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.

Slow start to northern wet season likely

The Bureau's mid-month climate outlook indicates a strong likelihood that rainfall across most of northern Queensland and the Northern Territory will be below average during the October–December period. While the El Niño–Southern Oscillation (ENSO) is currently neutral, recent observations and model outlooks indicate a weak and short-lived El Niño remains possible in 2018. The Bureau's ENSO Outlook remains at El Niño WATCH, meaning there is approximately a 50% chance of El Niño forming in the coming months; double the normal chance.

Cooler than normal waters in the eastern Indian Ocean and model outlooks indicate an increased likelihood of a positive Indian Ocean Dipole (IOD) developing.

Reduced rainfall across northern Queensland and the Northern Territory in the early months of the wet season, which officially runs from October to April, is a typical outcome of both El Niño and a positive IOD. If a positive IOD occurs concurrently with El Niño, rainfall deficiencies typically associated with El Niño are generally exacerbated and more widespread.

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

Continuing tropical cyclone activity in the northern hemisphere

Cyclonic storm Daye, made landfall at Odisha, a state of northeastern India, on 21 September. Heavy rainfall affected the region, including 331 mm observed at a site in West Bengal, generated by the system's outer rain bands. As a relatively weak storm, with peak intensity equivalent to an Australian category 1 tropical cyclone, Daye caused minimal wind damage.

A stronger system, typhoon Trami (Paeng), is currently located to the east of the northern Philippines and is forecast to track northwest towards Taiwan and the Ryukyu Islands of southern Japan. Its current intensity, equivalent to a high-end category 4 tropical cyclone on the Australian scale, with maximum sustained winds of 195 km/h, is forecast to be maintained for the next day or two.

Trami (Paeng) is the 24th tropical cyclone for the western North Pacific region in 2018, compared with the long-term average of slightly less than 18 at this time of the year. The number of typhoons (equivalent to a category 3 or stronger Australian tropical cyclone, or a United States' hurricane) is slightly below average this year with ten, compared to the average of just under eleven.

For tropical cyclones in the western North Pacific, warnings and information are issued by the Japanese Meteorological Agency

Madden–Julian Oscillation redevelops over the Americas

After being weak or indiscernible for several weeks, a pulse of the Madden–Julian Oscillation (MJO) has recently developed over the Americas. Most international models forecast the MJO to strengthen further as it tracks eastwards over American and then African longitudes in the coming week or two. An MJO pulse over the region at this time of the year would typically lead to suppressed cloudiness and rainfall over a large area of the northern hemisphere extending from India to the western North Pacific Ocean, including the northern Maritime Continent. Further weakening of the monsoon over India and South-East Asia and less favourable conditions for tropical cyclone development over the western North Pacific region are likely in this scenario. Stronger-than-usual westerly winds also typically develop over the tropical Pacific Ocean in this situation, potentially assisting El Niño development.

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

Product code: IDCKGEW000

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

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