Tropical Climate Note

Issued on Tuesday 14 October 2014

Tropical cyclone activity

This past week has seen tropical convection mainly focused over the Bay of Bengal, parts of India and over the northwest Pacific Ocean.

Very severe cyclonic storm Hudhud, which developed to cyclonic storm strength on 8 October, became the strongest storm to form over the Bay of Bengal this year. Hudhud moved slowly northwest and developed rapidly, reaching peak strength shortly before making landfall near Visakhapatnam, Andhra Pradesh, India on Sunday 12 October.

The main focus of the tropical activity in the northwest Pacific Ocean was associated with typhoon Vongfong (Ompong). Typhoon Vongong reached Category 5super typhoon strengthlast week, becoming the most powerful cyclone of 2014 to date. Typhoon Vongong impacted Japan over the weekend, but had weakened significantly before impact.

Madden-Julian Oscillation

Recent cyclone activity over the west Pacific Ocean and Bay of Bengal is unlikely to have been influenced by the Madden-Julian Oscillation (MJO) as little or no MJO signal has been detected during the past week. While the MJO often contributes to intraseasonal variability of global monsoon systems other sources of variability also influence global monsoon patterns. Warm sea surface temperatures and favourable atmospheric conditions this past week have increased the risk of tropical cyclone development over these regions.

Most climate models indicate a new burst in MJO activity may develop and strengthen over the western hemisphere and Africa in the next two weeks; however, the strength of the MJO signal is uncertain. If the MJO strengthens over Africa it may act to supress activity over the northwest Pacific and hence reduce the risk of tropical cyclone activity.

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

El Niño—Southern Oscillation in neutral state

While the Pacific Ocean continues in an ENSO-neutral state, persistent warmth in the tropical Pacific Ocean and a recent weakening of the trade winds in the west equatorial Pacific may provide some further warming towards El Niño thresholds. Recent observations and model outlooks indicate there remains a 50% chance of El Niño developing during the last quarter of 2014. The latest NINO3.4 sea surface temperature anomaly is +0.5°C. The latest Southern Oscillation Index value is -3.5.

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

Tropical Cyclone Outlook

El Niño conditions usually decrease overall tropical cyclone activity around Australia. For the Australian tropical cyclone season ahead, average to below average tropical cyclone activity is most likely for the Australian region. The Australian tropical cyclone season runs from November to the end of April and there is always a risk of tropical cyclone development even in El Niño years.

Next update expected by 21 October 2014| Product Code IDCKGEW000

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