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.

Northern rainfall onset likely to be earlier than average

Last Thursday, 30 July, the third issue of the Bureau’s Northern Rainfall Onset (NRO) outlook for season 2020-21 was released. The chance of the first rains for northern Australia arriving early in 2020-21 is higher than average over much of inland northern Australia, with the highest likelihood across southwestern, central and some coastal parts of Queensland, and southern Northern Territory. Other parts of northern Australia have roughly equal chances of an early or late rainfall onset.

'Rainfall onset' relates to the timing of the first significant rains observed after 1 September. The measure of 50 mm is used for this time of the year, as it is considered to be sufficient rainfall to stimulate pasture growth after the dry months of the northern dry season (May to September).

Earlier than usual rainfall onset is linked to La Niña forming during spring, which would increase the likelihood of above-average rainfall across much of Australia. Expected warmer-than-average temperatures across the waters around northern Australia are also conducive to above-average rainfall.

The next update will be released Thursday 13 August, with fortnightly updates continuing until the end of August.

Read more about the northern rainfall onset

Madden–Julian Oscillation moving across Maritime Continent

A pulse of the Madden–Julian Oscillation (MJO) has continued to track eastwards during the past week and is now located to Australia's north, in the western Maritime Continent. Most climate models indicate the pulse will slow down in the coming days before weakening, although some indicate it will strengthen further and remain discernible for at least another week.

At this time of the year, an MJO pulse over the Maritime Continent has only a small influence on rainfall patterns across northern Australia. Further north, parts of the Maritime Continent, including Papua New Guinea, and South-East Asia typically observe above-average rainfall.

Read more about the Madden–Julian Oscillation

Tropical cyclone activity over the western North Pacific Ocean

For the first time since at least 1949, no named storms (i.e. equivalent to a category 1 or stronger Australian tropical cyclone) developed in the western North Pacific basin in July 2020. In a typical year, this region sees between 3 and 4 tropical cyclones in July. This continues the well below-average tropical cyclone activity in the western North Pacific Ocean this year. Only one typhoon (equivalent to a category 3 Australian tropical cyclone) had been observed to the end of July 2020, compared to the long-term average of about 5.

In the past week, 2 named storms developed over the western North Pacific Ocean, bringing the 2020 total to 4 tropical storms, compared to an average of between 8 and 9.

Ex-tropical storm Sinlaku passed over Hainan Island and the east coast of northern Vietnam on 2 August as a weak tropical storm (equivalent to category 1 Australian tropical cyclone). Sinlaku generated strong winds and heavy rain as it made landfall. As it tracks further inland as a tropical depression, it is expected to produce heavy rains across parts of mainland China.

Typhoon Hagupit (Dindo) formed to the east of the Philippines and has recently tracked towards the north. It passed close to Taiwan in the last 24 hours and more recently made landfall on mainland China's east coast with mean winds estimated at more than 125 km/h.

The active MJO pulse over the Maritime Continent, along with another tropical atmospheric wave—an equatorial Rossy wave—contributed to the development of tropical cyclones Sinlaku and Hagupit. 

Further tropical cyclone information and warnings for this region available from the Japan Meteorological Agency

Product code: IDCKGEW000

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

Product Code: IDCKGEWWOO