Madden-Julian Oscillation (MJO)


MJO phase diagram

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*Note: There are missing satellite observations from 16/3/1978 to 31/12/1978.

The MJO phase diagram illustrates the progression of the MJO through different phases, which generally coincide with locations along the equator around the globe. RMM1 and RMM2 are mathematical methods that combine cloud amount and winds at upper and lower levels of the atmosphere to provide a measure of the strength and location of the MJO. When the index is within the centre circle the MJO is considered weak, meaning it is difficult to discern using the RMM methods. Outside of this circle the index is stronger and will usually move in an anti-clockwise direction as the MJO moves from west to east. For convenience, we define 8 different MJO phases in this diagram.

Average weekly rainfall probabilities

These maps show average weekly rainfall probabilities and expected 850 hPa (approximately 1.5 km above sea level) wind anomalies for each of the 8 MJO phases. Green and blue shading indicates higher than normal rainfall would be expected, while red and orange shading indicates lower than normal rainfall would be expected. The direction and length of the arrows indicate the direction and strength of the wind anomaly. The darker the arrow, the more reliable the information is. The relationship of the MJO with Australian rainfall and winds changes with the season (which can be selected at the top).

Average outgoing longwave radiation (OLR)

Outgoing longwave radiation (OLR) is often used as a way to identify tall, thick, convective rain clouds. These maps show the difference from expected cloudiness based on the position of the MJO. The violet and blue shading indicates higher than normal, active or enhanced tropical weather, while orange shading indicates lower than normal cloud or suppressed conditions. The direction and length of the arrows indicate the direction and strength of the wind anomaly. The darker the arrow, the more reliable the information is. The relationship of the MJO with tropical weather patterns changes with the season (which can be selected above the maps).

Global maps of outgoing longwave radiation (OLR)

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Global maps of outgoing longwave radiation (OLR) highlight regions experiencing more or less cloudiness. The top panel is the total OLR in Watts per square metre (W/m²) and the bottom panel is the anomaly (current minus the 1979-1998 climate average), in W/m². In the bottom panel, negative values (blue shading) represent above normal cloudiness while positive values (brown shading) represent below normal cloudiness.

Regional maps of outgoing longwave radiation (OLR)

Click on the boxes to view a timeseries of cloudiness for that region.
Map of regional cloudiness Dateline Vanuatu Coral Sea Fiji Nauru & Tuvalu Solomon Islands New Guinea Northern Australia Micronesia Malaysia & Indonesia Guam & Marianas Philippines Indochina Southern India & Sri Lanka

Below: OLR totals over the dateline

Click to see full-size graph of OLR totals over the dateline.

The graphs linked to this map show the OLRs for the different regions within the Darwin RSMC area. The horizontal dashed line represents what is normal for that time of year (based on the 1979 to 1998 period). The coloured curve is the 3-day moving average OLR in W/m². Below normal OLR indicates cloudier than normal conditions in this particular area, and is shown in blue shading. Above normal OLR indicates less cloudy conditions and is shown in yellow shading.

Daily averaged OLR anomalies

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Westerly wind anomalies

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Time-longitude plots of daily averaged OLR anomalies (left) and 850 hPa (approximately 1.5 km above sea level) westerly wind anomalies (right) are useful for indicating the movement of the MJO.

How to read the Time-Longitude plots

The vertical axis represents time with the most distant past on the top and becoming more recent as you move down the chart. The Horizontal axis represents longitude.

Eastward movement of a strong MJO event would be seen as a diagonal line of violet (downward from left to right) in the OLR diagram, and a corresponding diagonal line of purple in the wind diagram. These diagonal lines would most likely fall between 60°E and 150°E and they would be repeated nearly every 1 to 2 months.

Tropical cyclone activity in Australian region

Tropical cyclone Tiffany was named on Sunday, 9 January 2022. Tiffany is the fourth tropical cyclone observed in the Australian region in the 2021–22 season. After making landfall on the Cape York Peninsula, Queensland, during Monday 10 January, Tiffany weakened to below tropical cyclone intensity as it moved further westwards over land. On Tuesday morning, ex-TC Tiffany moved over the waters of the eastern Gulf of Carpentaria, where it is expected to re-intensify. Based on current forecasts, Tiffany is likely to cross the eastern Top End coast of the Northern Territory (NT) during Wednesday 12 January as a category 2 storm, before weakening into a rain-bearing depression over the northern NT.

Another tropical cyclone also recently developed in the Coral Sea, close to Fiji. Tropical cyclone Cody was named by the Fiji Meteorological Service on the morning of Monday, 10 January, forming to the south of the main Fijian island of Viti Levu. Based on the current forecast track, Cody will move further south over open waters and is not expected to directly impact any populated land masses.

Read about warning advice and information for Australian tropical cyclones and South-west Pacific Ocean tropical cyclones

Madden–Julian Oscillation expected to weaken

A moderate to strong pulse of the Madden–Julian Oscillation (MJO) moved generally eastwards across the western Pacific region in the past fortnight. This pulse is forecast to weaken, with some climate models predicting it will become indiscernible in the coming week. In addition to the MJO, equatorial Rossby (ER) wave activity appears to have contributed to tropical weather patterns around northern Australia and over the South-west Pacific region in the past week, assisting the formation of tropical cyclones Tiffany and Cody.

While the influence of the MJO is likely to diminish, the ER wave may lead to further enhanced weather across the South-west Pacific in the coming fortnight. The ER wave is not expected to significantly influence northern Australia's weather patterns in the coming fortnight. However, if the MJO remains discernible and continues tracking east towards the tropical Americas, it would typically increase the likelihood of drier than average conditions developing over tropical Australia.

Read more about the Madden–Julian Oscillation (MJO)

La Niña-like rainfall pattern forecast for northern Australia

Atmospheric and oceanic indicators of the El Niño–Southern Oscillation (ENSO) show La Niña continues in the Pacific Ocean, with climate models suggesting La Niña will persist until early in the southern hemisphere autumn. Along with above-average water temperatures around Australia, this climate state increases the likelihood of wetter than usual conditions for much of the Australian tropics.

Rainfall outlooks from the Bureau continue to depict a signal that broadly resembles a typical La Niña rainfall pattern, with moderate to high chances of above-median rainfall across much of eastern Australia and parts of northern Australia. Northern Western Australia has a roughly equal chance of above- or below-median rainfall in the February to April period. 

Read more about the current climate drivers in the Climate Driver Update

The Tropical Climate Note has changed

On 18 May, the Tropical Climate Note was renamed the Tropical Climate Update. It is published fortnightly, on alternate weeks to the Climate Driver Update.

The Climate Driver Update provides a summary of the major climate drivers affecting Australia, including tropical climate drivers.

Product code: IDCKGEW000

ACKNOWLEDGEMENT: Interpolated OLR data provided by the NOAA/OAR/ESRL PSD, Boulder, Colorado, USA.

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