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.

Very warm days for 2017 dry season so far

The northern Australia dry season commences in May and continues until the end of September each year. Apart from the east coast of tropical Queensland, this period sees generally dry conditions across most of northern Australia with many districts observing less than 50 mm, on average, of rainfall during the 5-month period.

Averaged across northern Australia, rainfall during the current dry season is tracking at less than half the long-term average as at the end of July. However, the more significant feature during 2017 has been the daytime temperatures. Northern Australia (the area north of 26°S, which is the southern border of the NT) experienced its highest mean daily maximum temperature for May to July since records began in 1910. The mean daily maximum temperature in 2017 was 1.93 °C above average for the May to July period (previous record was +1.46 °C in 2002).

The exceptional warmth has continued into August across much of northern Australia, particularly in Queensland and the Northern Territory where many sites are currently tracking well above average for maximum temperature. Further information on monthly and seasonal climate statistics can be found in the Bureau's climate summaries.

Overnight temperatures have also been warmer than average in many parts, but not as significantly as the daytime temperatures. At Darwin Airport, for example, the overnight minimum has dropped below 20 °C on only 25 nights so far this season—less than half of the dry-season average.

Tropical activity and flooding rains continue in northern hemisphere

The 11th tropical cyclone of the 2017 northwest Pacific cyclone season formed over waters to the northeast of the Philippines. Tropical storm Hato (Isang) is moving in a westerly direction towards southern mainland China, near Hong Kong. Hato (Isang) is predicted to strengthen marginally, but is not expected to become the fourth typhoon of the season in the northwest Pacific prior to landfall. Tropical cyclone activity to the end of August has been near-average (based on 1981–2010 climatology) for the number of named storms, but below the long-term average for typhoons (sustained winds of 118 km/h or greater; approximately seven typhoons). For information on tropical cyclone activity in the northwest Pacific region go to the website of the Japan Meteorological Agency.

This time of the year typically sees the Indian Southwest Monsoon at it northernmost extent. During September the monsoon normally starts its withdrawal across the Indian subcontinent, tracking gradually southwards before moving into the southern hemisphere during the Austral summer. So far, the subcontinent has seen near-average rainfall during this season's monsoon. The monsoon trough and an associated tropical low lies over northern India and has continued to generate widespread rainfall, which has led to extensive flooding in northeastern India, Nepal and Bangladesh. Reports indicate that more than a third of Nepal and Bangladesh have been flooded and over 16 million people have been affected across the three countries. Since the flooding and associated landslides commenced, more than 600 fatalities have been reported.

Madden–Julian Oscillation expected to strengthen

The Madden–Julian Oscillation (MJO) has remained weak and indiscernible for August so far. While not unanimous, most international climate models surveyed by the Bureau forecast the MJO signal to strengthen marginally in the coming seven days. Of these, the majority of models indicate that the MJO will re-develop over the Indian Ocean and track eastwards towards the Maritime Continent.

When the MJO moves over the Indian Ocean at this time of the year, cloudiness and rainfall is typically above average over the Indian Ocean, most of India, parts of South East Asia and the northern Maritime Continent region.

For northern Australia, rainfall is not significantly enhanced or suppressed under these circumstances, however overnight temperatures are typically above average across Queensland and parts of the eastern Northern Territory.

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

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

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