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.

Widespread rainfall continues across Indian subcontinent

Heavy rainfall due to the active Indian Southwest Monsoon continued across much of the northern Indian subcontinent. Locations affected spanned the breadth of the subcontinent, from Pakistan in the west to Bangladesh in the east.  Widespread flooding, landslides and multiple fatalities in several regions were reported. The northern part of the Indian subcontinent has experienced the heaviest rainfall in the past week as an active monsoon trough remained near-stationary over the region. Multiple tropical lows developed within the trough in recent weeks providing further focus for the rainfall. The northern limit of the monsoon is over northern India, slightly further south than its average position for this time of year. To follow the progress of the Southwest Monsoon, see the India Meteorological Department's monsoon page.

Parts of South East Asia, particularly Vietnam, also experienced flooding rainfall in the last week due to tropical storm Talas which made landfall over Vietnam’s central provinces during Monday. Loss of life along with property and crop damage was reported.

Madden–Julian Oscillation reappears over Indian Ocean

The flooding and tropical storm development over India and South East Asia coincided with a strengthening Madden–Julian Oscillation (MJO) signal over the region. The MJO signal is currently over the central Indian Ocean where it typically enhances rainfall over India and, to a lesser extent, South East Asia and the western Maritime Continent.

In Australia, when the MJO is over the Indian Ocean at this time of year, it usually strengthens the easterly winds over the Coral Sea and northeast Australia. As a result, parts of Queensland, particularly northern coastal regions, typically see above-average rainfall. The MJO can also contribute to warmer minimum temperatures over the Top End and most of northern Queensland at this time of year. These effects across northern Australia typically diminish as the MJO moves further east into Maritime Continent longitudes.

Most climate models suggest the MJO signal will persist over the Indian Ocean at relatively weak amplitude, while some indicate it may marginally strengthen and move into the eastern Indian Ocean or western Maritime Continent in the coming week. In either scenario, the Indian monsoon would be expected to remain active, whereas the latter scenario would typically result in above-average rainfall over South East Asia and much of the Maritime Continent in the coming week.

ENSO-neutral climate state continues

Atmospheric and oceanic indicators used to measure the El Niño–Southern Oscillation (ENSO) are currently within neutral bounds. All international climate models surveyed by the Bureau indicate the tropical Pacific Ocean is likely to remain ENSO neutral for the remainder of 2017.

The Indian Ocean Dipole (IOD) remains neutral. Two out of six climate models suggest positive IOD thresholds will be reached during winter-spring, with only one model suggesting these levels will last long enough to be considered a positive IOD event. A positive IOD is typically associated with drier than average conditions over much of central Australia and parts of northern Australia during the build-up months of September to November.

See the Bureau’s ENSO Wrap-Up for official El Niño, La Niña and Indian Ocean Dipole information.

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

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