Weekly Tropical Climate Note

Issued 16 December 2014

Madden—Julian Oscillation to strengthen over Indian Ocean

The moderate to strong Madden—Julian Oscillation (MJO) that recently moved eastwards along the equator at Australian longitudes has weakened over the western Pacific this past week. It is now so weak that it is unlikely to still be influencing tropical weather.

Model forecasts indicate a slow moving MJO will strengthen in the tropical central or eastern Indian Ocean this week. While there is some uncertainty concerning its strength and speed, some models indicate a weak MJO will be over Australian longitudes during the last week of December moving eastwards into the west Pacific Ocean in early January.

When the MJO is located over the Indian Ocean at this time of year, as some models are indicating will be the case for the next fortnight, it increases the risk of tropical cyclone development in the region. Likewise, as the active MJO moves over Australian longitudes, it increases the chance of monsoonal rainfall over northern Australia as well as tropical cyclone development across the Australian region.

See the Bureau's MJO Monitoring for more information.

Northern Australia heats up

This past week has seen a rise in temperatures across northern Australia. A heat-low, an area of low pressure that forms over very warm land surfaces, has formed over central Australia. This weather pattern has increased westerly wind flow and temperatures across northern Australia and caused some rainfall over the Kimberley region. High temperatures are expected to continue for most of this week.

El Niño—Southern Oscillation nears El Niño thresholds

Oceanic indicators of El Niño—Southern Oscillation (ENSO) are hovering near El Niño thresholds; however, atmospheric indicators such as trade winds, cloudiness and rainfall have either remained near average or only temporarily approached thresholds. The latest NINO3.4 sea surface temperature anomaly is +0.9 °C. The latest Southern Oscillation Index value up to 14 December is −5.1.

Regardless of whether El Niño is declared, El Niño-like impacts are likely to continue. For Australia, this means a drier and warmer summer than normal is likely for many.

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

Next update expected by 23 December 2014 | Product Code IDCKGEW000

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