Madden-Julian Oscillation (MJO)

The Madden-Julian Oscillation (MJO) is the major fluctuation in tropical weather on weekly to monthly timescales. The MJO can be characterised as an eastward moving 'pulse' of cloud and rainfall near the equator that typically recurs every 30 to 60 days.

MJO phase diagram


*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)


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

OLR Archive:   

Westerly wind anomalies

Winds Archive:

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.

Indian Ocean tropical cyclones in both hemispheres

Two cyclones have straddled the equator in the Indian Ocean during the past week, but are of no threat to the Australian region. The official start of the tropical cyclone season in the southern hemisphere (November to April for the Australian region) coincides with a transitional pattern of broadscale wind flow by which well-defined low pressure troughs can be observed across tropical regions on both sides of the equator. This has led to twin tropical cyclones simultaneously active over both the northern and southern Indian Ocean during the past week. Cyclonic storm Gaja, over the Bay of Bengal, remains active: it is a relatively weak system that may develop further to an intensity comparable to an Australian category 2 tropical cyclone. Gaja is predicted to make landfall on the southeast coast of India in the next few days. The southern hemisphere storm, ex-tropical cyclone Bouchra, developed to the west of Sumatra, south of Gaja.

Tropical cyclone warnings and information for India can found at the Indian Meteorological Department.

Madden–Julian Oscillation moves over Maritime Continent

A moderately strong pulse of the Madden–Julian Oscillation (MJO) continued to track eastwards across the Indian Ocean during the past week, and now lies over the Maritime Continent. As this sustained pulse of the MJO tracked over the Indian Ocean to its current position, it likely contributed to the formation of the tropical cyclones which formed over the Indian Ocean. More generally, this MJO pulse contributed to enhanced rainfall at many locations across the Indian Ocean, South-East Asia and the western Maritime Continent.

The MJO pulse also assisted the formation of a related tropical atmospheric wave called an Equatorial Rossby wave. These waves have been observed across the Indian and Pacific oceans in recent days. Equatorial Rossby waves are often associated with twin tropical lows straddling the equator and, along with the MJO pulse, assisted in the formation of Gaja and Bouchra. Interestingly, twin tropical lows are also apparent over the Pacific Ocean, just to the west of the Date Line. However, neither of the Pacific systems is expected to intensify to a tropical cyclone.

International climate models predict the MJO pulse will move further east but weaken in the coming days. Prior to it weakening, the MJO is likely to contribute to further enhanced tropical rainfall about the Maritime Continent. At this time of the year, an MJO over the Maritime Continent has only a minor influence on rainfall across Australia's far north.

See the Bureau's current MJO monitoring for more information on the MJO.

El Niño ALERT continues—dry start to wet season likely

The Bureau's ENSO Outlook remains at El Niño ALERT, meaning there is approximately a 70% chance of El Niño occurring in the coming months. Sea surface temperatures in the tropical Pacific Ocean have exceeded El Niño thresholds, with models predicting further warming of the ocean is likely. However, ENSO atmospheric indicators (such as the Southern Oscillation Index and cloudiness near the Date Line) are yet to indicate that the ocean and atmosphere have coupled and are reinforcing each other. Coupling is needed to sustain an El Niño event.  

Positive values of the Indian Ocean Dipole (IOD) index persist, continuing the positive IOD event which has been in effect since about mid-September. Models predict a return to a neutral IOD during November.

El Niño and a positive IOD at this time of the year increase the likelihood of a drier than usual start to the northern wet season for Queensland and the Northern Territory. El Niño is typically also associated with a later-than-usual monsoon onset for northern Australia.

See the Bureau's current ENSO Wrap-Up for more information.

Product code: IDCKGEW000

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

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