropical activity in the northwestern Pacific Ocean.

The Madden-Julian Oscillation (MJO) has been weak and indiscernible this week and is unlikely to have influenced tropical convection. Other modes of tropical variability, such as tropical storms have played a larger role in determining where tropical convection was focused this past week. The MJO is expected to remain week over the upcoming two weeks, and hence is unlikely to have a significant influence on tropical weather.

See the Bureau's MJO Monitoring for more information on location and tracking of the MJO.

ENSO and the Indian Ocean Dipole

Despite most ocean and atmospheric indicators falling short El Niño thresholds, model outlooks and recent observations indicate a late season El Niño is still possible. The risk of El Niño developing by summer is estimated to be at least a 50% chance (see the Bureau’s The latest ENSO Tracker for more information on the likelihood of El Niño). The latest NINO3.4 sea surface temperature anomaly is +0.5 °C. The latest Southern Oscillation Index value is -10.

During an El Niño, the northern wet season and monsoon typically arrive later than normal, with northern Australia tending to have lower than usual rainfall from September through January. El Niño is also associated with below normal rainfall across large parts of southern and inland eastern Australia during the second half of the year. The southwest Indian monsoon often brings less rainfall than usual during El Niño years. See the Bureau's ENSO Wrap-Up for official El Niño information including computer model projections.

The Indian Ocean Dipole (IOD) in the tropical Indian Ocean has returned to a neutral state, and the latest IOD index value is 0. All climate models surveyed by the Bureau indicate the IOD will remain neutral during the coming months.

Next update expected by 30 September 2014| Product Code IDCKGEW000

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