Weekly Tropical Climate Note

Issued 31 March 2015

Monsoon break continues for Northern Australia

The Australian wet season formally ends on the last day of April. While in the wet season, there is always a chance of wet weather, including impacts from tropical cyclones. However April is a transitional month where periods of either wet or dry season type weather patterns can occur. The Madden-Julian Oscillation (MJO) has been contributing to the current dry conditions observed across northern Australia. The MJO often determines if Australia sees a final burst of wet weather conditions in the month of April.

Currently an active MJO is located over the far western equatorial Indian Ocean, enhancing tropical activity in this region. The MJO is also likely to be contributing to the lull in tropical activity currently observed across South-East Asia, northern Australia and parts of the southwest Pacific Ocean. Forecast models indicate that active convection over the western tropical Indian Ocean is likely to move slowly eastwards. However, most models suggest the MJO will weaken as it moves towards the Maritime Continent region in the week ahead. If the MJO weakens it will have little influence on northern Australia; neither suppressing nor enhancing tropical rainfall. Occasional storms may return to the tropical north, especially in coastal regions where humidity remains high. While another burst of the monsoon is unlikely, wet conditions can develop without the influence of the MJO.

See the Bureau's MJO Monitoring for more information.

Typhoon Maysak in northwest Pacific region

An early season tropical cyclone has formed over the northwest Pacific Ocean. Typhoon Maysak has already made a direct hit on the Micronesian state of Chuuk and is tracking westward. It is expected to impact the Philippines later this week.

El Niño may develop in 2015

There is about a 50% chance of El Niño developing in 2015. Sea surface temperatures (SSTs) in the far eastern Pacific Ocean have warmed for the second consecutive week. The SST anomalies in the NINO1 and NINO2 regions in the far eastern Pacific are now above +1 °C for the first time since August last year. The latest weekly NINO3.4 sea surface temperature anomaly in the central Pacific is +0.7 °C. All regions show a warming trend pointing toward a potential El Niño later this year. The latest 30-day value of the Southern Oscillation Index (SOI) is −10.7. An SOI value of less than −8 that is sustained for several weeks can be an indication of El Niño.

All international climate models monitored by the Bureau predict the tropical Pacific Ocean will reach or exceed El Niño thresholds by mid-year. However, predictions from climate models at this time of the year have less accuracy than predictions made at other times of the year. Hence caution should be used when using model guidance alone to predict the likelihood of El Niño.

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

Next update expected by 7 April 2015 | Product Code IDCKGEW000

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