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

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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.

Monsoon finally becomes established over northern Australia

Monsoonal flow has become established over much of northern Australia, as the monsoon trough moved south over the Australian mainland. While relatively weak (based on low-level wind speed), the monsoonal conditions have generated significant rainfall in parts of far northern Australia from the Kimberley region of Western Australia, across to Cape York Peninsula in Queensland. The largest rainfall totals recorded in recent days have been in the Northern Territory, associated with the monsoon trough and embedded slow-moving tropical low currently located near the base of the Territory's Top End. Several coastal locations in the Top End's north and east have observed daily rainfall totals in excess of 150 mm, and event totals of more than 500 mm (Bing Bong Port on the southwest Gulf of Carpentaria coast had recorded over 600 mm to 9am 23 January). There is variation among forecast models on the location and strength of the tropical low over the coming days.

The largest rainfall totals during the current monsoon burst are likely to be associated with tropical lows in the monsoon trough. Some models indicate the eastern Top End and western Gulf of Carpentaria will remain the favoured regions for any tropical lows, while others suggest the western Northern Territory or Kimberley region will be the focus for tropical low development in the coming days. Models also indicate the monsoon trough will extend into the Coral Sea later in the week, increasing rainfall over Cape York Peninsula and raising the potential of a tropical low forming in the Queensland region. In all regions, there is a heightened risk of tropical cyclone formation with any tropical low that moves over open water.

For up-to-date information on tropical cyclones in the Australian region, visit the Bureau's Current Tropical Cyclones webpage.

Madden–Julian Oscillation over the Maritime Continent

A moderate to strong pulse of the Madden–Julian Oscillation (MJO) lies over the western Maritime Continent. Climate models generally agree the MJO signal will maintain its strength, or weaken marginally, and track eastwards over the coming week. At this time of the year, the MJO over the Maritime Continent is typically associated with increased cloudiness and rainfall over northern Australia. Historically, the effect on rainfall for northern Australia peaks as the MJO moves over the eastern Maritime Continent. A broadscale westerly wind flow is typically established over northern Australia and the southern Maritime Continent in this scenario. This means the current monsoon conditions will likely continue; with widespread, enhanced rainfall for northern Australia in the coming week.

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

Weak La Niña in the tropical Pacific Ocean

A weak La Niña pattern continues in the tropical Pacific. Most models suggest this La Niña will end during the southern autumn.

La Niña typically brings above-average rainfall to eastern Australia, including northern Queensland, during the first few months of the year. However, a weak La Niña will have less influence on Australian rainfall than a strong event.

See the Bureau's current ENSO Wrap-Up 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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