Weekly Tropical Climate Note

Issued 27 January 2015

Niko, first South Pacific tropical cyclone this season

On 20 January, an area of low pressure near Tahiti developed to tropical cyclone strength and tracked south across French Polynesia. Tropical cyclone Niko was not especially strong nor did the centre of the storm pass over any islands, but it caused flooding and gale force winds over Tahiti from the storm's outer rain bands.

Niko was unusual because tropical cyclones occur less frequently over the southeast Pacific compared with the southwest Pacific and usually only develop in El Niño years when sea surface temperatures in the region are warmer than normal. Sea surface temperatures across the tropical eastern Pacific Ocean, including the waters surrounding Tahiti, have been warmer than normal for several months and likely contributed to the cyclone's development. See the Bureau of Meteorology's ENSO Wrap up for official El Niño information.

It is also likely that the Madden-Julian Oscillation (MJO) contributed to the favourable conditions for tropical cyclone Niko's development. Over the past week the MJO has been present, but weak, over the tropical Pacific Ocean. This placed the MJO in a location favourable for enhanced convection over the southeast Pacific.

The MJO is forecast to remain subdued for the coming week and is not expected to be a major influence on tropical weather. See the Bureau's MJO Monitoring for more information on location and tracking of the MJO. The risk of tropical cyclone development across the South Pacific remains high while warmer than normal waters are present in the region.

Next update expected by 3 February 2015 | Product Code IDCKGEW000

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