Weekly Tropical Climate Note

Issued 28 July 2015

Madden-Julian Oscillation weakens over the Indian Ocean

Over the past week, an active Madden-Julian Oscillation (MJO) has moved eastwards into the western tropical Indian Ocean, enhancing the Indian monsoon and likely contributing to the recent suppressed convection over much of South-East Asia and the northwest Pacific Ocean. The MJO has weakened in recent days. Forecasts for the MJO this week are mixed, however, there is an indication that a weak signal may reappear somewhere over the western hemisphere. When models forecast a retrogression of the MJO signal (westward rather than eastward movement), this is often an indicator of interaction with other large scale drivers or tropical waves, as this is counter to the current understanding of MJO behavior. Current forecasts indicate the MJO signal will be weak and therefore not likely to have a strong influence on tropical activity over the coming fortnight.

See the Bureau's MJO Monitoring for current MJO information.

Widespread heat across northern Australia

Much of northern tropical Australia has experienced widespread unseasonably warm daytime maximum temperatures in recent days, with several locations recording record high temperatures for this time of the year. This warming was associated a slow moving high pressure system centred over central Australia. The high pressures system directed light and humid winds over the tropics. This weak and humid flow allowed daytime temperatures to reach as high as 36.8 degrees Celsius in various locations across northern Australia. The heat is expected to ease in Northern Australia but likely to traverse south to the Pilbara and Gascoyne regions of Western Australia in the next few days.

El Niño continues to strengthen

El Niño continues to develop in the tropical Pacific Ocean. Weakened (or reversed) trade winds continue to cause the tropical Pacific Ocean to warm. All international climate models surveyed by the Bureau of Meteorology indicate El Niño is likely to strengthen and persist into early 2016. The latest weekly NINO3.4 sea surface temperature anomaly is +1.5 °C and the 30-day SOI value to 26 July is −14.7.

Cloudiness near the Date Line in the tropical central Pacific was enhanced this last week; a typical pattern during El Niño. Meanwhile, to the west of the Date Line and across the Maritime Continent suppressed convection was observed, a feature of El Niño compounded recently by the Madden-Julian Oscillation (MJO).

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

Next update expected by 4 August 2015 | Product Code IDCKGEW000

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